Variable Bench Power Supply





Introduction: Variable Bench Power Supply

This is a simple adjustable bench power supply I built to help me in my instructables. 8 )

Some time ago I build another using a computer (ATX) power supply, but this kind of solution provides fixed values: 3.3, 5 and 12 volts. This is the less expensive solution you will find (just if you have an ATX as spare), and is useful if you will work just with these values, but this is not my case.

This project works with around 0.8V-29.4V ~ 5A.

Let’s do this…

Step 1: Materials

Here is a list of materials I used for this project:


- 1 x LTC 3780:

Price: US $14.20

- 1 x 12V 5A Power Supply:

Price: US $9.40 (if you decide to go with 12V 2A 24W price is US $ 4.89)

- 1 x Voltage/Current Display:

Price: US $ 3.99

- 1 x 500kΩ Potentiometer:

Price: US $ 2.49

- 2 x Binding post:

Price: US $ 0.38

- 1 x AC Switch:

Price: US $ 0.99

Of course you will need cables, weld iron, AC plug, Heat Shrink Tubing or isolate tape and miscellaneous that all Maker has.... ;

Step 2: CASE

If you have a plastic or metal case to use, it’s up to you. I prefer use wood and build it by my own.

I will not enter in details regarding the case dimensions because I believe that it is not important, and the size will be different if you decide to use different components. So, find a case that fits your project and let’s go!!

As you can see I decided to use a PC cooler fan just because I had one, but it is not necessary. It is so cheap that I recommend using. I used black paint in the wood (fan entrance) to provide a better finishing. Using a drill (8mm) I opened 5 holes to the air exhaust.

I am a Maker, so I have lots of electronic parts that I use in my project. I like to use metal 5mm LED Mount Bezel Holder as the cable holder in the case, it gives a professional touch in the project…. 8 )


You just need to wire the components as showed in the electric diagram. Piece of cake.... ;

Some people are afraid with no protection of the original circuit, so I decided to improve the safety adding one fuse and grounding the circuit. Safety First!!!

Step 4: Wiring Everithing...

To install the potentiometer to control the voltage output you will need to remove the original mini potentiometer welded in the LTC board. Just use the soldering iron to remove this item and weld the cables as showed in the diagram.

Step 5: Testing

All cables connected its time to test the PS.

Bingo!! First project without any problems!!!!

Step 6: Knob.... ?

When I was concluding he project I noticed that I did not have a potentiometer knob! No problem, that’s the reason God gave us creativity…. 8 )

Using wine cork, a beer bottle cap and super glue I improvised one knob (MacGyver is my master…. Hahahaha)

Step 7: Final Touches

With everything inside the case, I applied a finishing to protect the wood case (wax) .

It is possible to install another potentiometer to control the current too, but to me this is not necessary.

Just it!!!!

See you soon!



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2 Questions

I wired according to this diagram but for some reason i don't get any voltage coming out of the blue wire of the display so the positive post doesn't give anything out. Is there any common reasons why that's happening?

What are the recommended measurements for the box?


What AWG wire should I use for this project as I have no idea if my 16 gauge spool would work.

Thanks for your support!

what is the minimum output current ?

Question. So, as I turn the knob, the pot, the display will slowly rise in both voltage and amps until I get the desired amount? Since voltage and resistance are directly proportional, those numbers ( V and R) will always be related since 12 Volts = 1 Ampere? I'm still learning on my own and don't want to toast any tests I decide to try. Thanks! =)

In the way I wired you just control the voltage (0,8 to 29,4 Volts is the range I have). Just select the desired voltage and when you connect the load, the actual current will be displayed.

One more question. What's the lowest voltage that I can dial in with this power supply? Thanks.

0,8 Volts is the lowest.