View Full Version : [queued] music string winding device

05-08-2020, 03:44 PM
Here some info about my main project: a music string winding machine.

It runs on 2 teensies, communicating via a serial line: a T3.5 controls the cockpit and handles display, buttons, calculations etc., and a T3.6 in a separate control box does low level stuff such as generating motor pulses with TeensyStep (https://github.com/luni64/TeensyStep). The machine controls the tension of the extremely thin winding wires with a pneumatic apparatus, so it also has to control air travel, pressure, valves, all fed by a small compressor.

I made a debouncing and deglitching library (https://github.com/jpk73/debouncetm/) inspired by this article (https://hackaday.com/2015/12/10/embed-with-elliot-debounce-your-noisy-buttons-part-ii/) as I needed my buttons also to be deglitched: my library polls buttons and writes the readings into a history and interpretes the history by masking it, fast and reliable (can also process long presses, double clicks etc). The machine has 2 analog pedals connect to it which are managed by TeensyTimerTool (https://github.com/luni64/TeensyTimerTool).

It's a very complicated project, it took me 2 years to built it, and still there are lot's of things to do. Here 2 examples of strings I made:

total string diameter 0.7mm, 2 alloys wound, wire thickness 0.12mm, ground to a metal layer of 0.06mm around the core

string wound with aluminium and copper wires, similar dimensions as above

in this video you can see how a string is wound

this video shows how the machine is used as a wire spooler

PCBs designed in kicad (2 circuits on one board)

I want to thank Paul and his team for all the work on the teensy, without it I would not be able to do stuff like that!!!

05-08-2020, 06:18 PM
So, you finally call it ready :-) Congratulations, this is really amazing work. I love the precision and the speed of the winding. Let the forum know when your orchestra streams a concert next time :-)

05-08-2020, 06:37 PM
Very cool and interesting project!

05-08-2020, 07:21 PM
So, you finally call it ready :-)

Sort of :-) Recently I pulled out the load cells and fitted better ones. There is always something to improve...

In my older posts you can see how I tried to write the pulse ramps by myself (starting on a DUE, see here: https://forum.arduino.cc/index.php?topic=486106.0), I even tried to generate the pulses with DDS signal generator modules. But thanks to your fantastic libraries I now have multiple motors running precisely and in sync! This helped me a lot.

Thank you!