LED for K-line Caboose Marker lights

Well, without seeing them, it's hard to be sure.  About the smallest LED you can find that's not surface mount is the 2mm ceramic models, I use them in a lot of places.  How large is the opening for the bulb?

The smallest i've been able to get are these 1mm surface mount LED's, C0402WM 20pcs Pre-soldered micro 0.1mm Copper Wired WARM WHITE SMD Led 0402 NEW ( item: 351249772568). They are also available in colors. A little tricky to work with as the wire is only .28mm (or something equally fine).

jackson

John,

From what I can measure, it is right at 3mm. 

Gene

In that case, you could use the 2mm Ceramic LED's, they work well for spaces like that.  You can also stuff a 2mm post LED in there, I sand the post and end to diffuse the light a bit.

Thanks for the suggestions. I did not think about the ceramic LED's. I will start looking for them. I was going thru some little parts bins, I had packed away for the move and found them.

Thanks

Gene

Digikey and Mouser have the ceramic LED's.  I scored a bunch a while back from some closeout outfit that was selling them for peanuts, so I bought all they had.

Another option is to use easy-to-find 3mm white LEDs and acrylic rod.  You can buy acrylic rod by the foot very cheap at your LHS in various diameters 1/16", 3/32", 1/8" for sure, and 1.5mm, 2.0mm, 2.5mm if your LHS is well-stocked.

So the idea is to form a collar using black heat-shrink tubing.  Acrylic rod behaves like fiber-optic tubing and is quite efficient at transmitting light without loss.  Since a typical marker housing might have side and rear facing lenses, you need to scatter the light.  It takes just seconds to file/sand acrylic rod. 

Tip.  If you are creating a, say, 2mm lens using 2mm acrylic rod, then when you heat-shrink the collar with a heat-gun, use a 2mm drill-bit as a proxy for the acrylic rod or else the rod will wither!

You can also use fiber-optic rod which is sold in 0.5mm diameter increments (1.5mm, 2.0mm, 2.5mm, etc.) but I've never seen this at the LHS so it's mail order which means shipping charges.

If you use acrylic rod, one trick I've used is to use flat-top LEDs, or simply file the top flat, then use CA glue to secure it to the end of the rod.  It bonds and transmits the light very well, the CA dries clear and passes the light.