I have been experimenting for quite a while now with robot gearmotors as a means of creating something that can be hand cranked, with just the right amount of resistance to turning. I have been encouraged by Nigel Eaton (Hurdy Gurdy maestro) to continue my effort to simulate a crank handle if at all possible and not give up on this aspect of the project. Again, where possible I am trying to keep the component costs down.

The Teensy microcontroller inside the DigiGurdy needs information on the rate of rotation of the crank. When the crank is turning, the Teensy can then activate the simulated drone strings and open melody string(s) to simulate what would happen when the rosined wheel rubs against or bows these strings in a real hurdygurdy. Furthermore, whenever the rotation suddenly speeds up, it can then also simulate the buzzing sound that this would normally produce, i.e. the rhythm part of a hurdygurdy. 

I have created a 3D printed chopper wheel which intermittently breaks the infra-red beam of a low cost sensor designed for this purpose. This structure has an unusual shape as it has to be somewhat removed from the area where your hand is cranking the handle to avoid damage, it also has to be shaped to fit onto the shaft of the fishing reel crank I am using, while also allowing access to the grub screws that hold the handle onto the motor and also fit over the end of the motor.

I used software with interrupts for reading position encoders etc. but had major problems as the program would freeze and crash when connected to the phone but not when using the Serial window of my laptop. I eventually found a frequency counter library designed for the Teensy microcontroller and this works really well.

I now have all the functions above more or less working OK, i.e. the drones come on when you turn the handle, the trompette buzz sounds when you accelerate your rate of turning and you are able to play the melody on the keys once the handle is turning. I am very pleased with the outcome so far.

The next step is to redesign the enclosure for this so it is more in keeping with the rest of the DigiGurdy so can be added to the end in a modular manner.