Computer PSU’s are great for DIY projects! Power supply units adhering to the ATX standard will provide 5v, 12v and -12v, and usually lots of it! These PSU’s also include short circuit protection, so you dont have to worry about blowing up your power supply.
There are many examples of great ways to turn a regular ATX PSU into a powerful benchtop power supply, so I am not going to focus on that. Recently though, when scavenging som old computer equipment at work, I got my hands on a server PSU. The cool thing about this was its handy form-factor, and that it could deliver 47 amps of 12V power! That is quite a lot in my opinion, and should be great to power current hungry devices like stepper motors, solenoids, chargers etc.
The PSU I got hold of, have the following information on it:
- HP PS-2601-1C-LF
- HSTNS-PL09
- Part no.: 398713-001
- Spares no. : 405914-001
The output from the PSU are PCB traces meant for an edge connector. The PCB is two-sided, and both sides are shown in the pictures below.
The problem was that I could not find the pinout for this supply anywhere! According to the sticker, this PSU supplys 12V and 5VSB. The ATX standard defines 5VSB to be always on, as long as the mains is connected to the PSU. The 12V however, must be turned on, usually by grounding one of the other pins. By checing for conductivity, I found quickly that all 4 corners of the connector were connected to the protective earth. It was therefore reasonable that this was ground. Also, as the 5VSB is always on, it was easy to find, by plugging in the power supply, and measuring the voltage across ground and the other terminals. 5VSB proved to be the remaining large connector on the bottom side.
As the 12V terminal must supply 47A, I was certain that this had to be the largest terminal on the top side, as this had roughly the same surface area as the ground terminals combined. I could not measure 12V though.
On regular ATX supply’s, there is a green wire that must be connected to ground to enable the 5V, 12V and -12V outputs. I suspected it had to be the same for this. But it was not. After much trial and error, it proved to be necessary to ground 2 of the terminals to enable the 12V. This may have something to do with server PSU’s having an kill-pin in addition to the regular enable-pin.
Now, the two enable/kill pins were connected to a switch via 1K resistors. When the switch was closed, the resistors were grounded, and the PSU turned on. And 47 amps of pure electrical power was on the ready!
The short circuit protection was also tested, in the crudest way possible. The 12V was connected directly to ground, and the PSU turned of. Flipping the switch on and of again, started the PSU without any complaining. Nice feature!
Based on trial and error, the following pinout seems probable:
Enter The Geekcave 
was the resistors nessesary?
LikeLike
The resistors are cheap protection in case of a malfunction, but they are not really necessary. I recommend you use them. However, the value of the resistors is not imortant. Anything between 470R to 100k should work, I would guess.
LikeLike
Is it possible to separate ground and protective earth, to use it in a 24v setup?
LikeLike
Not to my knowledge, no.
LikeLike