I’m planning to attempt to hack a bathroom scale to put an ESP8266 into it, roughly following this guide. I want to put a co2 cylinder on it and be able to measure how quickly it is consumed based on the weight change over time.
I anticipate having to learn some more about opamps in order to measure the small signal from the strain gauges using the ESP’s ADC pin. I might even finally get to use the new scope!
Before I go buy a brand new cheap digital bathroom scale from London Drugs, does anyone have one they want rid of? They’re not expensive — I just prefer using up old trash before buying new trash.
Yep, I upgraded to a Fitbit Aria a while back and still have my old digital scale kicking around - would be very happy to free up the space. Will put it in the Dropbox tomorrow.
Thanks @DeNomad! If you’re otherwise going to junk them, I’d be happy to have a go at repairing or hacking them. Drop 'em off at the space some time and put my name on them.
On Tuesday night @hectorh and I spent some time with the scope on the bathroom scale donated by @rsim. There is a single strain gauge with a wheatstone bridge and 4 wires. Unfortunately the circuit board is little more than a COB and there doesn’t seem to be any digital signal I can tap, or even an amplified analog signal. So with this scale I think I’d either have to tap the LCD data lines, or just wire the wheatstone bridge to a brand new controller. I’ve ordered a part to do the latter.
This project was a success! I purchased a HX711 module to amplify the small signal from the strain gauge, and just disconnected all of the other existing electronics. Now I can query the module over i2c from my ESP8266.
If anyone still has scales like this that are maybe partially broken, I’d be interested in a couple more. I’d like to put two into my kegerator so that I can monitor the keg fullness.
