20 May 2016

After a frustrating few days I have finally got the Vibracelet working. There were two problems to note:

1. Sensitivity of the piezo sensor; and
2. Wiring of the attiny85.

The piezo sensor was nowhere near sensitive enough to pick up normal level sounds from a mobile phone or doorbell. However, I finally managed to solve this by using an exponentially weighted moving average in the ADC code of the attiny. The sensitivity still needs some adjustment and a method of adjusting/calibrating on the fly but that can wait for another day.

The difficulty with the wiring resulted from a lack of pins on the attiny. I solved this by tying the CE pin of the NRF24L01 to VCC (3.3v). This isn't ideal as it will increase battery drain but I will look at ways of multiplexing the CE pin later. If I can find no other solutions I may need to change my microcontroller. Any suggestions are gladly welcome.

Finally, I took a short video to show it working in all its glory. There is still a lot to do but I am pleased with progress to date.

Great Success!! Anyway, I had best tidy up before my wife realises I have mutilated her doorbell...