So I built this hardware ages ago but it was up to the software to do the heavy lifting. I finally decided to pick this up again after finally getting around to figuring out the software platform I was going to use for my projects (updates for my other project coming soon). I decided Node-Red was the most appropriate as the data flow paradigm is well suited for sensor based data feeds.

But this is about the hardware so read on.

The donor device was the kitchen scale I had laying around which is a Salter 1036. Inside there's a strain gauge that attaches to the top and bottom plates by two screws on each side. It is then connected to the display board by 4 wires: VCC, GND, S+, S-. The PCB then handles the zeroing, measurement unit and display. I initially soldered my wire on the pads but that made the display show 0 so I decided to skip keeping the device functional and move everything to the ADC. One thing to note if you're following the images is that the wires coming from the gauge have different colours going through the thick cable: red-red, green-green, white-yellow, blue-black. The next bit was pretty simple: order the appropriate (read cheapest) ADC for strain gauges, the XFW-HX711 (other HX711 variants are available), and hook it up to an Arduino. The breakout board offers two channels but most libraries deal with only one. Speaking of libraries the ones available have a tendency to use the analogue pins for digital communication in their samples but whatever. I'm not going to question them.There's not much more to it. I might revisit it with some buttons and maybe an NFC reader with tags at the bottom but I want to get this one working first. Tune in next time for the firmware and software setup, where all the interesting things happen!

Acknowledgements: Shout out to the original article that suggested using the HX711 for this.