Runaway Ardufocus when using APT auto focus routine

[GixerJas]

Inspired by the Ardufocus project, described in the post linked below from 2017, I built the focuser from the parts that came in an Arduino starter kit, printed a case and fitted it to my C8 SCT.

I had made a fine focuser years ago so I setup the Ardufocus to turn the fine focus knob. The setup work really well manually using the ASCOM Ardufocus driver but struggles with the auto focus routine in APT and also repeated presses of the negative fast movement button where in both cases it tries to return the step count to zero.

I've set the large step movement to 100 and the small step movement to 10. I'm wondering I need to make the large step movement bigger so that changes in the FWHM value are more obvious, but as the forecast is rubbish it's not looking likely that I'll be able experiment for a while. I'm hoping that someone else may of experience with the Ardufocus and may be able to offer some advice.

So far the focuser has cost me almost nothing and it would be great to get it fully functional.

 

[Adreneline]

Interested to see you appear to be using a circular profile pully belt to transfer drive from the stepper to the focusser. This may be a total red herring (apologies in advance) but many (many) years ago as part of my degree I made a hifi (?) turntable using a dc motor and direct belt drive to the rim of the turntable (copied a commercial design available at the time) - made the whole thing from garish coloured perspex. I did all the calcs to size the pulley and turntable so the dc motor gave the desired 33 rpm. First test resulted in the rpm being substantially out - nothing to do with my calcs - all down to procession of the belt on the pulley and turntable rim. Had I used a toothed belt there would have been no problem. In the end it came down to trial and error to size the pulley correctly to the turntable diameter. Procession of the belt caused real problems which I would have thought would be exacerbated with backward and forward movements and repeatability of exact relative positions required with a focusser.

Apologies again of this is a complete red herring.

Adrian

P.S. I have made stepper and d.c. motor focus units and always used toothed timing belts - mind you I have still had problems with autofocus in SGPro.