Lab Power Supply

Here is a great power supply project. No, it isn’t just some simple case mod with binding posts. A lot of thought was put into this, plus a lot of disclaimers. I wouldn’t be too scared though, Andy Batts has got a lot of information covering most everything you need to know: Dell’s weird wiring, expected current, using a sandbar load, and not poking around inside while the thing is plugged in. I’m going to do this to a couple power supplys because it is sure to make future projects a lot easier.

[thanks momotarosan]

27 thoughts on “Lab Power Supply

  1. discharging capacitors don’t feel so chippery either.

    I always preferred to just stick wires into the molex connectors, but this is definately an improvement. I like the idea of hackaday posting enough hacks for a nicely hacked hacker lab.

  2. This is great. I have some old AT power supplies just sitting around. This would be a great use for them. Of course the mod will be a little differant with an AT power supply, but it gets me in the right direction.

  3. I’m already using an old PS for powering up stuff :) but this project is alot cleaner. Very nice.

    This has inspired me to use a variable VRM and an old DMM to make a tunable PS. If anyone has done this please post a URL!

  4. Warning!

    Altough the voltages are low, the power these supplies can deliver is enormous. A good 350 watt supply can output 5V with 10’s of amps.
    So what? You think…

    Imagine you are working on a breadboarded circuit containing a lot of logic chips. One 74LS00 has been miswired VCC to ground, and ground to VCC.
    When you reverse logic chips they become low ohmic resistors with a voltage drop (2 diode drops).
    Result, exploded chip, damaged breadboard, melted wires.
    This was a old AT 400W powersupply out of a server, it had a rating of 5V 30A. It didnt even shut off like it should do as it was just a heavy load to the powersupply.

    Fuse the connections with polyfuses set at 1amp. To prevent accident of this nature. They are cheap, and going to save you some parts someday.

  5. #8 first off you can use it to save money. These can retial for $50+ and have the same functionality. But you would USE it to power any gizmos and gadgets you are working on, I use one for powering radios.

    This is not a new story, I saw it in QST, an amateur radio magazine. It was called the ‘st louis switcher’ for whatever reason.

    here is a thread that has links to a lot of articles including the one from QST. An excellent mod.

  6. Ive done this to several psu’s ive found lying on the side of the road. They work great, I use one to run my Dynamite Peak Charger(you rc people out there know what im talkin about) when I am not at the races. Ive seen tutorials like this before, but this one is much more in depth.

    Thanx HAD keep en comin 8)

  7. What a great hack! I really like this idea because it provides a convenient ground connection for my anti static strap. Coincidently, I built something similar just a few weeks ago and I have a few suggestions from my experience:
    –This a great use for an old AT power supply instead of trashing it. The pinouts are a bit different but it’s easy to figure out with a voltmeter
    –The old AT power supplies typically have built in power switches which are convenient
    –FUSE EACH SUPPLY BUS – Fried electronics smell horrible, I know from experience.
    –Desolder the power supply connector from a dead floppy drive. The pins will fit into your breadboard nicely.

  8. I’ve used one of these for almost two years. I made it out of an old gateway pentium pro ps. The best thing about it is that although it puts out 20 amps at 5v, it shuts off instantly if there’s a short. For the instant shutoff alone it’s invaluable.

  9. this is for use in a lab enviornment? it says the voltage is about 5? im not sure what kind of ‘lab’ this is for, but when i buy lab grade power supplies usually the first spec i’m interested in is stability, and +,- .5v is not very good to say the least.

  10. Not a lab “grade” power supply but rather a power supply for tinkering and projects; think hobby lab. Besides lab power supplies easily cost >$100. This is just a simple hack to get some low level dc supplies; which could easily be extended to build a stable, accurate supply by adding a linear regulator. There are plenty of uses for a cheap PS like this.
    As to the fan it seems like it the power supply did not include an internal fan in its design.

  11. I’m trying to build an external SCSI case using an existing tower case. But without connected to tha mainboard of a PC, the power never turns on. I’m desperately looking for a tip to force the power supply to turn on. I just want it to supply the 12V to the many scsi drives.
    Is there a way to do this?

  12. I just finished building one of my own using a gateway 200 watt power supply. This tutorial guided me through pretty easily, but I did stumble at one point. It may sound stupid, but make sure that the posts you use DO NOT make electrical contact with the enclosure. I am sure glad that I had fuses on the lines. Now I just need to figure out how to make this thing look a little better. The posts are screwed into a piece of cardboard just sitting on the table.

  13. I’ve seen reference to this project before, but I do very few 5v projects. It would be great to get more output at 12v from one of these. I notice the average 250w PS usually supplies about 60w at +12v. Does anyone know of a way to sacrifice some of the other outputs to get greater 12v output.

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