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
Resistor calculations for low voltage bulbs on DCC
Re: Resistor calculations for low voltage bulbs on DCC
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.
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.
Mike Ruby