I’m building an automatic cat feeder (well updating an existing design). I’ve got a set up where I want to measure the weight of a water bowl and food bowl and since I’m not concerned with exact weights just values of empty and full I wanted to use FSRs. I have them set up separately with two different force sensitive resistors, but in each circuit I have a problem with the values decreasing over time with the same test weight on them.
I have used both this coffee pot example and the Adafruit tutorial circuits, but the same thing happens time after time, I get slowly decreasing values. For example, the empty the circuit reads 4094, I put a weight on it and get 3604 and it will them continue to decrease by one or two slowly over time (i’m measuring an average of 10 readings every 10 seconds). I cannot work out why this is happening - any ideas?