Adding marker lights lenses to Williams F-3A

[lionelsoni]

John, I was assuming that he was planning to power them from the track, that is, with AC.  There is no need for any other diodes in an anti-parallel LED circuit.  Each LED protects the other.  An LED is, as its name indicates, a light-emitting diode.  So the reverse voltage on neither diode can exceed the forward voltage of the other diode.

This economy would not be possible with a DC voltage supply, since one of the LEDs would always be off.

[gunrunnerjohn]

lionelsoni

Whether you go with LEDs or light pipes, keep in mind that you can file or saw either to a more realistic lens shape, then polish with toothpaste.  If you choose LEDs, simplify the circuit by wiring the two LEDs in anti-parallel, that is, in parallel with cathode to anode.  Then you need no other reverse-polarity protection, since they protect each other.  You also need only a single ballast resistor for the pair.

Actually, you should still use a diode, LED's don't like reverse bias.  Also, if you have DC, which is what many command systems put out, you must wire the LED's in the correct polarity if you want them to light at all.

All of the LED's I've put in TMCC equipment have been powered by DC from the control boards, polarity recognition is mandatory.

[lionelsoni]

Whether you go with LEDs or light pipes, keep in mind that you can file or saw either to a more realistic lens shape, then polish with toothpaste.  If you choose LEDs, simplify the circuit by wiring the two LEDs in anti-parallel, that is, in parallel with cathode to anode.  Then you need no other reverse-polarity protection, since they protect each other.  You also need only a single ballast resistor for the pair.

[gunrunnerjohn]

I buy my LED's in bulk and solder on my own resistors and diodes if necessary.  For most diesels, I use 3mm LED's for headlights, they're sized right for the openings.  For markers, I use the 2mm ones.  Unless there's no clearance behind the location in the shell, you can mount the LED right there, no light pipe required.  For markers, I usually use a pretty high value resistor to dim them down a bunch, the last one I did I used 4.7K resistors across 12 VAC with a diode for the markers.

 

[Buckeye Riveter]

I have thought about doing the same thing.  I have been working with LED lights from http://www.modeltrainsoftware.com/ledlights1.html

I have only been using the 5mm for headlights, but I think the 1.8 mm may work for the marker light. 

 

[NYCentralFan]

Has anyone tried (and succeeded) to add clear or colored lenses to a Williams F unit?

There's a dimple in the casting that just screams for a drill bit and a stemmed crystal or solid rod that would draw light from the interior.  I would prefer clear.

 

 

There used to be an old trick of taking some clear plastic rod and holding it close to an open flame to ball the end, but I'm looking for something a little more drop in...

Does anyone know of a clear bead or mushroom shaped crystal that will fit in a drilled hole and act as a fiber optic rod to draw the light from the inside?

Thanks,
Mario