Using a PC Power Supply instead of Wall Warts

Binding posts: Here is Radio Shack's selection of binding posts.

Putting a pot inline with the output of the power supply is not a good idea. The pot will have to carry the full current being used by whatever device is connected to the power supply. Small pots are not designed to carry much current.

A typical small pot is good for 0.5W. At 12V, this works out to 0.04A. Practically any load you place on the power supply will draw more current than that.

- Jeff

 

Thanks for the link. Even the guy at Radio Shack couldn't find them online and we did look in the audio section were there suppose to be in all three I've been in.

And thanks for the advice. I don't know the rating of either pot. They are from a big old junk box.

 

That's funny that the RS guy could not find them. All I did was go to the Radio Shack web site and search for binding post. Not exactly rocket science.

Seriously, don't try to use those pots. That's not how you make a variable power supply.

- Jeff

 

I thought about the pots because I have an old book that show to use them in different ways and that was one of them. Also on the older cars that's what is used to dim the dash lights. Don't know about the new ones.
I'll get the thing work first and try setting up separately for safety. Or just use the cheapy LifeLike or the Railpower 1370 train controllers I have laying here. With those I can even get negative 15 volts DC and AC.
This is just something to keep me going on almost no income.

 

Please, if you are going to use a PC supply on your RR, make sure you fuse it. Some of these supplies can put out 20 or so amps at 5 or 12 volts and that is more than enough to fry components, burn wires and start fires. And keep the size of the fuse low, like 3-4 amps depending upon your need.

And to Flash' question, yes you can kill yourself inside the box if it is plugged in. Sure its only 110 volts. . .

And yes, I am using one of them on my layout to power my CTI-electronics components. I also us a 12 volt fan out of a computer with a wall wart or the pc supply to power a cooling fan that keeps my DCC system well ventilated. Both my Lenz and my NCE system boxes run hot. My layout DCC current drain is always from 2.5 -3.5 amps. (I have another one of those computer fans with a 9 volt wall wart sitting behind one of my old laptops that gets too hot and another one that blows on my TMobile VOIP and Comcast routers. 9 volts slows the fans a mite and in the case of the laptop, reduces the noise level.

Just my 2 cents

Joe Daddy

 

The voltages inside a PC power supply may be much higher than the "mains" or "house" voltage. Because of the way switch mode power supplies operate, a PC power supply may produce internal voltages of 300V or more.

They are pretty easy to convert to general use, but please respect the fact that lethal voltages reside inside the box.

- Jeff

 

It is not the voltage that is the issue, it is the current. About 50 ma, 0.050 amps is enough to stop the heart.
I have a plugin device that I use to check GFI protected outlets that trips them a 5 ma, 0.005 amps.

Having worked with electricity for forty years. it is known among electricians that 110 volts is the most dangerous voltage because most people "think" it is to low to cause any problems.
Many a person has been killed by a electric drill with a metal case that did not have a third ground pin on the plug or the pin was cut off because it was an “inconvenience”.


You might get away using a pot for a few light bulbs. Most “standard” pots in my thirty year old junk box are 2 watt and many from RS are about the same.


Rich

 

Hello all.

From time to time I see this conversion preformed to a PC power supply and a few years back I put up a how-to page to show people how to do the conversion "without" opening the case. If you would like to check my how-to please follow this link. Hobby Power Supply