What resistance do LEDs need?
What resistance do LEDs need? LEDs typically require 10 to 20mA, the datasheet for the LED will detail this along with the forward voltage drop. For example an ultra bright blue LED with a 9V battery has a forward voltage of 3.2V and typical current of 20mA. So the resistor needs to be 290 ohms or as close as is available. How do you check voltage drop on an LED? You could find the LED voltage by using a multimeter with diode function. 3. You could connect a battery to the LED and a potentiometer. Start with a high resistance...