Wiring a Light Question

[jonathan]

I always tend to show my ignorance in all things electrical.  But someone always comes along and rescues me.  So here we are again.

The following pics show the bulb I've inserted into my reverse light can in a former Connie tender (now an 0-8-0).  Also, a couple of pics of the board in the tender.  Where do I tap in to make the light work?

The two tabs marked "input" look promising.  I could always add a diode to make it reverse only.  I'm guessing, of course.  I was also wondering about soldering to the DCC dummy plug, or inserting the wires into the right holes, and pushing the dummy plug back in, to hold the wires?

Thanks, yet again.

Regards,

Jonathan

[Jim Banner]

Those tabs marked "input" are connected to the tender and locomotives wheels, so they would be a good place to pick up track voltage.  And as you have already figured out, you could pick up track voltage at the decoder socket.  Easiest way would be to solder one wire to each of those solder blobs.

Your idea of adding a diode is a good one.  Just cut it into one of the bulb leads.  If it doesn't work properly, that is, if it is on when the locomotive moves forward and off for backwards, just reverse the diode end to end.

I assume you used a 12 volt bulb but you might still want to add a little bit of resistance if the back up light is too bright.  You can fine tune the light by putting a 27 or 33 ohm resistor in series with it, for example, between the bulb and the diode.  If the light is still too bright, you can keep adding resistors in series until it is the brightness you want.

If you want to go a step further, you could replace the bulb with a 1.25 volt one and run it off a 1.2 volt voltage regulator to give you a constant brightness light.  This would be a good choice on a switcher which is often backed onto a car or cut of cars at low speed.  A simple constant brightness circuit would let the switcher crew see what they are doing when they need to the most.  If you are interested, we can talk more.

Jim 

[jonathan]

Jim,

Thanks, that's just what I needed to know.  I'm leaning towards the diode idea.  Sounds much easier than I had imagined.  You always make it sound like a reasonable and doable project.

I went for the 12v GOW bulb for cosmetic reasons.  It fits in the metal tube perfectly.  The bulb will never be too bright as the Spectrums run quite well on 6-7 volts.  It won't burn out either.  I can live with that.

I have a directional and constant lighting circuit from Miniatronics.  I'm saving that for the next project engine that calls to me.  Working up the nerve (and the piggy bank) for a brass project.

Regards,

Jonathan

[jonathan]

Decided to wire the lights to the dummy plug.  I could do all the soldering with the plug safely removed from the tender.  Greatly reduced the chances of me melting something critical.  I like the brightness of the light at around 40% power.  Will play with the diode in the morning.  Diodes can be had at Radio Shack for about 70 cents a piece. 

Great tip, Jim.

Regards,

Jonathan

[Jim Banner]

Good point about soldering to the dummy plug because you cannot harm the board that way.  I will remember that for next time.  We all learn from one another.

Jim

[jonathan]

Diode installed.



Just need to build some tender steps.  Bachmann 0-8-0 road switcher, ready for service.



Regards,

Jonathan