ATX power supply to power gear - Page 1
Forum section: electronics / beginners

author: edy
author_rank: Super Contributor
timestamp: March 15, 2015, 08:33:40 pm
content: Hi everyone,Just a quick question as I have seen various options and not sure what is best. I have an ATX supply and want to use it to power some drives externally. I know about shorting green to black to give supply a sense for power-on. Also, I understand I need a load in it from the moment it powers up to function properly.I have a few questions. The ATX supply has a switch on the back, can I just short green to black permanently? Some people suggest using a switch to connect green-black. Why do I need another switch?Also, for creating a load, some suggest a 10 ohm 10/20 W power resistor shorting red to black. But others suggest using a small 12v bulb (what wattage would suffice?) which would double as an "on" indicator.Lastly, my understanding is there is a brown sense wire that I should join to an orange 3.3v to keep the supply on as well. I only need to join one orange and use the remaining ones to a binding post if I need 3.3v out?I'm getting my info from here:http://m.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-SupplyIs it safe to assume then that you can get all sorts of step voltage differences by joining almost any voltage wire to any other, as long as there is some load? And if the current is too high will the supply shut off or burn up?

author: george graves
author_rank: Super Contributor
timestamp: March 15, 2015, 08:58:38 pm
content: You don't need a separate switch, but some people find it handy.Maybe there is some ATX power supply spec for a minimum load, but weather it's followed is another thing. My guess is your "drives" will provide that load. And yes, most if not all power supplies will shut off you short them out.Plug them in and give it a shot.ATX power supplies make a poor bench supply IMHO. It becomes so handy to dial in a voltage, and see the current draw of your circuit. Not to mention limiting current. $150 will get you a korad KA3005P. Or you can go with something older - that's not a bad way to go either.

author: edy
author_rank: Super Contributor
timestamp: March 15, 2015, 09:02:08 pm
content: Ok, thanks. I'll give it a try. If my drive is plugged in that would be enough of a load. I'll just short the green and black and flip the switch. That should power up the drives. I'll short the sense lines as well to help with regulation.... Brown to orange for 3.3v, pink to red for 5v, and yellow to one of the thinner yellows for 12v, as far as I understand. Thanks.

author: edy
author_rank: Super Contributor
timestamp: March 15, 2015, 11:15:55 pm
content: Just a few photos... can't seem to find the brown wire. Will have to look up the specs for this one, and it is a 20 connector type.

author: miguelvp
author_rank: Super Contributor
timestamp: March 16, 2015, 01:16:16 am
content: Yes you can short the green wire with common black to turn the PS_ON, I leave a wire in there myself.QuoteSo on Version 2.0, which is what I have, it will be pin 16 shorted with pin 17 but any other COM can do other than 17. I added in red in the picture the pins I use. (16 & 17)Yours seems to be Version 1.0, so that means pins 14 with any COM for example 15, or in other words the green with any black one.I've been using one here and there and even if my wire is not permanent nor the most beautiful piece of wire it does the jobEdit: Strange enough, mine seems to have -5VDC (white wire) normally they are not connected as in yours.Edit: the brown wire you are looking for is grey on mine and on the diagram above.and from the link you supplied it says:QuoteBut mine doesn't need that to be connected to stay on, some modern ones I've heard that they will turn on, and later will turn off because of the Power OK (PWR_OK) not being fed. So unless yours behaves that way I wouldn't bother with the grey cable.Edit: thought I resized the image to 800x600 but I guess I didn't, so I fixed it.

author: Fat
author_rank: Regular Contributor
timestamp: March 16, 2015, 04:46:08 am
content: I use one on my bench for easy power. It works ok if you only want the standard volts. I find it a bit more trouble than it's worth, so I have a new lab supply on order. Once it comes the ATX will move to the back of the shelf.