Kevin Ross replied to the topic 'INDI focuser driver for Waveshare Stepper Motor HAT for Raspberry Pi' in the forum. 16 hours 24 minutes ago

Sorry, I just now saw your post.

I use the "sync" feature for that. I just type in a large enough number (usually 5000) and hit "sync" in the focuser INDI control panel. It now things the focuser is at position 5000.

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Kevin Ross replied to the topic 'Always focus from one direction' in the forum. 6 days ago

Very well. That certainly makes it easier for me, since I've already done most of the work in my Waveshare driver. :)

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Kevin Ross replied to the topic 'Moonlite focuser doesn't move with 3.4.3 KStars MacOS' in the forum. 7 days ago

I don't have an easy answer for you, but some tips.

1. You could try different versions of INDI, and compare the debug output logs. Compare a working vs non-working, and note any differences (especially differences in commands sent). That might point to the culprit.
2. If you can build INDI from source, then I would do a "git bisect". It will automate the process of trying different builds, narrowing it down to the one exact code commit that broke things.

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Kevin Ross replied to the topic 'Always focus from one direction' in the forum. 7 days ago

DerPit wrote: But couldn't (shouldn't?) that capability go to the general INDI focuser class, so that <em>any</em> driver can benefit?


Doing it there, rather than in the Ekos UI, is also an option. I hadn't considered that.

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Kevin Ross replied to the topic 'Always focus from one direction' in the forum. 7 days ago

knro wrote: So you can implement this in your driver with Ekos needing to know about it. Once you detect a switch in direction, you perform the large move and then go back to that position again. As far as Ekos is concerned, it's just waiting for you to finish your move.


I've already done that. I was asking if putting this in Ekos as a universal solution was better. :)

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Kevin Ross replied to the topic 'Always focus from one direction' in the forum. 7 days ago

Well actually....

I looked at that picture. 21 iterations to reach focus! Wow. Polynomial works pretty well for me, and usually in 7 or 8 iterations.

I suspect a universal anti-backlash mechanism would be useful, so that it isn't tied to one focus algorithm.

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Kevin Ross replied to the topic 'Always focus from one direction' in the forum. 7 days ago

Excellent! I'm glad I asked before implementing! :)

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Kevin Ross created a new topic ' Always focus from one direction' in the forum. 7 days ago

Hello,

I have recently written an INDI driver for a DIY focuser. One thing I've implemented is the ability to always approach focus from one direction, to eliminate backlash. But it seems to me this is the kind of thing that would be universally applicable to almost all focusers. So do you think it would make sense to implement this in the Ekos focus tab? Some extra options under "mechanics" perhaps?

The current anti-backlash implementation in most focus drivers is a fixed number of steps that get added when changing directions. This requires a lot of trial and error, or careful measurement. The approach I've implemented (which I believe is the same method used in Sequence Generator Pro) is to always approach focus from one direction. For example, if the focus needs to move in, then move in the desired number of steps. If it needs to move out, then move out the desired number of steps, plus some arbitrarily large number of steps, then move in to the desired position.

Does this sound like a good idea, and should it be in Ekos focus module?

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Sweet! Another satisfied customer! :)

Sounds like you might not need the geared stepper.

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Congrats on the progress! :)

For myself, auto selecting a single focus point has never been reliable. I either need to manually select a single point, or use full field mode. Full field mode is the method I use now. You can even tell it to limit itself to the central part of the image, if you prefer.

I use the polynomial focus method. It seems to work well enough. I never tried the linear. I might give that a try. Some people say it works better.

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Very nice! Just curious, what are using to control the stepper motor? The Waveshare HAT, or some other (possibly Arduino) controller?

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esb wrote: And a problem like this wouldn't be complete without a facepalm. I just noticed with the stepper attached to my RedCat, if I ran it from 0 (fully retracted) to nearly max (500) and then back to 0, it kept missing the zero point by a few degrees (it was always short). It turns out the grub/set screw for the pulley attached to the stepper is loose. Double-d'oh! That means I have at least 10+ steps of backlash. I'm guessing it will work much better with a tight pulley.


Consider yourself getting off easy! When I did the Rowan belt mod for my Orion Atlas mount, one of the set screws on a pully deep inside the mount wasn't tight enough. Took me a month to figure out why I was getting such bad backlash in Dec movements! So I had to tear the mount apart to tighten that screw. I put blue Loc-Tite on those screws, just because I was mad at them!

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Hah! Looks like esb was all over it! We both posted essentially the same thing!

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El Corazon wrote: My 2 cents on this is that upon microstepping down to 1/32 and using only one step for each move, the motor does not have enough torque to reliably move that one microstep.


When using the Waveshare INDI driver that I wrote, a single step in the INDI control panel will equate to 32 microsteps at the motor. I always end on a full step boundary. I use microsteps for smoothness and quietness, not for increased resolution. If it were to stop on less than a full step, then the motor would need to have power applied to it constantly to hold that position, thus using more power and causing the motor to get warm (or very hot if you haven't tuned the current limit). But with my approach, that allows me to turn off power to the motor when not actively moving for focus.

So I'm not sure if that is esb's problem of it not always moving the same amount with a single step. Does that also happen if you disconnect the belt, just letting the motor run free? If it works fine when the motor is running free, but misses a step when connected to the belt, then it is most likely a lack of torque. You can try slowing down the motor with the delay settings, since stepper motors lose torque when running faster. You can also try using less microstepping via the DIP switches. You will need to modify the source code to match the micrstepping setting of the DIP switches. Eventually I'll make that a configurable option in the INDI control panel.

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