power supply

[Anonymous]

Does anyone have information on building transformers for HO?

[nedthomas]

Here is a web site to look at.
http://home.cogeco.ca/~rpaisley4/CircuitIndex.html

[claycts]

QUOTE: Originally posted by nedthomas

Here is a web site to look at.
http://home.cogeco.ca/~rpaisley4/CircuitIndex.html

Great site, I learn something every day, even at my age.
Thanks
George P.

[Anonymous]

great thanks for the link. now i have a more solid idea of what needs to be done.

[TomDiehl]

I'm assuming you're talking about power packs, and not winding your own transformer.

Try to find a copy of either of the original books, "Electronics Projects for Model Railroaders" or "More Electronics Projects for Model Railroaders."

[sansouci]

Tim Eckert of Eckert Engineering builds power supplies for Marklin layouts. Not sure of his email or web address.

[Anonymous]

I've been toying with building one for myself. To do it right it's a MAJOR engineering challenge if you want a properly protected high-power unit.

Power supply manufacturers cheat by using trasformers with a high resistance in the secondary windings. While this creates heat at high loadings, it also limits the current flow during shorts. They also cheat by not trying to regulate the output voltage and letting it drift all over the place.

The better but more technical option is to design an electronic current limiter, preferably with a crowbar action to drastically limit the current output at very low output voltages.

I once designed one with all the bells and whistles, and the material costs were in excess of $200. Cheaper to buy one unless you just HAVE TO HAVE a 10 amp DC power supply for your train.

Mark in Utah

[nedthomas]

Good point. In building our own power supply the most important item is the transfromer and they are hard to find today. Years ago Radio Shack sold 18 volt 3 amp transformers that were ideal for model railroad supplies. (Radio Shack seems to be getting out of the parts business). The throttles I built were rated 12 vdc and would current limit at 3 amps. They were built in two sections - first a 13.5 volt 3 amp regulated power supply using the LM 723 intergated circuit and the throttle section. Each section required a power transistor on a heat sink. The regulated part needed to be 13.5 volts to allow for the drop in the throttle series power transistor. After building about 25 units for myself, club and friends I'm happy to say all are still working. I was able get the heat sinks and a few other parts as scrape from work. Did I save any money? Probably not, but I had the pleasure of building them and I get to say "I BUILT THAT and isn't that what the hobby is about.

[Seamonster]

QUOTE: Did I save any money? Probably not, but I had the pleasure of building them and I get to say "I BUILT THAT and isn't that what the hobby is about.

My sentiments exactly! [:D] Electronics has been my hobby since I was a youngster, before I got into model railroading. I won't say how long ago that was, but vacuum tubes were King then. [:I] I've built lots of electronic gadgets for my layout that I could have bought, but I got immense satisfaction out of building them. In addition, I'm able to build something unique that I need that isn't available commercially.