Picture of Mini adjustable power supply
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When designing this power supply, my objective was to have it as portable as possible, so you can take it almost anywhere. One of the reasons I want it to be so portable is because every time I go to visit my family and friends abroad, they always have something for me to fix (or at least “try to fix” ) They have a soldering iron, but that’s about it. That’s why I made the voltpen, this mini power supply, and a mini usb sound card oscilloscope (Instructable to follow soon).

I made other power supplies, but none of them had current regulator. This time I decided to use the LM2596 instead of the normally used LM317 or LM350, so I could also adjust the current.

The beauty of this unit is that you can connect it to any DC source from 7.5V to 28V. So I can just take it with me and connect it to a laptop power supply for example. The output voltage will be very close to the input voltage, maybe about half a volt less. It can also be use as a voltmeter without being powered for voltages from 2.5V to 30V and as an ammeter from 5V. And It’s great for charging batteries.

Enough talking, lets cut to the chase..

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ksan15 months ago

can you tell me how to connect correctly ?

i get reading from volt meter...
amp meter no reading....

Mini adjustable power supply sample.jpg
newtonn2 (author)  ksan14 months ago

Hi there, sorry for late reply.

You have the negative of the voltmeter connected to the output. Do not connect that negative. Only the amp meter should be connected to the negative.

ksan1 newtonn24 months ago

like this? sorry my English not that good

vimajks6 months ago
Hi newton,
the three wires from the voltmeter where do they go? Do we connect the thin black wire but where does it get connected?
jjsuico7 months ago


Instead of the LM2596,

Will this module work:


rpotts29 months ago
Any idea what the 6 pin header is for next to the output current pot?
rpotts2 rpotts29 months ago
NM. I found it. It's a solder matrix kinda thing. Looks VERY similar to my LCD driver's address block: Solder 1 pair, get some option, & so on
mrx23dot10 months ago

I wasn't able to limit current under 300mA with 10K pot, should I increase its value?

yoyolo10 months ago
What's the hottest it's gotten during normal/heavy use ?
mrx23dot11 months ago

Do you agree with that for Current control a logarithmic potmeter is more useful for low current stuff?

mrx23dot11 months ago
Hi again,

What do you think about displaying the max current set, with a pushbutton shortcircuiting the output trhough a 0,1-1 ohm 5W resistor?
newtonn2 (author)  mrx23dot11 months ago

Give it a try, that most probably works.

mrx23dot11 months ago

Hi newtonn2,

For me it is not clear when is it in CC or CV mode.
E.g. I set const 3V, but on your video when you turned up the current pot the voltage went up!
That would kill my MCUs.

Is there a hack to make it CC+CV mode, so voltage won't rise?

Great project!

newtonn2 (author)  mrx23dot11 months ago

It will be fine. If you adjust the voltage fist at 3V, it will not go higher than 3V. If you adjust the current, it will not go higher than the adjusted current. In the video I didn't stop moving the knob after it got to the maximum, that why it appears that the current knob its afecting the voltage.

I hope that makes sense

MAZDA137711 months ago

I want to make power supply board. can you take me schimatic power supply board?

Poppy Ann1 year ago

Hi Newtonn2,

whilst i have not made the circuit like you have i am using the boards to give me current/voltage control as i like to play with electronics/arduino but seldom get to make anything permanent I had never heard of these devices i have a low priced computer psu and use the circuit to give me the current/voltage control as in the past when testing circuits i would get the magic blue smoke on several components when i got it wrong.

i have been using these meters:-

eBay item number:141197770442 from china at £1.39

eBay item number: 390799784629 from UK at £3.79

which have both voltage and current in the one device which would make fitting into a box a little easier due to only having one hole to cut.

good luck with the competition.

regards Poppy Ann

newtonn2 (author)  Poppy Ann1 year ago

Hi Poppy Ann.

That is a very good idea, using the PSU along side the voltage regulator.

I used one of those meters for my small bench power supply, you can see it here:


I'm very happy with the performance of those meters.

About the contest... I won second place !! :) I'm already using the tools Instructable so kindly sent me!

Thank you very much

Regards, Newtonn2

Hi Again,

i just came across this item and gave it a try it works great and the nice thing is there is nothing to do to get it working i just hot glued it to one of my breadboards and connected the power and for £7.62 including shipping is well worth it.


the output current limit can be set in 1mA increments and the output voltage in 0.01V increments, down to 0V. It remembers the last settings for voltage/current when it's disconnected from power, and the output is off by default

, this saves messing with the little ten turn pots to set it.

newtonn2 (author)  Poppy Ann11 months ago

That is very cool! I will defenitely get one of those.

acetaz1 year ago
The amp meter wire the thin black n red go to input n the thick white is output out same as thick black is that right n the volt meter white n red go to input too yes .is that right newtonn2
newtonn2 (author)  acetaz1 year ago
Hi acetaz,

The amp meter connect the thin red wire to input, don't connect the thin black one to anything if you are reading from the same source.
The thick black wire is negative reading input, the thick white is negative reading output.

The volt meter, read and black are input, white is positive measurement voltage.

I hope that enuf for you to get it working, please post some photos once you have it done.
acetaz1 year ago
Where does the white wire on the volt metre go .n do we leave both black wire out form the amp n volt metre thank it a good project to do it look cool man
newtonn2 (author)  acetaz1 year ago

Hi acetaz, The schematic and all the info you need are in steps 5 and 6. What extra information do you need?

acetaz1 year ago
Newton can u please change the wire colour to exactly wat on the volt n amp metre so it easier I keep trying but can't get the volt n amp to move I m new to this thank u
acetaz1 year ago
Can some1send me a proper volt n amp wiring thank
djbetterly1 year ago

So everything seems to be working pretty good..kind of. I'm getting a reading on the ammeter, but I'm not sure what it correlates to as it doesn't adjust either. Any thoughts?

Ploopy1 year ago


jhodso1 year ago
Hello Newtonn2,
I was just curious if you were close to finishing the instructables for the Small DIY bench power supply.
Just wondering;)
stevenarango made it!1 year ago

i made one like yours But mine is just a big bigger and its enclosed in a nice wooden case.

But all the Schematics are just like yours Same Materials. Cheers


thanks bro.. nice to hear from you. how are you?

newtonn2 (author)  stevenarango1 year ago
That looks cool! I love it!
I don't know why I just can't figure out the ammeter. everything else is built and working fine, but the more I think about the ammeter wiring the more I second guess myself. I just need help with the thick wires. can someone tell me exactly where to hook them?
zerblatt007 made it!1 year ago

Almost finished! :)

Just missing display filters for the almost-too-bright 7-seg displays and descriptions in the LED window.

Strange thing: I had to use only the tiny black wire on the amps meter, to get it to measure correctly. A bit odd, so I probably have to check that some time.

newtonn2 (author)  zerblatt0071 year ago
That looks awesome!!!

Did you try just with the thick wire? That is what I had to do to get a good reading, the thin wire may be not strong enuf to handle the power.

Thank you very much for sharing photos of your power suppy!

Yes, I did try using it, since you had that in your description, but I only got a 0.00 reading.

The thin wire will handle the kind of current I plan on using this for, so that should not be a problem. I did not mount a heath sink either, as while testing this the chip did not get warm at all.. :)

Some other strange thing: I had mounted a faulty CC/CV LED and while it was mounted the current readout was maxed out to 10A. Soldered in a new LED and the problem was gone..

gmonsivais1 year ago
Would this be suitable for a bench power supply or should I make one from an atx psu

ATX power supplies does not allow you to regulate the current consumption (as far as I know), so if you short circuit something there it will probably give you max current and then power down - or burn up. (They usually have no fuses you can change) And maybe burn your experiment in the process (and let the magic blue smoke out).

If you short circuit this (and normal Lab PSUs) it will give you the current you chose, but not more. Often that is sufficient to save your ICs, transistors or whatever you are working with, sometimes even if you connect the VCC/GND the wrong way.

There are no guarantees if you connect something wrong, but this circuit can save you some problems at least.

And if you sometimes want 4.5 instead of 3.3, 5 og 12V, you have to regulate the ATX PSU output in some way anyway.

newtonn2 (author)  gmonsivais1 year ago
Hi there,
That depend on your needs. What would you use the bench power supply for?
umarnl1 year ago

if we want to run it with 220v as input then what wo do ?

newtonn2 (author)  umarnl1 year ago
Hi umarnl. You need a transformer and at least a bridge rectifier and a couple of condensers. But you can connect any AC-DC transformer up to 28V. Surely you can find more than one hanging around at home.
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