08-07-2019, 08:57 AM
100 and 120 are probably both fine, but it really depends on the forward voltage of the LED.
You need to keep the current to around 5mA max because that is all the microprocessor will output on a port.
Look at the datasheet for the diodes you are using to determine their forward voltage. Then use this formula to calculate the proper resistor:
3.3 - fwd voltage / .005 = resistance in ohms
You need to keep the current to around 5mA max because that is all the microprocessor will output on a port.
Look at the datasheet for the diodes you are using to determine their forward voltage. Then use this formula to calculate the proper resistor:
3.3 - fwd voltage / .005 = resistance in ohms