Christmas 2018 sitrep of catPooPee. There is a fly in my ointment
The weighing system for litter box plus cat works fine for clearly indicating that a cat is present... but I can do that with the motion videos. Need to get to accuracy and precision and repeatability to weigh their deposits. Initial weight data indicates goofy things like litter box weights tiny tiny bit less after the cat's visit than before. Don't think the cat comes to the litter box to eat dirt so that finding is suspect. My first guess of the errors in repeatability or showing small weight changes over very short period of time comes from the haphazard way in which I constructed the platform on which the litter box rests and which holds the three load cells. Take a look at my thrown-together platform and hazard some guesses (please)
platform0 pix link: http://dabeak.com/platform0_3strut_3LC_ ... 2357~2.jpg
platform0: 3/8" plywood scrap for planar surface. 1/2" AL angle used to fab struts that hold load-cells (at extreme ends). arduino and load-cell amps mishmashed willie nillie toward center. Assembly contacts floor by 3 M4 hex head bolts and extreme end of load cell. The 'struts were intended to stiffen the plywood to minimize sag when loaded.
My guess is that in taking path of least resistance for fabrication, the floor contact points are a few degrees off plumb. The off-plumbness is aggravated by the platform not being stiff enough. Fully loaded with litter box, litter and cat there is a perceptible sag in middle. When cat jumps out after 'event' the sag rebound plus stiction of the floor contacts probably changes how far off vertical the contact points are oriented.
Next action is to remount all the load cells to ensure vertical force vector and to stiffen platform to eliminate sag.
After reading up on the HX711 load cell amp I see lots of folks chasing both noise and drift issues. I'm sure I'll get to that but that's fine tuning compared to errors that I have now.
Still convinced that cats are extra-terrestrial engineers.