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470 Ohm resistor what you need to do is use a resistor in line with each led. This will drop the current to the required level to safely power the led. In order to work out the resistance you will need, you need to know the supply voltage the voltage drop of the led and the current at which you want the led to operate. ok supply voltage is 12v. voltage drop of led is 4v(approx) and typical operating current for led's is 20mA. resistor required = supply voltage - voltage drop / current(in amps) 12-4/02 = 400 ohm resistor (next closest value is 470 ohm) so you would need a 470 ohm resistor in series with each led in order to operate them from 12v at a forward current of 17mA(017A)