Model Railway Forum banner
1 - 1 of 1 Posts

·
Administrator
Joined
·
10,002 Posts
>Resistor values quoted by various sources seem quite conflicting
The resistor value depends on the voltage level of the output driving the LED and the current required by the LED to provide its rated output. As you may remember from your physics lessons, Ohm's law is V = IR where V is volts, I is current and R is ohms.

You get the volts value from the output of your decoder and the I from the data sheet on your chosen LED. Remember that the I in the formula is for Amps. LEDs take milliamps so remember to enter 10ma as 0.010 in your calculation. Since you now have V and I, you can calculate R as V/I;

For the power rating (watts), use P = IV where P is the power in watts. V and I are the volts and amps as before.

So for every combination of LED (I rating) and decoder output (volts) you will get different results for resistor value.

I hope this helps (and that I got it right!)

David
 
1 - 1 of 1 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top