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I got a 750W (12VDC, 62.5A) power supply (I don't have it with me right now so I can't remember the model) from a old server and I was thinking on using it to create a lab bench power supply. My question is if it's worth it. I don't have any power supply and I can't afford spending much money on one. I'm a beginner in electronics so it would also be a project to get some experience from. I was thinking on using some components to have some fixed voltage levels and also a adjustable one. I would like if someone could give me some advices on this.

The components I was thinking of are: 3.3V - LM317 (1.5A max) and other regulator for more max current. 5V - LM7805 or LM317 (both 1.5A max) 12V - Directly from the power supply

Adjustable: LTC3780 (1-30V) (10A), using a display to show voltage and current and a few potentiometers.

Is this worth the money and time? Both for usability and experience.

Also, is it possible to have both positive and negative voltages?

Thanks in advance!

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  • \$\begingroup\$ 12V is kind of low, and 62.5A is fairly unwieldly. I'd stick to using it as a fixed 12V/5V/3.3V supply than converting it into a variable bench supply. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Jun 16, 2016 at 19:00
  • \$\begingroup\$ You can find many threads on conversion of server power supplies for hobby use on various RC hobby forums, e.g. this thread on the Dell DPS-600 on RCGroups. They often include tips on parallel and serial use, fan mods to reduce noise, etc. \$\endgroup\$
    – Bill Dubuque
    Jun 16, 2016 at 19:24
  • \$\begingroup\$ So should I just get the fixed outputs? And forget about the variable voltage output, even if just from 0 to 12V? Thanks, I'll have a look on that link! \$\endgroup\$
    – José Coelho
    Jun 16, 2016 at 21:18
  • \$\begingroup\$ The most important difference between a lab supply and just a normal power supply is a current limit. It doesn't necessarily have to be adjustable, but it has to act reasonably nice at the point of the limit. That's what you should likely want to focus on when converting it. \$\endgroup\$
    – pipe
    Jun 17, 2016 at 10:00
  • \$\begingroup\$ And by "current limit" I don't mean the integrated "hard limit" in the LM317 - it's there to protect the LM317, not your project. \$\endgroup\$
    – pipe
    Jun 17, 2016 at 10:02

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Your main problem will be the overwhelming noise. Those things are loud. Loud noise means you're not going to want to use it, and that's a crappy bench supply.

Other than that, it's certainly a decent project, although I would start slow and forget about an adjustable 1-30V and a negative voltage. Increasing the voltage or making it negative is a whole different project involving step-up and inverting switch regulators, none of which you want to handle right now as a beginner.

Whatever you do, make sure you can use another power source, so you can hook it up to something less loud, maybe a second hand laptop supply.

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  • \$\begingroup\$ I had it working for a bit (to see if actually works outside the server itself), it makes some noise but I think it's pretty tolerable. I don't intend on doing all the steps at once, it's kind of a steps project. I'm first planning on having the fixed voltages, then move to the variable voltage and then the negative. So you're suggesting to don't use that power supply but instead a old laptop/printer... supply? \$\endgroup\$
    – José Coelho
    Jun 16, 2016 at 21:24
  • \$\begingroup\$ Depending on the voltage and current you want, "wall wart" type power supplies may be a reasonable solution. They are available in a range of voltages and currents (and you can, of course, follow them with another voltage regulator if you want a lower voltage.) \$\endgroup\$
    – Peter Bennett
    Jun 16, 2016 at 22:34
  • \$\begingroup\$ I have one of those already. I just thought it would be a good idea to make the power supply to get some experience and have a power supply since I don't have any. \$\endgroup\$
    – José Coelho
    Jun 19, 2016 at 22:49

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