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Dog Weigh Scale
Sunday, April 04, 2021
Made a scale to weigh the dog.  Uses load cells and an Arduino Nano to read the cells and show the values on the LCD display.   It is self-taring so that all one has to do is turn it on, wait 3 seconds for it to zero, then (the hard part), convince your dog to sit on it.  (Photo shows an Arduino UNO but I used a Nano because of smaller footprint.)

I used plastic that I had kicking around but you can use 1/4" plywood if you want.  I support the wood on the 4 load cells using 1/4" aluminum strips.

I replaced the plastic because it was too slippery and worrisome for the dog, putting a piece of rug on top of the plywood.   I calibrated the scale using some calibrated weights.

Hover over photo for description, click for larger.

The four square silver things are the load cells
1/4" aluminum strips support the wood base, contact the load cells
Dimple mates with the top of the load cell
Load cells and "combinator" board for many wires.
Schematic of the arrangement
Made my own "combinator" board.  Chip is pre-amplifier
Bottom of combinator board
Another schematic of the setup
The plastic is from some old signs.
I used a generic (Amazon) plastic box and 4 line LCD display (I2C).  9 volt battery is inside box.
System is self taring: goes to zero with no weight.