PC Power Supply Help

Pat, You can use a PC supply. Yellow is plus 12 volts. You can use any black wire for return. One supply could power every switch machine on the NJHR layout if they used Tortoise machines. They draw about 5 ma when moving and maybe 16 ma when not (stall current of the motor). If your PC supply is an ATX type you will want to jumper the green wire on the 20 or 24 pin connector to one of the black wires to turn it on.

Pete

Pat,

If you google how to convert PC Power supply you will find all you need to know on how to convert the old PC power supplies. I did several with left over PC power supplies. It's quite simple and you get a decent supply for 5 and 12 VDC. To check your usage now connect your voltohmmeter in series with one side of the wallwart feed and set your meter to measure amps.

Pat, you can get the voltages from the main connector.  The pinouts for both are below, and you can get mating connectors by buying an ATX extension cable.  Note that the ATX1 and ATX2 supplies have the same pinout except for the extension at the bottom with the four extra pins.  Of course, you also have 5V and 12V on the disk power connectors.

You jumper the PS_ON# to COM to turn it on or off.

Note that some power supplies require a small load on either the 5V or the 12V supply output to properly regulate, and early ones wouldn't stay on without the load. 

I have a 24pin <-> 20pin ATX adapter cable that I can bring you if you wait a month.

Wow!

Thanks to all. 

John:

With the information you provided, I'll see if I can't make this work.  If I need the cable, I'll let you know.  Thanks for the generous offer.

My switch machines and all the related relays are now happily powered by the PC power supply.  The switch machines run a little faster and, more importantly, the Atlas non-derailing boards haven't failed to throw since I made the change.

Thanks again to all who offered assistance.

At work I needed 12V pronto, I took a PC Power supply, jumpered it on, and put either a 45ohm or 90 ohm resistor across the 5V and put it in the airflow of the fan of the PS.

Think there was some shrink sleeve or fiberglass sleeving in there some where to keep the power resistor from touching the case. A little quarter watt won't cut it.

Correct, it usually requires about an amp load to maintain proper regulation.  I think some of the newer power supplies will regulate without a load, but I know the older ones require the load.

John,

You are correct.  The newer ones do not need a load.  Also, server power supplies are cheap and will give you more amps than I think a O layout would ever use.  I use a lot of server supplies to charge RC batteries.

The weapon of choice these days is the HP DPS-1200FB. 

Nice article on how to here... http://www.rchelination.com/se...1200fb-power-supply/

Other server supplies work just as well.  http://www.ebay.com/sch/i.html...+supply&_sacat=0

Some convert easier than others.  Some have pins you can just tap off and not have to open it up.  Remember there are very large capacitors inside these things that can hurt you.

These are awesome just to have on the bench for a power source.

Before buying on online, check with your local recyclers. Our department alone recycles about a dozen desktops a month. No shortage of power supplies around here.

Pete

Yep, there's no reason to spend a lot of money on a PC power supply.  I know a number of people that have old PC's that they're wondering what to do with...

I would add, put a 2 or 3 amp fast blow (AGC 2or AGC3) fuse in the 12V (and 5V if used), just in case there was a short somewhere (Murphy, ya know)........

And if you add a diode or two (1N400x) in series with a +5V lead you can power alot of Miller Engineering signs or used in Woodland Scenic building displays, or use +5V straight out for street and house lighting.

Lots of power in a PC supply so might as well use it!!

One diode should do the trick.