/ohm/ - Mud Power Edition

[Anonymous No.1434867]

burned-out thread: >>1423156 (Cross-thread)

>I'm new to electronics, where to get started?
There are several good books and YouTube channels that are commonly recommended for beginners and those wanting to learn more, many with advanced techniques. The best way to get involved in electronics is just to make stuff. Don't be afraid to get your hands dirty.

>Books?
Beginner:
Forrest Mims III, Getting Started in Electronics
Charles Platt, Make: Electronics
Michael Jay Geier, How to Diagnose & Fix Everything Electronic

Intermediate:
Kybett & Boysen, All New Electronics Self-Teaching Guide
Paul Scherz and Simon Monk, Practical Electronics for Inventors

Advanced:
Paul Horowitz and Winfield Hill, The Art of Electronics

>YouTube?
mjlorton
BigClive
paceworldwide
eevblog
EcProjects
greatscottlab
AfroTechMods
Photonvids
sdgelectronics
TheSignalPathBlog

>Project/idea websites?
http://adafruit.com
http://instructables.com/tag/type-id/category-technology/
http://makezine.com/category/electronics/

>Components/equipment sources?
Mouser, Digi-Key, Arrow, Newark are global full-line distributors with small/no minimum order.
RS Components (Europe)
eBay/AliExpress sellers, especially good for component assortments/sample kits (caveat emptor)
Your local independent retail electronics distributors
ladyada.net/library/procure/hobbyist.html

>Circuit simulators?
This mostly comes down to personal preference. These are the most common ones though:
LTSpice
CircuitJS (quick, dirty, interactive)
NI Multisim
CircuitLab
iCircuit for Macs

>PCB layout software?
KiCAD (recommended), why use anything else

>My circuit doesn't work. Halp?
Check wiring, soldering, part pinouts, and board artwork if applicable, then post schematic. Supply ALL relevant info and component values when asking for help.
>Li+/LiPo batteries
Read this fine resource first: https://www.robotshop.com/media/files/pdf/hyperion-g5-50c-3s-1100mah-lipo-battery-User-Guide.pdf
>I have junk, what do?
Take it to the recycler.

[Anonymous No.1434873]

>>1434867
Link to vid of OP image
https://www.youtube.com/watch?v=_zCsAfEbVRc

[Anonymous No.1434876]

>>1434867
Why they put caps on gates of fets?

[Anonymous No.1434888]

So I don`t know if anyone remembers a guy asking about a circuit to turn off a 50W LED before his apartment burnt down and stayed off until user input? I wasn't able to do anything since those months but today I just built it on the protoboard and it works. It is simpler than the things I asked and the things suggested here, it's the first "thing" I design and build from nothing. My biggest trouble was sensing the temperature with the only thermistors the shit stores arround here had (50 fucking Ohms) without using too much current. Ended up using a LM317 and shenanigans. Thanks everyone, when I solder and finish it up I'll post here.
>>1434876
High frequency bypass? Idk to be honest. Try looking up the FET small signal model and doing a equivalent circuit.

[Anonymous No.1434902]

>>1434888
here is what one dude suggest (thanks dude). I did not draw the transistor diodes (for the spikes caused by the relay) and some other shit but that's the idea.

I don't know what solution is better but it just werks.

[Anonymous No.1434910]

>>1434876
it may be to improve the consistency of the turnon/turnoff times of the fets. not sure if motor windings need flux balancing like in a transformer but i don't think they do.

[Anonymous No.1434913]

>>1434888
>High frequency bypass? Idk to be honest. Try looking up the FET small signal model and doing a equivalent circuit.
Dunno.
Maybe limiting current to gate somehow?
>>1434910
They don't need. That is something to do about driving mosfets

[Anonymous No.1434972]

Maybe you guys are interested in contributing some questions to this IoT project
https://docs.google.com/spreadsheets/d/1ftvf90NiXOEyCy-tXcxCc1RVPpXnUvVidGqROjrgMok/edit#gid=998950558
Since it is /diy/ and /ohm/ related

Explanation here
https://www.youtube.com/watch?v=WDeMFwwtFiU

[Anonymous No.1434987]

>>1434972
fuck off googlemind

[Anonymous No.1435011]

Ok, a few quick questions that should be fairly straight forward.
These kind of electric tea lights, what makes them flicker? There doesn't seem to be any components in them beyond the led, the battery and a very primitive switch.
Can the flickering frequency be altered somehow? As they are they are mostly on but I'd want it the other way around (I'm building some wargaming terrain and want some spooky-style flickering lamps).
Would it mess things up if I extended some wires from the led to the battery? I would like to keep the battery in a better location. (I've only worked with systems where wire gauge and length has been relatively unimportant before).

[Anonymous No.1435015]

>>1435011
a controller circuit inside the LED modulates current, look closely and you'll probably see a second chip
no, you'd have to build your own brightness controller
shouldn't be, the wire's voltage drop would be a few tens of millivolts at most and a device meant for operating from a wide battery voltage range wouldn't even notice

[Anonymous No.1435020]

>>1435015
Thanks for the quick answer!

[Anonymous No.1435044]

>>1435011
>>1435015

Follow-up question, is there any cheap, small component that could be put in line with the led to slow the frequency down. Or any other way to solve my problem (that doesn't include programming a micro-processor to do the work).

[Anonymous No.1435050]

>>1435044
no, but this level of mcu programming is piss easy, its actually fun

[Anonymous No.1435054]

>>1435044
>>1435050
try these fuckers http://ww1.microchip.com/downloads/en/DeviceDoc/40001239F.pdf

[Anonymous No.1435058]

>>1435050
Fair enough, I guess I'll pull the wires through for now and look more into it.

[Anonymous No.1435061]

>>1435054
or, alternately, these fuckers http://ww1.microchip.com/downloads/en/DeviceDoc/Atmel-8127-AVR-8-bit-Microcontroller-ATtiny4-ATtiny5-ATtiny9-ATtiny10_Datasheet.pdf

[Anonymous No.1435063]

>>1435050
>>1435054
Thanks, I'll pull some wiring through for now and then look into it.

[Anonymous No.1435066]

How viable is to make a 220/12v transformer for a power supply? Here in this shithole a 220/12 3A costs like 30$ plus shipping. Anyone ever tried this?

[Anonymous No.1435074]

>>1435066
Winding transformers is hell, so nah. But look around some more, you can probably find one for under 20$, less if used or torn out of some other junk equipment.

[Anonymous No.1435078]

>>1435074
can you tell me some type of junk that has normal transformers? There are lots of homeless here so anything with copper on the street disappears almost instantly but maybe I get lucky. I have a flyback transformer here though. But currently I have no use for 1,5kv..

[Anonymous No.1435082]

>>1435078
why do you need ac?
a 12V3A switch-mode power supply shouldn't cost more than $15 shipped, all over aliexpress
12Vac3A transformers are going to be a bit rare. low-wattage stereo receivers are good places to get ac transformers but they may be somewhat higher than 12Vac

[Anonymous No.1435084]

>>1435082
I need anything larger than 6V. I want to build a proper lab power supply from retification to regulation. I have a 12v 5A smps here I use for some high power LEDs. I'm tired of using a abortion I made out of phone chargers for testing stuff. Such is the life in the third world. If it gets too hard I think I'll just use a smps and go from there.

[Anonymous No.1435087]

I have a shitty cassette player. It has lots of hiss and noise in the output.
Is there something I can put before the final output (trs jack) that can help reduce it?

[Anonymous No.1435100]

>>1435084
an old style auto battery charger
most frequent problem is the rectifier dies - gets thrown out

[Anonymous No.1435141]

>>1434902
That first 393 will probably require a pullup resistor also.

>>1435050
>mcu programming
Just use a LFSR and a 555 mate. Dedicating even an ATtiny to a single flickering LED is kinda stupid, though not necessarily more expensive.

[Anonymous No.1435155]

>>1435141
I'm doing my own thing. that circuit:
>>1434902
What do you think?

[Anonymous No.1435174]

>>1435141
>pullup
it has one. R1
>LFSR and 555
how's he going to fit that in the tea lite? also how's that not going to be more expensive than a single 30 cent micro, especially once you factor in wiring?

[Anonymous No.1435180]

Can you recommend me a microcontoller that can be programmed by Arduino (I'm too broke to buy a programmer) for BLDC motor control.
It should have 4-5 FAST ADCs (3 for BEMF detection, and other 1/2 for current limiting), 3 PWM outputs with ajustable frequency, and couple of timers... But I'm not 100% sure.

[Anonymous No.1435181]

>>1435180
Oh... Two more ADCs, 3 more outputs... Dunno.

[Anonymous No.1435183]

>>1434867
Why did nobody tell me how awesome this stuff is? Solder suckers literally suck in comparison

[Anonymous No.1435186]

>>1435183
I use some fine stranded 6mm^2 wire and half of Louis of flux. Way cheaper.
Anyway, solder sucker is good of 2+ layer boards through-hole, while wick is good for SMD and single layer boards.

[Anonymous No.1435187]

>>1435180
how about the STM32F103 bluepill? 2x1Msps ADC, lots of PWM out, plenty of timers. the board is $2, and can be programmed via UART or SWD (ST-Link clones cost about $4)

[Anonymous No.1435191]

>>1435187
Hm... Seems legit.
Is programming for ARM any different than programming for AVR?

[Anonymous No.1435194]

>>1435186
Does this mean a Louis Rossmann is now a valid measurement of flux?

I find solder suckers to be good for removing larger amounts of solder without needing to apply more flux, while wick is best used with flux, a relatively clean board, and for removing smaller amounts of solder.
The real gold is to have a desoldering iron if you don't mind the maintenance (those hollow tips get clogged all to hell, esp. with unleaded solder, constantly have to be cleaned)

[Anonymous No.1435200]

>>1434876
Capacitors stabilize the gate voltage. That is all. probably just ripple rejection. Remember, a motor may need a nominal speed, or a device may have issues with a voltage that's just out of range. Modern smaller mosfets can have ridiculous I/V curves, so a ripple of 50mV could turn into 400mA and cause a lot of issues if the mosfet is operated in the linear region. I'm not exaggerating, I think I have a mosfet around here with 8 Siemens of transconductance.

>>1434913
Alternating fets is terrible. They have a capacitance, so to charge/discharge you need a lot of current at high frequencies. A typical trench-type mosfet can easily exceed 1.5A at 1 MHz. ( I was doing some "high power" design work with those frequencies. )

>>1435066
Gang transformers. Only have to watch the current limits. 220->120->12 or a 120->6 should be fine on 220->12. Get yourself a regulator like the 7812 or a switch-mode version, RMS vs peak voltage will fuck you.

>>1435183
I've had good and bad experience with it. I think the fresher it is (less corroded, even a little), the better it works. Also probably depends on flux, as per usual.

[Anonymous No.1435201]

>>1435194
>Does this mean a Louis Rossmann is now a valid measurement of flux?
Yes. In fact pretty good unit.
>I find solder suckers to be good for removing larger amounts of solder
I did it always by shaking a board while blob is hot and liquid.
>without needing to apply more flux,
Not much flux is needed tho. 1/50th of Louis would be fine. You need to remove oxides from small footprint, slightly smaller than tip
> while wick is best used with flux, a relatively clean board, and for removing smaller amounts of solder.
I use wick to tin toner-transfer boards. I use cheapest 50/50 solder for this.
Wick really helps to make a layer thin.

[Anonymous No.1435203]

>>1435191
it's still C or C++ I guess, but other than that, yeah
ST has a free configurator tool (STM32CubeMX) that lets you set up pins and clocks as you like, then writes init code for the core and the onboard peripherals to switch everything on in the correct order. also includes low-level and medium-level libraries for managing the interfaces instead of fiddling with registers directly, but nothing stops you from skipping CubeMX entirely and going raw Makefile for everything if you'd rather
I hear there's an arduino backend for these if you would prefer, but I don't know how much of the peripherals' capability they expose. probably not much

[Anonymous No.1435206]

>>1435200
>A typical trench-type mosfet can easily exceed 1.5A at 1 MHz. ( I was doing some "high power" design work with those frequencies. )
That is a lot of current. This is why I want to make it work at lower freq. Less heat, much efficient. More noise from motor... Actually I'm doing it just to make some noise. Driving quiet e-bike is fucking dangerous.
>Modern smaller mosfets can have ridiculous I/V curves, so a ripple of 50mV could turn into 400mA and cause a lot of issues if the mosfet is operated in the linear region. I'm not exaggerating, I think I have a mosfet around here with 8 Siemens of transconductance.
Okay. I'll check curves of my fets.
>>1435203
Okay.
I guess I'll order programmer and chips from china. Because in my shithole this is expensive.

[Anonymous No.1435209]

>>1435206
>Actually I'm doing it just to make some noise. Driving quiet e-bike is fucking dangerous
you should just put a playing card in the spokes then

[Anonymous No.1435218]

>>1435206
https://www.fairchildsemi.com/datasheets/FD/FDB6035AL.pdf

Here's one I think I bought some years ago. Lower voltage (30V max) but 68S of transconductance. Since it's not high-voltage, it's gate charge is only 15nC, but the resistance is also 1.5Ohm. 1MHz is 30nC*1e6 / 1sec = 30mA. Not too bad.

Look at https://www.st.com/content/ccc/resource/technical/document/datasheet/2f/d2/8c/46/49/6b/47/bf/CD00003377.pdf/files/CD00003377.pdf/jcr:content/translations/en.CD00003377.pdf

It looks like those don't need much either. I think my problem was I was looking at shoot-through and PMOS. Those are 4.5 Ohm on resistance though, which is a quite a lot of dissipation needed.

MOSFETs have advanced a lot, you could probably search through mouser/digikey if you wanted something optimized and were willing to shell out a few more $/component.

[Anonymous No.1435233]

>>1435209
That is not /ohm/ level gimmick.
Also chink controller is quite shitty. It runs hot on non-full throttle, but runs cool on full (when it doesn't do much PWM limiting). So it has shitty driver, or MOSFETs with enormous gate capacity.
My friends ebike with KU63 (PCB looks identical) with similar motor runs relatively cool.
Marking on MOSFETs on both controllers is dremeled away.
>>1435218
>https://www.fairchildsemi.com/datasheets/FD/FDB6035AL.pdf
I need some 60-120V ones with 30+ amps. And Rds as low as possible.
For ex. TK72A08N1,S4X
https://toshiba.semicon-storage.com/info/docget.jsp?did=13152&prodName=TK72A08N1
72A, 3.2 mOhm, isolated TO-220 (no need for thermal pads), 80V
>MOSFETs have advanced a lot,
Agree. I've been searching for tranies like 3 years ago, and they were way shittier and more expensive.
I guess it is due to solar power and EV stuff.

[Anonymous No.1435234]

>>1435233
And yeah, P-FETs are too resistive. Only N-FETs and bootstrapping.

[Anonymous No.1435242]

>>1435234
>>1435233
A really annoying thing that can bite you, if you're switching fast, you need an equally fast *ground-pull*, corresponding to a gate driver pulling double-duty, or a powerful resistor. In the one you linked, they use a 4.7Ohm resistor for their pull-down, and their off-time is almost 100ns i.e. 1/10 of a microsecond. If you're operating around 1MHz that can introduce really bad behavior. A 50% duty cycle would also be 5W average heat generated just in the charge timings outside of the mosfet. So it's actually over 2A + the mosfet current, which would would be relatively negligible. A proper pull-down would prevent that inefficiency. or a lower switching frequency, though you'd still run into it a little.

[Anonymous No.1435248]

>>1435242
Well, I'm not planning running it at 1 MHz. I think I'll run it in 50-5000 Hz range, to make it audible and make driver work simplier.
By the way, why most pre-build controllers have PWM switching frequency around 8-16 KHz? To make it silent?

[Anonymous No.1435260]

>>1435248
Probably just a convenient frequency. Higher frequencies tax inductors, you don't need more than quality, whatever. Majority of adults can hear 10-16KHz, and inductors can always have whine, so I'd doubt that's the reason.

>to make it audible
Square pulse sounds terrible if you want to directly put that into a speaker. Filtering can work pretty well to make it sinusoidal.

[Anonymous No.1435276]

>>1435260
Well, it is quite quite.
Also, may be it is to maintain coils energized, dunno.

[Anonymous No.1435284]

>>1435248
higher frequency allows cleaner waveforms at higher speeds and better balance between phases, which should save power and extend range

[Anonymous No.1435302]

>>1435284
At high speeds there is no PWM.
Cleaner waveform is not requited at all. It literally replaces mechanical commutator. It is BLDC.

[Anonymous No.1435314]

I'm designing a synthesizer.
the function generator I will use has two inputs, so it can generate two tones at once.

If I press one switch, it will finish a circuit with input 1. If I press two at the same time, one input should go to input 1, and the other input 2.

what kind of circuit am I looking for to block one of the signals so it diverts from the connection to input 1, to another circuit connecting it to input 2? The way I'm imagining it it would use XOR gates but I'm not sure

I also need to make sure only two keys can be high at any given time, even if the user presses more than two keys at once. Or maybe not, it might sound cool

[Anonymous No.1435319]

>>1435314
I can't think of any of the early analog polysynths that did not use software to do voice channel allocation. then again, they were allocating notes amongst 4 or more channels
what are you using to scan the keyboard? that's the part of the system that should be making channel allocation decisions because it knows when keys are pressed and released. also why not simply round robin? in that case you'd be less likely to have the tail of previous notes interfering with the new note

[Anonymous No.1435320]

>>1435174
Well I never said it would be, but two SMD ICs (one SIPO shift register and one XOR) soldered to one another sans PCB could be pretty compact.

>>1435314
Not sure what level of digital you're going for, but you're going to need quite some array of logic gates unless you just feed them all into an MCU. I don't know how many keys you want to go for, more than 12 and that becomes really tiresome. It would be nice if there were 2-of-16 encoders or something to that effect. Whip up a truth table for a simple (4-6 key) situation, K-map it, and see if it simplifies well without XORs. There are multiple arrangements you could use for your truth table, and the simplest to make a table of probably aren't the most compact gate-wise. At least you'll have plenty of do-not-care conditions.

[Anonymous No.1435332]

Will this work? (It is 1/3 of bridge driver)

[Anonymous No.1435338]

>>1435332
>>1434876
Btw, I'm trying to remove extra parts from here. Chink a chink circuit...

[Anonymous No.1435352]

>>1435320
>pretty compact
sure, but still not as easy or as simple to put together as a single SOT23-6 and a resistor, *and* control over the effect is indirect and possibly lacking
>feed them all into an MCU
high I/O-count FPGAs would be cash for this sort of thing, if anon doesn't need anything too fancy like pressure sensing (and could possibly use capacitive sensing even if he does). there would probably be enough room left over in a modest FPGA for a simple MIDI state machine and UART, if desired

>>1435338
kek, there's a term for that already: look up Muntzing
>will it work
as drawn, I doubt it. when either of the input transistors turn on they'll be shorting out the supply rail

[Anonymous No.1435363]

>>1435352
There a bog-standard FPGA people here get for pretty cheap? Or a PLA/PAL/CPLD or whatever's hip these days.

Oh and the second one won't short the rail because of the diode. Still a whacky circuit with twin power rails.

[Anonymous No.1435369]

>>1435363
personally, I like Lattice's iCE40 series. they're pretty low-cost, pretty friendly, have respectable density and speed, and there are versions available in hobbyist-friendly packages like TQFP
>second one won't short the rail
the bootstrapping makes sense but Pic related does not

[Anonymous No.1435374]

>>1435369
"to MCU" implies the bottom line is not a ground. So if that transistor is on the line would be... something

It's weird because using an NPN on the high-side has very unpredictable results.

Still not entirely sure what the point of the circuit is. The original design looked like a three-pole commutator driver.

[Anonymous No.1435379]

I wired up an LM317T voltage regulator as per tutorial and then supplied it with 5V from my breadboard supply.
I set the two potentiometers to have resistances to give me 3V on the output, but I am only getting 1.5V, what is going on?
Both the wiring and resistor values are correct, since i just followed the tutorial and used an equation seen there. The resistor going to the ground is 4.7K and the other one between adjust and output is 3.7K. I calculated it with the standard Vout = 1.25(1+(4700/3700)+(5×10^-5 )*4700 which gives 3.1V
So why the shit am i getting only 1.5V?

See pic, i only erased the capacitators since i am not using them, since they are optional.

[Anonymous No.1435383]

>>1435379
This is the tutorial i am using
https://youtu.be/IjJWWGPjc-w?t=2m42s

[Anonymous No.1435387]

>>1435363
>iCE40
adding, the iCEcube software is a hot mess but it works well enough once you work around its idiosyncrasies
that said, Altera MAX Vs sourced from ali/ebay might be cheaper per I/O pin, if that's the main selection criterion. and Quartus Prime is bloated but much less of a hot mess
>circuit
also adding, there is a direct path for current through the e-b junctions of both transistors, and the resistor won't stop it. they probably will an hero the moment the power comes on

>>1435374
that would indeed be nonsensical. I assume that note referred to the bases of the logic input transistors
>three-pole commutator driver
indeed that's what it was. that anon is trying to Muntz the design. the totem-pole drivers in the original look pretty well optimized tbqh, the resistors surely being there for a reason

[Anonymous No.1435397]

>>1435379
LM317 has a minimum load requirement, which is part of the reason why the manufacturer tells you to use a rather small resistor for R1, around 220R.
Also, remove the capacitors only after you've verified that the circuit works with them.

[Anonymous No.1435401]

>>1435397
I'm not using caps because i don't have any. Also it's really annoying how like 90% of circuits just have random capacitators all over the place that seemigly do nothing and tutorials don't usually even mention them or say they are optional.

[Anonymous No.1435404]

>>1435401
caps add stability

>it's really annoying how like 90% of circuits just have random capacitators all over the place
>not having a box full of caps of different sizes

[Anonymous No.1435405]

>>1435379
the first lesson you must learn is to read the datasheet. Specially the aplication notes.

[Anonymous No.1435406]

>>1435401
capacitors are there to filter noise and make things smoother. usually people just throw 0.1uF ceramic ones all over the place and a couple of 10uF and 1uF in regulators and stuff like that.

[Anonymous No.1435410]

>>1435406
>0.1uF ceramic
ceramics that large? I use polyester for that value

[Anonymous No.1435413]

>>1435410
104s are pretty common ceramics, not that large provided we're not talking SMT.

[Anonymous No.1435415]

>>1435410
but you don't have any

[Anonymous No.1435418]

>>1435415
i have box full of poli caps
are ceramics superior to poli?

[Anonymous No.1435425]

>>1435379
>dyi goes down
>i got this
>rewire that shit
>connect to power
>starts smoking
FUCK
I had a brain fart and connected the Vout as a common ground, i hope my expensive agm deep cycle battery isn't dieded
I needed you shits and you were offline and i ended almost burning my shit down

[Anonymous No.1435430]

>>1435369
>>1435332
Oh... I meant connecting bottom tranies to bases of two resistors.

[Anonymous No.1435434]

I'm trying to program an atmega328P through an arduino, avrdude initialises correctly but reports an invalid signature of either 0x000000, 0xff0000 or 0x0000ff. wat do? The MCU hasn't been used before and I don't have any external crystals to try out with

[Anonymous No.1435449]

>>1435413
huh. I have yet to see THT 22µF caps, but they're cheap and easy to find in 0603 SMD

>>1435418
they're way cheaper and have lower ESR

>>1435434
check your wiring, slow down the clock

>>1435425
I explicitly ignore you because of your cutesy "capacitator" shit. you need to go back

[Anonymous No.1435458]

>>1435449
>lower ESR
this type suffers from microphonia

[Anonymous No.1435461]

>>1435374
>"to MCU" implies the bottom line is not a ground.
No. Bottom line is ground. I just fucked up circuit completely.
This one I guess is more correct

[Anonymous No.1435464]

>>1435458
Not a problem with basic power supply bypass capacitors.
Not a problem in most other cases, either.

[Anonymous No.1435466]

>>1435461
no, it's not. Pic related is literally nothing more than two diodes in series
you should really try running these through a simulator first. try falstad.com/circuit/circuitjs.html

[Anonymous No.1435469]

>>1435461
Pretty sure as soon as you turn on the lower transistor you'd have a short.

>>1435466
Falstad's thing is ass to use and doesn't give you good data/timings for certain stuff. PSpice is easier.

[Anonymous No.1435478]

>>1435434
replying to myself, had to output 8MHz clock from arduino to MCU external clock, should've bought crystals

[Anonymous No.1435485]

>>1435469
>>1435466
Okay.
But can I replace those BJTs with N and P fets with relatively low capacitance on gate to control mosfets?

[Anonymous No.1435486]

fug, charging phone with a 13V battery using the lm317 is shit, it is wasting a ton of energy as heat, can't wait for the buck converter order to arrive

[Anonymous No.1435487]

>>1435485
You're misunderstanding a lot of things. Learn more about how bjts and mosfets are enabled/disabled

[Anonymous No.1435488]

>>1435486
>>>>13V to 5V with a linear regulator
Literally what were you expecting?

[Anonymous No.1435489]

I got a lambda probe, 4wires coming out, 2black, white and blue. They all show open circuit with each other, is that normal? Shouldnt at least one pair of wire had a couple of ohms for the heater?

[Anonymous No.1435496]

>>1435478
should've bought chips with internal oscillators :^)

[Anonymous No.1435500]

Raspberry pi car stereo guy here

I got a ground loop noise isolator in the mail but it doesn't really work that well. Did I just get a shitty one? It eliminates the sort of static that gets higher pitched with my engine RPMs, but whenever I try to play music from my pi, a different sort of static comes back. I don't get it. When the pi boots up, there is no static, but as soon as I try and play some audio, the static comes back.

Maybe a better ground loop isolator will help. Anyone have any ideas? Should I try a thicker ground wire?

[Anonymous No.1435503]

Why are traffos so fucking expensive? I wanted to build a simple invertor because the jews are selling them for like $40, but the traffo costs like $30 so there isn't any point in not buying one

[Anonymous No.1435504]

>>1435487
>You're misunderstanding a lot of things
More likely I've completely forgot everything.
>>1435487
>Learn more about how bjts and mosfets are enabled/disabled
MOSFETs are enabled by charge on gate. And gate is isolated, so it is relatively simple to understand. By adjusting voltage on gate - resistance of drain-source is changing.
While BJTs are controlled by current, and they have such structure, that it can be considered as two diodes, connected with same ends to base. And I completely forgot about this. By adjusting current through base - voltage drop of collector-emitter changes.
And since BJTs are controlled by current - there should be a resistor to limit base current. (250-1k usually, but it depends on coefficient). And MOSFETs are controlled by charge, so resistor there limits inrush current, to prevent burning the gate, so its' resistance is relatively low (47-100 omh usually, but I guess it depends).
So. By replacing those NPN and PNP transistors with N-FET and P-FET there will be no short, since gates are isolated.
Also I can swap PNP and NPN, but voltage will be greatly reduced, thus big MOSFET won't open fully and will produce much heat.
>>1435469
Even without lower tranny.

[Anonymous No.1435505]

>>1435066
It was a common practice long time ago. That said, it's kinda tedious and normal electronics stores don't have transformer steel anymore. There's eBay, though. There's also the option of salvaging the steel (and the primary winding) from an old transformer, but that too is much more tedious with modern day transformers than it was with very old transformers.

[Anonymous No.1435506]

>>1435500
the pi's internal audio output is kinda cheezy. try a better audio DAC. USB audio DACs are cheap

>>1435503
material costs and assembly costs. it takes a lot of iron to store all that magnetic flux and a fair amount of time to wind them

[Anonymous No.1435509]

>>1435500
>Raspberry pi car stereo guy here
Shouldn't that be pretty easy? Just take the signal from the headphone slot on the RPI, put it through a simple amplifier and into the speakers, done

[Anonymous No.1435510]

How exact do I have to get with the voltage to not destroy connected usb devices? The standard is 5V so would say 5.5V be a problem?

[Anonymous No.1435513]

>>1435504
I want to check the circuit but I'm not feeling it. Do you have a printer or a drawing tablet? Figure out your own pathing, would only take 4 diagrams

[Anonymous No.1435518]

>>1435509
That's exactly what I did and it leads to a ground loop.
>>1435506
I'll try that.

[Anonymous No.1435519]

>>1435518
you have to connect all grounds

[Anonymous No.1435522]

>>1435510
The nominal maximum is 5.25V. Typically stuff meant for 5V operation has absolute maximum supply voltage rating of 6V (new stuff) or 7V (older stuff).

[Anonymous No.1435528]

>>1435510
>would say 5.5V be a problem?

nope. a lot of chargers are rated 5.1, 5.3, 5.6, etc to account for the voltage loss along the skinny USB cable. highest i've seen is 5.9V. if you're autistic or chickenshit, you put a schottky diode in series with the cable to drop about 0.3V

[Anonymous No.1435534]

>>1435513
>I want to check the circuit but I'm not feeling it.
Ok, I'll redraw it.
This controls bottom fet.
>Do you have a printer or a drawing tablet?
Only a laser printer.

[Anonymous No.1435536]

>>1435534
Top part is similar, but has bootstrap cap and diode

[Anonymous No.1435537]

>>1435534

why do you need a push-pull stage to drive a FET?

[Anonymous No.1435538]

>>1435504
plot twist: as if the finite rise-times of real world signals were not enough, you now have an RC time constant in your circuit. Pic related

>>1435537
I suspect he'll need something to drive the high side anyway

[Anonymous No.1435542]

>>1435538
>plot twist: as if the finite rise-times of real world signals were not enough, you now have an RC time constant in your circuit. Pic related
Not cool... I see two solutions. Add resistor to reduce current... Or replace those fets with optocoupler.
Or just copy Chinese schematic, because it works good.
>>1435537
To drive high-side. And to charge/discharge power fets faster, to reduce heat.

[Anonymous No.1435548]

>>1435542
Or use dedicaded IC for driving fets...

[Anonymous No.1435551]

>>1435542
>Or just copy Chinese schematic, because it works good.
I would unironically do this, if you don't want to use a gate driver IC

[Anonymous No.1435556]

>>1435551
Agree.
I think I will use gate drivers or chink circuit. But I still don't quite get how Chinese circuit works.
I guess I'll have to simulate it...

[Anonymous No.1435562]

>>1435538
Is this why the FETs/BJTs are often put in common-collector arrangements?

[Anonymous No.1435567]

Am I going to have to buy matlab if I want to learn dsp?

[Anonymous No.1435570]

>>1435562
bingo

>>1435567
or buy a rasPi that comes with free Mathematica, ig

[Anonymous No.1435609]

So if i step down voltage by doing a square wave by turning on and off a mossfet with no extra sugar like caps or inductors (so the powered device is connected directly to mossfet output), could that still power devices?

[Anonymous No.1435611]

Can someone give me a idea on how to choose the appropriate transistor for a project?
Like, obviously for blinking LEDs you can use just about anything, but I'd like to get into audio amps and radio transmitters.

There's just so freaking many of them I don't even know where to start, aside from the really obvious choices like using a mosfet for high voltage loads

[Anonymous No.1435612]

>>1435609
any but the simplest device would complain. y tho

[Anonymous No.1435613]

>>1435612
because i don't want to wait a month for the chink shit to arrive so i want o ghetto it, but i don't have any of them fancy inductors and shieeet so i have to make do with a raspberry pi zero turning on and off a mosfet really fast

[Anonymous No.1435618]

>>1435609
If it's just an LED or even a simple brushless motor driver (like the ones in 2-wire fans) sure. But if it's charging your phone fuck no. You can mock Class-D it by feeding a tuned square wave into a low-pass LC filter with appropriate time constant, which will output an approximately constant voltage. This will sag with loads though, so you may want to run a linear regulator off this instead, since your shitty credit card computer doesn't have any ADCs for active feedback. Might be able to work with a comparator or three. But just wind your own inductors, it's pretty easy.

[Anonymous No.1435621]

>>1435618
>linear regulator
if i feed a square wave into it, do i get a smooth straight line on the other side?

[Anonymous No.1435624]

>>1435611
>audio amps
just about anything would work. noise in the audio band is important, as is unity-gain frequency. also, some transistors may be more linear than others
>radio
the topology of your circuit is the first guiding criterion, followed by the S-parameters (or equivalent) at your chosen frequency and bias voltage/current, which you will need to see if you can tune around with the other components in your circuit. parasitic capacitances also work their way into consideration

>>1435621
no, read the post, you need a capacitor or forget about this entire project until the boat arrives

[Anonymous No.1435639]

>>1435621
Only if you feed the regulator a filtered signal, i.e. with a low-pass filter. If you use an RC filter then you'll be making a fair bit of heat, that's why LC filters are essential for this purpose. It's pretty much just a buck converter but with shitty/no feedback.

[Anonymous No.1435708]

10 steppers for 70c anyone? I find it hard to imagine a use for one of these.

[Anonymous No.1435727]

>>1435708

that's what annoys me. an awesome deal for something that I can't use.

[Anonymous No.1435734]

>>1435708
Emmm... MCU controlled vibrator?

[Anonymous No.1435736]

>>1435708
Man, I'm sure they suck, but if those had really good resolution we could build a pocket printer
>>1435734
or that

[Anonymous No.1435737]

>>1435708
speculating wildly, but maybe they could latch a door closed?

[Anonymous No.1435739]

>>1435736
*pocket 3D printer, could have swore I was in the 3dpg thread...

[Anonymous No.1435740]

>>1435727
>>1435737
About 4mm of travel, going by eye. Could close some very small and well-formed latch, but not a strong one. A solenoid would suit that purpose far better, the precision of a stepper is wasted. I was looking for tiny stepper motors to see about designing a conventional but automated coil winding machine, with a small linear stepper to move the wire feed from side to side, and I guess there are some tiny inductors that you could use with this, but it isn't exactly something you'd build unless you only ever needed such tiny coils. Best other use I can think of is moving mirrors by a small amount, moving a aperture by a little over a beam width, or perhaps interferometry. I bet it's got a fair bit of slop with that ~1mm v-shaped thread though.

>>1435734
The thing would probably let the smoke out with more than a mA, but if you're one of those guys who like to use an arduino uno to PWM a lightbulb...

[Anonymous No.1435747]

>>1435740
>solenoid
the screw force and the ability to stay locked when non-energized might be important for some applications, especially light-duty security like pill dispensers
or, for things like raising/lowering compact disc spindles or doors or cassette tape heads. it would be interesting to know what these were actually manufactured for

[Anonymous No.1435749]

>>1435740
>The thing would probably let the smoke out with more than a mA,
You've 10 of those.
>but if you're one of those guys who like to use an arduino uno to PWM a lightbulb...
Why to use Arduino, when based attiny85 exists?

I wounder what toque does this thing has.

[Anonymous No.1435750]

>>1434867
I've been checking my local shithole electronics part store... And they were selling Renesas RL78 controllers for dirt cheap. (1/3 of similar AVR or PIC).
Had anyone programmed for those? And how do I program them?

[Anonymous No.1435751]

>>1435747
Actually pill, cat food, gum-ball, etc. dispensers isn't a bad use at all. But a brushed DC linear motor is still probably better for those. Things like a tape deck could well be the intended purpose, since the tape itself is only 5mm wide or so, it would also explain the large amount of them for very cheap prices. No clue how info is actually written to the tape though, and if there's anything from side-to-side across the tape in the first place.

>>1435749
That was the point, the only reason you'd want to make a vibrator that requires MCU control is if you're the person that uses far more advanced systems than necessary to perform a task, of which dimming a light bulb with an arduino uno is also arguably an example.

[Anonymous No.1435754]

>>1435751
from what I remember of Travan drives, there is longitudinal motion involved in reading/writing. could aslo be useful for adjusting VHS head azimuth
never really got to experience much in the way of other tape drives before "Shugart's Law" made them uneconomical in favor of HDDs

[Anonymous No.1435755]

>>1435708
moving a wiper on a digital linear pot?

[Anonymous No.1435819]

>>1434987
>looking at electronic books at bookstore
>author writes "You can contact me at [e-mail]"
>book instantly dropped

Seriously, fuck people that unironically have geemail and use it these days. Email is 2$ a month from dozens of vendors that are not huge privacy violating monopolies. There's no excuse.

>>1435500
A ground loop noise isolator is just a transformer for each line. Blocks DC, allows AC audio to pass. Open it up and if you don't see transformers you got screwed. It's probably something else causing noise.

[Anonymous No.1435826]

>>1435819
A big enough cap works fine, and with signal level stuff, i.e. the 3.5mm pi output, you really won't need a big one at all provided the amp/preamp's input impedance is nice and high. To get a 20kHz corner high-pass with a 1MΩ input impedance on the resulting high-pass filter, you only need 8pF of capacitance.

[Anonymous No.1435842]

>>1435556
Shit. Chinks are fucking geniuses.
Their gate driver works perfect.

[Anonymous No.1435844]

>>1435819
If you think google doesn't already have dirt connected to your online fingerprint you are sadly mistaken. Even if you use protonmail the encryption doesn't mean anything if it's only on 1 side

[Anonymous No.1435898]

>>1435842
Okay. Good.
How do I select MCU for this purpose? I guess it should have fast ADC, external interrupts, 3+ channel PWM timer....

[Anonymous No.1435901]

>>1435898
didn't you ask that on the last thread?
you look at parametrric selection guides for CPU families that interest you and find the specs you want
you read
and you read
and you read

[Anonymous No.1435911]

>>1435901
>didn't you ask that on the last thread?
Maybe. I've asked this shit on 3+ places...
>you look at parametrric selection guides for CPU families that interest you and find the specs you want
I don't have any preference to any CPU families. I just want it to be cheap and work.
I guess I'll try first on Atmega328, since I've couple arduinos laying around. But there are not much external interrupts, and I need 4 at least for sensored operation.
And then I guess after that I'll have more exact criteria for MCU.
But at this point I think I'll need
- 3 PWM channels. More bit - more better
- 6-7 external interrupts (3 for halls, and 3 for BEMF zero-crossing detection, and 1 for current limit?)
- 3 ADCs (throttle, brake lever, shunt?)

I just don't know. I've programmed only AVR, Atmega 328 168 8 and ATTiny 85, 45. All arduino-related stuff.

[Anonymous No.1435926]

>>1435911
If an 85 or 45 is enough pin-wise, and you have one lying about, I'd go for that.

[Anonymous No.1435927]

>>1435911
did you take a look at the STM32F103 yet? it meets those criteria and, best of all, has an internal oscillator so you don't need to deal with crystals
see also STM32duino

[Anonymous No.1435935]

>>1435926
85/45 are definitely not enough pin-wise. And they are slow.
But 8/168/328 should work. They have enough pins, they have enough PWM channels, 6-8 ADCs. And more importantly people had done BLDC controllers with it. Some were shitty, and some are quite decent. Actually some pre-made ESCs use 168.
>>1435927
I took a look.
I liked everything, price is good (tiny bit more expensive that arduino nano), features proper high-frequency fast ARM CPU, many I/Os, much PWM. Also USB bootloader is avalible. But delivery from china sucks. It takes like 2 month to deliver to my shithole on average.
And in my shithole those chips are expensive. Like 10$/pcs
Anyway, I am going to order couple blue pills, because it is quite nice thing.For 3$/board you can't beat this.
Also I know that Xiaomi scooters use STM32 as controller... So there will be only problems in shitty circuit design and shitty software.

[Anonymous No.1435953]

>>1435935
you should have paid for express shipping :^)
yeah, it's kinda tough to justify an 8-bit processor with the 32-bit option being so close in price

[Anonymous No.1435961]

>>1435953
>you should have paid for express shipping :^)
30-90$ for tiny board is not worth it. It is better to get it locally. Or wait.
Should I get ST-Link for flashing bootloader (if I would need for some reason)?
>yeah, it's kinda tough to justify an 8-bit processor with the 32-bit option being so close in price
Yea. But I guess manufacturing price is same.

[Anonymous No.1435964]

>>1435961
you could use the ST-Link (easiest, also gets you real-time debugging) or you can use any USB-to-UART adapter. I thought I saw an arduino sketch for talking to the F103's built in bootloader but I might have been drunk

[Anonymous No.1435992]

So I want to make my car niggerproof and install a lojack, since I live in an infesetd area where car theft is rampant.
I looked at commercial jojacks and their prices are a fucking joke.
So basically here is what i'm thinking. I would run a wire from a car battery to a buck converter, step it down to a voltage for raspberry pi zero board, which would be hidden somewhere in the car.
Then on the rpi i would connect a gsm module and a gps module which would be broadcasting the car's position at all times.
Does this seem like a decent idea?
I would also use one of them current detection modules with a small battery connected, which would power the raspberry, in case Tyron tries to get smart and disconnects the car battery.
I added the prices and the whole thing comes about 12 (FUCKING TWELVE) items cheaper than a decent commercial solution

[Anonymous No.1435993]

>>1435992
>items
times

[Anonymous No.1435996]

>>1435992
sure why not

[Anonymous No.1436008]

Lazy fucking chinks, LAND THE FUCKING PLANE ALREADY i need my shit

[Anonymous No.1436010]

>>1434867
does a through hole version of this part exist and what is it called? its a 1.8v/5v level converter
74LVC1T45GW,125

[Anonymous No.1436011]

>>1436010
>1T
nope. if you're interfacing with 1.8V it's generally assumed you're using SMT and have no problem with it
srsly tho y u no breakout board?

[Anonymous No.1436012]

>>1436011
that could work for me, but it's another expense.

[Anonymous No.1436013]

>>1436012
so what's wrong with SOT23 then?

[Anonymous No.1436015]

>>1436013
i have no idea is the sot23 larger. i assume it is the same size as the sot363. I lack the skill to use smt pcb design programs. I can handle through hole fritzing without much issue though.

[Anonymous No.1436018]

>>1436015
yes, SOT363 are very smol
SOT23s are somewhat larger. still smaller than a 2.54mm grid and probably wouldn't work well on a perfboard unless you did some magic with fine wire and Kapton tape
it may be time to git gud with KiCAD. 5.0.0 final was released very recently

[Anonymous No.1436020]

>>1436018
I'd give smt a shot, i've found some footprints in fritzing, but the larger the better. do you have any part suggestions for a sot23 verion of 74LVC1T45GW,125

[Anonymous No.1436021]

>>1436018
SN74LVC1T45DBVR
thanks for the help, I found this part, I think it'll work.

[Anonymous No.1436022]

>>1436020
yes, that's the same function in the correct package. you can probably find an equivalent part in SOT23 in many other manufacturer's single-gate logic catalogs too
another option, if you think you might need two, is the 74LVC2T45DCT, which comes in the still easier to handle SOIC-8

[Anonymous No.1436023]

>>1436022
I'd consider it but i'm a n00b to electronics and not sure how to adapt the circuit. I've soldered smt before but when the pins are too close together I can't prevent solder bridges, that's why i stick to through hole.

[Anonymous No.1436026]

>>1436023
ahhh. extra flux really helps a lot when working with SMT. I really have to recommend you get a cheap chink flux pen, it will be worth the dollar or two. a good iron, preferably with temperature control and fine tips, also helps. so does thin solder. that's probably a bit more investment than you want to deal with right now, which is fair, but get the flux
it also helps to clean the molten solder off your iron before you do the SOT23s and add the tiniest bit possible just to get it a little wet where you'll be soldering
final bit of advice: watch youtube videos of SMT soldering for noobs for a while

[Anonymous No.1436028]

>>1436026
I bought the flux pen on your suggestion. I have a decent hakko iron. i was into ham radio for awhile so had to make up cables and do minor repairs. I just got old enough that I stopped being able to level up my skills.

[Anonymous No.1436069]

>>1435708
Build a tiny 3D printer that prints from atoms

[Anonymous No.1436075]

Is this even possible?
There is no way a cap can hold a charge for more than an hours of two
https://youtu.be/EdwDvz47lNw?t=11m52s

[Anonymous No.1436127]

>>1436075

the theory is correct but it doesnt apply to computer power supplies, since the high-voltage caps have permanent loads on them which will discharge them quickly, in seconds.

but i have pulled caps out of my parts bin and measured a significant voltage on them 2 months after i'd used them. depends on how leaky they are.

[Anonymous No.1436134]

>>1436075
portable chargers use supercaps

[Anonymous No.1436136]

>>1436127
>use capacitor once
>put it in a closet
>50years later
>accidentally touch it
>die
no way

[Anonymous No.1436143]

>>1436127
>>1436136
Isn't this why you're supposed to short the capacitor's leads before and during storage?

[Anonymous No.1436156]

>>1435844
That's not the point. 3/10 strawman.

[Anonymous No.1436161]

What are those "SJ1" and "SJ2"?

https://wiki.wemos.cc/_media/products:d1_mini_shields:sch_relay_v2.0.0.pdf

[Anonymous No.1436165]

>>1436161
Ohh I get it, are those solder jumpers?

[Anonymous No.1436175]

>>1436165
Looks that way, yeah

[Anonymous No.1436190]

My bench power source is coming along well

[Anonymous No.1436193]

>>1436161
>>1436165
I literally searched SJ1 SJ2 circuit. Looks like it standards for "solder jumper"

[Anonymous No.1436194]

>>1436190
Break out the -12V too. I've been too lazy to make a negative voltage supply.

>>1436175
Is it LOL-IN or LOLI-N~ :3

[Anonymous No.1436197]

>>1436194
>-12V
what would be the use for that? On top of that -12V is only 0.8A

[Anonymous No.1436200]

>>1436197
anything where you need a 24V split supply, of course. audio processors come to mind

[Anonymous No.1436240]

Does this apply to single phase power tools?

The current taken by the motor, Im will INCREASE if the voltage V is reduced and the power factor will be REDUCED for a given connected load.

https://www.quora.com/What-happens-to-the-current-to-an-induction-motor-when-the-terminal-voltage-is-reduced

Ie woulld a power drill draw more current on a long extention cord as opposed to a short one, when doing the same amount of work?

[Anonymous No.1436260]

>>1436240
>Ie woulld a power drill draw more current on a long extention cord

absolutely not. there was some dude on this board that kept repeating that nonsense until i showed pics of what actually happens: lower voltage leads to lower current, as common sense would tell you.

[Anonymous No.1436265]

>>1436260
Oh, the constant power guy? That was a laugh.

[Anonymous No.1436278]

>>1436175
Thanks!

[Anonymous No.1436280]

How can I compare op-amps in audio applications?

[Anonymous No.1436283]

>>1436260
I'm not "that guy" but...
I thought current went up slightly because there is less back-emf because there is more drag and less torque because there is a lower voltage.
Motors aren't merely ohmic devices, speed and load matters too.
What pics did you show? Now I'm curious.

[Anonymous No.1436294]

>>1436283
>What pics did you show?

pics of power-meter showing a drill drawing 198W at 120Vac (1.6A) at full speed but only 81W at 60Vac (1.35A) .

[Anonymous No.1436296]

>>1436280
First you define the specific properties you want to compare and then you query the databases of manufacturers/suppliers.

[Anonymous No.1436311]

>>1436190

this is an amazingly bad idea. whenever you make a mistake, wires will glow red, components will explode, your breadboard will melt. coz the supply is quite happy to put out 30 amps into a reversed transistor or whatever screw up you did without the short-circuit detection kicking in.

fuses? buy 'em in quantity coz experimentation is all about making mistakes. and, of course, semiconductors die in microseconds, while fuses take milliseconds to blow.

[Anonymous No.1436346]

>>1436311
oh c'mon, glonuts are safety devices

[Anonymous No.1436349]

>>1436296
K

So which criteria of an op-amp are most relevant to an audio application?

[Anonymous No.1436353]

>>1436346
you see ivan, when nut glow from heat, you need no thermography

[Anonymous No.1436355]

>>1436349
there are many ways to use op amps in an audio application. vocal eliminators might put CMRR at the top of the list. power amps might favor rail-to-rail outputs and high drive current. mic preamps might prioritize noise figure (at least in the audio bands) and input impedance, with a careful eye on sufficient gain-bandwidth product. crossover distortion is almost always undesirable in an audio application. maybe minimum supply voltage matters if you need a circuit to run from a 9V battery or a USB power supply
tl;dr: look up some op amp datasheets, see what is specified, and see what looks like it would be important for that op amp's role in *your* circuit
tl;dr2: buy a stack of NE5532s and make sure you have at least a 10V or ±5V supply

>>1436346
дaвaй, лизaть eгo

[Anonymous No.1436396]

>>1436311
>whenever you make a mistake, wires will glow red, components will explode, your breadboard will melt

[Anonymous No.1436402]

What subjects in EE would be most beneficial to helping me learn how to build analog synthesizers?

like, how to generate wave forms, how to make voltage controlled oscillators, voltage controlled filters, how oscillators work, how filters work, how to make an ADSR envelope circuit...

is there a specific subfield that covers these topics?

[Anonymous No.1436408]

>>1436402
Signals and Systems. You won't touch a circuit in that course, it's all math but it's important to understand.
That and any analog electronics class.

[Anonymous No.1436409]

>>1436402
you're going to have to be a generalist and understand the basics thoroughly. also, git gud at algebra and maybe a little calculus. then you can apply your general signal processing skills to the audio domain
maybe better to start by building other people's designs first and trying to understand them thoroughly, then checking against their written theory of operation. it might even be educational for you to build and then tweak component values, listen along the signal chain, etc

[Anonymous No.1436440]

>>1436346
Wow. I only now had noticed red LED.

[Anonymous No.1436441]

>>1436355
>дaвaй, лизaть eгo
nice google translate.

[Anonymous No.1436445]

>>1436441
thanks, it was actually yandex

[Anonymous No.1436481]

>>1436190
This isn't an original idea, people are using old PSUs as power sources all the time. Protecting yourself against too much current is trivial, you can use fuses, but most people use some simple current limiting circuits. So even if you short circuit nothing will happen. You can even combine fuses with current limiters etc.

[Anonymous No.1436491]

>>1436240
IME, power tools normally use universal motors rather than induction motors. So lower voltage will result in lower current and lower speed.

With synchronous motors, the speed is dictated by the AC frequency, so lower voltage means higher current.

[Anonymous No.1436496]

How exact are zener diodes? If i have 5V zener, can i expect current 0 - 4.99V be 0A and current 5V> be same as zener not being there?

[Anonymous No.1436498]

>>1436496

yes, that's exactly how ideal zeners work. real zeners, tho, have curves. if you put too little current through them, they wont zener properly, and as you increase the current, the voltage increases slightly, maybe 5-10% before it starts to get too hot. also, the breakdown voltage varies with temperature.

if you need very accurate reference, then you buy a voltage reference, not a zener.

[Anonymous No.1436499]

>>1436498
Not to mention that the curve for lower voltage zeners (idk like less than 10V) is much closer to the positive bias curve than it is to a straight drop-off like your image. 5V zeners subsequently are fucking awful unless you're putting a constant, low current through them, and at that point might as well just use a reference diode.

TL;DR use linear regs for low voltage.

[Anonymous No.1436518]

>>1436496
The initial tolerance is usually 5%, albeit better diodes exist. The breakdown is rather gradual with 5V and lower voltage zeners, while higher voltage zeners are better. And like everything, zeners have (quite significant) temperature coefficient. 5V zeners are somewhat better than the rest in this respect.

The closest thing to an accurate zener is the so called reference diode, which has a zener and a temperature compensation diode in series. This improves particularly the tempco, but reference diodes are available with quite tight initial tolerances, too.

Reference diodes are rarely used, though. Usually people use IC references, which are available as "zener-like" shunt references, too. They're generally much closer to the ideal zener than zener diodes are. However, if the off-state leakage is the most important parameter to you, you might need to build something more complex using an opamp or whatever.

[Anonymous No.1436527]

What is that big yellow cube thing on the left?
Also they seem to be using a step down converter for the voltage, why not use different windings on the transformer since it's already there to turn ac into dc?

[Anonymous No.1436530]

>>1436527
It's a crumply paper package so I'm guessing it's something like an inductor or flyback transformer. The tiny transformer you see at the bottom right is probably just a common-mode suppression choke, since it's mounted much closer to the input pins than the main switching transistor and optocoupler, which the flyback transformer is next to. Nearby you'll find some other noise isolation components, such as the yellow box capacitor there. The black package is probably a MOV or PTC, likely a MOV since the silver package behind the choke looks like a thermal fuse.

Switched-mode power supplies are far more efficient (space-wise) than conventional transformers, since space efficiency of transformers increases with frequency and switched-mode power supplies rectify 50Hz mains before switching them at many kHz. It sounds like a function of Faraday's law, but who knows.
>it's already there to turn ac into dc
I hope you meant something else.
>a step down converter for the voltage
The entire circuit board is a step down converter, unless you were just referring to the entirety of the circuit sans the rectification and filtration/safety.

Watch some bigclivedotcom, he takes apart shitty wall adapters, power banks, light fixtures, etc. and traces out their circuit, explaining how they work.

[Anonymous No.1436534]

Is there something like op amp for current?
Basically, I want something that is like "If current of 1A or larger is going through this wire (into some unknown load) then this this other wire will go from 0V to 2V (or something).
A practical example would be for example, if my circuit is drawing more than some preset amount of amps a red LED will turn on. What would be some SIMPLE way to achieve that?

[Anonymous No.1436539]

>>1436530
so switched mode power supply is just a regular step down converter?

[Anonymous No.1436553]

>>1436534

if you're talking about DC currents, there are dedicated over-current detecting chips. or you can make your own using an op-amp and comparator. it's a very simple concept: you place a a 0.1-ohm resistor in series with the load, and compare the voltage across it against a 0.1V reference voltage. when it exceeds the reference, the comparator will flip to tell you you're above 1A.

AC over-current is usually detected using current transformers for safety.

ref: https://www.electronicdesign.com/power/prevent-system-damage-fast-accurate-over-current-detection

[Anonymous No.1436554]

>>1436534
use a resistor to turn current into voltage

[Anonymous No.1436555]

>>1436539
Well they're two big circles on a venn diagram. There are step-down converters that are not switched-mode i.e. transformers or linear regulators, and there are switched mode power supplies that are not step-down, i.e. they boost voltage.

>>1436534
There are current amplifier ICs, but they're probably not what you're looking for since they're somewhat expensive and are specialised for high-accuracy measurements. and in a pinch a BJT can function as one (with a pretty high gain, non-constant input impedance, and plenty of thermal drift on both those fronts). A better method is to just use a comparator and a shunt resistor. The shunt resistor will have a resistance much smaller than that of the load, so you can just get a voltage output V = I*R which you feed into a leg of the comparator. This voltage will be pretty tiny, so use a few resistors to make a divider between Vcc and GND to get to yourself a reference at your trigger voltage, which you feed into the other input of the comparator. When the voltage across the shunt passes that of the divider, the comparator will switch. A standard shunt value will be maybe 10mΩ, and a simple single comparator IC is the LM311, though there are countless components to choose from. Make sure to read the datasheet well and take notes from any example circuits.

[Anonymous No.1436572]

I must be a real fucking special snowflake.
Every time i go to an electornics store they don't have half the shit I want.

like 0.1 power resistor
>uhhh sorry sir we don't have those like ever, we have this one here it has been here for 5 years and we wont have any more ever probably
thermal double sided tape
>uhh sir does that even exist? literally nobody asked for that before
optocouple that can be operated by 2-5V and can handle <= 100V DC
>uhh sir you need an exact part number, it's literally impossible to find out the operation values of the part without the exact part number
oh really? if that was true then how would anyone search for a part number they needed in the first place?


like seriously, i am so tired of this mom and pop small town bullshit

I am ordering everything from china from now on. Not only they have literally everything i want but it's also 10 times (or MUCH more) cheaper but i often end up ordering 20 different stuff as well because "Holy shit they are are selling ....that? i had no idea they even made those"

[Anonymous No.1436576]

>>1436572
>mom and pop small town bullshit

what sort of small town has mom and pop electronic stores?

[Anonymous No.1436578]

>>1436576
it's actually just the pop running it but you get the drift

[Anonymous No.1436619]

>>1436190
umm.... i may have fucked everything up, but i am not sure how... i turned on the beeper thing on my multimeter to check for shorts before connecting power and the things beeps on fucking everything, if i put one probe on a red wire and another on red, beeeeeep, if i put one on black and one on the PSU metal case... BEEEEp..... one probe on red wire and other on the PSU case... also beep.... what the fuck... why is everything short circuted? i was super careful and the only thng even physically touching the case is the green-yellow safety wire (apart from the mobo setting on raised screws)

[Anonymous No.1436620]

>>1436619
>if i put one probe on a red wire and another on red, beeeeeep
well, of course
>if i put one on black and one on the PSU metal case... BEEEEp...
good
>one probe on red wire and other on the PSU case... also beep...
low impedance dude

do you have the diagrams?

[Anonymous No.1436622]

>>1436620
shit i meant read wire and black wire beep together

I am pretty sure red and black should NOT beep because that would mean the second i connect it to power it will start pumping 30A through them

[Anonymous No.1436623]

>>1436622
*red
god fucking damn it

[Anonymous No.1436624]

>>1436620
you know what i am going for it, i am going to trust you and connect the deadly 230V DC
If i die i just want you to know that it will be 100% your fault.

[Anonymous No.1436625]

>>1436624
*AC
holy shit i am going full retard today

[Anonymous No.1436626]

>>1436622
>the second i connect it to power it will start pumping 30A through them
your supposed to put a load there

[Anonymous No.1436627]

>>1436626
holy shit, it worked all 3 voltages are there and nothing is smoking
But one thing i don't get is that the voltages are kind of shit, like on the 12V rail i have 12.5V on the 5V like like 5.3V, why isn't it more precise? And i'm not totally retarded so i did connect the sense wire to the 3V output wires

[Anonymous No.1436770]

>>1436527
>step down converter
the inductor on the left is probably there for fine ripple filtering

>>1436534
there are pre-fabricated current sensors that output a voltage proportional to current and carry several amps. the ACS758 is an example

>>1436572
how about you pore over dozens of datasheets like every other electrical engineer has learned to do instead of expecting free consulting for a 50 cent part? amerifat detected

>>1436627
they don't need to be. 5% high is fine and probably due to winding tolerance of the transformer. those voltages will be dropped a bit along the wires and further regulated on the motherboard and peripherals. high is therefore better than low

[Anonymous No.1436874]

>>1436622
Your continuity meter simply puts a small voltage across the leads (with current limitation probably in the form of a resistor), and when enough of a current flows it states that there is continuity. By applying your DMM in buzzer mode across something that already has a potential across it, you're pretty much guaranteeing that a current will flow and trigger the buzzer, provided you get the right polarity. It doesn't actually mean anything about the resistance between the two voltage rails. If you switch it to resistance measuring and measure across the 30V chances are the thing will give you a negative resistance for the same reason.

[Anonymous No.1436890]

>>1436770
>and further regulated on the motherboard and peripherals.

well, for an expert you are clueless about this. NOTHING further regulates 5 volts down to 5.3, not in the consumer products world, and if you actually worked with circuits and components you would know this.

[Anonymous No.1436891]

>>1436890
> 5 volts down to 5.3,

lol I meant nothing regulates 5.3 down to 5 volts.

[Anonymous No.1436893]

>>1436890
but plenty of devices regulate 5V down to Li+ charging voltage, or boosted to whatever odd 8.3V some piece of analog circuitry might need if no 12V rail is available.
>lol
go troll somewhere else, reddit

[Anonymous No.1436896]

>>1436893
>but plenty of devices regulate 5V down to Li+ charging voltage

how is that related to the dumbass who said that the boards regulate 5.3 down to 5?

can you read, LOL?

[Anonymous No.1436909]

>>1436896
fun fact: at least one Gigabyte motherboard regulates the 5V rail to get DDRx supply voltages. you should show us exactly where anyone other than yourself claimed 5.3V was regulated down to 5V, because that would be a ridiculous statement and I'd be correcting them too

[Anonymous No.1436910]

>>1436909
>pic related

[Anonymous No.1436922]

is it normal to feel like a complete retard when making your first project? it works on the protoboard but I'm soldering it on a perf board and god I feel like a brain dead kid. It's my first time soldering anything and my circuit looks uglier than death

[Anonymous No.1436929]

>>1436874
He tested it with the PSU off. I tested some resistors with my meter and it beeps with 47 ohms.
Output impedance of a PSU is supposed to be low.

[Anonymous No.1436930]

>>1436922
>is it normal to feel like a complete retard when making your first project?
perfectly normal
>It's my first time soldering anything and my circuit looks uglier than death
perfectly normal, also cheap soldering irons solder like shit
if you need to watch some videos on soldering

[Anonymous No.1436931]

>>1436572
>trying to buy components at any bricks-and-mortar store
that's a losing game. it's only worth resorting to that if you desperately need common parts same-day.
Get your shit on digikey or mouser or something comparable. you can get exactly what you need, for cheap, and find it by filtering detailed specifications.
you're only torturing yourself if you're trying to buy components in a store. Shop at the mom-and-pop hardware store all day, sure, but buy your electronics the way the pros do.

[Anonymous No.1436934]

>>1436922
if it's your first project you probably ARE a retard, for now. this stuff takes time to learn and you're going to be bad at it for a long time until you get good. that's how it goes, just get all the experience you can and don't get discouraged. same as with everything else.
post pics of your circuit

[Anonymous No.1436970]

>>1436929
In that case he might have just been testing across the reverse polarity protection diode, if there was one. Flipping the leads would rectify (heh) that.

[Anonymous No.1437027]

>>1436931
Local stores have some advantages such as seeing what you are buying before buying it.

Seeing a switch or a case in person can be invaluable.

[Anonymous No.1437092]

>still waiting for new geiger tube to arrive
>open ball of foil to see if the bead of americium i took out of a smoke detector is still there
>it's not
I'll have to tread carefully.

[Anonymous No.1437100]

>>1437092
>americium
probably got shot

[Anonymous No.1437117]

>>1437100
There's a good joke here somewhere. Like bombarding americium with beta particles to stimulate electron capture, or perhaps even a ballistics test.

[Anonymous No.1437124]

If i want to turn square wave into DC, what is the advantage of using a buck converter over a simple low pass filter?

[Anonymous No.1437126]

>>1437124
you mean an LC filter over an RC filter? obviously, R's just going to waste power while L stores it

[Anonymous No.1437128]

>>1437126
I mean that in the buck converter they are using an inductor to smooth the output, while in the simple circuit i seen they are using a cap instead

[Anonymous No.1437131]

>>1437128
>in the buck converter they are using an inductor to smooth the output
Doubtful, that inductor is how the potential is changed in the first place. Look up how buck converters work. The output diode and capacitor is what is used to turn the resulting sawtooth wave(?) into DC.

A simple low-pass filter, LC or RC, will sink any higher frequencies to ground via a capacitor, decreasing their amplitude by a factor determined by the capacitance and resistance/inductance chosen. LC filters do so twice as effectively as RC filters, but more expensively and less compactly, hence why they aren't typically used unless one wants something where a lot of power isn't being wasted in the resistor. Feed a square wave into one of those and out you just get a square wave with rounded-off leading edges, not DC at all.

But by replacing the resistor in an RC filter with a diode, you're only allowing the current to flow into the capacitor in a single direction. This means this sawtooth wave will charge up the capacitor to near its peak value, but as the wave drops back down again the output capacitor's voltage will remain constant, provided the load is insignificant. Plot it in spice, or any other of myriads of simulation software out there if you still have questions.

[Anonymous No.1437136]

>>1436934
I took it apart, I have another identical tiny perf board and will try again with the stupid errors in design and layout in mind now.

[Anonymous No.1437140]

>>1437136
also it's weird how the basics of EE are relatively easy to get but for analysing complex stuff you need to have a very large ammount of experience on how each block or part behaves because applying the basic stuff would be too much work or impossible.

[Anonymous No.1437144]

>>1437136
Plenty of flux, anon.

[Anonymous No.1437158]

>>1437144
>Plenty of flux, anon.

[Anonymous No.1437160]

>>1436909
>. you should show us exactly where anyone other than yourself claimed 5.3V was regulated down to 5V,

(first of all, why was my comment removed?)

anyway, this guy says this:

>>1436627
>But one thing i don't get is that the voltages are kind of shit, like on the 12V rail i have 12.5V on the 5V like like 5.3V, why isn't it more precise


that's where the 5v and 5.3 volts came from.

then this guy says this:

>>1436770
>those voltages will be dropped a bit along the wires and further regulated on the motherboard and peripherals.

and that's what I don't believe, that motherboards and peripherals EVER take 5.3 volts and pass it through a regulator to get 5 volts.

[Anonymous No.1437166]

>provide 5v
>check behind a 1kohm resistor with a multimeter
>5v
>add a single led diode in series
>check again
>2.3v
Why and how?

How do I check how much voltage drop will a resistor cause? (I'm learning arduino rather than electronics so forgive me)

[Anonymous No.1437169]

>>1437166
>Why and how?

could you show these circuits, including where you connect both meter probes?

[Anonymous No.1437170]

>>1437166
you know LEDs have a voltage drop of about 2 volts?

[Anonymous No.1437172]

>>1437169
It was more or less like this.
Recreated from memory. I don't know how to properly draw schematics.

[Anonymous No.1437174]

I want to make my own bench power supply
I want it to have a load switch, so that I don't have to turn it on and off every time, or disconnect the project every time.
What would an appropriate mosfet for this purpose be? the DC current for mosfets as stated in datasheet graphs show that DC current for mosfets at 30 VDS or more is like 100mA
I want to be able to run 3A or so at 30V
what do I do / where do I look?
There must be a better way than just looking at every mosfet datasheet to see which has the best DC current rating for that voltage?
Anybody have any mosfets for that purpose they can recall off the top of their head? Or know of a better way to do it?

[Anonymous No.1437176]

>>1437172

Learn Ohm's law, V = IR.

Learn how voltage dividers work. Note that in your upper circuit there is no return path, meaning you have an infinite resistance in series with the 1k, so all the voltage is dropped across that "resistance".

Learn how diodes work; the basic voltage-current relationship is fairly simple.

If you understand both of those, you will see that your circuit is behaving normally.

[Anonymous No.1437179]

>>1437174
>What would an appropriate mosfet for this purpose be?
use a manual switch in series with the output

[Anonymous No.1437185]

>>1437179
If I did that, then I would introduce switch bounce into the output

[Anonymous No.1437187]

>>1437174
If it's your own design, turn it off / set the output to zero from the control side. For example, use your switch to set the reference voltage to zero.

[Anonymous No.1437188]

>>1436534
Use a current sense resistor, an op amp and a reference voltage

[Anonymous No.1437189]

>>1437187
That sounds like a good idea anon
That's part of the other problem I have - selecting a linear regulator that can give me zero volts. Was intending to use pass transistors with an LM317 and a negative rail to trick it into giving me zero volts.. but I have a feeling that below 1.25V, it won't be able to supply the required current.
And to be fair, I'm not even sure that's the best idea intead of just using op amps and such for voltage control of transistors anyway

[Anonymous No.1437191]

>>1437189
>I have a feeling
Me too.
It's all about the post count, isn't it.

[Anonymous No.1437210]

I don't think this would be the right thread for me to ask but I'm looking for a decent 120v -> 100v 1500w~+ step down transformer with at least two output sockets for Japanese electronics. Any recommendations that won't shit itself after a month of moderate usage?

[Anonymous No.1437218]

>>1437185
add filter caps on your projects, you should anyway

[Anonymous No.1437285]

>>1434867
Idiot here, help please.
My power supply is fucked.
My multimeter was damaged and I'm waiting on a new one. I needed to check the voltage of something that is 15-20 volts DC, which is in the output range of my per supply.
When charging batteries in the past, I noticed the voltage of the battery showed up on the power supply's meter. In a desperate attempt to get the voltage, I did the obvious thing. There per supply was unplugged, there were Sparks on the banana plugs, the wires in my hand got real hot real fast. There DC gauge into the negative. After switching the wires around the DC gauge did nothing and hasn't moved since.
Now my power supply won't put out voltage. It's starting in constant current mode with 0 volts being shown at full current. The current limiting knob will adjust the current on the built in ammeter all the way to the max value.
While powered off, a continuity test says there is a dead short between positive and negative in the power supply.

[Anonymous No.1437291]

>>1437285
You shorted it which caused large current flow and it melted something.
If you were lucky it only melted a fuse, if not you have to check what burned and replace it, for example a melted resistor etc.

[Anonymous No.1437296]

>>1437285
There is a dedicated circuit with the banana plugs and the gauges wires go to this circuit. There is a dog on this circuit which shoes continuity to go either way. Idk if continuity is the same as a a doid check. The other doids in my party him don't do this no matter which way I test them. The short might be elsewhere in the same circuit as this diod.
I have no clue what I'm doing.

[Anonymous No.1437297]

>>1437291
I have it apart right now. I don't see any burn marks. I don't know what I'm talking about, but my thoughts are that a blown fuse wouldn't cause a permanent short circuit. I'm attempting to figure out how the front panel circuits are held in place right now

[Anonymous No.1437303]

>>1437291
I looked and I can't find any fuse.
The only things I don't recognize are marked with a prefix of "R" on the board and have an ohms symbol on them, and some green thing, the leeds, and a round hole in it with one side actually being round and the bother side had three notches cut out flux capacitor style, with a board prefix of "Q"

[Anonymous No.1437315]

I'm thinking of combining a microprocessor, temperature sensor and WLAN circuit for remotely monitoring temperatures. In the future I'd like to add other sensors. Would it be possible to drive this using batteries, or will it draw too much power?

[Anonymous No.1437317]

Is it possible to make an active 2-way loudspeaker crossover controllable with CMOS logic? I'd like to have some control over the crossover frequency. Can I somehow use a CD4017 counter to connect one of several different resistance values to the filters?

[Anonymous No.1437320]

>>1437315
WiFi is a power hog. choose a different radio protocol

>>1437317
Pic related

[Anonymous No.1437331]

>>1437285

there's often a diode placed across the output jacks, in the reverse direction, whose purpose is to protect the supply when someone does the exact same stupid thing you did: plug in an external voltage backwards.
it sounds like this diode has suicided itself since it reads continuity both ways. you need to snip one end of the diode, and retest it. if it's the same story, then removing it probably will bring the supply back to life. otherwise, you may have burned the power transistors that feed the output. test those using the diode function or continuity.

>>1437315

you can get ready made temperature transmitters working in the 433Mhz range that work off 2xAA cells for months. brand name La Crosse Tech is one example. presumably you can tune one of these receivers (pic) to the same frequency, and decode the signals.

>>1437317
>Can I somehow use a CD4017 counter to connect one of several different resistance values

nope, but you're close. the CD4016 is a quad analogue bilateral switch, which will do sorta of what you want. other numbers to look at are 4066, 4051, and some others i forget.

[Anonymous No.1437334]

>>1437320
>WiFi is a power hog. choose a different radio protocol
Too bad. What are the popular protocols atm? I'm not too versed with radio communication, and would like to find something that's widely supported.

[Anonymous No.1437337]

>>1437334
Bluetooth if you need native host support
Nordic Wireless' proprietary nRF 2.4GHz protocol if you need something longer-range, chips are cheap enough to build a whole network of them and very low power

[Anonymous No.1437341]

>>1437337
Thank you very much!

[Anonymous No.1437347]

>>1437331
>>1437296
>>1437291
>there's often a diode placed across the output jacks, in the reverse direction, whose purpose is to protect the supply when someone does the
Thank you, I went ahead and pried off the diode and now it makes voltage and will go into constant voltage mode.
I'd feel better if someone told me how much of an idiot I am though

[Anonymous No.1437349]

>>1437347
Replace the broken diode or the next time you screw up it's bye bye source

[Anonymous No.1437355]

>>1437349
I have every intention of doing so before I use it again. Are diodes like this super specific it are they basically rated like fuses?
Thanks for the advice

[Anonymous No.1437362]

>>1437355
diodes are rated for different voltages and currents you need a specific one

[Anonymous No.1437373]

>>1437362
Ok thank you

[Anonymous No.1437378]

>>1437355
look at the one you have and it has stuff writen on it. get one with the same stuff

[Anonymous No.1437390]

>>1437378
Will do, need to find the solder wick and shit before I mess with any of that. This thing is like permanently attached via the banana plug sockets

[Anonymous No.1437397]

>>1437390
you can melt the solder and push it out.

[Anonymous No.1437401]

>>1437397
Yea but the the posts are anchored in a solid plastic piece on the other side of the front panel. To do it that way would be tedious. Because all three are connected. I don't see a way to get it apart and other way.

[Anonymous No.1437410]

>>1437401
just cut the bad one out and wire in the new one more sanely

[Anonymous No.1437417]

>>1437410
I assume you mean just solder the new one in on the other side of the board. That's a good idea.
It's a little difficult to get the iron in right now due to the angle, I don't know if I can even desolder the old one with the board still mounted

[Anonymous No.1437433]

What sort of core material could they be using to concentrate flux?
https://fluxtrol.com/magnetic-flux-control-in-induction-heating
Is it just a ferrite core? Wouldnt that heat up also by the induction?

[Anonymous No.1437436]

>>1437433
>What sort of core material
um, the medium being heated?

[Anonymous No.1437443]

>>1437436
No not the medium, thats regular steel. Watch the video, they show before and after shots of heater coils with a flux concentrator added to it. That could it be?

[Anonymous No.1437445]

>>1437443
Do you think the device has capactiance of any kind

[Anonymous No.1437446]

>>1437445
The fuck has capacitance have anything to do with magnetic fields?

[Anonymous No.1437455]

Besides existing, am i doing anything stupid here? It's a thermal shutoff for a led

[Anonymous No.1437456]

>>1437446
You'd be surprised.

[Anonymous No.1437457]

>>1437455
the low thermistor value and 741 are the shit I have at hand btw

[Anonymous No.1437459]

>>1437457
Is this for shutting off the let if it gets hot?
Topically, I don't think leds should be getting that hot.
If you're dealing with high power leds, are they not stable while in the same circuit it does their temperature really fluctuate that much?

[Anonymous No.1437460]

>>1437459
it's a 50W led, it has a heat sink I made out of aluminum rails but it'll be left alone in my apartment so I'm not taking any chances.

[Anonymous No.1437466]

>>1437460
Oh yeah fuck that.

[Anonymous No.1437475]

>>1437455
resistors on LM317 are way too large. read the datasheet
>V+ to ground
wtf is going on with the opamp's power supply? please redraw
>relay
is this the latching relay with manual reset?

[Anonymous No.1437478]

>>1437475
fuck I'm a retard, it sould go into the emitter. Thanks abou the resistors

[Anonymous No.1437488]

Can i put 2 linear (not pwm) constant current led drivers (same type) in parallel to double the current of a led?

[Anonymous No.1437493]

>>1437488
I don't see a problem.

[Anonymous No.1437507]

>>1437478
btw, hotkey U sets the reference designator, V sets the value
make sure you put this on a solderless breadboard before you put anything together permanently. it looks like the relay will drop out when temperature exceeds the set point.
also add some positive feedback so the relay doesn't chatter when it gets close to the setpoint

>>1437488
sounds iffy, could throw off current sensing if you aren't running them from isolated supplies

[Anonymous No.1437511]

>>1437507
I was just thinking using two LM317s in parallel with seperate current-setting resistors. No feedback other than an internal resistor should work just fine, but if the drivers require external feedback then you're right they might have a problem or two. Depends on what he means by "constant current led drivers" I guess. Never checked inside a standard LED driver myself anyhow.

[Anonymous No.1437520]

>>1437460
Why not use a constant-current circuit? It'll blow the LEDs in case of parallel failure, but it causes the LED's to have a negative temperature-power curve. Thermistors are nice, but they can be unreliable, only work over specific ranges, and you have to watch for whether your circuit fails-open or fails-closed.

It'd literally be easier to put an older/cheap mosfet on your low side, use a voltmeter and potentiometer to find a good current point, and heatsink that shit. I say old
+/cheap mosfet because a lot of the power ones have RIDICULOUS I/V curves.

Voltage regulators can act in constant-current mode, but they require a resistor reference, which is usually Iout/1.25V ^2 R power dissipation often. I think I've seen some ~.625V vref regulators, but not high power or something.

[Anonymous No.1437521]

>>1437520
My power equation is wrong. I think it's R/1.25 for 1.25V regulators.

[Anonymous No.1437524]

Is it possible to diy your own PCB with planar transmission lines/stripline on it?

Is it possible to get good control of trace impedance?

[Anonymous No.1437532]

>>1437521
I = V/R = 1.25/R
P = V^2/R = 1.5625/R
But using an LM317 will likely not be feasible for a 50W LED unless you're really cutting your max Vf close to your Vcc. I wouldn't like running one over a watt or two even with a heat sink, since the reference might shift.

I'd instead go for one of those switching converters, like the common LM2596-based buck converters. I know the models with three trimpots have constant-current capability, though by the looks of things some models with only two do also. On the three-trimpot models one is voltage max, one is current max, and the third is something to do with battery charging.

[Anonymous No.1437537]

>>1437532
>LM2596
In fact these things cost barely more than a dollar over on ali.

[Anonymous No.1437545]

>>1437355

to make your life simple, you can just wrap the diode leads around the banana plugs on the outside of the case, and tighten. something like a SB5100 (5A 100V) diode should do the job.

>>1437455
the resistor on the emitter of the transistor is not needed. and it will screw things up unless it's very small, coz it steals voltage from the relay. connect emitter straight to ground.
also, you should use a single rail comparator (lm339) instead of a picky op-amp. the 741, for example, has a recommended minimum power supply voltage of +-10V, so you're 14V short.
also, the comparator needs about 5% hysteresis or that relay is gonna chatter like mad before it flips ON or OFF for good.

[Anonymous No.1437547]

>>1437520
I've seen a few switching regs with 600mV Vrefs, and a few designed specifically for constant-current LED driving with <250mV Vref

>>1437524
I have no idea what all's going on there but I am diamonds

>>1437532
Pic related shows a boost converter mod, an analogous mod can be done on a buck converter

[Anonymous No.1437550]

>>1437547
Looks pretty shitty to be honest, no adjustability. But if you need the boost capability (which I don't think the original guy does) it's definitely a viable method. I'll also have to look for those sub-250mV regulators. Those things better be able to dissipate a fair bit of heat however.

[Anonymous No.1437595]

>>1437027
>switch or a case
yeah, I agree. Switches I'm usually OK with just by studying the drawings, but whenever I buy a case I end up buying a few of slightly different sizes/styles because there's no way to be sure without seeing and holding it.
What local places would even have a good selection of cases, though? When radioshack still existed they only had those terrible plastic "project boxes" and sometimes slightly less terrible metal jiffy-style boxes.

[Anonymous No.1437605]

>>1437172
This is something very important for a beginner to understand.
The 1.89 volts here is the LED's forward voltage. All diodes have a forward voltage drop, for LEDs it's in the range of 1-2 volts, for most small-signal diodes it's about 0.7 volts. it's dependent on the way the diode is constructed and it varies with current.
The diode has a voltage across it, but no significant resistance, so if you connected your diode with about 2v forward voltage directly to a 5v supply, you'd have about 3 volts into a dead short. The current would go very high and the LED would burn out.
When you put the resistor in series, that 3 volts is dropped across the resistor and the current is equal to that voltage divided by the resistance.
So this is how you size a resistor for an LED at whatever voltage you want: The supply voltage minus the LED forward voltage, divided by the desired LED current, will give you the value of the resistor you should use.

The meter read 5 volts with just the LED because without any current flowing through the resistor, the voltage has to be the same on both sides. The resistor "pulls up" the voltage to 5v. The meter doesn't have very much resistance in it to pull that voltage down.
The more resistance you have between that 1k resistor and ground, the lower the voltage will be at the low side. This is called a voltage divider.
Meters are made to have very high resistance (1 - 10 Mohm) so the low side of your 1k resistor will stay very close to 5 volts. Try this with a 1 Mohm resistor or higher, and you'll see a lower voltage because the meter's own resistance is enough to pull it down.
this is also important to learn, sometimes the meter can affect your circuit and make misleading measurements.

[Anonymous No.1437607]

>>1437210
Most 100v stuff seems quite happy at 120. Do you have specialty equipment?
1500 watts is a tall order.

[Anonymous No.1437638]

>>1437607
>1500 watts is a tall order.

no kidding. i have a 250W travel adapter that weighs 9 pounds.

[Anonymous No.1437697]

I received a computer the other day with a faulty power unit. I haven't opened it up yet. But what could possibly be wrong with it and is it likely it can be repaired?

From the outside the case looks in great
condition so I'm ruling out water damage.

[Anonymous No.1437699]

>>1437697
Fuse, thermal fuse, maybe a fuse in conjuction with a MOV or cap if you got lightning'd. Those are the easy things that are designed to die first on the input. On the output it could be a cap or fuse also. The thermal fuse mentioned above could be wound inside a flyback transformer, so check for that. Otherwise just look for shitstains.

[Anonymous No.1437703]

>>1437699
Inside the PSU. Two boards.

[Anonymous No.1437705]

>>1437703
Start from the board to which the mains first enters and check any fuses around there. Tracing out any traces that should be GND and HOT and checking first the continuity along them is a starting place, and once you've done that you might want to plug the thing in and see that the voltage is at the right level at each point.

[Anonymous No.1437712]

>>1437191
What?

[Anonymous No.1437723]

>>1437697

these things are notoriously difficult to fix coz everything is inter-related. the path of least resistance, after checking fuses, would be to replace it with a regular PC power supply (usually free coz it was pulled out of an old Pentium 4) by splicing similar colors together.

it appears to have 4 diff colored wires. all the yellows are probably +12V, and blacks are ground, which is the same in PC supplies. green is likely the same as green in PC supplies: you short it to ground to turn it on. white is presumably 11V standby, which is a problem. i'd splice in a separate 12V 1A charger and put 2 diodes in series with the positive wire to lower it to 10.8V.

of course, this is all just guessing. documentation would be needed to confirm.

[Anonymous No.1437727]

>>1437189
You're looking for the LT3080. That can go down to zero volts. True zero. Not very close to zero. Rather than having a voltage reference it uses a precision current reference instead and there's a way to set it for the voltage you want with external resistors or some shit. Read that datasheet. If for whatever reason you can't make do with that you probably want some switching regulator, buck-boost. Honestly you're probably better off with this for a PSU than a linear regulator based designed but it is slightly more difficult to design and switching regulators are noisier but if noise is a big concern just whack a 12-pole LC filter on the output and she'll be right.

[Anonymous No.1437735]

>>1437697
check the caps and fuse. If theyre fine (caps not bulging or fuse blown), its less than its worth to fix.

Even if you replace the fuse, it's liable to blow again. Possibly because the caps are bad.

[Anonymous No.1437736]

>>1437735
There's one fuse right next to the plug entrance on the smaller board rated 8Ah. It's not the removable type, it's connected to the board. Testing resistance it has about 1.5ohms. I think that confirms continuity is good. All the caps look good, no singeing anywhere.

Thanks for the suggestions.

[Anonymous No.1437743]

>>1437736
Did you use a psu tester? I have an AcBel PC9053 240W supply which was used in a compact prebuilt.

The motherboard in the prebuilt was bad, not the supply.

[Anonymous No.1437761]

What is a glass passivated bridge rectifier?

[Anonymous No.1437778]

>>1437507
What do you mean by drop out? I want it to shut off and stay shut if it gets too hot until I go there and press a button (connected to the bjt base).
I'm still grasping at feedback, how I would do that?

[Anonymous No.1437780]

>>1437545
The resistor is about 100 ohm. The pcb relay I have here is 0.36W so I think that would do. How to add hysteresis? It and feedback are some thinks I'm having dificulty with (I haven't started on control and signals yet)

[Anonymous No.1437786]

Is there some easy way to turn current into proportional voltage?
I need to set up an opamp to trigger when certain current is reached.
Normally this would be easy, i could simply use a resistor after VCC and measure voltage drop with the opamp across it.
But the problem is that i do not know what the VCC voltage will be, so it is not possible to tune the op amp properly for a specific current.
So I need something that will output voltage proportional to the current regardless of VCC voltage.
Hopefully it makes sense.

[Anonymous No.1437787]

>>1437524
It boils down to your tolerances, that is, how accurately you can etch what you want. Usually home etched boards try to use rather wide microstrips to reduce the effects of small errors in dimensions.

[Anonymous No.1437788]

>>1437780
>>1437778
and also, how would the relay chatter if the op amp driving the BJT that activates it shuts off after the relay opens?

[Anonymous No.1437790]

>>1437786
Either put the resistor on the ground side of whatever you're measuring, or measure both the top and bottom of the resistor, take the difference.

[Anonymous No.1437791]

>>1437790
I don't see how that would help. The voltage drop across the resistor changes based on the voltage going in, so the voltage drop will be always different when the input voltage change, even if i put it on the ground part. This would only work if the load regulates voltage for itself which it doesn't.

[Anonymous No.1437792]

>>1437791
You can't know absolute values so setting the op amp won't do but op amps are good for diferences. Get the voltage drop and multiply it by the inverse of the resistance using another opamp or the same or what ever. Bamm you got current

[Anonymous No.1437793]

>>1437761
>bridge rectifier
https://en.wikipedia.org/wiki/Diode_bridge
>glass passivated
That's just how the individual diode chips are protected. It's a manufacturing/reliability detail which does not really matter to you.

>>1437786
Pic related is a well-known way to do it. You have to pay some attention to the opamp selection, as not all of them can handle inputs near the positive rail.

[Anonymous No.1437794]

>>1437792
Can you post a simple schematic?

[Anonymous No.1437800]

>>1437793
>inputs near the positive rail.
what do you mean by that?

[Anonymous No.1437807]

>>1437800
Many opamps work badly or not at all when their inputs are too close to opamp's positive or negative supply voltage. In this case the inputs are at positive supply voltage when there's no current.

[Anonymous No.1437810]

>>1437807
The only ones i have are lm324n

[Anonymous No.1437815]

>>1437810
>lm324n
>Large Output Voltage Swing 0 V to V+ − 1.5 V
Looks like you'll be fine near the negative rail, but not near the positive rail. It can be a bit of a pain dancing around these rail limits, but it's not usually too hard to factor in to your design.

[Anonymous No.1437816]

>>1437815
I'll just drop some voltage going into the inputs with a resistor and that should fix it

[Anonymous No.1437820]

>>1437816
You just want to measure current, right? I don't see the problem with a shunt resistor from your load to ground, with that voltage fed into an opamp input. I think it can take that input voltage range, though I may be wrong.
>the full input common-mode range (0 V to V+ − 1.5 V)
Pops up a few times after all.

[Anonymous No.1437826]

>>1437820
I'll try to attach it to the ground then it's doesn't have to be super precise, i just want it to detect overcurrent of 0.5A or higher

[Anonymous No.1437827]

>>1437791
voltage drop across resistor is proportional only to the current through it.

[Anonymous No.1437831]

Transistors don't need pull downs like mosfets right? Since The current you feed it actually flows through the base unlike a mossfet

[Anonymous No.1437835]

>>1437831
>Transistors don't need pull downs like mosfets right?

do people actually learn electronics by asking every single question in an online forum? At some point, why don't you go read an article or a book about electronic devices, and save yourself a ton of frustration. Or relocate to /r/arduino where idiotic questions generate long polite threads.

and no, they don't. If you had ever read anything about mosfets you would know why they need pull downs. Hint: gate capacitance. I'd go into further detail but I doubt you know what a capacitor is.

[Anonymous No.1437840]

>>1437835
>and no, they don't.
It's a common practice to add them to mitigate the effects of the leakage currents, though.

[Anonymous No.1437845]

>>1437835
Wow a big strong bullyman, i bet you get all the pussy

[Anonymous No.1437860]

>>1437786
I don't know if it's intentionally what you're doing, but you sound like you're trying to make a voltage-controlled resistor.

I went through it, to do it analog requires an analog multiplier, because you're multiplying the proportion of reference * VCC scale. (resulting in a fixed voltage across a BJT or mosfet).

This can be done high frequency in a feedback model, but it still requires an analog multiplier.

Maybe a voltage-controlled PWM could be used to pulse a gate component. It'd have a max current/voltage dependent on both input and VCC, but it might work well enough.

[Anonymous No.1437863]

>>1437860
I have an idea, same person. If you had a frequency AND pulse-width controlled modulator (two input) you could have a capacitor in parallel with a mosfet. In uncharged state, the cap is a relative short, but when it rises, it needs to be drained. By turning on and off the mosfet at the right frequency, you can drain the cap in the right time frame to limit ripple. The pulse-width is needed so that you limit current through the mosfet. There's an interaction in both dimensions, because you want to drain the cap above/below a certain amount, but at the right frequency, it buffers your potential developed. There'd be heat loss in the capacitor, so higher frequency less ripple would reduce energy lost in the capacitor. A resistor across the capacitor might work to reduce capacitor losses and reduce frequency needed. This also depends on mosfet I/V curves and capacitance. It might work in principle, if tuned and tested properly.

Yes I am making a record. I swear to god if you patent this I will sue the shit out of you. I really need a high-power voltage controlled resistor.

[Anonymous No.1437864]

>>1437863
Resistor in series of course. ree.

[Anonymous No.1437969]

>>1437778
drop out, as in turn off, tune out, the opposite of pull in. the voltage output of an op amp swings in the opposite direction of that of a pulled-up LM393-style comparator
>741 on a 6V supply
I don't know about that
>feedback
add a resistor, from the output to the + input of the opamp/comparator, about 10-20x as large as the resistors you have there already
please fix your schematic and especially use the "annotate" button so we can uniquely identify your components

[Anonymous No.1438005]

>>1437969
well.. plugging the opamps positive rail to the does not work (it needs constant user input at the base to be on ). Now it's a LM358 btw. I'm designing it with the parts I have here in mind so that is why there are some series resistors. Thanks for bearing with a retard learning to create stuff and use kicad.

[Anonymous No.1438006]

>>1438005
Anyone has an idea to shut the whole thing off when the opamp triggers?

[Anonymous No.1438009]

>>1438006
Power the whole shit via relay contacts.

[Anonymous No.1438011]

>>1438009
won't the Huge fuck LED switching bamboozle things? Idk, burn transistors or fuck shit up?

[Anonymous No.1438012]

>>1438006
much, much better
still, lose R8. the relay will not reliably pull in with it in place
when you calculate the R4/(R4+R5) voltage divider, remember that R6+R7 should be considered in parallel to R4 when the relay is off and in parallel to R5 when the relay is on
>shut the whole thing off
you could use the relay to supply power to the whole circuit (U1 pin 2 to relay pin 1) and add a momentary-on start button in parallel with the relay contacts. the relay would be on at all times during normal operation (if there's a timer, put it between the LED and the relay) and the relay would therefore need to be rated for 100% duty cycle (some are not, check the dataheet)

>>1438011
if the relay can handle the LED's current, it can handle the tiny bit extra from the control circuit, you'll be fine. LEDs won't kick back like an inductive device e.g. a relay would, and if you protect it with a freewheel diode like D1 you'll be fine in any case

[Anonymous No.1438045]

>>1438012
>still, lose R8. the relay will not reliably pull in with it in place

right, but at the same time, the dude needs to put a resistor (1K) in series with the base so the transistor doesnt short the op-amp's output. it'll work without it, but it's bad form.
also, R9 is useless.

[Anonymous No.1438046]

>>1438045
>>1438012
thanks.

[Anonymous No.1438193]

>>1437863
JFETs?

[Anonymous No.1438267]

I'm seeing about making a simple potentiometer-controlled variable USB load with a MOSFET, but I don't have any rail-to-rail comparators lying about. Anyone know a good way of getting an extra negative power rail like this?

[Anonymous No.1438275]

reposting in here

52 KB
I got a Craftsman multimeter 82008. I'm trying to use the resistance function but it's reading way too high as far as I can tell. the reading and the unit keep bouncing around until it settles around 7 ohms, even when I just touch the tips together. what the hell? is this supposed to do this

[Anonymous No.1438278]

>>1438275
7Ω is a bit high for touching the leads together, but not that unusual. It's auto-ranging so it should be expected to jump around before it settles, maybe for a second or three. What else were you measuring that gave you too high of a reading? Ensuring the thing is in the right mode is also important, since it points to capacitance and diode-check and continuity also, it might like to flip from one to the other.

[Anonymous No.1438279]

>>1438267
>comparators
you need a real op amp that can vary the gate voltage continuously
also most common comparators/op amps are good down to the - rail, so as long as both inputs stay below Vcc-2, you'll be safe. make sure you have a MOSFET that has an adequate Ids for the max Vgs your opamp can supply (there's usually a graph in the datasheet), also do be aware of power dissipation through the MOSFET and heatsink it appropriately

[Anonymous No.1438288]

>>1438279
Both worked in the sims, but looks like op amps are a little more useful. Well I do have an LM324N that looks like it should work, but it is a DIP14 and feels a bit wasteful. Maybe I'll build in some other op-amp circuits to the PCB just because I can. Maybe something to visualise ripple? I'll definitely be careful with how much power I try to pull with this setup, I've seen the massive heat-sinks and fans on proper models. I suppose that's why they're so expensive, because the whole circuit of one opamp, shunt, trimpot, resistor, and MOSFET should be something you can sell on ali for $1. I might try just epoxying the FET into a piece of vinyl tubing that I shove over a tap for cooling, but we'll see how that goes.

I also have an LM249DP, whatever the fuck that is.

[Anonymous No.1438296]

>>1438288
this is why it's a good idea to have some dual op amps/comparators in stock
>cooling
yep, that's exactly why they cost. also power resistors get expensive
>LM249DP
high-speed specialized op amp. might not be stable for this application

[Anonymous No.1438297]

>>1438275

you can use the REL button to zero the meter.
- short the leads. read 7 ohms
- hit REL. reads 0 ohms
- take measurement

anyway, thats what the manual says (the lil booklet that comes with the device that nobody ever reads). i cant confirm coz i wouldnt touch an auto-ranging meter ever.

[Anonymous No.1438301]

>>1438275

you can use the REL button to zero the meter.
- short the leads. read 7 ohms
- hit REL. reads 0 ohms
- take measurement

anyway, thats what the manual says (the lil booklet that comes with the device that nobody ever reads). i cant confirm coz i wouldnt touch an auto-ranging meter ever.

and the reason for the high reading and jumpy results is that the probes are probably oxidized, at both ends, and the function switch also could be oxidized. if you're feeling adventurous, open it all up and spray contact cleaner. on the switch contacts you can use an eraser instead, but contact cleaner for the wiper that rubs against the contacts.

[Anonymous No.1438305]

>>1438296
I do have a couple of dual op-amps, but they're more for audio purposes and so are meant for ∆V = 12-24V. I've got a dozen more standard models on their way from china though.

But I'm using no power resistors, the shunt will dissipate only 40mW, all power is taken by the FET. Though now that you mention it I could just have a power resistor that would take up maybe 2V at 2A, to lessen the load on the FET. It would mean I'd have to worry about noise/ripple from the shunt and also less about the resistance of the traces around the shunt. 1Ω 5W should be fine, though I'll still mount it to the heat-sink.

[Anonymous No.1438313]

>>1438305
>all power is taken by the FET
ohh, I see now. no, that's sound
>the traces around the shunt
ideally you want that resistor to dissipate as little power as practical so that its value and therefore the calibration doesn't change due to temperature. on the other hand you would like a large value there to keep op amp asymmetry from inducing nonlinearities. imho 0.1 ohm seems a reasonable compromise: 30A "full-scale" at Vcc-2V, up to 3.1A current for a 1W device, 5mV opamp error means a relatively manageable 50mA system error, and (full disclosure) I have a small bag of them sitting on my desk, lel

[Anonymous No.1438314]

>>1438313
Mate this thing is for USB, I'm not pulling more than 2A, maybe 4 if I want to really test the thing, like for dual-port power banks and such. You're right about the drift caused by a heating-up resistor, it's the only thing that will effect the calibration. I'd use a 0.1Ω if I had one, but I can only get 10mΩ shunts locally (of which I already have two), so I'll stick with them.

Since I've got direct feedback I don't think any op-amp non-linearities will be a problem, since I'll always use this paired with a standalone USB tester. The only unideal effects I'll need to deal with will be those that change over time, i.e. temperature caused ones. If I etch this thing I can also attempt to make the shunt inside the PCB with a thin trace, which might save me on that single part. I'll probably want to etch it anyhow since doing so can give me a USB jack on the board itself.

[Anonymous No.1438341]

I i plug in op amp across a resistor how do i take the voltage drop across it and make the op amp pump out exactly that * 100?

[Anonymous No.1438344]

>>1438341

since your google is broken, let me guide you to this: http://www.circuitstoday.com/differential-amplifier

[Anonymous No.1438366]

>>1438344
Stop being a bully. Google is blocked in my country.

[Anonymous No.1438376]

>>1438301
>>1438278
thx bros

it's a motorcycle rotor. cleaned the contacts and rubbed some fine steel wool on them, guess I'll try that on the tips too.

I figured it was the auto function that was complicating things for a caveman like me, just wanted to make sure before I decide to go get a simpler multimeter

[Anonymous No.1438378]

Any idea how difficult it would be to design a robotic arm controlled by brain signals? Thinking about final year project and I'd prefer getting into something related to future health care than networks

[Anonymous No.1438379]

>>1438378
Just connect the arm to the computer and control it with a keyboard, since the keyboard is controller by your hands which are controlled by brain signals, boom easy A

[Anonymous No.1438380]

Im using a windshield wiper motor to move a sieve.
Today the motor killed the third PC PSU, how could i protect the PSU from the motor?

[Anonymous No.1438385]

>>1438366
calm down, samefake. /ohm/ is the safe space for actors hired to play dumb.

[Anonymous No.1438386]

>>1438378
The simplest brainwave stuff is easy, just alpha and beta brainwaves which can make a neat binary control system: https://youtu.be/mPbtR4vorgY
But doing any more than that might require a significant amount of research. I'll look into what existing brain monitoring software we have at the very least.

[Anonymous No.1438394]

>>1438378

Mattel makes a toy called Mindflex, which, from memory, uses a custom chip that they developed, and which is available separately for people to design around. this is all old news, dunno if any of it is still true today.

>>1438380

first i'd add a coil in series with the motor to block rapid current changes. i'd use the most turns i can get away with, without decreasing motor torque. then i'd add a big ass diode that can handle 2x or 3x the current, also in series. then wire another fat diode across the motor (in parallel) so it's reversed biased. the two diodes should prevent the generator effect from feeding a negative voltage back into the supply when the motor stops. either diode should work on its own, but having two makes it double-plus-good

>>1438385

okay faggot, you've hinted enough, now blow our minds if your newly discovered conspiracy theory.

[Anonymous No.1438410]

Do these look good enough for guitar pedals?
I'm having trouble sourcing quality electronic components in spain

https://www.amazon.es/Broadroot-Conectores-Clavija-Guitarra-El%C3%A9ctrica/dp/B0793R8SXC/ref=sr_1_4?s=sports&ie=UTF8&qid=1533389453&sr=1-4&keywords=6%2C5+mm+jack

[Anonymous No.1438426]

What is the purpose of Rg? I just tried the circuit without it and it works perfectly fine

[Anonymous No.1438427]

>>1438426
That is a differential amplifier, Rg acts with R2 as a voltage divider, such that you can tune the gain of V2 by changing the two. By omitting it, you are setting its gain at 1 permanently.

[Anonymous No.1438440]

>>1438426
Changing Rg changes both the gains and both of the input impedances.

In a practical circuit, you'd usually want R1||Rf and R2||Rg to be roughly equal, as that reduces the effects of imperfections in the amplifier (primarily, common-mode input current).

[Anonymous No.1438441]

>>1438440
>>1438427
Thanks, it seems to be finally doing what I want.

[Anonymous No.1438462]

>>1437545
>SB5100
I need 1n5402.
It isn't available
When looking at replacement parts there are different types specified and idk how to proceed.
http://www.allxref.com/search.htm?part=1N5402

[Anonymous No.1438477]

>>1438462
datasheet

[Anonymous No.1438503]

Holy hell mousers website is a steaming pile of shit.
I can't even check out. There is only a continue shopping button.
Made an account, still no checkout.
Won't even let me sign in.
Go to checkout as guest again, finally get to enter info, then it takes me right back to the cart.
In the past their website told me my order was to have $0 shipping on the shipping screen and the confirm order screen. They then billed me $10 for shipping anyway.

Where do you guys order small quantities of parts? Digikey charges outragous shipping also

[Anonymous No.1438578]

Can I control an active lowpass filter with a CD4016 IC like this?

[Anonymous No.1438580]

>>1438578
Corrected version

[Anonymous No.1438596]

>>1438503
I stopped shopping at Mouser when it was crashing the web browser on my ubnt14 box. Their loss.

When will these companies figure out that the fastest and most responsive components site will win.

But shipping there really isn't a lot of money. The next cheaper option is ebay or alibaba where you'll find counterfeits.

[Anonymous No.1438619]

>>1438596
>Shipping isn't a whole lot of money at mouser
Idk about that, they billed me $10 for shipping three capacitors valued at like $1.50.
Granted it was the best envelope I've ever seen, but I didn't want a $10 construction grade envelope. They would have been fine in a standard envelope with a 25 cent stamp and if not I would have happily rebought them to try again.

[Anonymous No.1438623]

>>1438580
no. R(on) isn't even specified for 5V operation and is likely to be larger than the resistors you're trying to switch in. use a different analog switch IC. happy searching
https://www.ti.com/switches-multiplexers/analog/products.html

>>1438619
see, digi-key would have shipped those in a small reel box for $4

[Anonymous No.1438627]

>>1438580
Which type of filter has R1/R2=1 and C1/C2=1/2?

[Anonymous No.1438644]

>>1438627
I found the formulae from here:
https://www.radio-electronics.com/info/circuits/opamp_low_pass_filter/op_amp_lowpassfilter.php

>>1438623
But dat boi (>>1437331) told me to use the CD4016

[Anonymous No.1438647]

>>1438644
not with those low resistor values, you don't. you might get it to work if you make them 20-50x larger and scale the caps down likewise and use a higher Vdd-Vss to turn the switches on harder

[Anonymous No.1438677]

>>1438644
Algebra.. You got it wrong. You have C2=2*C1 but it should be C1=2*C2. Regarding the switches, check the data sheets for 74HC4051 (1P8T), -52 (2P4T) and -53 (3P2T). These chips run on VCC=5V, VEE=-5V and VDD=0V (logic level 0/5V) and have a low enough channel resistance. Maybe one of them fits your needs. The 4016 has no VEE pin and no logic level conversion.

[Anonymous No.1438737]

>>1438503
Buy enough to get free shipping. I think Arrow has one of the cheapest requirements.

[Anonymous No.1438745]

>>1438376
set meter to read resistance
use alligator clip or jumper leads to keep test lead probe pins shorted
move/wiggle each lead at point where the most stress occurs
(just after the wire comes out of the handle or the plug end)
also twist lightly on the wires while holding the handle or plug
lead wires frequently fail due to frequent bending at these two points
I've also had them cause high resistance instead of complete open (infinite resistance)

[Anonymous No.1438783]

>>1438677
>HC
>with VEE
lol no, maybe you're thinking of the Harris DG* analog muxes
one can find plenty of 5V (or less!) analog switches with excellent R(on) on the order of 10 ohms at 15mA, even in grandpa-friendly 1.27mm SOIC packages. the SN74CBT3253 dual 4:1 mux, for example, would suit this application nicely if a proper digital pot is unavailable (which surely it is not?)

[Anonymous No.1438801]

If I can do:
20dBm - 10dB = 10dBm
Can I do:
20dB - 10dBm = ?

[Anonymous No.1438808]

>>1438801
Just convert from one to the other. I've personally not encountered dBm, but all dB are just the log of the ratio of your value to a known reference (multiplied by 10). For dB in sound the reference is the threshold pressure of human hearing, and for dB power it's 1W. I imagine dBm the reference is just 1mW, so:
>A_dBW = 10*log(a/1W) = 10*log(a)
>A_dBm = 10*log(a/1mW) = 10*log(a*1000)
Do the algebra yourself.

[Anonymous No.1438821]

>>1438808
I don't know why I didn't consider just working it out. Wish i used my brain sometimes. Thank you.

[Anonymous No.1438893]

Is there somewhere reliable where I can buy geiger tubes, just the tube without the counter? I'm located in Canada.

Also do I post about hardware algorithm implementation using asics in here or in g

[Anonymous No.1438895]

>>1438893
>algos
you can post in the

NEW THREAD
>>1438894
>>1438894
>>1438894

[Anonymous No.1438904]

>>1438410
OK I'm going to buy them how do I examine them to find out if they're good

[Anonymous No.1438909]

>>1438904
>OK I'm going to buy them how do I examine them to find out if they're good

they're crap, you can tell there's not enough plastic to make it solid. they were designed with minimum cost in mind. will probably break if you step on 'em in fact, you should try that; step on their necks and put an end to their misery.

[Anonymous No.1438910]

>>1438904
I think you're looking for something more like this
http://es.farnell.com/switchcraft-conxall/12a/toma-hembra-de-1-4-panel-2polos/dp/1192904

[Anonymous No.1438911]

>>1438783
RTFD, dude. It's pin 7.

[Anonymous No.1438912]

>>1438910
>http://es.farnell.com/switchcraft-conxall/12a/toma-hembra-de-1-4-panel-2polos/dp/1192904
I have no idea if they're good but since they cost 2€ per unit I guess they're gonna be pretty study, thanks anon!

[Anonymous No.1438915]

>>1438911
>These chips run on VCC=5V, VEE=-5V and VDD=0V
I don't see anything about logic level translation there.

>>1438912
de nada.
Switchcraft has a reputation for high quality. they tend to be used by manufacturers of low-to-medium range audio gear. the upscale stuff uses Neutrik
the open frame construction helps too. as long as your box is solid, so will the jack be. if you really need to protect against mechanical or electrical contact, you could fold thin polypropylene sheet and place it around the jack, or something

[Anonymous No.1438916]

>>1438915
>I don't see anything about logic level translation there.

try reading the datasheet, as the fag three posts up recommended.

[Anonymous No.1438917]

>>1438915
Since Neutrik is upscale, would this be better and cheaper?

[Anonymous No.1438919]

>>1438917

stop being a lazy spic and look at the page. see those yellow stars? they mean something. try to figure out what instead of asking here.

[Anonymous No.1438920]

>>1438917
haven't tried their 1/4" jacks. that one is isolated, which you might or might not want for your circuit, while the Switchcraft isn't
>€15 shipping
dios mio

[Anonymous No.1438923]

>>1438911
oh, neat

[Anonymous No.1438949]

>>1438920
Yeah, but that means if I buy more than 15 it's cheaper and possibly better quality, I think isolation will be an issue buy I can just ground it. I'll try and see what works, thanks.

>>1438919
5 stars isn't a comparison, it's a review, I'm asking for a comparison

[chipresistor122 No.1438949,1]

Hello I am still a bit confused about bridge rectifiers work. Are they just an assortments of diodes? What exactly do they control differently then diodes do?

[jacobgoona No.1438949,2]

Yup so a bridge rectifier is an assortment of diodes , generally it is 4 or more diodes. It helps convert AC to DC and only allows current to pass through in one direction.

[chipresistor122 No.1438949,3]

Ok but is there anything more to it ? or is it just an assortment of diodes? Do you put it together yourself?