DIY Bench Power Supply With Old Computer SMPS




About: 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'm a YouTuber so you also can see my all videos here

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

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

  • SMPS
  • Binding post click
  • Led with 220ohms resistance
  • toggle switch

Step 3: Opening

Open 4 screws from the top ( see the picture )

Step 4: 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

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

Step 6: 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

  • 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

  • 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

  • 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

  • Trim off the unused wire ( see the picture )

Step 11: Securing

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

Step 12: Closing

Now close the cabinet and tight 4 screws

Step 13: 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

3 People Made This Project!


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49 Discussions


9 months ago on Step 9

Hi there,
Firstly what a good idea! I love a good bit of recycling.
I must make one suggestion as I notice you have soldered the wiring before screwing it under the nuts on your terminals. You should be very careful because this of this practice because solder can cold creep under load which will degrade the quality of the contact and may even lead to loose wiring and arcing. When using screw terminals it is always safest to either use the wire bare or use a crimp terminal. If you must solder leave the section of the wire to be compressed by the nut solder free.


2 years ago


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

1 reply

2 years ago

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.


5 replies

Reply 2 years ago

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


Reply 2 years ago

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?


Reply 2 years ago

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.


Reply 2 years ago

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


2 years ago

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


2 years ago

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?

1 reply

2 years ago


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]


2 years ago

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


2 years ago

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 !!


2 years ago

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.


2 years ago

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


2 years ago

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.


2 years ago

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

1 reply