I need a cheap benchtop power supply

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Rakinos

[H]ard|Gawd
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I've gotten tired of ghetto rigging old psu's to test various circuits, so I'm looking for a cheap benchtop variable power supply that supplies around 0-25 volts @ 1-4 amps. Display is optional, but would be nice (I can always just hook my multimeter to it). As for cost, 40 bucks would be my max, 25 is preferable. I know I can get that good of quality/stability for that price, but I'm not going to be doing anything would need that stable of a supply.
 
the only way you are going to get something that doesn't 100% suck for that price is second hand off craigslist or ebay.
Rakinos said:
I've gotten tired of ghetto rigging old psu's to test various circuits, so I'm looking for a cheap benchtop variable power supply that supplies around 0-25 volts @ 1-4 amps. Display is optional, but would be nice (I can always just hook my multimeter to it). As for cost, 40 bucks would be my max, 25 is preferable. I know I can get that good of quality/stability for that price, but I'm not going to be doing anything would need that stable of a supply.
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My first inclination is to get one of these:

http://www.apogeekits.com/power_supplies.htm

There's about 10,000 different brand names for this exact power supply - they're cheap chinese crap, but they're very reliable. Look around eBay, etc. to see if you can get a better deal on one.

If you come across one, *DON'T* buy a Xantrex power supply. Blown up too many of them.
 
For cheap you could base on a 24V SMPS brick adaptor, here's one that will deliver 2.5A with short circuit and over voltage protection built-in, and more powerful models are available if you feel 4A is needed.

For variable output add an LM338 5A regulator on the back end but remember at high current and low output voltage you're creating a lot of waste heat - massive heat sink required, or, cheaper, a fan-cooled CPU sink.
 
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Yeah, I looked up variacs, but thats definitely not what I'm looking for. So far, the link you posted gee, seems the most promising, although a bit more than I would like to spend. I just need to save up a bit more money, right now photography and computers are eating up too much of my hobby budget ;)/
 
Rakinos said:
Yeah, I looked up variacs, but thats definitely not what I'm looking for. So far, the link you posted gee, seems the most promising, although a bit more than I would like to spend. I just need to save up a bit more money, right now photography and computers are eating up too much of my hobby budget ;)
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Forgive me, you did not state this had to be an AC unit. Bench top power supply could mean
many things. And you did say an old PSU was being used currently. Anyway, best of luck.
 
I am indeed looking for a DC unit, not AC, but Variacs put out an AC current.
 
Sure they put out AC, but rectifiers are cheap and effective. Throw a capacitor in parallel with the output and you have a variable *un-regulated* power supply.
 
Adrenaline said:
Sure they put out AC, but rectifiers are cheap and effective. Throw a capacitor in parallel with the output and you have a variable *un-regulated* power supply.
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Variacs are autotransformers - they put out *non-isolated* AC. You still need a second transformer after the variac for AC isolation, before your rectifier, or you'll end up with a "12V" (or whatever) output that you can electrocute yourself with.

And again, the output is unregulated. Which is fine for running a wide input range fan, a motor, a car audio amp or something - but again, you won't want to run a 5V microcontroller off such a supply.
 
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