If your LHS carries Miniatronics, they sell packages of white and yelo-glo LEDs. Some of these come with resistors, unfortunately they generally aren't the correct resistors for DCC - you want a 1K.
As for size, it depends on how the stock lights are set up. Even a 3mm LED is too big to direct mount in a twin sealed beam type of headlight in HO, but many locos use a palstic light pipe to provide the 'lenses' in the headlight and carry the light from a bulb. The P2k Geeps are like this. You can use either size of LED in them, and tape it in the same place the bulb was so it shines into the light pipe. On older Atlas/Kato units with long light pipes and one bulb in the middle, I cut down the light bars and used shrink tubing to attach an LED to each cut end. Right there is an example of how much more versatile LEDs are - LEDs don't even get warm, so they can rest right up agains the palstic with no danger of melting.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I've got calipers that I've had for many years. I just measure the opening (or the headlight that I pulled out of the opening). If you don't have calipers, might be another tool worth looking into. I think Micro Mark may have some reasonably priced ones. I'm thinking that cheaper ones would be good enough for hobby work.
One thing about the LED link I sent. They have a big variety of stuff, but they don't seem to carry any yello-glow, the white ones that look more like incandescent. I just buy those, if I need them, from one of the DCC places, mostly Litchfield Station.
Steve, thanks for the tip and the link. What gage is a decoder wire? And again how to you tell the sizes of head lamp opeings.
Cuda Ken
I hate Rust
Ditto. Decoder wire is so fine I can easily strip it off with a fingernail. Most wire strippers are too large to work well with such fine wire. One thing that might work but I haven't tried, decoder wire is about the same size as wire wrapping wire, and many wire wrap tools (the manual type)have a stripper built in. Wire wrap wire is solid, not stranded, so maybe it will work, maybe not. Also, I've seen ones that only strip one side of the wire, the side that gets wrapped around the socket post. If I happen on the one I used to have somewhere I'll give it a try.
I just pinch the wire between my fingernails and strip the insulation off. You can also ut the wire to length and touch the end with your soldering iron. The insultaion will pull back about an 1/8 inch from the heat.
Martin Myers
Micro Mark and Litchfield Station have wire strippers that will do wire from 22 ga to 30 ga.
For LEDs, http://www.moreleds.com/railroad.htm is a pretty good place to find a good assortment. I've bought from them twice. No problems and pretty fast shipping.
To this point, I haven't done any where the LED just fit in the loco. I haven't done that many yet, but so far, I either end up trying to get the dia of the LED smaller or just using clear acrylic as lightpipe and putting the led behind that,
This is a two fold question.
1 Today I hard wire my first decoder, the hard part was stripping the wires. I used a box cutter with a new blade and scraped the cover off to get to the wire strands. Besides taking to long, I lost a few strands and with as little as they give you, you need them all. Do they make wire strippers for wires that small? Other tips?
2 How can you tell the sizes of hole your engine has for headlight? As I install more decoders in my old DC fleet I was to install bulbs / LEDs in the opeing them selfs. My LHS does not have a good supply of light or LED's. Could you post a link to a good supplier?
Thanks Ken