01/03/2021 at 18:38 •
My unorthodox way of opening the kitchen scale had a side effect to melt some plastic around the screws. The deformation made it impossible to close back the enclosure, so I wanted to drill the screw holes a bit. Before this, I wanted to remove all electronic parts to avoid plastic debris going everywhere.
I was going to un-screw the load cell when this happened:
Well, that sucks. One of the two screws carrying the load cell snapped. They're meant to bear the entire weight of the cat feeder. I can't remove that piece of screw, and I don't feel comfortable in using just one screw. So the entire base is now useless.
I threw all the plastic away and kept the 5kg load cell and some of the electronics (could be useful in some other projects). And I'm 3D-printing a new load cell bracket.
01/02/2021 at 17:21 •
I thought it was an HX712 load cell ADC, but after a cleaning and a thorough inspection instead this IC shows itself as an LM324DG. Lesson learned: never make optimistic assumptions...
In the meanwhile I also scratched/shorted some pads so now the scale thinks the battery is low - but I'm powering from a lab supply!
Time to buy a proper HX711-based module I guess.
01/02/2021 at 15:46 •
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: