ATX Power Supply Conversion Quiz

Discussion in 'The Projects Forum' started by Farlander, Jan 6, 2009.

  1. Farlander

    Thread Starter Active Member

    Oct 14, 2008
    I wanted to check something before soldering. You can see where I soldered the 10W resistor between the 5V red and 0V black. This sits nicely behind the heat sink, suspended by the wires. For the connector ends, I want to use ring terminals but have to find some. Any safe/cheap way to tie these all together in some fashion that facilitates good connections?

    On the right are grey, green, black, and orange. The green and black connect to the power and ground of the LED toggle switch? The orange and the grey should be connected in order to allow the unit to run properly. Could the orange/grey be connected to the center terminal of the switch?

    Thnx in advance
  2. doug3460

    Active Member

    Oct 19, 2008
    Hi Farlander -

    I'm not an expert, but thought I'd try to help.:rolleyes:

    Farlander wrote:
    You're using an automotive LED toggle switch that's designed for 12V systems. A couple threads below your post you'll find mine & the group's discussion on some quirks in my schematic. Foremost is the green line is not 12V. I don't think even connecting the green & ground to your switch will allow the unit to turn on - & if it does, the led propably won't light. Check it & see.

    The other thing is, the GRAY wire is a POST wire (Power On Self Test). It's a 5V wire, running 10mA max. The PS will run without it connected to anything - it's there to send a signal to the motherboard in the computer that the PS has past it's check so it's safe to boot. In other words - it's function is to protect the motherboard, nothing else.

    Combining Gray & Orange would give you 5V+3.3V=8.3V, so I suppose you could put them together to run to another set of binding posts, but I would wonder why since it's an odd voltage. Hooking any supply line to the "accessory" terminal on your switch would probably be a bad thing, since the switch wants to send power to an accessory, not receive it.

    You might want to check for your "sense wire" to tie to the appropriate supply wire. The sense wire(s) are 22 AWG, while the supplies are 16-18AWG. Sense wires are usually colored the same as the supply line they are for, except the 3.3V one may be BROWN or ORANGE. Regardless, whichever sense wire(s) you have need to be tied to it's supply or the unit
    won't latch on.

    You might want to check Instructables for ATX supplies. One in particular there by "mat_the_w" seems to be a popular conversion. He shows how to connect an unlit toggle switch which he ties into the GRAY wire to light an LED.

    Good luck.
  3. Farlander

    Thread Starter Active Member

    Oct 14, 2008
    Thanks for the help. Currently I have green (power) and black (ground) connected to the LED switch. The switch lights up (although dim) and the unit powers on.

    The grey wire outputs about 0.2v rms... and seemingly does not need to be connected to anything for the unit to work.
  4. SgtWookie


    Jul 17, 2007
    You don't need the grey connected to anything. It's simply a limited-current 5v "Power Good" signal; it comes up when the power supply has turned on in the correct sequence.

    Saw in another thread that you'd tried connecting it to 3.3v; I have no clue why you would try that. You probably fried whatever it's connected to.

    Back to basics:
    All you need to get the thing going is to connect the green wire to GND via a switch, and have a load on the 5v supply. A single 10 Ohm power resistor might be enough. If your 12v supply regulation is poor, add another 10 Ohm power resistor across the 5v supply.

    If you're looking for binding posts/banana jacks, Radio Shack sells a pack of four (two red, two black) for around $4.