final: shoe insert pressure sensor array
For my much neglected final project, I fabricated a low-profile array of pressure sensors that fits in a running shoe. The sensors are multiplexed -- 24 of them are serviced by four transmit pins and six receive pins. I designed and fabbed a board, but unfortunately, machine building ate my life and I didn't get code running on it. The new sensor behaves beautifully, however, using my old TXRX board.
The image above is from my design for the vinyl cutter using kokopelli. I used my foot trace I made a few weeks ago and laid out points sampling the area. All geometry is instanced over these points, including sensor pads, shields, lines, paper substrate, and kapton guard.
Multiplexed TXRX board:
The unlabeled pads at the bottom are vias for a simple multilayer stack. In order to route the six voltage dividers, I cut a solder mask and routed copper strips over the top.
Hacking the ISP connection:
Processing sketch responding to new sensor:
I'm looking forward to getting this sensor working to its full capacity. I wrote the code to run on the Tiny44, but haven't tested it yet. Obviously, there is a trade off between the number of samples to accumulate for each reading and the measurement speed. To see the phenomena I want to measure, I'd like a measurement rate of roughly 100 Hz, but with 24 pads to take readings on, I think I'll have to lower the accumulation number to around 10. I hope this is still enough to average out noise.
Files: