Bench Power Supplies?

[Bergo]

I don't beleive I'm alone in my desire to have a good reliable bench power supply. I'm on the fence about whether to build, buy, or hack. Does anyone have experience, or opinions?
I'm thinking I"ll do one of three things:

• $100-$200 - Buy a used HP/Agilent 36xx bench power supply, something like a 3611 or 3617 that wil do 0-60V and 0-1A.
  $Free (almost) - Hack an ATX power supply by adding a resistor as load, a switch, power indicator lamp, and some binding posts for 12V and 5V
  $$$? - Try to build a switch mode power supply from scratch

Any opinions?

[rsilk]

Don't try to build a switching supply from scratch, it'll drive you insane. James, Tony and I were designing a big linear supply for a while. We've been looking for a good excuse to get back to it. I think we were looking at about $100 to build, and it would have (if I recall), 2 independent supplies, each with a variable voltage and current and digital metering for voltage and current.

[Bergo]

leaning towards picking up an HP/Agilent off of Ebay at the moment to be honest. I'm using an ATX compliant server power supply at the moment. it's actually a dual/redundant Enermax power supply, about 750watts, extremely overkill.

[ADDandy]

i bought one of these it seems to do the trick. gives you terminal posts, fuses and all that stuff. most people (like us) have an extra ATX power supply lying around anyways.

[Tetragrammatron]

I would love to have my own bench power supply instead of constantly cannibalizing various wall plug power cords from old electronics. Although I'm sure its easier to buy, I'd love to hack an old ATX power supply instead of buying. Building from scratch would be even more fun, but may be out of my realm. I'm sure if Ryan and Tony and James were in on it though, us lowly computer science types could be assisted in the making of it

[rsilk]

I'm just a lowly CS type!

We were planning on having it digitally controlled by a micro, which means lots of fun stuff could be done in software. Could have a PC interface to control the voltage, or do voltage sweeps, or log current draw over time, or just about anything. Lots of CSish stuff to do.

[Bergo]

Tempted to pull the trigger on this:

http://cgi.ebay.ca/HP-E3620A-Dual-Outpu ... 53e5bc9384

[Tetragrammatron]

How long does it take to hack an ATX power supply into a bench one? Could we run a class on it and everyone brings their own crummy ATX power supply (or maybe we could get a stash of old junker ones from a computer repair shop? *cough* OTV *cough*

[rsilk]

It takes about 3 seconds to hack an ATX supply into a sort-of bench supply -- just need to put a jumper across two of the pins on the motherboard connector. Then you can either hack one of the molex connectors off, or cut one of those sata adapters or Y cables in half. That'll get you 12v and 5v. If you want any of the other voltages you'll need to poke at the motherboard connector.

If the supplies are old busted junkers, they probably won't work terribly well, though

[Tetragrammatron]

Perhaps we could come up with an in house solution that makes it a little classier/nicer looking and hold a class on it.

Can an ATX power supply be made to supply variable voltage?