I asked a question similiar to this a few weeks ago but I need further clarification of this, Should I separate the computer PS grounds (black wires) from the AC chassis ground? I would be leaving the metal chassis grounded but would place fiber coupler washers between the chassis mounting tabs and the power supply component board which removes the board ground from the chassis. On Rob Paisleys web site under power supplies he says to do this yet on other posts about using computer power supplies nothing is mentioned about doing this.
Secondly the PS has 2 +12 volt rails and I have cut off the heads of the leads and have no way of knowing which red wire goes to which rail. One is a 10 amp and the other rail is a 13 amp rail. Can I just combine all the red wires or do I have to separate them according to the rail they go to?
Bob D As long as you surface as many times as you dive you`ll be alive to read these posts.
NO, do NOT separate the ground wires from the power input ground or the case!
You should not be inside the power supply tinkering around unless you have extensive experience with electrical wiring and electronics -- you could wind up electocuting yourself.
The problem with trying to go by someone's advice such as the Paisley article you mention is that there are different types of power supplies and he may not have the same type that you're working on.
Charles I do have 50 years experience with electrical wiring both service & as a civilian BUT 0 experience in electronics, which is why I ask all these electronic questions. Paisley was talking about the same power supply as I was referring to. A regulated power supply. I would never go inside the case with the power on or inside the case with the power off until all the capacitors have lost their charge.As far as being electrocuted goes I know the feeling of being HUNG UP on both 120 volts and 277/480 volts and was fortunate enough both times to have a partner who knew what procedures to do in such a case but that was when I was young, dumb & reckless & thought I was invincible. I thought that as long as the case was grounded & I touched it and if there was a short to ground that would blow the CB . I would still like an answer to the second question
*cringes painfully*
Other than putting a simulated small load on the supply using a sand bar for the regulators, I would not do it. You are asking for trouble modifying a power supply with that many amps.
I mean I use one, but I kept my modifications to a minimum. If the supply is UL/CE listed, then chances are all the safety pieces are there and no other modifications are needed.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
You are going to have to open the case and trace the wires to their appropriate rails. Make sure it's unpluggedOn most of the computer power supplies I've converted, I saved two red, two yellows, and two black wires per rail. Blacks are all common, but having a pair for each rail lets you set the outputs up easier. The balance of the wires, I just cut out close to the board. I connected the pairs of each color together. These became my outputs and negative. I wouldn't worry too much about a UL listing. That was gone as soon as you cut the plugs off.
Martin Myers
Yeah, trace the wires.
Generally, I find that if someone has to ask this question, they probably should not be messing with the power supply. I am experienced with this stuff and I see no reason the mess with the wires. I just put a light load on the power supply and leave everything else alone. I use some barrier strips.
I use some of Rob's ideas. That is why he gives a warning for his projects.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Rich I just want to use a ATX supply and having read Robs statement "Do not connect the ACpower ground to the common of the Power Supply" made me ask this question because I get a 0 resistance reading when I measure between the AC ground & the PS ground. You being experienced tell me if this reading is correct and then I will let it go at that. Have you ever traced wires from a 2 rail +12 volt And +5 voly supply It is not easy. If I can just join the 2 rails together (the 2 + 5 volt outputs) under the +5v binding post and the wires from the 2 +12 volts rails under the +12 volt post let me know.
Thanks
subman...Should I separate the computer PS grounds (black wires) from the AC chassis ground? I would be leaving the metal chassis grounded but would place fiber coupler washers between the chassis mounting tabs and the power supply component board which removes the board ground from the chassis. On Rob Paisleys web site under power supplies he says to do this yet on other posts about using computer power supplies nothing is mentioned about doing this...
subman...Paisley was talking about the same power supply as I was referring to. A regulated power supply...
I'm mentioning this because I don't want anybody to think that Rob Paisley is giving out bad advice. I don't see anywhere on his site that he advises separating the power supply ground from the chassis ground on a power supply that has such a connection. In fact, on his "Circuit Commons" page he specifically says not to:
If a circuit has a direct connection to an EARTHED ground, it is there for safety of the user and the equipment. DO NOT break an EARTHED common connection for any reason.
On his "Power Supplies" page, he does show some circuits where he states "Do not connect the ground of the AC power to the common of the power supply," but these circuits are not indicative of what is in a PC power supply. Just because these are regulated power supply circuits and PC power supply circuits are regulated does not mean they are the same, there are several types of regulated power supply circuits.
CXS Robert thanks for your answer. I have found a good site wwwplaytool.com that answers the question about joining the +12volt outputs together. DON`T
subman CXS Robert thanks for your answer. I have found a good site wwwplaytool.com that answers the question about joining the +12volt outputs together. DON`T
That would only apply to one with multiple 12V 'rails'. Older power supplies didn't have this, and every 12V connection was commoned inside the power supply, as was every 5V connection. There are some newer ones that are also using a single massive 12V rail instead of multiple rails of around 20 amps each.
This is also indicated on the rating sticker on the side of the power supply. Do not combine rails.
There's really no need to go inside a computer power supply to modify it. Just get some matching molex connectors and put fuses, binding posts, and the load resistor on a small external perfboard, and plug in the power supply. Plus if the one you have dies, you can simply plug in another one. And do not just run one 12V or 5V bus - connect multiple terminal strips or binding posts, and fuse each one to a reasonable value like 1-1.5 amps. The full output of the computer supply is enough to weld with, you don't want this getting directly to your stuff without some sort of protection.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I would caution you on using an ATX supply for only 1 of the voltages. Most are designed to have loads on all the different voltages (+/- 5, +/- 12, 3.3, etc) and may not work correctly if you are only using one or 2 of them.
Some newer designs convert everything from the AC input to 12v, and then use a DC-DC transformer circuit to go from 12v to the rest. These should work fine, but for the price you'd pay, you are better off getting an actual 12v source.