lighting a roundhouse

[pdlethbridge]

I'm redoing the lighting in the roundhouse using 12-16w GOW and GOR bulbs. I now control the turntable with a DH123 decoder that I want to use to control the lighting. I want to have a light in each of the 3 stalls that could be turned on as a group. I have 22ohm resistors to control the inrush current to protect the decoder. I was planning on wiring them in parallel to keep a bad bulb from darkening the rest. Any thoughts or suggestions before I start would be greatly appreciated. Thanks, Paul

[Jim Banner]

I like your line of thinking.  But watch out for overloading the decoder's lighting output.  If your grain of wheat bulbs are rated 50 or 60 milliamps each, three of them will draw 150 to 180 milliamps.  The 22 ohm resistor will reduce the lamps voltage about 1.5 volts but will have a smaller effect than expected on their current.  On the other hand, many H0 decoders are rated only 100 milliamps per function output.  Bottom line, three lights could let the smoke out of your decoder.

A better solution is to use a small relay, one with a coil that draws less than your decoder's rating.  If you connect a relay coil to a decoder function output, you MUST put a diode across the decoder to absorb the inductive kick back when you turn the lighting off.  A cheap diode such as a 1N4001 (or 1N4002, etc.) will do just fine.  One end of these diodes has a white bar painted around it.  Connect this end to the blue (positive) wire that goes to one of the relay coil connections.  Connect the other end of the diode to the function wire (probably white or yellow, or more likely both) that goes to the other relay coil connection.  Use the relay contacts to switch your lights on and off.  Now you can switch many GOW bulbs on and off with the decoder.

Diagram available on request.  Comes with a free bottle of Asprin.

Jim

[Steve Magee]

Hi Paul

Just thinking outside the square for a moment, if the lights in your roundhouse are bulbs, not LEDs, have you thought of using the motor circuits to power the bulbs? This way they can not only be turned on and off, but the brightness can be adjusted to suit ambient lighting, day/night operation, etc.

I used an old Lenz decoder in a Spectrum heavyweight car to try this out some time ago, and it worked out OK. You can even use the lighting outputs to provide, say, LED lighting over a workbench - or in an inspection pit for a really nice effect :-)

Steve Magee
Newcastle NSW Aust

[pdlethbridge]

I use the digitrax DH123 and it has2 fx's. The green and purple wire are what I was thinking of using so each stall could be lighted individually. Each would have a 22 ohm, 1/4w resistor and along with the white wire, would control the lights. Now the blue wire would be attached to each, right? and thats where the resistors would go. white, light, resistor, blue wire: purple, light, resistor, blue wire: and green, light, resistor, blue wire. If that makes sense. As each would turn on separately, I shouldn't have the inrush problem. I just gave myself a headache, Jim, I need those aspirins.

[Doneldon]

12 bulbs is an awful lot of light for a roundhouse unless it's a huge one.  They weren't lit up like a library, you know.  There was relatively dim general lighting and then specific task lighting.  This was economocally driven.  You'll also have to contend with a good deal of heat from all of those bulbs. 

If you want something unique, why not put in some minimal general lighting and use small LEDs to provide limited areas with brighter light?  You could also use one of the (yes, almost trite) arc welders in the building.

[Jim Banner]

PD,
That sounds good and will avoid overloading the decoder.  But you will have to upgrade to a DH163 decoder to get those green and violet wires working.  Unless you were lucky enough to get one of those DH123 decoders which is really a DH143 which Digitrax never officially made.

I'll get one of those aspirins off to you as soon as I find a round box two feet in diameter to ship it in.

Jim

[pdlethbridge]

The 123 has fx3 so I think they'll work. I checked here.
http://www.digitrax.com/v1/dh123.htm
http://www.digitrax.com/v1/ftp/ditchlights.pdf