# LED power consumption question. Answered

I need to power 62 LEDs in series. Does this mean I also need 62 1K resistors? And if I do, does that mean I need a 248V power supply?! Isn't each LED a 2V power consumption as well as each resistor? That math doesn't seem to add up at all, any help (and lessons in powering LEDs) is greatly appreciated. Thank you for the help!

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Depending on the colour of the LED, it will 'eat' from 2 to 4 volts of your power supply. This is called the 'forward voltage drop (Vf)'. So you could power up to 4 LEDs with a 3V Vf from a 12V supply. However, this is only half the story. You also need to limit the current through the LEDs to (usually) a maximum of 25mA. This is where the resistors come in. To calculate, work out the total voltage drop (add the Vf's together) and then subtract this figure from the supply voltage. Divide this by the desired current to get the resistor value. You don't need to connect them all in series. The best way would be in banks of 4 or so with a resistor for each bank Tell me the LED colours and what supply voltage you're using and we'll work out the best arrangement.