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Converting a computer ATX power supply to a really useful lab power supply
by abizar on December 15, 2007
Table of Contents
intro: Converting a computer ATX power supply to a really useful lab power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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step 1: Harvesting the ATX power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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step 2: Preparing the ATX power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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step 3: Drill holes for attaching binding posts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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step 4: Attach binding posts and start wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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step 5: Connecting the wires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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step 6: Wrapping up the connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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step 7: Testing the power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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step 8: Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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http://www.instructables.com/id/Converting-a-computer-ATX-power-supply-to-a-really/
intro: Converting a computer ATX power supply to a really useful lab power supply
Computer power supplies cost around US$15,but lab power supplies can run you $100 or more! By converting the cheap (free) ATX power supplies that can be found in
any discarded computer, you can get a phenomenal lab power supply with huge current outputs, short circuit protection, and very tight voltage regulation.
In this instructable I will show you how to quickly convert one of those many computer power supplies into something that you can use to power your electronics projects,
for electroplating, for electroetching, for heating wires for foam cutting, etc.
The voltages that can be output by this unit are 24v (+12, -12), 17v (+5, -12), 12v (+12, 0), 10v (+5, -5), 7v (+12, +5), 5v (+5, 0) which should be sufficient for most
electrical testing. Many ATX power supplies with a 24-pin connector for motherboards will not supply the -5V lead. Look for ATX power supplies with a 20-pin connector,
a 20+4-pin connector, or an AT power supply if you need -5V.
PLEASE, YOU ARE WORKING WITH AC VOLTAGE!!! IF YOU ARE NOT SURE OF WHAT YOU ARE DOING - DO NOT ATTEMPT THIS.
These instructions were originally posted by me on http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply
step 1: Harvesting the ATX power supply
1) Unplug the power cord from the back of the computer. "Harvest" a power supply from a computer by opening up the case of the computer, locating the gray box that is
the power supply unit, tracing the wires from the power supply to the boards and devices and disconnecting all the cables by unplugging them.
2) Remove the screws (typically 4) that attach the power supply to the computer case and remove the power supply.
3) Discharge the power supply by either letting it sit unconnected for a few days, or by attaching a 10 ohm resistor between a black and red wire (from the power cables
on the output side). Using a resistor will only take a few seconds to fully discharge the power supply.
4) Gather the parts you need: binding posts (terminals), a LED with a current-limiting resistor, a switch (optional), a power resistor (10 ohm, 10W or greater wattage, see
Tips), and heat shrink tubing.
http://www.instructables.com/id/Converting-a-computer-ATX-power-supply-to-a-really/
step 2: Preparing the ATX power supply
5) Cut off the connectors (leave a few inches of wire on the connectors so that you can use them later on for other projects).
6) Open up the power supply unit by removing the screws connecting the top and the bottom of the PSU case.
7) Bundle wires of the same colors together. The color code for the wires is: Red = +5V, Black = Ground (0V), White = -5V, Yellow = +12V, Blue = -12V, Orange = +3.3V,
Purple = +5V Standby, Gray = power is on (output), and Green = Turn DC on (input).
step 3: Drill holes for attaching binding posts
8) Drill holes in a free area of the power supply case by marking the center of the holes with a nail and a tap from the hammer. Use a Dremel to drill the starting holes
followed by a hand reamer to enlarge the holes until they are the right size by test fitting the binding posts. Also, drill holes for the power ON LED and a Power switch.
step 4: Attach binding posts and start wiring
9) Screw the binding posts into their corresponding holes and attach the nut on the back.
http://www.instructables.com/id/Converting-a-computer-ATX-power-supply-to-a-really/
step 5: Connecting the wires
10) Connect one of the red wires to the power resistor.
11) All the remaining red wires to the red binding posts.
12) Connect one of the black wires to the other end of the power resistor.
13) One black wire to a resistor (330 ohm) attached to the anode of the LED(see the next image)
14) One black wire to the DC-On switch
15) All the remaining black wires to the black binding post.
16) Connect the white to the -5V binding post, yellow to the +12V binding post, the blue to the -12V binding post, the gray to the cathode of the LED.
Note that most power supplies have either a mauve or brown wire to represent "power good"/"power ok". Check the ATX plug (the plug with many connections) to
see if there is a small mauve or bown wire plugged into the same hole as an orange wire (+3.3V) or a red wire (+5V). If the small wire is connected to the orange
in the ATX plug then do the same, hook these two together. If it is connected to the red, then hook it to the red wire. This wire must be connected to either an
orange wire (+3.3V) or a red wire (+5V) for the power supply to function. When in doubt, try the lower voltage first (+3.3V).
step 6: Wrapping up the connections
17) Connect the green wire to the other terminal on the switch.
18) Make sure that the soldered ends are insulated in heatshrink tubing.
19) Organize the wires with a electrical tape or zip-ties.
20) Check for loose connections by gently tugging on the wires.
21) Inspect for bare wire, and cover it to prevent a short circuit.
22) Put a drop of super-glue to stick the LED to its hole.
23) Put the power supply cover back on.
http://www.instructables.com/id/Converting-a-computer-ATX-power-supply-to-a-really/
step 7: Testing the power supply
24) Plug the power cord into the back and into an AC socket.
25) Flip the main switch on the PSU (on the back). The fan will come on.
26) Check to see if the LED light comes on. If it has not, then power up by flipping the switch you placed on the front.
27) Plug in a 12V bulb into the different sockets to see if the PSU works, also check with a digital voltmeter. It should look good and work like a charm!
step 8: Troubleshooting
# If you are not sure of the power supply, test it in the computer before you harvest. Does the computer power on? Does the PSU fan come on? You can place your
voltmeter leads into an extra plug (for disk drives). It should read close to 5V (between red and black wires). A supply that you have pulled may look dead because it does
not have a load on its outputs and the enable output may not be grounded (green wire).
# If the LED light does not come on, check to see if the fan has come on. If the fan in the power supply is on, then the LED may have been wired wrong (the positive and
negative leads of the LED may have been switched). Open the power supply case and flip the purple or gray wires on the LED around (make sure that you do not bypass
the LED resistor).
# ATX power supplies are "switch-mode supplies"; they must always have some load to operate properly. The power resistor is there to "waste" energy, which will give off
heat; therefore it should be mounted on the metal wall for proper cooling (you can also pick up a heatsink to mount on your resistor, just make sure the heatsink dosn't
short anything out). If you will always have something connected to the supply when it is on, you may leave out the power resistor.
# You can add a 3.3 volt output to the supply by hooking the orange wires to a post (making sure the brown wire remains connected to an orange wire) but beware that
they share the same power output as the 5 volt, and thus you must not exceed the total power output of these two outputs.
# If you don't feel like soldering nine wires together to a binding post (as is the case with the ground wires) you can snip them at the PCB. 1-3 wires should be fine. This
includes cutting any wires that you don't ever plan on using.
# The +5VSB line is +5V standby (so the motherboard's power buttons, Wake on LAN, etc. work). This typically provides 500-1000 mA of current, even when the main
DC outputs are "off". It might be useful to drive an LED from this as an indication that the mains are on.
Options: You don't need the switch in the front, just connect the green and a black wire together. The PSU will be controlled by the rear switch, if there is one. You also
don't need the LED, just ignore the gray wire. Cut it short and insulate it from the rest.
http://www.instructables.com/id/Converting-a-computer-ATX-power-supply-to-a-really/
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Comments
36 comments Add Comment
DBLinuxLover says:
Oct 7, 2008. 1:18 PM REPLY
Out of curiosity, what would happen if you only used 1 wire, instead of bundling them all together, then attaching them to the binding post?
abizar says:
Oct 7, 2008. 2:58 PM REPLY
You don't need to bundle ALL the wires like I did. Though would use a few for the +5V and for the 0V, for all the rest 1 wire should be more than enough.
DBLinuxLover says:
Oct 8, 2008. 12:08 PM REPLY
Yeah i plan to use about 3 for +5 and ground. Thanks for the advice.
shadeofsound says:
Oct 7, 2008. 12:55 PM REPLY
Hey great instructable! I'm building my own at the moment and I wanted to know if you had a specific reason to exclude the 3.3v line or was it just something
you didn't want to include when you did it?
abizar says:
Oct 7, 2008. 2:56 PM REPLY
No, in retrospect wish I had included the 3.3V, also had run out of binding posts.
DBLinuxLover says:
Oct 7, 2008. 1:19 PM REPLY
There isnt really a reason. If you want it, go for it!
SpaceShipOne says:
Sep 18, 2008. 11:25 PM REPLY
Nice job
I built one of these from another Instructable, and it has been incredibly useful. the only down side was that I managed to shock myself while testing. I added
an extra fuse into the ground side, so if i I use too much current it will blow. This is easier to replace than hunting around for the fuse in the case
http://www.instructables.com/id/Converting-a-computer-ATX-power-supply-to-a-really/
barney_1 says:
May 28, 2008. 6:30 AM REPLY
Great instructable, thank you!
I just completed this project yesterday. I worked mainly off of your project with a few additions from two others by using crimp ring terminals and adding one
additional LED.
I used Eagle Cad to lay out the holes. I printed the template, drilled the holes, then printed onto nice paper and applied it with packing tape for the label.
The others:
http://www.instructables.com/id/ATX--%3e-Lab-Bench-Power-Supply-Conversion/
http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/
DBLinuxLover says:
Sep 18, 2008. 6:11 PM REPLY
Wow dude. Thats really really awesome. Liking it alot. If you don't mind, I think i may model mine after yours.
abizar says:
Aug 24, 2008. 11:23 AM REPLY
Looks really professional!
kruser495 says:
Oct 6, 2008. 8:03 PM REPLY
i only have one gray wire. i dont have a brown. what do i do?
richh10 says:
Aug 28, 2008. 10:14 PM REPLY
For those of you out there that have a Dell power supply that they want to use for this, you may discover that they use a non-standard color code. I was able
to find an explanation of it in an "Informit" article.
Grey is PC On, Orange is Power Good, and Blue/Whites are 3.3V. There is not a "Sense" wire indicated. Everything else is the same as the depicted in the
picture.
( http://www.informit.com/articles/article.aspx?p=339053)
pcludeg says:
Aug 12, 2008. 8:48 PM REPLY
hallo dost ,
thanku for thish project
prakash_ludeg@rediffmail.com
Goldtechnic says:
Jun 20, 2008. 12:54 AM REPLY
Hi, i just spray painted my atx. While waiting for it to dry, i did the wiring. I would like to find out, where might the purple standby wire go? shorted with the red
+5 wire? Please advice. Thank you =)
abizar says:
Jun 20, 2008. 2:45 PM REPLY
Purple put's out 5V even when the PSU is inactive. You could leave it disconnected.
Goldtechnic says:
Jun 21, 2008. 1:21 AM REPLY
Alright, Thank you very much=)
008 says:
May 29, 2008. 9:05 PM REPLY
Finally got around to finishing one up this afternoon! One issue I had was that if the brown wire was connected to anything the PS wouldn't power up. There
was a small gauge orange wire which was crimped with one of the larger orange wires, which is all that needed to be connected for "Power OK". No idea
what Brown is for on my PS, so double check the orange wires to see what small wire is joined to it before you start plugging brown wires in.
The +12v line is putting out 11.6v, close enough for me. However, on the -12v line (blue), I am only getting -4.6v. Any clue? Thankfully I don't really need 24v
yet, but would like to figure it out eventually.
http://www.instructables.com/id/Converting-a-computer-ATX-power-supply-to-a-really/
agis68 says:
Apr 6, 2008. 7:13 AM REPLY
Verry cool. It's all i needed......Thanx pal
johnpombrio says:
Mar 30, 2008. 8:02 PM REPLY
Just a couple of things. I have an ANTEC 550 watt supply that does NOT need a load. Seems to work fine without one! On my brand new honker 750 watt
Cooler Master, all I needed for a load was to connect an old DVD-ROM drive to the connector and it switches on fine! Now none of this makes a small
pacackage mind but it IS a power supply! So try jumpering the green wire on the large connector to the black wire next to it (pins 16 and 17) and see if the
fan spins up FIRST. As for not being regulated without a load, not true any more with the low power requirements of sleep and hibernate modes.
barney_1 says:
Jan 22, 2008. 8:34 PM REPLY
Will this work for the 10 ohm >10 watt resistor?
http://www.radioshack.com/product/index.jsp?productId=2062291&cp=&sr=1&origkw=resistor&kw=resistor&parentPage=search
burzvingion says:
Feb 29, 2008. 10:15 AM REPLY
Hopefully you haven't purchased that yet. That is only a 2W resistor, however, by ohm's law and the power law, P = E 2 /R. Therefore, when E = 5V and R
= 10 ohms, P = 2.5W. This should be the absolute minimum value resistor you should use. Here is a better choice:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=RHRB-10-ND
burzvingion says:
Feb 29, 2008. 10:20 AM REPLY
nevermind, upon looking again, it seems that is a 10W resistor, but radioshack is just too cheap to use real pictures of their products and instead
uses the same picture of a 2W, 10% resistor for all of their wirewound resistors... just another reason not to shop there.
barney_1 says:
Feb 29, 2008. 1:53 PM REPLY
Well, I do like the convenience of Radio Shack when all I need is a $2 resistor.
n0ukf says:
Mar 22, 2008. 12:49 PM REPLY
While they are a convenience, they've been slowly reducing their parts section over the last couple decades.
I've also found (and complained to the corporation) that their phone plugs and other connectors are nearly useless because it's nearly
impossible to tin the terminals. They should be nickel plated, not chromed. At least Switchcraft and some others pre-tin the terminals for you
(and they don't start with chrome plating either).
barney_1 says:
Mar 22, 2008. 2:32 PM REPLY
I whole-heartedly agree. How I wish I had some type of supplier in town that had even a modest supply of logic IC's and a larger supply of
semiconductors.
The chromed terminals have at times been a difficulty for me too. The convenience will keep me going back, but I'd spend more if they
had a selection that included more than just resistors and caps.
n0ukf says:
Mar 23, 2008. 12:14 PM REPLY
Everybody that has ever tried to use them should complain to RS (corporation, not just the stores) about the chromed terminals.
abizar says:
Jan 23, 2008. 2:45 PM REPLY
should work well, make sure it is attached to the metal to suck the heat out.
samurai1200 says:
Jan 13, 2008. 5:22 PM REPLY
This worked perfectly. Nice easy project with a clear-cut result. I have yet to try this under load, that'll be for tomorrow.
One minor thing i noticed was that my LED attached to the grey "power ok" wire was very dim. I measured the voltage at the grey wire, and its almost exactly
5v. So i ran the LED at 20mA, and it was really dim. Then I switched out the resistor and ran it at 30mA, then 40mA. I only have 1 type of LED, but is there a
chance that the grey wire is really limited current-wise?
abizar says:
Jan 14, 2008. 3:08 PM REPLY
20 mA current should light up all LED's quite brightly. Could it be possible that your LED already has an integated resistor? Best would be to test with
another LED. (Had a similar problem - had got a bunch of LEDs at a flea market, could not get the LEDs to light, thought they were all bust, turned out
that the LEDs were photodiodes!)
http://www.instructables.com/id/Converting-a-computer-ATX-power-supply-to-a-really/
T3h_Muffinator says:
Dec 15, 2007. 9:20 PM REPLY
hmm.... I've seen this before.... somewhere..... with those EXACT images.....
tstraub says:
Dec 15, 2007. 9:33 PM REPLY
It was on wikihow.com http://www.wikihow.com/Convert-a-Computer-ATX-Power-Supply-to-a-Lab-Power-Supply
abizar says:
Dec 15, 2007. 9:49 PM REPLY
Yep, my posting on wikihow - request was to put it on instructables too.
xsmurf says:
Dec 16, 2007. 8:38 AM REPLY
You should have mentioned that, I love the wikihowto article. I was going to start flaming like nobody's business ;P
Big up for putting it here too :)
T3h_Muffinator says:
Dec 15, 2007. 10:14 PM REPLY
Ahhh okie! Just making sure =)
Awesome!
fegundez1 says:
Dec 16, 2007. 4:53 AM REPLY
very good,and useful too!thank you.
GorillazMiko says:
wow, looks hard
all technologyish andstuff
http://www.instructables.com/id/Converting-a-computer-ATX-power-supply-to-a-really/
Dec 15, 2007. 8:33 PM REPLY