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Author Topic: My hacked ATX PSU  (Read 3369 times)
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Mods.... I won't take offence if you want to move this thread.

Hi all,

Instructables has a number of examples of hacked ATX PSUs, such as this one which is quite fancy, what with the fuses and switches and LEDs.

I took a simpler route and thought you might like to read about it and see a pic....

I decided to dispense with a switch and so I just grounded the green wire inside: as long as the mains is on, there's DC. Then I took a bunch of wires out through various existing holes in the case, and wired them to a connector strip which you can see on top of the box. First 4 from left are black ground wires invisible in the pic against the case, followed by 2x 3v3 (orange), 4x 5v (red) and 2x 12v (yellow).

There's a dedicated Arduino USB-B power plug as you can see: that's hardwired inside to a red and black 5v / ground pair. Although I cut the surplus wires off, I kept a couple of reds and blacks coiled neatly in the case for future use- might end up with 2x Arduinos or maybe another model with a different USB plug.

Green thing on the front is a 10W power resistor- without this there's no load to switch the supply on; it's mounted in front of the fan for cooling.

That's basically it: works a treat.


* atx psu hack.jpg (172.13 KB, 759x775 - viewed 217 times.)
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Something only an Arduino enthusiast could love.. It looks a proper monster... Fuses are there to protect the innocent... By leaving them out you are proclaiming that you are... USE THE FUSES, Jim... THEY do serve a purpose... Fire protection.
I'll bet you are relying on the internal fuse... What size is it?.
One more thought and that is to place a switch in the start wire, that way you can shut down the power without being so hard on the primary rectifier as it won't be a full start every time you power up the supply. Instead you will be enabling the output..

Bob
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Thanks for sharing!
You could have +12V feed a 7805 to take advantage of its limiting (1 amp short cct.) and o/p this on the terminal block as well.

Your most expensive component will protect your fuse.  smiley-wink
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The way you have it in your schematic isn't the same as how you have it wired up! That goes for me too.

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I think you should have fuses. During a short circuit, these supplies can source many tens of amps. Not too good.
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Ok!.... I'm getting the message on the fuses, thanks.
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I use these PSU's for everything some of the current one's have more than 3 or 4 useable voltages i wanted to use one for my Arduino test lab/rig i figured a PSU would have to be stable for a motherboard to function correctly, Anyway i'm dusting of one now to use for a better power supply, just wondering besides proper fusing is their anything else i should be using to ensure i have clean/safe power for my projects ?
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I take a different approach. Rather than cutting the wires and driving into the case, I get a 20/24pin atx connector and plug it into the power supply. I connect plugs or termianals to the other end of my connector.

Very flexible and minimum amount of work.
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I take a different approach. Rather than cutting the wires and driving into the case, I get a 20/24pin atx connector and plug it into the power supply. I connect plugs or termianals to the other end of my connector.

Very flexible and minimum amount of work.
And for the lazy like me, here's three I found earlier.
http://www.phenoptix.com/products/dangerous-prototypes-atx-breakout-board-bench-power-supply
http://www.robotshop.com/eu/cytron-atx-power-supply-breakout-board-right-angle.html
http://www.robotshop.com/eu/sfe-benchtop-power-board-kit-5.html
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Quote
here's three I found earlier.

those are even better: plug-n-play.

Those atx power connectors are fairly difficult to find.
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@ *dhenry* Why would you say that ?. There is one on every trashed mother board.. Going back quite a ways. Good re-purposing of junk?.

Bob
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Quote
here's three I found earlier.

those are even better: plug-n-play.

Those atx power connectors are fairly difficult to find.


Well I have a handful laying around from stripping dead ATX motherboards for usable parts.
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I use these PSU's for everything some of the current one's have more than 3 or 4 useable voltages i wanted to use one for my Arduino test lab/rig i figured a PSU would have to be stable for a motherboard to function correctly, Anyway i'm dusting of one now to use for a better power supply, just wondering besides proper fusing is their anything else i should be using to ensure i have clean/safe power for my projects ?

Use a decent quality supply (avoid companies like Deer, L&C and most other no name brands like the plague). You don't want a noisy (electrically) PSU killing your projects (let alone these have a tendency to die catastophically).

Have a base load on all of the rails. PSU's do NOT like being cross-loaded in general (this means lots of amps on one rail and virtually none on another). Heavy loading on one rail can cause one of the others to drift up to a volt from their listed voltage. This is the purpose of the large resistor in Jimbo's design. It provides a base load to help prevent the effects of cross-loading.
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A good computer PSU is close to a $100 bucks.
For a little more money, you can have one of this. $105 (LINEAR PSU... not switching!)
Constant voltage, constant current, programmable, 5Amps, USB connection for monitoring/remote

It looks like the old problem that EEVblog found 6 mos. ago are now fixed.
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Well Yeah the power supply IS very Nice... If I had the money for both the supply and the shipping..
But a re purposed Motherboard for the connector and the power supply from the case that the Mo-board came out of can usually be had for free.. So about $10.00 and a few hours time would get a good fixed but multiple output voltage supply  which was the thread's original subject..For that matter a 0 to 2 A,  .9 to 20 V Switcher type circuit assy can be had for about $12.00 from China... with built in CC/CV controls (10T pots PCB Mtg) and either switch selectable current  or voltage monitoring. Not 5A... Well Not $105.00 either, even with the modifications required to make it look professional in appearance and plug into the mains wiring Too (It takes a discarded Laptop PSU  and about $25.00 in parts, 2 pots and the switches, etc)... Also to be found @ any Radio Shack.
Seriously that looks perfect for a 3V3, 5 and 12 V PSU with great current capacity and a better price AND using ALL NEW Parts can done very nicely for about $60 - $70.00... On the cheap... FREE. there are also many variant's on the idea of free.

Bob
{Edit Added link to part source}
You can get the part here among several..
http://www.ebay.com/itm/170929163665?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649
And free shipping Too, mine took 9 day's to arrive
« Last Edit: January 15, 2013, 07:34:53 pm by Docedison » Logged

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I have bought old but decent quality computer PSUs for $10 at the thrift store.

You may need a load resistor that draws atleast ~1 amp on the 5v line at all times to maintain good voltage regulation on all lines.
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Avoid throwing electronics out as you or someone else might need them for parts or use.
Solid state rectifiers are the only REAL rectifiers.
Resistors for LEDS!

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