Hi guys i have a device that has 6 3mm red less wired in series and i want it to run from a cars 12-13v power, can anyone tell me what value resistor i require ?
Cheers
Charles
Maybe 56 - 150 ohms or so.
Red leds use 2v each (“voltage drop” / “forward voltage”) x 6 in series = 12v. Voltage varies on a car though so without a regulator brightness will vary too. 14.5v or more when the engine and alternator is running.
Some led resistor calculators LED series/parallel array wizard LED resistor calculator
May I chime in and ask at which point do you use a resistor vs a constant current driver?