Hobbyist Current Limited Power Supply/Kit?

[SnakesAndStuff]

I'm a tinker/hobbyist that just joined the forum. I wanted to reach out and say hello.

Does anyone here have suggestions for a cheap kit (or even complete build) for a hobbyist DC power supply with current limiting capabilities. I'm thinking 0-30V up to 2-3A output?

I know it might be faster/easier to buy an already built device, or build a kit. I might do that for a first variable output power supply, but would also like to find design ideas and build one as well for the experience. I've designed/fabbed PCBs in the past (both in house and sending out) and have a very basic, fundamental electronics level of understanding.

Thank you in advance!

[CountChocula]

Howdy! There are very inexpensive buck/boost converters (like this one, for example) that you can use as a starter bench PSU—you can just toss it in an enclosure, add a couple banana plugs, and it's good enough for basic applications. They also have the advantage of being quite compact and using low input voltage, which means that you don't have to mess with mains power if you're not comfortable with it. The downside is slightly noisy output (because it's a switch-mode power supply), and relatively slow transient response. It's otherwise pretty handy, especially when you're starting out.

Building your own supply is a pretty cool project, quite challenging for a beginner, and full of wonderful rabbit holes you can go down to learn stuff. If you want to get a kit, there are a bunch of classic designs that you can buy off eBay for cheap (like, say, this one, which I have seen a bunch of times).

If you want to come up with your own design, a search on this forum will reveal a treasure trove of ideas, as this is a topic that comes up very often, and there are plenty of resources on the web—I found Rod Elliot's website, really useful, because it's well written and clearly explains how things work—you just need to ignore all the warnings about what a terrible idea it is to build your own power supply .

[SuzyC]

Keep in mind that the P/S kit suggested by CountChocula has the following caveats:
1) You need to buy or salvage a transformer from a audio amp, but otherwise you must buy something at least rated 24V @ 3-amp. For this, my first P/S I got one free salvaged from a discarded solid-state audio amp.
2) No metering, but 7-Seg LED displays for monitoring voltage and current are easily ebayable. You will have to design your own current sensing circuit, but voltage measuring is just a voltage divider of two resistors and a calibration potentiometer.
3)This P/S kit will likely deliver 30V at <100mA or so. It will maybe deliver 2-3-amps at 24V, but it will overheat if you want 3-amps out at 3V. You might need a 5-in computer case fan and certainly a larger heatsink then supplied in the kit.

Need an enclosure for your P/S?
I built one on the cheap using a  less than 1$ USD (1-loaf/1-liter approx volume sized kitchen baking) breadpan made of thin tinned steel. Very easy to drill and make holes in and very easily to solder to. So easy to drill  holes for banana plugs, power LED, etc.

Got a free large heatsink from a discarded desktop PC power supply and mounted it on the side of the breadpan. Heat sink served also as a handle to move it around.
5)Think of adding a screw-cap chassis mount fuse holder (got one free from a old audio amplifier). Be careful to ask advice about safely wiring the 120/220V for a power switch(got one free from the same ATX PC P/S). You can find advice on this, and also how to meter current on this site. Same ATX P/S also had a perfect 3-Pin standard PC 120/240V power connector,  and I mounted this on the pan and the ground pin on the connector allowed safe grounding of the breadpan chassis. If you  can find a desktop PC P/S you can take it apart and see how to carefully wire the mains AC to the internal PCB safely.
It conclusion, It was fun to build and cheap as well, funky but very useful for my projects. It was easy to repair and modify and complete its building in steps.

[ledtester]

You'll find a lot of posts on the 0-30V, 2ma-3A power supply kit.

Some links I recommend reading are:

- https://www.eevblog.com/forum/beginners/diy-0-30v-0-3a-again/

- https://www.paulvdiyblogs.net/2015/05/tuning-030v-dc-with-03a-psu-diy-kit.html?m=1

You might also be interested in Paul's blog posts on his new power supply design partly for his views on the problems with the 30V, 3A kit:

https://www.paulvdiyblogs.net/2017/07/my-new-power-supply.html?m=1

[SnakesAndStuff]

1) You need to buy or salvage a transformer from a audio amp, but otherwise you must buy something at least rated 24V @ 3-amp. For this, my first P/S I got one free salvaged from a discarded solid-state audio amp.

I probably should have mentioned that I do ham radio stuff, guitar pedal builds, etc. So I probably should have mentioned I have other power supplies laying around that are less adjustable than my current needs. I'm very comfortable sourcing transformers etc if needed as well!

And thanks to the others that have replied as well!

[Doctorandus_P]

There has been written a lot about this power supply kit, which is understandable, as it's a quite usable supply for a small price.

There are long threads on:
electronics-lab.com/community/index.php?/topic/26825-0-30-vdc-stabilized-power-supply/
electronics-lab.com/project/0-30-vdc-stabilized-power-supply-with-current-control-0-002-3-a/

And there, I found a link to what probably is the origin of this powersupply, designed with the 741 (which can have an upto 44V power supply). The article starts on page 40.
https://americanradiohistory.com/Archive-Practical-Electronics/70s/Practical-Electronics-1978-10.pdf