Introduction: DIY Bench Power Supply With Old Computer SMPS

Picture of DIY Bench Power Supply With Old Computer SMPS

Hey! everyone My name is Steve .

Today i'm going to show you How to make a Bench Power Supply With Computer Power Supply

Bench Power supply is very useful in electronics field it is very easy to make it with a regular ATX power supply

Click Here to See The Video

Let's Start

Step 1: Features

Picture of Features

Supply Output

  • 3.3 V @ 30A
  • 5 V @ 25A
  • 12 V @ 10 A

it's my specification all it's depend upon your power supply power output


  • Green Led ( power indicator )
  • Toggle Switch (On/Off)

Safety Features

  • Short circuit Protection
  • Over load Protection
  • Over Heat Protection

All this Built in your ATX Power Supply

Step 2: Stuff I Used

Picture of Stuff I Used
  • SMPS
  • Binding post click
  • Led with 220ohms resistance
  • toggle switch

Step 3: Opening

Picture of Opening

Open 4 screws from the top ( see the picture )

Step 4: Drilling

Picture of Drilling
  • Mark the position for drilling with a marker ( see the picture )
  • First Drill with small drill bit and then go for bigger
  • Drill total 8 holes ,6 for binding post , 1 for led , 1 for switch

Step 5: Installation

Picture of Installation
  • First start with installing the binding post ( see the picture )
  • then install the led
  • and then install the switch

Step 6: Connection Led & Switch

Picture of Connection Led & Switch
  • First cut green and black wire and solder them on the toggle switch ( see the picture )
  • And then cut orange and black wire and solder with a 220 ohms resistance on the LED

Step 7: Cutting

Picture of Cutting
  • Cut 3 Yellow & 3 Black , 3 Red & 3 Black , 3 Orange & 3 Black wire
  • Cut the Length to reach all the connection
  • Don't cut too small


  • Yellow wire gives you 12 V
  • Red wire gives you 5 V
  • Orange wire gives you 3.3 V

Step 8: Wire Grouping

Picture of Wire Grouping
  • Twist the 3 wires and make a bunch ( see the picture )
  • Do The same with all the wires
  • To make it looks less messy

Step 9: Connect

Picture of Connect

  • Connect those 6 wire to the binding post and tighten the nut ( see the picture )


  • Yellow & Black - Black And Red Terminal of first Group
  • Red & Black - Black And Red Terminal of Second Group
  • Orange & Black - Black And Red Terminal of Third Group

see the picture for more information

Step 10: Cutting

Picture of Cutting
  • Trim off the unused wire ( see the picture )

Step 11: Securing

Picture of Securing

use a cable tie to tie loose wire ( see the picture )

Step 12: Closing

Picture of Closing

Now close the cabinet and tight 4 screws

Step 13: Finishing

Picture of Finishing

Now mark the terminal

  • First binding post 12V
  • Second binding post 5V
  • Third Binding post 3.3V
  • Led
  • Switch (On/Off)

Click Here to See The Video

You Just Made It

Now just Plug the power and enjoy

Thank you for visiting my Instructables

Stay tuned for next Projects


EricV73 made it! (author)2017-06-13

easy to do and fun to used XD

stuyo made it! (author)2017-01-25

This is my Lab PSU, made of a very old AT unit (this is a good thing because you power it on with a switch). Been serving me well for the past year. Also added some PC Modding bling :)

richieacc (author)2017-01-12

This is really great! Thanks for posting.

There are some other useful pins on the PSU that I would make use of:

Purple: +5VSB (
When there is AC plugged into the supply, this wire carries +5v, WHETHER THE SUPPLY IS ON OR NOT. So this could be connected to the build to show that the supply is getting AC power.

Blue: -12v

White: -5v (Not always available on modern PSU's)

The following combinations are possible:

-12v & gnd = 12v

-12v & 3.3v = 15.3v

-12v & 5v = 17v

-12v & +12v = 24v

+3.3v & +5v = 1.7v

+3.3v & +12v = 8.7v (this should be close enough to 9v for most applications)

+5v & +12v = 7v

Use them in the order listed for negative and positive respectively.


jduf (author)richieacc2017-01-24

good point but be careful of the max current, very low for +12 & -12

Hyshinara (author)richieacc2017-01-12

Oh, nice! So maybe I could make one with a rotary switch with different wire sets connected, to choose between 1.7V, 3.3V, 5V, 7V, 8.7V, 12V, 15.3V, 17V, and 24V?

fastedi (author)Hyshinara2017-01-12

I thought same but if you need more than one type voltage,you can not have all in same time.Design really depends of personal use.

Hyshinara (author)fastedi2017-01-12

Ah, that would be the tradeoff then, I suppose.

José RamónL1 (author)richieacc2017-01-12

may you plase share photos o videos with this idea? Thanks

wonstoneyoo made it! (author)2017-01-17

I have made one but some altered, the terminal arrangement, spacing 19mm because I could use the fixed width twin terminals with it.

I don't know why the photo is up side down.

WannaDuino (author)2017-01-15


you must always use a DUMMY LOAD RESISTOR. 10 Ohm 5W. that big white ceramic block type of thing.

slimtender. (author)2017-01-15

Excellent job, it seems like mine (I made one similar 2 years ago). This one is more compact anyway...

47miky (author)2017-01-13

Question Steve, Why is it that you don't mention anywhere about the transitor (not sure of spelling), you don't mention it at all in the instructions but when you watch the video you can see it when you connect the yellow wire to the led? Is it not necessary?

its a resistance for driving the indicator led

TheRadMan (author)2017-01-12


Please remind viewers to use only UL listed, classed Power Supply modules.

I did not see UL symbol/stickers but I see the obvious safety label on one side.

I noticed that the remote enable is used, by pulling the PS_ON# pin to ground,

but the power supply still operates internally, in a sleep mode.

Even when an ATX is disconnected from the IEC310 power cable,

the PCB switch-mode capacitors are still somewhat charged,

and can painfully remind any fingers of that (residual) charge.

Always check that the IEC310 receptacle has a low resistance connection

to the case, and that the binding post rear insulators are used

to isolate the high current DC connections. Perhaps , ring-spade crimp

terminals should be used at the rear of the binding posts,

but I am encouraged to see many of your preparations and treatments,

in your pictures, actually enhance safety and isolation/insulation.

Perhaps, you have formal Electronics training.

Modification of ATX modules is the most affordable way to create a test bench

power supply.

If there is an unintentional short in the 3.3V, 5V or 12V D.C. rail(s)

we hope that the feedback monitor shuts down that ATX PS per the

conventional wisdom , by disabling the switchmode drive.

[ CET in 1979]

Hyshinara (author)2017-01-12

Neat! Now I know what to do with my old PSU! :D

Filbert11 (author)2017-01-12

Excellent !! A comment: It is key to get the right power supply - as you have done. Many/most computer power supplies do not have that much open space inside the case!! I have made two of these - and neither one let me put everything inside the case !!

TunerFreak (author)2017-01-12

Nice instructable! One comment though, a lot of people seem to order their parts from China to keep cost down, but you can get the same parts from TaydaElectronics for the same price and it ships from the US. (Not sponsored, just like the site). They even stock arduino clones and breakout boards.

RobertZ7 (author)2017-01-12

Oh, by the way, the blue one, 蓝色, gives you -12 V. Just saying.

RobertZ7 (author)2017-01-12

haha, I can see the Chinese written on the board! 红色,绿色,黄色~~Good job! Save some money for buying a power supply.

GaryP76 (author)2017-01-12

Steve, what would you charge me to build and ship complete to me?

you can easily make it . it's not too hard

Imanolddogwithnewtricks (author)2017-01-12

Nice one, Steve. I guess that this is an idea that lots of makers/recyclers have thought about....but you are one of the few who have put your thoughts into action. Keep it up matey. A well explained and well illustrated Instructable.

thank you very much

popeyedave (author)2017-01-12

In just the last few days i have found 2 new uses for old power supplies, this and powering LED shop light strips, now i am happy the Electronics recycler guy i was waiting on has not came yet! I think i have 5-6 old PC Towers that are about to be disassembled, anyone else have any other uses for power supplies or other PC leftovers?

GaryP76 (author)2017-01-12

and I just threw away my last axt power supply while cleaning out my workbench. dang

José RamónL1 (author)2017-01-12

Really nice project. Thanks a lot!


captclearleft (author)2017-01-12

Thanks, This is a great tutorial / video. Well Done!


MarkBolduc (author)2017-01-08

Nice walk through, Steve. I was just working on this myself as I am working on a Rasberry Pi project and need some external power for some stepper motors. The old PC power Supply was in the drawer waiting to be used. Your clean cut version makes for a very nice benchtop power supply. Thank you for sharing.

you are most welcome

gm280 (author)2017-01-04

Nice reuse of a computer power supply. I have a few suggestions. I would use terminal ends on all the wires and crimp them in place and attach them with the nuts to the binding posts connectors. Wrapping wires together and soldering them is good, but not necessarily in this case. Crimp connectors make a better cleaner setup. And this is a typical switching power supply, hence no large transformers. That is why you are getting those large amperages from it. One thing I like to do is install an LED for each output voltage. That way you know that the output is present if the LED is lite. Of course you need to calculate the correct current limiting resistors for each LED output as well.

Christ204 (author)2017-01-02

Hi Steve, have i overread The usage of load resistors ? Or don't you need them ? As far as I know it's good to have them in either the 5v or the 12 v line. ( around 10 ohms at 10 watts) Or am I wrong? best regards Chris

better to use a 10 ohms as a dummy load

Where , in which line ? 3,3 v , 5 v , 12v ? Or all?

do it on 5V line

MarkH43 (author)2017-01-02

Its nice to see old tech been reused,.. but the unskilled diy-er should be very careful when solder wires/joints within the power supply as solder splutter can very easily create unexpected shorts,.. protect the exposed electronics when creating solder loops for the tags etc.

Also,. users should be aware these supplies all share a common ground,.. so they are NOT isolated,.. also using one of these units as a test bench supply is never a good idea as there is no control over the current,.. other than during a short, and in my many years of electronics, a current controlled supply was essential when developing new kit.

These units are designed to work within another enclosure,.. so they are never strictly speaking exposed to the outside world, all that is considered is the expelling of excess heat etc,... not stopping foreign objects from entering the control electronics.

Be safe not sorry!!!

yeah but this is just a basic power supply.

Btw thanks for feedback

chadk2318 (author)2017-01-02

Thanks for this great 'DIY' write-up Steve! I've wanted to re-use one of my old ATX power supplies to build a bench top power supply for sometime now, but I was a little intimidated due to my inexperience with electronics. Now, thanks to the way you break it all down in your Instructable, I'm about halfway through building my own now. Thanks again! -WCK


3DPlaneLiner (author)2017-01-02

It is good to see how compact you can make this. One comment though.

You NEED to load the main regulating output, even if you're not attaching any load to the supply.

Most of the time it is the 3.3V or 5V output that is resopnsible for the regulation loop internally. Depending on the design of the power supply, that constant load should be around 1 to 3 amps, so on the 3.3V output, you should shunt this with a resistor of some 1.5 ohm, but with a rating of 10...20 watt!!.

Beware, it gets really hot and you could put it against a metal plate to cool.

Only then you will have a warranted 3.3V, 5V and 12V output. If you don't do this, you'll probably blow out some circuits that you attach to the supply due to poor regulation behaviour of the power supply in transient conditions.

Further on, BE SAFE!, these supplies are designed for internal use. They have large openings that give access to high voltage parts. Putting it on a desktop without further protection can be dangerous for electrocution if you have wires and components lying around on your desk.

Rajkumar2506 (author)2017-01-02

Is this power supply withstand for lighter loads. Iam asking this question because SMPS will have accurate voltages but if you check the current of 3.3V,5V,12V.It will be around 5AMPS. Which is very high current.If you connect any LED to 5V the LED will be burst because of High current.If you also connect 5V DC motor,the copper winding in DC motor will have less resistance.This copper winding cannot withstand resistance for 5AMPS.For 5 AMPS current the copper winding will act like a Pure wire.So if you connect DC motor your SMPS will burst.I had already tried it and find out the reason for burst of SMPS which is as mentioned above.So you should connect resistor to suppress the current from 5 AMPS to 2 AMPS.So usage of 2 AMPS current is safe.

Gaming Hawk (author)2016-12-31

Should there be a resistor in the build so that the power supply does not smoke?

the resistance is just for led

sorry let me rephrase my question/ statement. The resistor I am talking about should be a bigger one to put some dummy load on the system so that it does not start smoking if you watch this video from great Scott it should make more seance.

you can use it externally .

DaveV16 (author)2017-01-01

This would be better if you wire a 9 volt plug in there also

Sorry ATX power supply don't gives 9 volts

russ_hensel (author)2016-12-31

Welcome to the club: Just a note to let you know I have added this instructable to the collection: Encyclopedia of ATX to Bench Power Supply Conversion


Take a look at about 70 different approaches to this project. This topic is one of the more popular of all instructables.

thank you

About This Instructable




Bio: Hi my name is Steve and i'm a Creative and I got Technical skills i can build anything just stick to my account . I ... More »
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