# Cutting back a 24v power supply?



## paintjockey (Jan 3, 2008)

I have a 24v power supply. I work for a sign copany part time and came across a 120volt(AC) in 24volt DC out 5A power supply for led lighting. It's for closed outdoor locations. It was a retro fit so it is virtually brand new. I want to use it for the lighting on my layout. My problem is that i need to down grade it to 12v. Is there an easy way to do this? It has no manual control for voltage so that isn't an option. 
Thanks-Terry


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## dbodnar (Jan 2, 2008)

Terry - I wouldn't bother - keep it around for future use with your trains and find another power supply for the lighting. Some types of DC power supplies can be modified to provide a lower voltage but it can cause problems, too - 

The best way to get 12 volts DC is to salvage a computer power supply from an old PC - they put out 12 volts, 5 volts and a variety of other voltages - the 12 volt side of the supply is frequently rated at well over the 5 amps you have on your 24 volt supply. There are any number of articles on the Internet about reusing these supplies - Here is one to get you started: 

http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply 

dave


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## chooch (Jan 2, 2008)

Terry, 
You could always wire two 12V lights in series. There are some issues doing this, but it will work. 








By wiring the lights in series, 12-volt lights will operate with a 24-volt system. The diagram above shows two 12 volt batteries. Just substitute your 24V power supply + / - in their place. The issue with this is that if one bulb fails, both in the series will stop working. Not a bad trade I would think if you wire them so they are easy to replace when needed. 
Nothing extra to buy, and not losing much of your power to heat loss using a voltage regulator. Good luck.


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## altterrain (Jan 2, 2008)

http://www.bakatronics.com/shop/item.aspx?itemid=444


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## John J (Dec 29, 2007)

You could always go to Radio Shack and get a 12 volt regulator. Mount it to a heat sink. 

You might have to watch how much you put on it. But then again you just add two or three regulators. 

Depends on how much you got and how much the power supply will handel


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## fcwrr (Jan 14, 2008)

Terry: Install a regullar wall dimmer (the kind with the knob) in the 120 volt supply. Use a volt meter and turn the dimmer up to the 12 volts or what ever you want. I've done this with the garden lighting systems (Malibu) to dim down the lights in my railroad. You can use the various lights available for garden/outdooor lighting. Most of them are 12 volts. When dimmed down they really look great in buildings, etc. 

FCWRR Ralph


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## paintjockey (Jan 3, 2008)

Some good simple ideas i never thought of, thanks! I just came across another supply today this is a 12v out power supply, but sadly it has some health problems. At any rate all i wanna do is light up a few buildings and in the future maybe a street light or twelve. I'll give this a shot and report back. 
Thanks again, 
Terry


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## Dan Pierce (Jan 2, 2008)

A computer type of supply will not work on a dimmer. 

I agree that the 24 volt supply shpould be reserved for powering trains, and just get the Malibu type of transformer for the outdoor lights.


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## paintjockey (Jan 3, 2008)

At the moment, I think Mrs. paintjockey would be a bit peeved if i took the power supply out of the computer. Since my power source was free I'm gonna do a few tests with it, that way if i ruin it, it really won't matter.


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## Bill Swindell (Jan 2, 2008)

If you are just using this to power light bulbs, you can simply use a 12v transformer. You don't need a DC power supply. Take a look at this link: 

http://www.allelectronics.com/cgi-bin/item/TX-125/790500/12_V.C.T._%22#64;_5_AMP_POWER_TRANSFORMER_.html


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## paintjockey (Jan 3, 2008)

I guess my point was that this thing was free and if there was a cheap (next to free) easy way to downgrade it. That 12v power supply may be the answer though. 
Thanks 
Terry


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## Torby (Jan 2, 2008)

Yea. Save that nice supply for running trains and get something cheap for lighting your lights. Otherwise, run your light bulbs in pairs like Chooch suggests.


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## Skip (Jan 2, 2008)

12v switching industrial power supplies are pretty common on Ebay and go quite cheap. They'll need case for outside and switch and cord (or, as I did on my 24v one I use for track power: "switched cord"). Many have voltage trim pots to adjust the voltage. Many of these are made in Taiwan, but are of good quality. Many of the taiwanese ones are oem-branded by US companies. You can also by 12v wall warts in fairly good amp ratings at any electronics supply/surplus store.


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## Guest (May 7, 2008)

anybody of you thought about this? 
the transformers, that come with modern telephones. these telephones don't serve for eternity. the transformers, (most often 9V DC) are good to hook on two or three flashlightbulbs. or a couple of christmaslights.


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## Torby (Jan 2, 2008)

I keep those for misc projects


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