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Capabilities Question / Re: Ramping rates control
« on: February 26, 2015, 22:24:45 »
The problem with my Japanese mount is that it is heavy and consequently has a high gearing ratio, 9000:1 for the RA and a bit less for the Dec axis. Both axis use 6V/1.2A, 200 step motors so the final 'performance' is only 0.72"/full step for the RA. To get even a slow slew speed (0.6 deg/s) with that sort of ratio means the steppers need to spin very fast, which increases the coil impedance, reduces the current (unless offset with over-voltage) and quickly stalls ... so yes, I always have the steppers slewing very close to their performance limit. The ability to fine tune the ramp rate is critical in my situation.
While I don't doubt what you say about the difficulties in achieving variable ramp rate control (I'm a retired electronics engineer) I do know this has been achieved, as mentioned, in other controllers. Details, including source code, for Mel Bartels' old but successful system (over 1000 built) are at http://www.bbastrodesigns.com/StepperSystem.html. I don't have any details for the German FS2 but I know it has 256 levels of slew rate adjustment.
While I don't doubt what you say about the difficulties in achieving variable ramp rate control (I'm a retired electronics engineer) I do know this has been achieved, as mentioned, in other controllers. Details, including source code, for Mel Bartels' old but successful system (over 1000 built) are at http://www.bbastrodesigns.com/StepperSystem.html. I don't have any details for the German FS2 but I know it has 256 levels of slew rate adjustment.
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Capabilities Question / Re: Ramping rates control
« on: February 25, 2015, 03:37:40 »
Hmmm ... that's a bummer 
Both my old Bartels controller and current FS2 allow both stepper ramp up and down rates to be varied to find the fastest ramp rate to/from full slew speed that doesn't stall the steppers. The Bartels allows both variable linear and 'S' slopes but, from memory, I think the FS2 only has a variable linear slope. Both steppers on my heavy mount are very sensitive to the ramp up/down rates, which also depends on whatever overvoltage I apply to them, and the only way I can find the fastest setting is by trial and error. Typically I needed to set the ramping time for a few seconds (>2) but I don't recall the actual values, which was different for each stepper.
Without the ability to vary the ramp rates I'm reasonably certain the AstroEQ will not work with my mount
Both my old Bartels controller and current FS2 allow both stepper ramp up and down rates to be varied to find the fastest ramp rate to/from full slew speed that doesn't stall the steppers. The Bartels allows both variable linear and 'S' slopes but, from memory, I think the FS2 only has a variable linear slope. Both steppers on my heavy mount are very sensitive to the ramp up/down rates, which also depends on whatever overvoltage I apply to them, and the only way I can find the fastest setting is by trial and error. Typically I needed to set the ramping time for a few seconds (>2) but I don't recall the actual values, which was different for each stepper.
Without the ability to vary the ramp rates I'm reasonably certain the AstroEQ will not work with my mount
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Capabilities Question / Ramping rates control
« on: February 24, 2015, 03:21:57 »
My first post: Is there any way to set/change the slew ramp-up and ramp-down rates in AstroEQ? I ask this as these rates have a big impact on a stepper motor's ability to start and stop slews without stalling. Previous (Bartels) and current (FS2) stepper controllers that I have do have this ability ... unfortunately they are not EQMOD friendly.
Thanks,
Spectrasouth
Thanks,
Spectrasouth
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