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| whammoed:
I will break this down for you using ohms law: Lets say you have an led and the ratings are: Volts: 2 amps: 0.030 (30 milliamps) so, lets find the resistance of the led: R=V/I R = 2/0.30 R = 66.7 now lets say you want to use this led on a 12 volt source, lets find the resistance needed to only pull 30 milliamps: R-V/I R=12/.030 R= 400 so, you need and extra 333 ohms (400-66.7) of resistance to use the led on a 12 volt supply. You can likely find a 330 ohm resistor to do the job. (pick a common resistor value close to the calculation) |
| whammoed:
I will confirm also, once more that a 12v automotive led bulb is ready to go on any 12 volt source. Even if you don't believe me, a cars alternator can typically deliver over 100 amps. How many pc power supplies are rated for over 100 amps on the 12 volt rail? Even if I am full of it, sounds like you're safe to me. |
| Sinner:
--- Quote from: whammoed on February 06, 2006, 06:56:07 pm ---to figure out the resistor you need (if you need one) you need to know the amps and volts for the led and the volts you will be supplying. this site will do the calculation for you: http://ourworld.compuserve.com/homepages/Bill_Bowden/led.htm --- End quote --- What I've been saying from the begining is that I don't know the amerage of the bulbs...I'll have to take your word on it and try...what's the worst that can happen??? It blows and starts a fire in my cab, when I'm not home... :) Thanks for the explanation... |
| TOK:
--- Quote from: whammoed on February 06, 2006, 07:15:27 pm ---I will confirm also, once more that a 12v automotive led bulb is ready to go on any 12 volt source. Even if you don't believe me, a cars alternator can typically deliver over 100 amps. How many pc power supplies are rated for over 100 amps on the 12 volt rail? Even if I am full of it, sounds like you're safe to me. --- End quote --- I will re-confirm it. I've had 3 of these lighting my trackball for over a year plugged right into the 12v lead of a PC power supply. You don't need to dick around with resistors, just hook them up. |
| Toonces:
--- Quote from: Sinner on February 06, 2006, 08:41:21 pm --- --- Quote from: whammoed on February 06, 2006, 06:56:07 pm ---to figure out the resistor you need (if you need one) you need to know the amps and volts for the led and the volts you will be supplying. this site will do the calculation for you: http://ourworld.compuserve.com/homepages/Bill_Bowden/led.htm --- End quote --- What I've been saying from the begining is that I don't know the amerage of the bulbs...I'll have to take your word on it and try...what's the worst that can happen??? It blows and starts a fire in my cab, when I'm not home... :) Thanks for the explanation... --- End quote --- If you look at the ratings of some of the brightest LEDs they run around 30milliamps. each. So if you have a cluster, if you add them all up, you are going to need a hell of a lot of them to even get 1 amp. |
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