how many volts do you need to light an led

[heywier427]

i hooked it up to 12 volts and i just burned it out. ive got lots of cool ideas and 100 10mm leds to play with. whats the right resistor to put in line? thanks

[99q45t_vl]

LED Model? Manufacturer?

[Q451990]

There's a lot that goes in to engineering LEDs, but typically the "forward voltage" is 2-4VDC. At least looking at a spec. sheet that I have here for Lumileds.

You'd want to hook them in series

12V --> +O - --> +O - --> +O - --> +O- --> Ground

In this example - 12V is split four ways, so you're putting about 3VDC on each LED.

From what I can tell, there are a lot of other considerations - including managing heat, and making the circuit capable of working under various voltage conditions. (Line voltage may vary from 12V with the car off to about 14V when it's running). So this is a starting point. I think the limiting resistor in most circuits is to make the circuit less variable with voltage changes.

Here's a link to some technical data. http://www.lumileds.com/soluti...#docs

Typically my head starts hurting half way into this project and I take some time off. Last time I looked at it was about a year ago.

Good luck!

Heath

[DrewQ45]

You should work for KFC. LOL

http://www.kpsec.freeuk.com/components/led.htm

[heywier427]

not sure how i should take that...

[DrewQ45]

not sure how i should take that...

Whatever you do, don't take it seriously. I said that seeing as how you fried the LED.

drew

[qsiguy]

Most common small LED's that I use in vehicle security run on 3 volts, I use them all the time on 12 volt systems. You just need to put a 1K ohm resister in series with it. You can also find 12 volt versions but they are usually more $$ so just get a pack of 1K ohm 1/4watt resisters and you're good to go.

Added: Just read the LED info link above, good info. Use the 1K if you will run each LED by itself or use their formula if you are going to run a few in series.

[Q45tech]

http://www.theledlight.com/LED101.html

14v minus 3.4= 10.6 divide by current [12ma]= ~~833 ohms

All depends on color and specs and how you want to derate for life and brightness..........temperature must be considered.

http://members.misty.com/don/ledx.html

[heywier427]

thanks for all your help guys. so i should be able to find these at radio shack? here are my ideas: map lights, rear courtesy, license plate lights, cluster of back up lights, underneith door handles. underneith mirror. i just love how the bright white almost a light blue, shines off my pearl paint. can you think of any other uses? i have the 10 mm leds they are freakin bright!! i absolutly need them for backup lights. i can get 3 rows of 4 in there so that should be plenty! thanks again.