I am building a simple motor controller and wish to add LEDs to indicate when the motor is energised one way or the other.
I am aware of online utilities such as http://led.linear1.org/1led.wiz which assist in calculating the resistor required for an LED at a given voltage, but my problem is the given voltage (motor supply voltage) can range from 3v to 36v.
What is the recommended approach in selecting resistors when the voltage is not known in advance?
The only option I can think of is to use a resistor for the maximum rated voltage and make do with very dim LEDs (if they light at all) at the lower voltages.
Alternatively I gues I could use a pot but that is a pot per LED which will mean 4+1 pots for a dual motor + motor power supply LED. Seems a bit over the top to add 5 pots and then top expect the user to set all 5 pots depending on the motor supply voltage...
Any advice would be appreciated.