Importing cheap equipment and test gear is something of a mixed blessing. It allows you to outfit your lab without emptying your bank account, but on the other hand there’s usually a reason it’s cheap. Of course, the retail price of a piece of hardware shouldn’t be the metric by which we measure its quality, but there’s got to be a few corners cut someplace when they are selling this stuff for a fraction of what the name brands are charging.
A perfect example is the ZHIYU ZPB30A1 electronic load, available from various online importers for about $30 USD. While the price is right for an adjustable load that can handle up to 110 W, it’s got some pretty glaring shortcomings. In an effort to address at least some of those issues, [Luca Zimmermann] has been working on an open source replacement firmware for the load’s STM8S microcontroller.
[Luca] quickly discovered that the device’s STM8S005K6 chip is write protected, so unfortunately you can’t just flash a new firmware to it. If you want to unlock additional features, you need to perform a brain transplant. Luckily these chips are quite cheap, and you can probably add a couple of them to your cart when you order he ZPB30A1.
With the new GPLv3 licensed firmware installed, the device gains constant power and resistances modes (stock firmware can only do constant current), serial logging, and support for adjusting the value of the shunt resistor. There’s even a basic menu system to shuffle through the new modes. There’s still a couple features that haven’t been implemented, such as automatic shutdown, but it’s already a considerable upgrade from the stock software. Now we just need some details on the slick custom enclosure that [Luca] has put his upgraded ZPB30A1 into.
[Thanks to Benik3 for the tip.]