Dog Water Bowl Scale, Part 3: Final assembly and installation

In my previous post, I covered the mechanical construction of the scale. In this post, I finish assembling the scale, calibrating it, and installing it.

After painting I put feet on the scale so it won’t soak in water spilled on the floor.

Adding feet to the scale
Adding feet to the scale

…then bolted the Arduino 101, Load Cell, and Load Cell Amplifier to the bottom plate.

The parts bolted into the final assembly
The parts bolted into the final assembly

Here’s what the bottom looks like, with the USB (power, really) cable snaking out of it.

The underside of the finished scale
The underside of the finished scale

Next step: calibration.  I read out the scale value for the empty scale; that’s the Offset. I then weighed a nominally-5-pound exercise weight on a food scale, then placed that weight on the scale and calculated the difference in value divided by the measurement from the food scale – that’s the Scale; the Slope; the second calibration to perform.  With those two measurements complete, the calibration was complete.

Weighing the calibration weight
Weighing the calibration weight
weighing the calibration weight on the scale
weighing the calibration weight on the scale

Then to test the calibration, I weighed the partially-filled water bowl on the food scale, then weighed it on the bowl scale, and read the BLE (Bluetooth Low Energy) Arduino 101 output on my phone.  Happily, the two readings were close: 1.168 kg vs. 1.170 kg.

Weighing the water bowl on the 'standard' food scale
Weighing the water bowl on the ‘standard’ food scale
Weighing the bowl on the bowl scale
Weighing the bowl on the bowl scale
The water bowl weight read on my phone
The water bowl weight read on my phone

I then modified the Raspberry Pi Node.js Service from my Dog Bed Scale to read the one weight from the bowl scale rather than the five weights from the dog bed scale.

With everything working, I created a stream on data.sparkfun.com, finished off the scale with a cutout from a waterproof placemat and placed the scale and the Raspberry Pi in the family room – score!

The installed scale - and yes, I used a Minions placemat on the top
The installed scale – and yes, I used a Minions placemat on the top

You can view the stream of data on Sparkfun’s data warehouse, at https://data.sparkfun.com/streams/ZGaqKmR75DtQrx80a4vW. All the source, mechanical notes, materials list, etc. are Open Source, on Github, at https://github.com/bneedhamia/CurieBLEBowlScale.

What might you make from this sort of scale? A dog food scale, a scale under your cat’s favorite sleeping spot, a scale under your coffee cup at work?  Have fun!

Next, I’ll see what the scale says about Pippa’s drinking and when we fill her bowl.