Resistor Values for Richmond Controls Golden White LEDs

Hello All,

Thanks to Michael, I have done some legwork for all those that have decided to do some lighting on their buildings using Richmond Controls "golden white" LEDs.  The site Michael highlighted in another thread basically does the Ohms Law calculation for you to figure out the proper resistor value required to protect an LED in a circuit, then rounds the calculation to the nearest commercially available resistor (don't get glazed-over eyes out there yet). 

To get the resistor value you need to take the voltage of the circuit (which is the supplied voltage from your power pack minus the LED forward voltage rating) and divide that number by the current ratiing of the LED in ohms.  In the case of the Richmond LEDs, both the 5mm and 3mm devices are rated as having a 3volt forward voltage and a current capacity of 20ma.  Remember that a milli amp (ma) is 1/1000 of an amp, so for our calculations we use .02 amps.  As you can see how simple this is, you can now easily figure out the proper resistor for any LED when you know your power supply voltage and the forward voltage and current rating of your LED.

I have taken the calculations a step further.  As I have installed my LEDs in some impossible-to-get-at places, I want to run them very conservatively.  So I have also included calculations assuming only supplying 15ma to the LED.  They will be slightly less bright, but should also last indefinitely (although at their max current they are typically rated at 100,000 hour life.)

Anyway, here is the list.  Just figure out how much voltage you will be supplying your LEDs, and the proper commercially-available dropping resistor will be shown to the right.  The calculation is assuming running the resistor in series with the positive leg of the LED.  Now that wasn't so bad, was it?!

Kerry