Kitchen scale teardown

A project log for Cat Feeder Watchdog

Hack a kitchen scale to check that my automatic cat feeder really delivers the amount of food I expect.

Enrico GueliEnrico Gueli 01/02/2021 at 15:460 Comments

It was a bit harder than I thought, but I finally managed to open the old kitchen scale I had lying around:Two of the screws didn't leave their place even though I put some spray on it (just realized I put contact cleaner instead of WD-40... d'oh!). Any attempt with screwdrivers only stripped them more and more. So I took my soldering iron and heated the screws while applying some force to separate the two plastic parts, waiting for the plastic around to soften. Success!

Inside I found what I was hoping to find: a load cell and the handling circuit. And felt lucky to find the analog frontend separated by the IC blob:

The IC is not the well-known HX711 but it's probably a HX712, its low-power version according to the manufacturer, Avia Semiconductor.
I wanted to tap into the digital lines connecting the two ICs but had no luck so far finding the right pins. The conformal coating on top of everything on the analog part doesn't help either.