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Picture of Mini Linear Variable Power Supply (1.2-20 V , 2 Amp)

No matter what project we are working on,a power supply is always needed to power it or test it. The required voltage will always be different for different projects.So here is an easy way to built your own compact yet powerful linear variable voltage power supply which can produce any voltage between 1.2 to 20 volt with 2 ampere current but still takes less space than a coffee mug on your work table.It is also very useful in cases were the adapter go missing for different electronics like desktop speakers etc and it can also be used for charging batteries.

Step 1: Things You Will Need:-

1. LM338K voltage regulator IC X1

2. 4700uf 50v capacitor X 2

3. Variable resistance potentiometer 10k X 1

4. 220 ohms resistor (1 watt) X 1

5.12K resistor (1 watt) X 1

6. 2.7K resistor ( for led) X 1

7. LED X 1

8. Diode 1N4007 X 2

9. Capacitor 0.1uf X 1

10. Transformer ( with 15 volt at transformer output) X 1

11. 2 amp diodes X 2 (in case of central tap transformer)

X 4 (in case of ordinary transformer)

12. Mini volt meter X 1

13. Small plastic connector for taking output voltage X1

14. Any metallic watch can.

15. A power chord with ground.

16. A 2 ampere poly fuse.

warhawk80802 years ago
patrick panikulam (author)  warhawk80802 years ago
Oh thanks, so that solves the IC burnout due to accidental short-circuits ryt, i will attach one immediate imidiately
Please insert this improvement into the instructions. Thanks!


Thank you! ;)

Nearly all of the LM338K are fakes. You either have to remove one from old equipment or pay over $50 for one if you want the real thing. There are other cheaper ones now, usually in a TO-220 package. Order from Digikey or Mouser.

What's the difference between the fake ones and the expensive ones?

Efficiency? Protection?

The fake ones could be anything. Often they are some type of 1A regulator. I had a few that just burned out.
andanaster2 years ago

very, interesting, i like this idea of recycle material

curiosity362 years ago

Clever. 'Juice' in a can so to speak.

patrick panikulam (author)  curiosity362 years ago
nedicman2 years ago

Wery nice, good idea. :-)

HBSkirmit2 years ago

Great project and I like your can for the housing. One important safety issue would be to use a three conductor power cord with a green ground wire. The ground wire should be attached to the metal can.

patrick panikulam (author)  HBSkirmit2 years ago
Thanks for the advice, I will do it for sure :)

Awesome power supply. Great job. check my power supply

Clearly your power-supply is very well done, but this simpler design seem better suited to my skill level ;) Seeing that yours seem more "capable" with the heatsink, fan, and the ferrite donut, can you elaborate on some of the additional features you built into yours. Thanks.

I checked out your Power supply earlier , it's darm cool
Anshu AR2 years ago


patrick panikulam (author)  Anshu AR2 years ago
Yonatan242 years ago

Does it have a short circuit protection module? I bought a kit a few years ago that has used this IC and it burnt out every time I short circuited it by accident. And replacing it every time was really annoying so I took it apart.

patrick panikulam (author)  Yonatan242 years ago
It happened to me once and I searched the whole net for a short circuit protection circuit for this IC but couldn't find anything. I had already made a low current variabl power supply using LM317 before I made this one, So I use that while testing a project .Once everything is working fine I move on to lm338k supply. I am planning on integrating lm317 into the can and use a dipole switch to switch between lm317 and lm338k ICs
ravijag2 years ago
Innovative way to house your project.. Liked it!!
patrick panikulam (author)  ravijag2 years ago
Thanks :)
gm2802 years ago

Interesting layout and container. Been a long time since I've seen a TO-3 steel cased regulator. Unusual and equally unique as well.

patrick panikulam (author)  gm2802 years ago

nice build. check out my power supply instructable using buck-boost converter

Thanks:),. I will surely checkout your project