Kalimba Controller with piezo-resistive fabric pressure sensor for displacement measurement

This simple controller is inspired by the south African kalimba. The kalimba lends itself to rapid assembly because of its use of a single central bar held down by two screws to trap the array of tines between two pivot points. Wooden tines are used in this prototype because they are faster to shape than the traditional metal and this controller doesn’t require the tines to be tuned. The flexibility of copper tape is exploited as strips follow the contour of the flat base around the curve of a half-round pressure pivot. Each tine is covered in conductive copper tape. Trapped between this copper strip and the base strip is a piece of peizoresistive fabric. The rear pivot of the tines also has a copper strip which is a grounding bus for the tines. The 18f2550 on the controller board has 10 ADC’s and sends an OSC-encoded estimate of the voltage formed by a pull-up resistor and the variable resistance pressure sensor of each tine. Notice that the length of each base copper strip is trimmed to simplify the wiring flow of the conductors to the microcontroller. The tines can be used in the traditional fashion to define the size of a “pluck”. Also they can be used as bend sensors after the pluck.


OSC encoded displacement by AdrianFreed
Pull-ups by AdrianFreed
Piezoresistive fabric by AdrianFreed