Very off topic, a simple LED circuit needed.

[JonnyBoy]

Hey guys. I am working on a project for my halloween costume for school (it's a competition and I don't want to lose).

I have this really campy cobra-head cane. I want to drill out where the eyes are and put in some LEDs and make the glow, for the extra cheese factor. Now, I can get LEDs and resistors and all that, I just need to easiest way to make a small circuit capable of running 2 LEDs (green) using a battery or something.

Any advice would be great.

Thanks.

[Buddabing]

Without knowing your LED specifications, it's impossible to give exact numbers.

Let's say your LEDs require 20ma of current and drop 2 volts each, and you're using a 9 volt battery, like are commonly used in smoke detectors. This is pretty typical.

For simplicity you can put everything in series. Battery, LEDs, and resistor.

To calculate the resistor, use v=i*r. V=the remaining voltage that is not dropped across the LEDs, which in this case=9-2-2=5 volts. i=0.02 amps (20 milliamps),

This gives R=250 ohms.

You can google for much more detailed info. The first link I got was http://unclean.org/howto/led_circuit.html

Regards,
Buddabing

[Gambit]

What would be cool, would be pulsing LEDs for the eyes.

Not flashing on and off, but slowly growing brighter then slowly growing dimmer.

[BobA]

Here is a circuit sold to fade on and off.  Used for LED eyes.  The picture will give you an idea of the parts needed if you want to build your own.

http://www.cowlacious.com/LightProd.htm

[MikeDeuce]

http://www.instructables.com/id/E9D2ZJ3FG0EP286JEJ/

Since it sounds like you just need it for a few hours, a flat battery, some wire, and a couple LEDs would do it.