Hi mate,
I have 3D printed a focus motor attachment & coupler for my C8.
I've shared a photo of my setup before here, I guess you can find it there.
What I like is that it still has a (big!) handwheel.

Would you like to have the design?
It uses a direct drive very flat Nema 17 stepper motor and the SilentStepper drivers (TMC2130) on a breadboard still.

Works flawlessly and runs absolutely smooth. I have attached a temp sensor and configured it to play well with the Moonlite protocol.

Cheers!
Bart

Hi Bart, thank you and would appreciate if you can share your 3D designs. I’m in the process of building mine.

One more thing is that your motor is much lighter and smaller (as I can tell from pictures) from the one I got, can you please also share your hardware specs as well?


Thank you
Mohamed

I use the autofocus routine in the Ekos focus module and it works well. I stuck with the default detection setting of gradient and the default algorithm of iterative. It tried the relatively new linear algorithm outlined in this link, but I never got it to achieve focus correctly: knro.blogspot.com/2020/02/kstars-v340-is-released.html

To be fair, I tried it once and just haven't had an opportunity to go back to it and troubleshoot. The default settings have been good enough for me since my attention has been on tweaking other areas of the setup. I'm pretty happy with my configuration so far, so it might be a good time to play with the linear algorithm again.

I use the MyFocuserPro, not the MyFocuserPro2 IDE, but assume much of it is interchangeable. The cranking power of a regular NEMA17 is plenty to lift a truck attached to a camera (figuratively speaking). A NEMA14 should be plenty. You can drive both from a DRV8825 stepper controller.

The beauty of building your own focuser is that once you have done it once, adapting it to another telescope is easy.

Also, with a DRV8825 you will have a stepper resolution of 6400 steps/rev, i.e. ~ 0.05 degrees, which more than likely is far better than the mechanical tolerance of your focuser.

All I can say is, I built one based on the MyFocuserPro (not 2) instructions and the result could not possibly (repeat; possibly!!) be better.

Jo

PS: Looks like Bart is using a slim version of the NEMA17 ( smile.amazon.com/gp/product/B00PNEQ79Q/r..._title?ie=UTF8&psc=1 ). I have that as well, but have not implemented it yet. Should work fine, though, I assume.

Thank you Jo, what confuses me a little is that the specs of the motor you mentioned in Amazon is “This is Short Height Bipolar Nema 17 stepper motor with 1.8 deg. step angle (200 steps/revolution). “

Is this specs still capable of 0.05 degree/step?

I would prefer using a lighter motor as the one I got is much heavier...


Thank you
Mohamed

The DRV8825 stepper controller allows you to select microstepping down to 1/32, i.e. 32x200=6400 steps/rev. In fact, you can use any microstepping mode in 2x intervals.
I am using my NEMA17 at 1/32 microstepping and the resolution is far better than required for my telescope, so you can try out how much resolution you require.

Thanks Jo for explanation. Is this settings from the driver interface or the Nano code?


Thank you
Mohamed

There are three physical microswitches on the DRV8825 control board. The DRV8825 spec sheet will tell you how to set them to have 1, 1/2, 1/4, 1/8, 1/16 or 1/32 microstepping modes.

In this video I demonstrate how they work:

www.dropbox.com/s/7pwzxom3mpi0z1m/Arduin...serInAction.m4v?dl=0


In each case, the stepper was instructed to move 1000 steps.

Neither the buck converter or the OLED are strictly required for the focuser to function. All you need is a 12V input, the Arduino Nano, the stepper, and the DRV8825 control board (with A4988 controller on the board). OLED, Temp probe, and LEDs for indicating IN and OUT motion are optional. It really is a very simple plug and play array.

Indeed Jo,
I used one of those slim line.
Nema 14 could also be ok, but I had the 17 lying around and a bit of headroom in the torque is nice to have.
I prefer the Trinamic fdrivers, for they are just absolutely smooth, which just 'feels' good.

Yes Mohamed, the code to control the stepper motor driver (microstepping, speed, acceleration etc) is in the Arduino code.
I'm busy now, but will upload files later this week.

Cheers!

Bart, where can I find the Trinamic driver code? Can you post it?

Jo

Edit: that photo was way to big,...

I'll post the finished board later.

Hi Bart

Is it possible to share the 3D print design for the C8 attachment? it will help me design my own or just use your design