Picture of Variable Lab Power Supply
I do a lot of work with low voltage electronics which often require various voltages. I was getting sick of constantly set up a series of batteries and then selecting the appropriate resistor just to test a single small part of a circuit. Ideally, I wanted to be able to dial in to a voltage simply and quickly and test. So that is what I made, a variable lab power supply for testing electronics. 

This variable power supply provides anywhere between 1V - 10.7V DC. It is really easy to make one slight adjustment to allow a range of AC voltages, but I never use AC, so I didn't bother. It is also really easy to provide 0V-36V, but I hardly ever need above 10V, so I left it with the smaller components that I had readily available. 

There are several other lines available off of the var psu including: 12V, -12V, 5V, -5V, 3.3V, GND, Variable (1-10.7V), and a mains-outlet extension (115V AC). The mimimum current limit on any of the lines is 2 amps, the max limit is 20 A on one of the lines. I forget the exact limits on each particular line. These limits will be based on the power supply unit (PSU) you choose to use in this project.

To all the comments I am sure will ensue, yes, I could have used a PSU and just installed binding posts, but I rather liked the geometry of this box. The size was right if I some day want to mount it to the workbench (when I get a real workbench) and there was plenty of space to install the fancy bells and whistles that I wanted (namely, the panel meters and the switch along with the variable line).

Anyways, this is a fantastic addition to your electronics workbench setup!
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russ_hensel2 months ago

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.

VicP13 months ago

What should be changed for higher voltages?

VicP13 months ago

What should be changed for higher voltages?

maxubergamer7 months ago

But i'm connect a DVD player power supply from the DVD player case how can i know how much amps i have in the output line of 12v+ \ 12v-

Onyx Ibex (author)  maxubergamer7 months ago

That is a good question beyond my level of expertise. I would imagine a DVD player power supply wouldn't handle a very high current (or even have a -12V line) but I could be wrong. Best recommendation is to just try various loads to determine what it can and can't handle (assuming it has protection circuitry to prevent overload damage)

thx a lot good instructables !

maxubergamer8 months ago

one more question . why you connect 12 volts in put to the schematic ? when you was can connect 12v+ with 12v- and get variable 22-23v max

Onyx Ibex (author)  maxubergamer8 months ago

While it is possible to do that, I think it is a better solution to use my way and here is why: 1) I rarely need a variable line above 12V but below 24V, 2) the -12V line has a much smaller limited current on it (I can't remember how low, but close to 300mA I think. Maybe you can spot the specs in an image somewhere) so a variable line up to ~24V wouldn't be able to source nearly as much current as the variable line I have shown. 3) finally, if you still want a variable line above 12V, just use the -12V line as ground and add 12 to whatever the variable meter reads :)
Hope this helps!

Onyx Ibex (author)  Onyx Ibex8 months ago

Looks like I said minimum is 2A on any line but I don't think I can get that with the -12V line. So not sure about that. I guess what i said above would hold still though. Depends on your PSU specs.

This is one of the nicest units I have seen..this would be a GREAT addition to anyones bench, Thank you for sharing this.

does anyone see that the lm317 t is without heatsink and it's gonna be bad if it gonna heat to match or this not problem if you have in the case fan ? good instructables and sorry for my bad English I am Israeli 15 yers old boy :)
Onyx Ibex (author)  maxubergamer8 months ago

Hasn't been a problem so far and I use it regularly. I rarely run at higher current or for extended duration on the variable line though. I moved the temp probe one there to see what would change but nothing much changed. Either it isn't a problem with the fans on or I am not pushing the limits enough :)

Onyx Ibex (author)  paradise974021 year ago


Eternal661 year ago
Hi, that is a nice PS. But have a big problem: max voltage is 12 volt indeed have power full power supply. my suggestion is using a buck-boost inverters that is available all around the world!!
Cattmy1 year ago
How can I add current adjustment to this?
Onyx Ibex (author)  Cattmy1 year ago
That would be a lot more challenging and I don't think I would be the one to ask. I toyed around with the idea of current regulation when designing this but decided it was too complicated for what I needed and could understand properly. If you figure it out, post a link or description of how to do it on this page if you remember. I would like to know as well.
novosysta1 year ago
i cant understand how thermometr is working if without resistance it has 26 on the screen.Tell me please .
paul czech republic
Onyx Ibex (author)  novosysta1 year ago
The thermometer was kinda a random add-on for me. I didn't know how to use it when I put it on and assumed it is working correctly. According to the sensor and panel (which came connected, from adafruit) all I had to do was plug it in I believe. And 26 seems reasonable so I assume it is working. I don't know what you mean by "without resistance". I do know that the thermometer is accurate (within 1 degree) of the temperature here. But since the box does not heat very well, the highest I have ever seen the display is 28. I didn't test it much at all I'm afraid. I hope I gave some info that might help you out.
Bongmaster2 years ago
sonic screwdriver ;) vital tool
Onyx Ibex (author)  Bongmaster2 years ago
i got the one thats actually a screwdriver too x3
vicsv2 years ago
I don't see the volt meter connections?
Wow this is complex.
LoL Yes sonic screwdriver.
Wait BONG Master? Jesuuuuus!