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DIY stand-alone controller for Ra axis and Vixen MT1 step motors - questions


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Hi! 

it's becoming subsequently harder to find hand controllers for Vixen MT1 motors --  there are different go-to solutions out there, e.g.

- onstep:  https://onstep.groups.io/g/main

- littlefoot: http://www.lfep.de/  (though the website w built instructions seems down atm?)
 

I'd be interested in sth simpler, namely a stand-alone controller for the Ra axis, similar to the Vixen SD-1 controller; powered through DC 9V input or USB ,  with  1x, 4x and 16x tracking speed, a pause button and a north/south switch . Are you aware of any well documented built instructions for Ra tracking available? (There is of course tons of material on running stepper motors w Arduino online.).

 

I'd pitch an Arduino-based controller, the main goal being to use standard, easily available components; I'd make the software and instructions available, tailored to Vixen MT-1 (bipolar) motors. I'd start with a breadboard setup, and once it's working try to fit this in a hand controller-sized box. Haven't worked w Arduino yet, but we've all a long winter ahead I reckon, so this might be a fun project for some Sunday afternoons.! 

 

What about these three standard main components:

- Arduino Nano Every ( ~ 10 Euro)

- MB 102  power-supply board (would allow to power via 9V DC and USB)  ( < 2 euros) 

-  A4988 bipolar stepper driver    ( < 2 euros) 

 

Any opinion on using different components? And please if I missed some project which is already documented, I'd be keen for links! 

 

Rapha

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Rapha,

Using an Arduino to control stepper motors is well documented and all the library files for the more common drivers such as the A4988 are well proven.  Without knowing how to write a line of code you can download examples, program a nano or uno and breadboard the driver and stepper and have it running.  However the difficulty comes to modify or write the code you need get the stepper to rotate the required number of microsteps to make the RA axis rotate through its gearing to counteract the Earth's rotation.    Coding in Arduino isn't difficult, just a bit quirky at times.

But all is not lost... you're not the first person who wants to use an Arduino to control a telescope... and a google will through up lots of examples and similar projects, and the code is freely available.  It may be  a simple case of downloading one and the changing the variables to match that which suits your mount.

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Hi Rapha.

A Nano is fine as an RA tracking controller.

I used DRV8825 stepper drivers which allow 32 microsteps rather than 16 for the A4988, and are more robust.

The Onstep wiki has details for a Basic Hand Controller which you could design your software to use.   https://onstep.groups.io/g/main/wiki/3860

It is not difficult to implement in stripboard if you don't want to use their pcb.

If you use a Mega2560 instead of the Nano, you would have the option of using the Onstep Goto software (which of course includes tracking) even if you don't use the Goto facility. The Onstep software won't fit on a Nano.

 

 

 

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Hi lenscap !

Quote

I used DRV8825 stepper drivers which allow 32 microsteps rather than 16 for the A4988, and are more robust.

marvellous advice ; that's just the type of suggestions I was hoping for by posting here. And yes, I had read through the onstep pages, which motivated me to attempt this . 

 

 

Hi malc-c ,  thanks for the encouragement! Not worried about the software, I code for a living, just wanted to ask whether for astro applications a different combination of hardware modules was suggested. And I agree there is lots of documentation online; I already linked to some in my original post. 

 

 

 

 

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