Introduction: DIY Lab Bench Variable Power Supply

Picture of DIY Lab Bench Variable  Power Supply

This project will give you the chance to build up a true laboratory variable power Supply 0,8 to 30 Volt 0-5A.

The core of the project is based on two main components:

5 Amper Step down Dc-DC module

  • Output ripple: 50mV (max)
  • 20M bandwidth
  • Switching frequency: 300KHz
  • Conversion efficiency: 95% (the highest)
  • Output current: adjustable maximum 5A
  • Output voltage: 0.8V-30VInput voltage: 5V-32V


Switching power supply recovered from an old PC.

Obviously, higher is the voltage of this component, and wider will be the adjustment range. In my case, I had a 19V and 4.5 Amper power supply

Unfortunately I have not been able to dip the photos step by step of the activities, but I think the explanation Will be enough even for the less experienced guy.

If you like the article ... do not forget to vote it for the contest ..

Step 1: Bill of Materials

Picture of Bill of Materials

All components were purchased on ebay from China, and you will also find them on Aliexpress

In the bill of materials I will show you the actual cost

Bill of material

  • 2 Banana bushes --- 0.40 $
  • 2 Potentiometer 10 KOhms --- 2.60 $
  • 1 DC-DC 5A Module Step Down --- 1.17 $
  • 1 DC 100V 10A Voltmeter Ammeter --- 2,8 $ or (1 Analog Voltmeter and 1 Analog Ammeter) but these are definitely more expensive
  • 1 Switching power supply of an old laptop PC (free for me)
  • 1 box for outdoor electrical installation --- 2.5 $


  • Welder
  • Pond
  • Screwdriver
  • Multimeter
  • Caliber
  • Hot glue

Step 2: Let's Start

Picture of Let's Start
  1. The first thing to do is remove the two 10 Kohm trimmers.

Looking at the board holding the two blue trimmers toward you, the left one adjusts the current, and the right one will allow you to adjust the voltage

With the trimmers removed we will going to to connect the two potentiometers.

Here we will attach three wire strings to each one.

This wire does not need a particular diameter, but to facilitate welding to the board it will need to be fine enough

For those of you who will chose a 10-turn potentiometers, be careful that the variable terminal is the number

2. With the old PC power supply disconnected from the CURRENT, go cut the output cable leaving a sufficient wiring harness, clear the poles and go check it with the multimeter the positive pole and the negative.

DO NOT FIDE the colors of the wires

Identified the poles you can go to connect them to the DC-DC Board.

Tip: Inputs and outputs are marked on the back of the board. I suggest you write them over.

It will come back util to you in the cabling phase

3. Now also connect the DC 100V 10A Voltmeter Ammeter.

If you have purchased a digital model, this will also be powered, so you will find it With two wires + and - to connect to the board input and three other wires to connect to the output of the three wires in the following way

Red -> Out (+)
Black-> Out (-)
Blue -> will be connect to the bush (-)

Check the wiring once again and when you are sure, switch on the power.

4. You will notice that the board is also equipped with some led. One on ignition, another telling you that the load is connected and the third will indicate the short circuit or Is working the current limiter Try adjusting the potentiometers to make sure that you have connected them properly and that the voltage and current are adjustable

At this point we can switch to inserting our laboratory power supply into a box. The size depends on the PC power supply that you are using, too If you may decide not to put it in the container but leave it outside

Ok let's go!

Take the caliber and measure the diameter of all panel components. Usually the bushes need a 6 mm hole and the potentiometer of 8 mm I miss you the task of finding the smartest way to do the holes for the measuring instrument you have chosen. Connect everything calmly and without hesitation.

WARNING: The output connection wire should have a sufficient diameter to carry the 5A, so my advice is to recycle a piece of cable That you cut off from the laptop power supply

To lock the board and the laptop power supply in the box you cane use the hot glue.

Close everything and label the basic information on the front panel; Adjustment of current, Adjustment of voltage, and max voltage and maximum current available from your new laboratory tool!

And now is the time to admire the result of your work.

If you like the article ... do not forget to vote it for the contest ... and for whatever ... write it on the board


rgco made it! (author)2017-07-14

Done! The scheme is the same but a few details differ:

For enclosure I used an old plastic nivea handcream pot - it was the first thing I found that seemed to fit the components and it's sturdy enough to fit all dials on the lid yet soft enough to cut the holes without a drill.

I left the external PS outside the enclosure and connect it with a DC jack. This way I don't need to cut the cable of the external PS. Unfortunately, the only PS that has a common DC jack, for which I could find cheap female jacks on aliexpress, are 12V. I'm using a 12V 2A PS of an external disk for now.

With 12V input the output is limited to ~11V which also means the potentiometers use a very small fraction of the full turn. I'm thinking of adding fixed resistors to the potentiometers to improve their sensitivity, e.g. adding 10k to the 'useless' leg. Any idea if that'll be OK? It'll behave like a 20k pot, I suppose that's fine but haven't tried it out yet. Ideally I'd replace the 10k potentiometer by a 5k and then add a 5k fixed, but I only have 10K.

I really think this PS is the best for everyone on a low budget, the total cost of the components (excluding external PS and enclosure) is about 4 EUR (2 for display, 1 for buck, 1 for pots, switch, jack), and to get a regulated PS with current limit and simultaneous digital readout of voltage and current is awesome. I've already been trying it out on NiCr wire and a Peltier element.

My plan is to keep an eye open for a stronger PS and better enclosure and make another one with more power. Cheers!

rgco (author)2017-05-29

Right what I need, no-nonsense regulated supply based on old laptop supply. Components ordered, will take a while. You got my vote!

MaurizioZ (author)rgco2017-06-09

Thanks rgco... and when your project will be complete don't forget to publish the pictur. :-)

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