A DIY bench PSU using parts from Banggood and ATtiny85 based control

I made a bench PSU using parts purchased from Banggood and it actually worked! Well not as well as I would have liked but anyhow I originally designed the PSU to have 0-30V at up to 4A output using a transformer salvaged from an audio amplifier and a XL4016 based regulator board from Bangood.

This didn't go to plan as the regulator module, advertised as 8A output is total BS. The heatsinks on the module are inadequate for half that current with them getting scalding hot within minutes. So I opted for 20V at 1.5A output limited by the choice of power transformers I had in my spares box.

I used a DSN-VC288 voltmeter and current meter, XL4016 based regulator, relay board and a ACS712 current sensor. I decided to add my own modifications by controlling the PSU by an ATtiny85 which operates the relay module on the output via a push button switch. The ATtiny85 also monitors the current drawn by the load and if it exceeds 1.75A it disconnects the load and lights a warning light.

Other problems I had was the voltmeter and ammeter was very inaccurate and required some modification and adjustment to get it reasonably correct. These cheap panel meters are not very good and the quality leaves a lot to be desired. Definitely no use where accurate readings are required.

This was intended to be a cheap PSU for a relative who is getting into electronics and I thought I'd make a power supply for him that was easy to use and could not be damaged by shorting it out etc. This project ended up as a success on that part but I wouldn't recommend building your own bench power supply if you are serious about electronics. Just buy one instead. Even a decent brand second hand one if required.

The interior wiring is a bit messy and I have yet to replace the insulating tape with shrink tubing once it arrived. Once this arrives I will tidy up the internal wiring and give it a full extended soak test.

Reviews of the DSN-VC288 and the XL4016 regulator module can be found on my blog along with a full article on this PSU build. You can also download the firmware for the ATtiny85 electronic fuse as well.

http://www.xlsemi.com/datasheet/XL4016%20datasheet.pdf - XL4016 datasheet

https://www.adrian-smith31.co.uk/blog/wp-content/uploads/2020/06/Electronic-Fuse-Schematic.jpg - schematic based on a transformer with a 28V AC and 6V AC windings (36V DC and 9V DC approx) final version used transformer with single 16V AC winding (about 21V DC after rectification) and panel meter power supplied from unregulated input of the XL4016.

https://www.adrian-smith31.co.uk/blog/2020/06/20v-1-5a-bench-psu-with-attiny85-based-electronic-fuse/ - download firmware and build article

#diyelectronics #attiny85 ... https://www.youtube.com/watch?v=or9SQd0LLKw