How to increase the max slewing speed from 1.0 dps to 2.0 dps?


Hi Howard and Kahlid,

This is Tong from Hubble Optics; we are trying to use OnStep for our UL scopes. First, I want to thank Howard for the wonderful OnStep Controllers which work really well, and to Kahlid for a lot of very helpful postings here. 


We have made a few MaxESP (V3) controllers using TMC5160 with 4.24q release; Our newly designed GoTo drive system are largely based on Howard Banich’s wonderful 28” Dob, a friend’s (Bruce) mod on our UL20, and Tom’s 22.4 OnStep showcase scope; Tom also shared his insight and experience with me and recommended me to post my question here.


Case 1:

With the total reduction ratio of 720, and AXIS1/2_DRIVER_MICROSTEPS to be 32,  and the AXIS1/2_DRIVER_MICROSTEPS_GOTO to be 8. The scope works very well at max slewing speed at 1dps (SLEW_RATE_BASE_DESIRED); but not any faster.  I  have attached the Config-32.h (Config.h) for this case

Case 2:

It seems that if we reduce the total reduction ratio by half to 360; and use 64 micro steps (AXIS1/2_DRIVER_MICROSTEPS); all other to be same as the case 1; we should be able to have the same tracking accuracy (in theory) but double the max slewing speed (SLEW_RATE_BASE_DESIRED) to 2.00 dps when the motor physically running at the same speed as the Case 1.  However, strangely. in this case the motors still visibly try to run at about twice of speed, and stalk most of the time.  I  have attached the Config-64.h (Config.h) for this case.

I will appreciate if you and others can help me to solve this issue.

Thank you and best regards


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