/diy/ - Do It Yourself

>>1564701
>coin battery
you can easily find datasheets for them that show just how much energy they store, and it isn't much at all, certainly not enough to spin any appreciable motor
>series circuit
good, it shows you understand Kirchhoff's voltage law
but now also consider Kirchhoff's current law. how much current does the motor consume at 3V? it's very high at startup, could be an order of magnitude higher than no-load running current. the current consumption also increases with mechanical load. in either case, your LEDs will probably be called upon to pass a lot more current than they can handle, and they go pop
so how about the LEDs? the V-I curve of an LED is fairly well known, Pic related is typical. since the motor has the same resistance as basically wire when starting up, pop
best bet for the noob is to power them separately. on the LED supply, add an extra battery to allow some headroom for dropper resistors (to prevent catastrophe due to too-fresh batteries). on the motor supply, just give it the 3V it wants
>brainlet
keked and saved

>>1431005
another nice item to have is the TPIC6C595, which is like an HC595 with open-drain 100mA MOSFET outputs

>>1431099
>i do not need to know what current it needs if i connect it directly to a 2v battery
oversimplified to the point of wrongness, but we'll let it slide for a sec
>i only want the resistor to drop voltage across it by 3V, not amperage
but voltage and current are interrelated by Ohm's Law. E = I * R. basic algebra, you need to know two to calculate the third. since the variable you can directly control is R, you need to know (available) E and (chosen) I to select R
the relationship of voltage to current through an LED or other silicon diode is non-linear. that red LED will conduct about twice as much current at 2.3V than at 2.0V, and will conduct almost no current at 1.0V. what's more, the LED heats up as current flows through it, and the LED's voltage at a given current drops as it heats up, which makes it want more current at the given voltage, which heats it up more, which, if unrestrained, eventually leads to it gorging itself on current and a very small kaboom. hence, always restrict the current going into an LED