I was checking the backlash on my Rig last night (Still cloudy in Texas)
l'mworking on getting APT auto focus to work
i use a Nema11PG27, direct drive copled to my 8" newt
at FULL STEP it has 14 steps of Backlash and
28steps at HALFSTEP
i mounted a dial indicator and watch for any slight movment of the needle.
you need to use a Magnifing glass to see it make a slight Tick of the needle arm since we are splitting HAIRS here
that explains why in the field at night and i try to operate the myfocuser i would have to CLICK CLICK .......
to find the sweet spot of focus
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Hi BJ
Its simple enough to add backlash into the firmware code, but I have resisted the temptation to do so. Most client apps have a backlash feature and if used, we would end up having two such competing systems trying to do backlash. So my view is that BL should be the domain of the client app. And if written right, could even self determine the amount of BL in the focuser in either direction and set itself accordingly.
The higher the microstepping value the higher should be the backlash. This is due to the positioning of the stepper between steps by using current, which requires coil power on in order towork. If using any microstepping (other than full) would recommend CP must be on, else the motor will "slip" to the nearest full step position after a move.
Thats a fairly large amount of BL for a direct coupled NEMA motor. I am not famaliar with the NEMA11 as I use the NEMA17 exclusively. There maybe sliht differences, I just don;t know. I havent had issues with the ones I have.
APT does have a specific backlash aid, and I would recommend looking at that in the help file if you have not already done so. It is possible to set the amount of BL in APT.
Regards
Robert
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I also have a nema17 but have not ck BL with my dial indicator
but looking at the specs they both show the BL SPEC as <=1°
the slop is in the gearbox
i cked my FOCUSER rack its good ,no noticable play or slop
just thought in would share my BL findings
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i pulled the NEMA 11 i was using. it seems the BL was getting worse, and i switch to a heavier CCMOS cam and I'm having troulble holding focus.
i went back to the NEMA17.
after checking BL on it. i found it has 14 fullsteps of BACKLASH too.
I put a dial indicator on the DRAWTUBE.
and go one direction, stop,zero the gauge and it takes 14 steps before you see the slightest movment of the needle on the dial gauge in the opposite direction
then it's 14steps the other direction to see the needle move.
also with power on the stepper you can feel the play by slight jiggle the focuser knob back and forth.
Is there a stepper to use without a gear reductionbox ?
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I was checking the backlash on my Rig last night (Still cloudy in Texas)
l'mworking on getting APT auto focus to work
i use a Nema11PG27, direct drive copled to my 8" newt
at FULL STEP it has 14 steps of Backlash and
28steps at HALFSTEP
i mounted a dial indicator and watch for any slight movment of the needle.
you need to use a Magnifing glass to see it make a slight Tick of the needle arm since we are splitting HAIRS here
that explains why in the field at night and i try to operate the myfocuser i would have to CLICK CLICK .......
to find the sweet spot of focus
Hi BJ
Its simple enough to add backlash into the firmware code, but I have resisted the temptation to do so. Most client apps have a backlash feature and if used, we would end up having two such competing systems trying to do backlash. So my view is that BL should be the domain of the client app. And if written right, could even self determine the amount of BL in the focuser in either direction and set itself accordingly.
The higher the microstepping value the higher should be the backlash. This is due to the positioning of the stepper between steps by using current, which requires coil power on in order towork. If using any microstepping (other than full) would recommend CP must be on, else the motor will "slip" to the nearest full step position after a move.
Thats a fairly large amount of BL for a direct coupled NEMA motor. I am not famaliar with the NEMA11 as I use the NEMA17 exclusively. There maybe sliht differences, I just don;t know. I havent had issues with the ones I have.
APT does have a specific backlash aid, and I would recommend looking at that in the help file if you have not already done so. It is possible to set the amount of BL in APT.
Regards
Robert
I also have a nema17 but have not ck BL with my dial indicator
but looking at the specs they both show the BL SPEC as <=1°
the slop is in the gearbox
i cked my FOCUSER rack its good ,no noticable play or slop
just thought in would share my BL findings
i pulled the NEMA 11 i was using. it seems the BL was getting worse, and i switch to a heavier CCMOS cam and I'm having troulble holding focus.
i went back to the NEMA17.
after checking BL on it. i found it has 14 fullsteps of BACKLASH too.
I put a dial indicator on the DRAWTUBE.
and go one direction, stop,zero the gauge and it takes 14 steps before you see the slightest movment of the needle on the dial gauge in the opposite direction
then it's 14steps the other direction to see the needle move.
also with power on the stepper you can feel the play by slight jiggle the focuser knob back and forth.
Is there a stepper to use without a gear reductionbox ?