The DCDC-MH works (a hack while waiting for Santa)

A project log for Low-Cost Programmable Power Supply

Chinese "LM2596 DC/DC buck converter with voltmeter" + "some wires" + "Forth" = "programmable power supply"

thomasThomas 12/24/2019 at 17:294 Comments

I tried out my new hot-air rework tool - replacing the µC works great!

I then traced a few signals (a first gist is here: and used the trusty W1209 binary as a starting point.7S-display, LEDs and key "S1" all work, and PD1/SWIM is used for half duplex console.

Here is the result:

Edit: gist updated (now including code).
In case someone wants to order a board: this seller seems to have the lowest price.


Ken Yap wrote 12/25/2019 at 14:03 point

BTW that's a really good price, even if one doesn't want to hack them, for a normal buck converter to turn all those wall warts that one accumulates with desktop external HDs, modems, laptops, etc, putting out 12V, 15V, 19.5V, etc., into 3.3V or 5V power supplies for projects. I have been using these buck converters: but those use USB sockets and one would have to get USB cables and connectors. That's good for phone charging, but phones have moved on to USB-C and smart fast charging. These have terminals and a voltmeter, albeit for a larger footprint.

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Thomas wrote 12/25/2019 at 15:34 point

That's right, the price is really good. Only 30 years ago good power supplies were very expensive, and no one would have trashed them like we do it today!

The board above is also good if you want to add some more safety to a salvaged power supply: the voltmeter can be used for monitoring the input and output voltage and, with just a bit of wire, one can have the "voltmeter" shut down the LM2596.

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Ken Yap wrote 12/24/2019 at 20:00 point

👍 Nice going.

Later today I have to check out the soldering and rework station Santa brought me. Merry Christmas!

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Thomas wrote 12/24/2019 at 22:10 point

Merry Christmas to you, too! Have fun with your new toys!

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