New motors for EQ3-II mount (or is it CG4?)

[bojan]

After getting hold of this little mount for free (thanks again MattT :-) ), I decided to replace RA motor with smaller one, to make the mount easier to pack and transport (I may want to use it for TSE 2028.. hopefully).

I decided to employ the second clutch I have (leftover from OnStep-motorized EXOSII, the first one was used on my other EQ3 ).

This time I machined the timing pulley (48T), so the belt transmission height is as low as possible, 36 mm).
Bracket for stepper is printed (same idea as for my C11 focuser, only slightly modified to fit this application).
The electronics will be Arduino nano, I used the modified sketch (arduinian for f/w code) published here. The stepper driver I am using is based on ULN2803 (8x) to support 2 motors.. I am now working on the code to add DEC motor (which is not really needed, but sometimes it is useful).
I intend to place electronics inside the mount, there should be enough space.. if not then in separate box (hand pad, with buttons).

[Nikolas (Nik)]

Great project, let us know how it all ends up

[bojan]

Motor mounted in place.
The belt tension can be adjusted by rotating the motor in holder, which can then be tightened by side screw.
I have to shorten the clutch screw a bit, to prevent the clash with small timing pulley (on the motor shaft).
Now, waiting for ULN2803 to arrive from AliExpress, and first phase of the project is done.

The next stage will be adding the DEC motor (both on mount and in the code).


NB:
I could have used NEMA17 thin stepper motor (400 s/r), height would be same/similar, but it would be more complicated to adjust the belt tension.. and resolution would be 5x worse so I decided not to go this way.

[bojan]

Arduino stepper driver, Schematic.

[bojan]

Electronics, even smaller than Nano (doesn't have USB adapter). It should fit inside mount (DEC).
I will have couple of holes drilled on DEC cavity (around polar finder) for connectors (power, hand-pad, motor(s-)).