DIY Lab Bench Power Supply

Introduction: DIY Lab Bench Power Supply

About: Awesome Electronics Tutorials, Projects and How To´s

Everyone has those older or newer ATX power supplies laying around. Now you have three options. You can throw them in your garbage, salvage some good parts or build a DIY lab bench power supply. The parts are dirt cheap and this supply can deliver more amps than some modern variable ones. Let's build it.

Step 1: Watch the Video!

The video gives you all explanation you need to build this project. But I will tell you the most important steps again, this way you can not screw this up.

Step 2: Order Your Parts!

Here is the list of parts I used in this project:


5x Binding posts (red):

1x Binding post (black):

1x Toggle Switch:

1x 3mm Green LED:

1x 3mm Red LED:

2x 220Ω Resistor:

Shrinking tube:

5x Binding posts (red):
1x Binding post (black):

1x Toggle Switch:

1x 3mm Green LED:

1x 3mm Red LED:

2x 220Ω Resistor:

Shrinking tube:
5x Binding posts (red):

1x Binding post (black):

1x Toggle Switch:

1x 3mm Green LED:

1x 3mm Red LED:

2x 220Ω Resistor:

Shrinking tube:

Step 3: Get the Right Resistor!

You may already noticed that we have to put a dummy load on the supply to keep it stable even when we only draw small amounts of current.

I recommend the dummy load should draw at least 0.5A.

Here is the calculation if you have most of your power on 5V/3,3V rail:



Buy it here:

Here is the calculation if you have most of your power on 12V rail:



Buy it here:

Step 4: Make the Correct Connections!

What does each wire mean and where does it connect to? You can find a schematic here which tells you how to connect the parts. Anyway here is my written version of this schematic:

Orange (3,3V) ---> 3,3V red binding post

Red (5V) ---> 5V red binding post

--------------> 10Ω 10W resistor

---------------> 220Ω resistor of 3mm green LED

White (-5V) ---> -5V red binding post

Yellow (12V) ---> 12V red binding post

Blue (-12V) ---> -12V red binding post

Brown (3,3V Sense) ---> 3,3V binding post

Purple (5V Standby) ---> 220Ω resistor of 3mm red led

Green (Power ON) ---> One side of the toggle switch

Black (Ground) ---> GND black binding post

-----------------------> Cathode of 3mm green LED

-----------------------> Cathode of 3mm red LED

-----------------------> 10Ω 10W resistor

-----------------------> other side of the toggle switch

Grey (Power Good) --> not connected

If you have most of your power on the 12V rail then you need to connect a 24Ω resistor to 12V instead of 10Ω to 5V.

Step 5: Success!

Everything works! Now you can build even more awesome electronics projects with the help of this bench power supply!

Feel free to check out my Youtube channel for more awesome projects:

You can also follow me on Facebook, Twitter and Google+ for news about upcoming projects and behind the scenes information.

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17 Discussions

I have a question, I want to build this project with an "old" power supply I have laying around. I found a schematic online define the minimum load (included image). Does this mean I need to put a dummy load on every voltage line to be able to use it properly?

Screen Shot 2017-08-15 at 11.43.27.png

hey, i was wondering: you say that you make a dummy load to keep it stable when drawing small ammounts of power. what exactly happens when you draw small ammounts of power without a dummy load?

Sorry I dont get ist with the dummy load.

You say it should draw about 0.5 A.

For the 5 V rail thats 10 Ohms. Ok, done. 10 Ohms* 0.5 Amps is 5 Volt.

But then you take two 10 Ohm resistors and install them paralell, doubeling the Amps to 1.0 Amp. At the same time you raise the lost power from 2.5 to 5 Watts wich means 5 watts of the theoretical output go te the dummy load and are converted to heat.

To make things even more confusing the resistors are drawn serial in the schematic resulting in an combined 20 Ohm resistor, and drawing only 0.25 amps instead of the recomended 0.5 in the text.

So..... whats right? 0.5 amps, two resistors or one, serial, or paralell?

I am sorry if I didnt use the right terms, but I am a native german speaker, my english is far from technical standart

2 replies

In parallel, the equivalent impedance (resistance) is given by this formula : Req = (sum of R^-1)^-1 .

Two 10 Ohms in parallel will be equivalent to a single 5 Ohms resistor.

Ok, I will try again.

Video says in the Overlay Text: 5V: 5Ohm 5Watt.

He uses two 10 Ohm in paralell, resulting in a combined 5 Ohm resistor.

That much is clear. Its also clear that

5V/5Ohm = 1 Amp


5V*1Amp = 5 Watt

absolutely clear as far as the Video goes.

BUT: In the instruction Text he says at least 0.5 Amps ( half as much as in the video). Correctly he gives the formula

5V/10Ohms = 0.5 Amps


5V*0.5Amps = 2.5 Watts (also half as much as in the Video)

To add some more confusion here comes the schematic with the Resistors in serial, instead of paralell. ( R3/4 47)

10 Ohms + 10 Ohms= 20 Ohms

5V/20Ohms = 0.25Amps

5V/0.25Amps = 1.25 Watts

Now we have 3 different Values for one Instruction. I would just like to know wich one of the 3 is right. If you tell me the Power Supply needs about 0.5 Amps of dummy load I can arrange that. But if you tell me it needs 0.25 and 0.5 and 1 Amp I get confused.

Second Problem is the Grey "Power good" Wire. The schematic connects it to the resistor of Led1. Text and video use a red wire on Led1. Text says Grey wire is not connected.

Again: 1 Problem, three solutions.

Hey i just wanna ask i can add another post for a 5volt with a 4amp or 5amp current? Because im gonna use that to charge 18650 batteries..

Is there a possibility to do that?

And also all of 3.3, 5 and 12 volts are all 16 amps, where should solder the brown wire?

My psu is Delta Electronics DPS-220U B-5 A if you wanna check it out..

I really need you held right now man..

Is it fine to use 2 resistors 10Ω 5w in paralel as shown in video????? It will be for 5v rail

hi guys, followed this tutorial, and I connected two 10 ohms 5W in parallel, exactly as shown in the video. the resistors are getting so hot that I afraid it will burn the wire. my question is it normal for this to get so hot ? or I simply did something wrong

Hi I build one but when turned it on the green led turns on for a second and turns off quickly and power supply does not turn on can someone help me thank you


2 years ago

Hi GreatScott!
I want to make one as well.
My Colourcodes are the same. Could you just tell me really quick, where you connected the GREY Wire to and Why?
Because you didn´t mention it in the video, but you can see it connected.

In your scematic you once connect it to an LED and Ground, but later in the listing it is not connected.

Best wishes

PS: Love your Channel on youtube!

1 reply

Found it out myself.
The video is wrong.
follow the scematic in step 4 and you´ll be good.

Hi everyone i'am new to instructable I'm looking to build a power supply out of a computer power supply i need 12v 4amp but the power supply says 12v 12amp for a amplifier please help me thank You

3 replies

the 'amps' or 'amperage' of a power supply rates the maximum current (or electricity) the power supply can deliver.
(Like how a firetruck can deliver more water than a garden hose).
Your computer supply can deliver 12amps wich is plenty for the amplifier to run off. Think of it as watering your garden with the firetruck, it's overkill, but it will do the job.

I forgot to mention this:
a computer power supply is not very clean. It can have noise on the outputs. If you have problems with noise on the amplifier, you can either try to filter the power supply with capacitors or build a linear regulated power supply but that would be costly.

I must have missed this instructable when published, but now:

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 most popular ( to write ) of all instructables.

Why don't you connect both 10 omh to 5V and 24 omh to 12V?

What's differrent between 208-8 10R 10% D and 208-8 10R 10% M and other characters?