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Old 16-12-2018, 09:05 AM
RobC (Rob)
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Join Date: Apr 2012
Location: Woodford , Queensland , Australia
Posts: 218
Peter,

Here is my 2 cents worth.

I have built three of these devices to date and have written the Arduino and ACOM compliant code to drive them. Two of the motors were based on the Nema 17 27:1 Stepper and the third on the Nema 11 27:1 Stepper. I have built two controller units. One based on the LN298 driver and the other on the micro stepping DRV8825.

I am not a fan of micro stepping because of the torque and heating problems. Turning the power off may cause the motor to slip to its natural position and the focuser could move from the CFZ. Although I used the DRV 8825 controller I do not micro step it. I full and half step the LN298 and DRV 8825. At full step mode the 27:1 steppers have roughly 5400 steps and 10800 steps in half step mode.

I plagiarized and modified the Arduino source code from the Texas thread. The ASCOM compliant focus driver code I wrote from scratch.

I use my focuser controller with both SGP and APT.

I have attached a photo of the Nema 17 connected to the course focus side of a 2.5" moonlite on the back of my North Group carbon fibre ED 127.

If I can be of any assistance to you please contact me.

Cheers

Rob
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