Hello everyone. I wanted to replace some of the lights in my car's cabin with LED's. I want to know what value resistor I would need if for example I would use 2, 4 or 6 LED's.
I was playing with some LED's today (12volts+ different resistors) and for some reason when I use 4 LED's one of them wouldn't be as bright as the other ones even though they were exactly the same. Can anyone tell me why?
Thanks a lot!
--- You take the supply voltage, subtract from it the LED's specified forward voltage and divide that difference by the LED's rated forward current.
The quotient will be the resistance required.
Then, in order to determine how much power the resistor will dissipate, multiply the voltage dropped across the resistor (the difference between the supply voltage and the LED's forward voltage) by the LED's forward current.
The product will be the power the resistor will dissipate, and you should use a resistor which can handle at least about twice that power in order to keep it relatively cool.
---
--- How did you have the 4 LEDs connected?
JF
The specs of the LED's I got are here:
I put them in a series connection and 1 of the 4 didn't shine as brightly as the others. Anyway I will use a parallel connection when I put it in the car.
Would you try to explain it more please? I'm just an amateur hobbyist and I'm still googling "rated forward current"
Thank you very much for the help John!
-- Since the luminous output is only given as "typical", then that LED is just putting out less light than the others. Probably substandard, but with no minimum stated there\'s nothing you can do about it.
are you placing them in series?
If you do not want to place them in parallel with a single drive resistor if that is what you're doing?
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