alastair-duncan
commented
3 years ago Thank you for the contribution. I've taken a look and the penny has finally dropped, very interesting.
I've come across a further foot pedal made by Adafruit which has been developed for this type of application. Its a bit more expensive than the expression pedal and has a slightly different operation, its more like the hall effect accelerator with a spring return, its based on a sewing machine pedal. I've not checked it out yet.
https://www.mouser.co.uk/ProductDetail/Adafruit/3739/?qs=wUXugUrL1qxuriSmy34Ptw%3D%3D
Easiest solution :)
Obviously the cmdLineTest.py code is not meant to be a complete solution - it's to test the PWM outputs from the microcontroller. It does allow testing of pulse width, duty cycle et al; for the time being it doesn't offer the ability to ramp up power for the individual pulses, but it's a possible thing to play with.
The more elaborate code will grow to incorporate the control pedal (once it arrives) & potentially a UI. Will sort a diagram out shortly - the flyback diode (1N4007) protection of the FET outputs is essential to avoid frying the FET when the solenoid powers off; that's incorporated into the external PWM module of the original, but a 2p diode is a little cheaper.