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Astroberry Focuser with Adafruit Motor HAT

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I'm starting this topic up as Kaczorek mentioned it would be prudent to start a seperate thread on this topic, with a shout-out to Christian for his modifications.
Regarding the development of an Adafruit version of the Astroberry autofocus driver. The Adafruit motor controller HAT appears to be an excellent alternative to the PiFace. Whereas the PiFace required 2 integrated boards to control stepper motors and is no longer produced. The Adafruit is an all in one solution at a quarter of the price and is still being manufactured. It also just came back in stock. IMHO an ideal DIY autofocus platform.
7 years 4 weeks ago #15534

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Indeed it's interesting piece of hardware. I'm waiting for it's available in my local store. As soon as I get it I can start with a driver. Unless somebody else will accept the challenge. In such a case I can help.
7 years 4 weeks ago #15571

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I am currently getting parts together in advance. I have the motor, and the Adafruit board. Plus I modeled everything and am ready to 3D print the rest. Once I get those all done I can theoretically begin to test anything you have written.
7 years 4 days ago #16230

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The Motor HAT is already available in my local store. I gave it a closer look and found out that it supports Raspberry Pi model A+, B+ and Pi 2. Raspberry Pi 3 is not on the list. This means I'm not going to buy it but I can develop a driver for it anyway. Let me know when you have all parts altogether so there is a piece of hardware for tests.
7 years 1 day ago #16279

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That's understandable. Indeed the website doesn't explicitly state the Raspberry Pi 3. But I suspect that is probably out of date information. I had to do a little searching to find information that suggests it is indeed compatible. As seen here. I am currently 3D printing parts as I am writing this. So I should be ready to go soon. Thanks again for time.
7 years 1 day ago #16280

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Hello Kaczorek. Great news here. I have finished assembling my 3D printed, stepper driven focuser and have driven it successfully with the example scripts Adafruit provides.
6 years 11 months ago #16470

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I tried to attach these before. But I think the files were too large.
Last edit: 6 years 11 months ago by Andrew.
6 years 11 months ago #16471
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I have a few more iterative improvements I want to make before sharing the STLs which I am happy to do. The design is custom made specifically for the old style Skywatcher rack & pinion focuser. As for parts list. I will put one together when I get the chance. The motor I chose was a NEMA 14 with 51:1 gear reduction.
If I were to start over from scratch I would have probably chosen a NEMA 11 with roughly half that reduction. It's a lot of motor, slow and lots of torque. A bit overkill. I also had to add an LM7805 linear power regulator circuit onto the free pads built onto the motor hat to convert 12V to 5V to drive the motor properly and make holes through the case of my Raspberry Pi for new port and power terminal for the HAT.
6 years 11 months ago #16498

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hi!
as a side product of my raspberry Pi based telescope control system TSC - github.com/selste/TwoStepperControl/wiki/TSC - i am developing a custom driver that interacts via SPI with the pi and consists of a arduino pro mini and DRV 8825 ... would that be of interest??? shoulde not cost much more than ~ 20 € in total ...
yours
wolfi
6 years 11 months ago #16504

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Well done! So it's my turn now to develop the driver for it. I will keep you posted of the progress.
6 years 11 months ago #16505

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Do you measure/sense that the focuser draw tube is at its limits?
6 years 11 months ago #16610

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Limits are preset in a driver i.e. pos 0 is starting inward position and 20000 is maximum outward position.
Sensing the limits would require additional hardware such as encoders or similar.
6 years 11 months ago #16611

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