Wii Balance Boards
We need more than just a scale. We need a scale that we can control and read with a Raspberry Pi and that will fit neatly under your refrigerator while keeping it stable. We need a scale with bluetooth that can communicate with the Raspberry Pi. We need a Wii Balance Board! We actually we need two.
Let's test connecting both Wii Balance Boards with the Raspberry Pi's. Decide which board will go with which Pi. You'll connect each board & Pi individually.
Take your first pair and let's start. Type the following command into the Pi:
$ cd ~
$ git clone https://github.com/InitialState/smartbeerfridge.git
Cloning into 'smartbeerfridge'...
remote: Counting objects: 12, done.
remote: Compressing objects: 100% (10/10), done.
remote: Total 12 (delta 2), reused 0 (delta 0), pack-reused 0
Unpacking objects: 100% (12/12), done.
You should see two python files in the new smartbeerfridge directory - smartbeerfridge.py and wiiboard_test.py.
$ cd smartbeerfridge
$ ls
README.md smartbeerfridge.py wiiboard_test.py
Run the wiiboard_test.py script to test communication and take weight readings from the Wii Balance Board:
$ python wiiboard_test.py
You will see the following response:
Discovering board...
Press the red sync button on the board now
Remove the battery cover underneath the Board to locate the red sync button. Make sure you press the button within a few seconds of running the script or a timeout will occur. Once successful, you will see something similar to the following:
Found Wiiboard at address 00:23:CC:2E:E1:44
Trying to connect...
Connected to Wiiboard at address 00:23:CC:2E:E1:44
Wiiboard connected
ACK to data write received
84.9185297 lbs
84.8826412 lbs
84.9275927 lbs
The wiiboard_test.py script is taking the number of weight measurements specified on line 10 and outputting the average:
# --------- User Settings ---------
WEIGHT_SAMPLES = 500
# ---------------------------------
You can play with this number by changing the value and re-running the script to see the variation in weight measured and time required for each measurement. Weigh yourself, weigh your dog, weigh whatever and see if the measurements make sense. To stop the script, press CTRL+C.
You'll need to repeat this step on your second set of Pi & Wii Balance Board.
Nintendo assumed you would always power your Wii Balance Board with four AA batteries and included no AC power adapter. Having only battery power would be a non-starter for this project considering the inconvenience of getting to the battery pack once it is under an 80+ lb refrigerator. Luckily, there are several third-party adapters made for the Wii Balance Board that we can use to provide constant power from a wall outlet. The Wii Fit Rechargeable Battery Pack is a perfect solution to our power problem. Replace the batteries with this battery pack, and plug the ac adapter into a wall outlet.
Having to pair the Wii Balance Board and Raspberry Pi every time we run our Python script presents a problem due to the location of the sync button. The sync button is inaccessible with a refrigerator sitting on top of it. We can fix this by making a hacky little lever using a pencil and three 3/8" felt pads as shown above. The rechargeable battery pack exposes the sync button to the underneath surface of the Board. Tape a pencil (or something similar) that spans from the sync button to the outside front of the Board. Stack three 3/8" felt pads (or something similar) on the center (ish) of the pencil to create a stationary pivot. Be careful to not expose too much of the pencil out from the Board as you don't want someone to accidentally kick it out. Flip the Board over and you can press the sync button by simply pressing down on the lever. Hacky but effective.
Depending on the surface that your refrigerator sits on, you may need to remove the rubber grip pads from the feet of the Board (the pads are simply stickers you can pry off). If you slide your refrigerator on a hardwood or tile floor to put it into place, the 3/8" felt pads can be placed on the Board's feet for easy sliding.
Once you have both boards connected and working it's time to install them!