DIY Bench Power Supply With Old Computer SMPS





Introduction: 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

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

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Please be positive and constructive.





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

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.



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

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.

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

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

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

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?