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INDI Library v1.9.9 Released (30 Nov 2022)

Bi-monthly INDI Library released with new drivers and bug fixes.

INDI focuser driver for Waveshare Stepper Motor HAT for Raspberry Pi / Rock Pi

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Ha... our messages crossed. I think the timing is indeed my problem. With the geared stepper, the inconsistent (even reversed) movement happens under zero load. I think I'm just pulsing the motor too quickly.
2 years 6 months ago #54514

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Hah! Looks like esb was all over it! We both posted essentially the same thing!
2 years 6 months ago #54515

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Correct, the ratio in that case is 13:1, the full circle of gears on the focus ring is 130 gears, if I remember correctly.
But you can take A LOT of strain off the motor when moving out, using the rubber band support see in my earlier pictures. That can reduce the strain on the motor by an additional 50% or more, depending on how strong the rubber bands are you choose to install.

Anyway, there is a lot you can do mechanically to support a weak motor with a poor transmission ratio.

And don't forget the reduced backlash. That is something that is difficult to eliminate using the belt drive.

I also added the FreeCAD files to the stl folder. Not sure you can translate them into Fusion360 format, but if you can, there they are!

Best

Jo
Atlas Pro AZ-EQ, ASI1600MM-Pro, ASI120MM-S, ES102ED, WO-Z61, Nikon D3300, ASI-EFW, ZWO LRGB,Ha,O3,S2 filter set
Last edit: 2 years 6 months ago by Jose Corazon.
2 years 6 months ago #54516

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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.
2 years 6 months ago #54518

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Well, all problems in astrophotography are mechanical or optical in the end....

:)
Atlas Pro AZ-EQ, ASI1600MM-Pro, ASI120MM-S, ES102ED, WO-Z61, Nikon D3300, ASI-EFW, ZWO LRGB,Ha,O3,S2 filter set
Last edit: 2 years 6 months ago by Jose Corazon.
2 years 6 months ago #54520

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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!
2 years 6 months ago #54521

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With my existing stepper, backlash now seems to be around 1 step. I can see clear consistent movement for even a single step and when changing directions at most that first step doesn't show full movement. I can see that with large moves in one direction followed by single step moves in the other. When does darkness get here? I really can't way to try it out again.
2 years 6 months ago #54522

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Its especially ironic because the grub screw is one of the first things I advise others to check for many different kinds of 3d printer issues. I need to take my own advice.
2 years 6 months ago #54523

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I still want to go head-to-head with your design.

Identical optical train, so it's just the focuser.

We got to have a competition, Eric!!!

:-)

Best, Jo
Atlas Pro AZ-EQ, ASI1600MM-Pro, ASI120MM-S, ES102ED, WO-Z61, Nikon D3300, ASI-EFW, ZWO LRGB,Ha,O3,S2 filter set
2 years 6 months ago #54524

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I win, been there done that :) I hate Helical's
Last edit: 2 years 6 months ago by Clive Garner.
2 years 6 months ago #54525
Attachments:

    redcat.avi

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That is cool! The key is the tension pulley. That makes all the difference for eliminating backlash, I bet.
Alright, you can be part of the Olympiad here.
I am not chickening out. I am still confident I will win.
:-)
Jo
Atlas Pro AZ-EQ, ASI1600MM-Pro, ASI120MM-S, ES102ED, WO-Z61, Nikon D3300, ASI-EFW, ZWO LRGB,Ha,O3,S2 filter set
2 years 6 months ago #54526

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Already tested, and it worked a treat, the last pic is of Rho, having used full autofocusing
Last edit: 2 years 6 months ago by Clive Garner.
2 years 6 months ago #54527
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