Background

We were using a low-cost ceramic piezo sensor to detect impact (vibration). The low-cost sensor presented a number of challenges:

1. In order to detect impacts, the sensor had to be directly, mechanically affixed to a surface where that impact was taking place; once the sensor was affixed to a surface INSIDE of a housing, it was not sensitive enough to detect events.
2. Having a sensor external to the housing was unacceptable from a usability perspective; the piezo wires were thin and prone to breaking and the user experience of having to attach an external sensor is fiddly and cumbersome.

I designed and prototyped a 3D-printed solution made up of a stretched membrane (internal to the device housing) that the sensor was affixed to. The membrane utilized a tensioning mechanism (similar to a drum head) used to keep the membrane tight enough for vibrations to travel through. It worked well, but we ended up spec’ing a different sensor (film type) instead to reduce mechanical complexity.