Author Options:

Led Nighttime Light Answered

I wanted to make a red LED flashlight, but wanted to run it with a 9v battery. What resistor would I need? I don't have alot of knowledge about resistors, so what size and color resistor would I need? I'm using a 10mm red LED, with a max forward voltage of 5v, max forward current of 40mA and a 5000mcd intensity.


You wanted to current limit that to 40mA. 40 mA from 9V is 9/0.04 which is 225 Ohm How exactly did you overload this, I'm interested... L

I plugged it into a 9v battery, and now it doesn't do anything.

Mmmm. Have you ever put your tongue on a 9V battery? I can post you some LEDs if you want some. L

Yes, but I just wanted to see it light up at the time, so I didn't think about it. What do you mean by "post"? Like send them to me?

It's pointless, after trying to "fix" it, I overloaded it, and burnt it out.

You definatly want a 7505 regulator or something similar like a adjustable lm307, but they're a bit more hence the adjustability. Other than that it's pretty much direct wireing if it's just one or two leds.