Author Options:

simple led circuit and switch resistor help Answered

I need a circuit with two large blue leds and a one switch it needs to be run off of a nine volt battery and I cant figure out what sized resistors I need and how many i might need?




Best Answer 9 years ago

It depends if your LEDs are wired in parallel or series. The calculator on this page is very simple and should help you figure it out.

A typical blue LED might have forward voltage of 3v and 25mA. If you run it off of 9v and wire them in series you need a 120 ohm resistor. But check the exact specifics on your LEDs to be sure.