Not quite sure, but I have an illuminated switch with an LED. Brightness specs are given "@20mA" and the forward voltage is given as 2.3V. I have a 24VDC supply.
What is a good value for the resistor? 24V@20mA gives me 120 ohms which seems low to me.
Thanks,
Dale
You have a decimal point in the wrong place. It should be 1200 hm:.
In fact, if you allow for the forward voltage, only 21.7 volts is left across the resistor. So that should be 1085 hm: to get 20mA
However, you won't loose much brightness at lower currents so you could use 1.5 khm: to 2.2 khm:. That would also be less likely to damage things if the voltage is a bit above 24V.
It may or may not be important for your application, but it dosen't hurt to also add a small ceramic cap (0.01uF or so) across the anode and cathode of the diode. It will help absorb voltage spikes that could be present if the LED was part of a larger system that could be subject to EMI.