# How to Build a Power Controller for Your Model Railroad



## dbodnar (Jan 2, 2008)

I just uploaded a video that shows how you can make a simple power controller for G-Scale trains.
The video is here





 
and the web page that goes into more detail is here

http://trainelectronics.com/PowerController/

dave


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## East Broad Top (Dec 29, 2007)

Very cool. Those old power supplies seem to pile up in forgotten corners of our workshops. This is a simple and inexpensive way to put them to use. 

Later,

K


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## Greg Elmassian (Jan 3, 2008)

The only issue to keeping it compact and cheap is that it is hard to find 24v power bricks from laptops, most seem to top out at just under 20.

Dave, what voltage drop do you experience in that setup, the loss from the raw power to the track output.

Greg - 6


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## dbodnar (Jan 2, 2008)

Greg - I rarely find anything above 20 volts from a laptop - some printers go to 24 or more but at reduced current.
MPJA does have a 24 volt power adapter for $15 + shipping
http://www.mpja.com/mobile/24-Volt-Adapter-Power-Supply/products/571/ 
eBay has them as well.

I'll check voltage to the track soon - I am in the middle of some other things right now

dave


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## Greg Elmassian (Jan 3, 2008)

No big deal Dave, and maybe you can post the answer on LSC too, since I may be gone by the time you have some free time.

Best Regards,

Greg - 4 posts left


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## dbodnar (Jan 2, 2008)

Greg - just did a test with the small controller that I put in the wooden box - got the following

IN - 18.8 OUT - 18.7 ---- Compaq laptop supply
IN - 23.5 OUT - 23.37 ---- Bench power supply

I was quite surprised - all measurements done with a good quality bench meter - link below

dave

http://www.newark.com/tenma/72-1020/multimeter-digital-bench-4-1-2/dp/74M7699


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## Greg Elmassian (Jan 3, 2008)

That's very surprising, must be FETs in the output of the controller.

Great! A nice recommendation for that controller for sure. I was worried when I saw the heat sinks on it. With that low of an "on" resistance, I'm surprised about even having heat sinks in the first place!

Even at 15 amps, and doing a worst case of saying ALL the voltage drop is in a single output transistor, and worst casing the voltage drop to 0.13 volts, you still get under 2 watts. 

Well, 2 watts does need some dissipation.


Greg - 3 posts to go


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## Totalwrecker (Feb 26, 2009)

Will there be fireworks?


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## toddalin (Jan 4, 2008)

Totalwrecker said:


> Will there be fireworks?



Total implosion I understand.


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