Using Computer Power Supplies

Discussion in 'FAQs' started by steamhead, Jul 7, 2008.

  1. steamhead

    steamhead Active Member

    I've seen suggested here several times that computer power supplies work great for some applications in model RR'ing....But...

    I have a couple of supplies which I want to use for lighting the structures in my layout, but to my surprise I find that the packs don't turn on when they're not integrated into the computer. They turn on when you push the computer's ON button....

    So I need to know which of the many leads coming out of the power supply bridge the circuit that turns it on. There are 4 leads numbered 3,4,5 and 6, each with 4 wires (2 black, one yellow, one red) which seem to be power leads.

    So...., does anyone know which of these leads will turn the power supply on, and how I should "jump" them to do it..?

    Thanks for any help you can provide...:thumb:
  2. Bob W

    Bob W New Member

  3. WReid

    WReid Member

    I have used a few as power supplies for RC battery chargers with great results.

    To get the power supply to turn on without the computer if it is an ATX version you will need to find the green wire on the large plug that plugged into the computers motherboard. Once you find the green wire make a jumper and hook it to a black wire on the same plug. It should now turn on.

    Another thing you may want to do is hook up a light bulb ( 1154 or 1156 tailight bulb ) using a red power wire and a black ground wire. This places a load on the power supply and allows you to be able to pull the rated amps from it. In short if it is able to supply 12 volts at 8 amps from the +12 volt yellow wire ( black for ground wire ) the light bulb will let you do so. Without the light bulb it will supply a lot less and some will not even work without the load.

    I used to have a link in my favorites folder on converting them. If you do a google search for " Computer power supply as a battery charger " you will find a number of links on how to do it.

    Wayne Reid
  4. steamhead

    steamhead Active Member

    Thanks for the input, guys...I've checked out the links you provided, and the explanation given...Thought I had this licked....:mrgreen:

    My PS's don't have a green ground wire....!!!! All the stuff I've read refer to the green wire....I also ran across a note stating that older Dell PS's didn't follow the "industry standard" for color coding....:cry: can I tell which is the ground..??
  5. YmeBP

    YmeBP Member

  6. steamhead

    steamhead Active Member

    Hi YmeBP.....Thanks for the links. I'd already latched onto a couple of similar links and figured things out. I've already converted a couple, and just finished installing one for my lights..!!! It's a snap - once you know how....:mrgreen:
  7. YmeBP

    YmeBP Member

    I'd actually be interested in seeing some photo's and maybe a quick (2 sentences) of how you did it. Right now i'm using the toy train transformers to run my switches and lights and i'm not so sure that is the best idea. I have to have multples in parallel to get the amperage i need.
  8. steamhead

    steamhead Active Member

    YmeBP....Here's the link that gave me the info I needed:

    In short...determine which color wire is the ON/OFF controller. Apparently on most non-Dell (older versions) it is a green wire that's bundled into the principal harness that plugs into the motherboard. Place a SPST (On/Off) switch between this wire and any black wire. Also place a 10 watt/10 ohm resistor (sandbar) between any red wire, and any black wire.
    Cut off all other wires that will essentially be useless to reduce the mess. I cut mine off about an 1" off the PC board. Remember to leave at least one yellow wire and one black wire which will be your 12v. output.
    I didn't use any binding posts as my units will be "dedicated" for one function only.
    Hope this helps....If you've got any questions...just holler..!!

    P.D. If you've got older Dell power supplies, the wire you want to use on the ON/OFF switch is gray instead of green....

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