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Re: Resistor calculations for low voltage bulbs on DCC

Posted: Tue Apr 14, 2015 10:18 am
by brianc
There was a good article in Model Railroader October 2014 about choosing headlight resistors.

I am not expert in these matters, but using the example quoted in the article you seem to be on the right lines.

Hope this helps.

Brian Clark

Re: Resistor calculations for low voltage bulbs on DCC

Posted: Tue Apr 14, 2015 1:44 pm
by Mike_R
Your calculations are correct except that the decoder drops around 2v. On the other hand it is better not to run the lamps at full current to give a longer life and allow some leeway if the loco runs on a layout at a higher voltage.

On using LEDs I use these http://www.rapidonline.com/electronic-c ... cd-55-1654 from Rapid Electronics. Mounted side by side they match the spacing of HO headlights, with the domed heads fitting into the holes. I connect each pair in series, so only one resistor is needed for the pair. I find them a lot brighter than lamps, should last a lifetime and produce almost no heat. I run them well under the max 30mA, usually around 10mA.