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Ok, I want to have a thing where ive got a battery pack, and then 3 toggle switches and one button switch, each one that is flipped/pushed lights up an LED and then the last one (button) lights up both the led and powers a small hobby motor or something like that. My question is, What do I need resistor-wise? (quantity, location, strength..)

Thanks!

Amendment I want to have the same idea going, but kind of have an extension cord running through it, so I plug the box in, and then plug something into a cord coming from the box.

## 7 Replies

Brennn10 (author)2007-02-15

Well your resistor solely depends on the amount of voltage coming from the batteries and the the amount of voltage the LED can handle. Are you wiring this is series or parallel?

LasVegas (author)2007-03-11

Actually, the resistor is dependent on the current rating of the LED. It's there to prevent overdriving and frying the LED. I've seen 3v LEDs connected to 120v with an appropriate resistor to limit the current. You calculate the resistor based on the voltage used and the current rating of the LED. IE: 120VDC / 30mA = 4Kohm Resistor.

Weissensteinburg (author)2007-02-15

I think parallel, my conflict is that one resistor would limit the final motor/whatever, so would i need to spilt the wires, and then have a resistor for each led? Im installing a diagram program now, and ill put up one for my plan.

Weissensteinburg (author)2007-02-15

This was my first idea.

Weissensteinburg (author)2007-02-15

I'm not sure yet..but can you answer this: Does the resistor go on the + or - wire? If i want to power (pulling a number out of my head..obviously not correct) two leds that require 2volts, would i just use a 2volt resistor?

lemonie (author)2007-03-11

It would help to know what you're trying to do.
But see here for your resitors:
http://ourworld.compuserve.com/homepages/Bill_Bowden/led.htm

Brennn10 (author)2007-02-15

What is your source voltage and the forward voltage for the LED?