View single post by CMmodeler
 Posted: Tue May 10th, 2011 05:29 pm
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Joined: Tue May 10th, 2011
Location: Loveland, Colorado USA
Posts: 6
Hi all,

I am a new member and this is my first posting.

As far a power supplies are concerned, I do not recommend wall-wart transformers.  The output voltage can go very high if lightly loaded.  I was using a 12v wall-wart to power a circuit with 17 volt tolerant IC's and blew the IC's because the voltage went over 20 volts.  I also do not recommend old train transformers.  They are a very unstable power source.

Computer power supplies work well.  They are also readily available and cheap.  One word of caution - computer power supplies are capable of high currents - fuse the outputs.  At the Greeley Freight Station Museum (, we use 17 or 18 computer power supplies on the 5500 sq. ft., HO scale Oregon, California & Eastern Railroad.  Each computer power supply has a line that has to be tied to ground in order to turn the supply on.  The +5v supply also needs a minimum load or the supply will shut down.  We have found that some computer power supplies (Compaq) are very sensitive to load changes.  To counter this, we put a 50 ohm 10watt resistor from +12v to ground as well as a 250uf capacitor in parallel.

As far as building lighting, the biggest problem with incandescent lighting is the heat.  A .3amp, 12volt bulb dissipates 3.6 watts of heat.  Most of our buildings are plastic and will have multiple lights per building.  I prefer LEDs.  Warm white LEDs have a yellow tint to them.  Avoid cool white LEDs - they have a blue tint.  A typical LED only requires .015amps and dissipates less than .05 watts.  10 LEDs produce less heat that one bulb even at 1/2 voltage.

I am currently working on a building lighting system that will cycle lights on and off.  It also can dim lights or blink lights.  More on that later.

Last edited on Tue May 10th, 2011 05:29 pm by CMmodeler

Darrel Ellis
Yes, I do still play with trains.
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