This is my build of myFocuserPro2 controller, i made a full version with rotary encoder.
I use it with a Nema 14 to focus my lenses, here is an example with my Samyang 135mm f2
And with a smaller round Nema 14 to drive my Altair Astro 102EDT.
I attached the motor to the fine focus shaft using a rigid coupler. I had to raise the current @0.28Amps (datasheet states that peak is 0.5A @ 8.5V) but now it has no problem holding and moving the focuser with 2.5kg of weight when pointing at zenith.
I know that using a geared motor to the coarse focus shaft is prefferable but these motors are big and the gearbox induces backlash that i want to avoid.
Is there any option for a geared stepper much more compact (especially shorter) than eg Nema17-pg27 and with zero backlash?
Once more, many, many thanks to Robert for his amazing project!
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That is really cool, an excellent build. I see you even put in the diodes for reshapping the stepper waveforms. Very nice. And that solid bracket, looks very professional.
I have yet to find a geared Nema14 which might be suitable. I am lately thinking that the NEMA14 0.9 degree microstepped using gear/pulley/belt is a viable alternative.
Thanks for the pictures, really awesome!
Regards
Robert
Author myFocuserPro2
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I'm using the square one at 1/16 microstepping mode to focus my lenses and the round one at full steps to focus my apo. These configurations give me enough torque and steps in the cfz.
The bracket is a simple 5mm thick aluminium L bracket which i shaped with a little of cutting, drilling, etc.
I'm already collecting the parts needed for the SQM meter project...
Best Regards,
Stamatis
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Hi Stamatis
I have been playing with both of those NEMA14 motors - great minds think alike. I have them on the bench at present with some new protoype focusers.
Be interested in your assessment, is there any noticeable backlash?
Also that big ring gear you have Samyang 135mm f2, care to share any information on that - like gear ratio, purchase or built?
Regards
Robert
Last edit: brownrb 2018-11-26
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I loved Athens, all of Greece actually. My family holidayed there for a month, we hired a car and drove aound, epidavros, nafplio, tiryns [birthplace of Hercules], olympia, sparta, corinth, mycanae, mystras, Monastry of Ousis Loukas, the monastries, cape sounion, delphi, diros and glyfatha caves [great pottery shop] etc, great wine and great food and great people, was a most excellent time had by all. This was 2001
Always wanted to return. Loved the restuarants down in Plaka, frequented them daily whilst in Athens.
Its one place I recommend everyone goes to at least once in their lifetime.
Thanks for the info, I had not seen the ring gears on ebay, looks real interesting. The quality is good?
You have to come again Robert, you have an excuse as there are at least x3 places you have to visit when in Greece, for example Aegean and Ionian islands, Macedonia, Crete etc...
Seriously, that was a very big trip, you have gone to places where i haven't! I'm glad you liked my country.
A lot of things have changed since 2001 but fortunately the beauty remained the same.
Regarding the gears, i think it is the best solution for lens focusing.
I have tried the belt-pulley method but i was never quite happy, i had to put a lot of tension to the belt to minimize backlash and prevent it from slipping and if the lens' support isn't good there will be tilt somewhere in the train.
The quality is very good, stiff enough and the teeth engage perfectly, i think you should give it a try...
Cheers,
Stamatis
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I never made the islands, but still have very fond memories of the mainland.
I think we were very fortuante that our first real holiday was in Greece. Kind a fitting.
I have a belt system on my canon f2 usm lens and yes, there is a bit of backlash, so am tempted now to try the tooth syste - thanks for posting, most appreciated
Regards
Robert
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Hello again!
I have a (small?) problem with my controller and i cannot find out what is wrong...
One of the phases is not drawing current, i put the multimeter in line with the blue cable and i don't get any reading. Everything seems fine with the other phase though... The result is that when everything is connected and i turn the knob the motor moves erratically. Until recently everything was fine.
I replaced the driver with a new one since my first thought was that the drv probably got fried somehow but nothing changed.
Any thoughts?
Stamatis
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If the motor is stuttering then its a wiring issue where one of the wires isno longer making contact.
I would unplug the stepper and check resistance on pins 1 and 2, then on pins 3 and 4. There should be anywhere from 5 - 30 ohms, Pair one is wired to pins 1 and 2. Pair 2 to pins 3 and 4.
If there is an open circuit then open the connector and check if the wires have come unsoldered.
Its unusual for a stepper motor to go faulty especially the type of stepper and how its being driven in this project. Any damage such as unplugging a stepper motor with 12V on is more than likely to blow up the drv8825 chip, not the stepper.
Measuring current is pretty much useless with steppers in this project we are using chopped waveforms (basically pwm signals to the motor).
There is a support video I can send you a link, I am not atthe right location right now but will be later today and will post it then, in the time being, check the wiring from drv8825 to connector, from connect to stepper using a resistance meter AND WITH POWER OFF.
Regards
robert
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Thanks a lot Robert!
It seems that i had two issues happening simultaneously, firstly a non stable connection between two cables and secondly a broken multimeter. It was a very cheap one (5€ or so) and i had it for several years so that was a very good excuse to buy a good new Mastech!
Everything is fine now.
I use the multimeter as a reference Robert, just to know how i have to adjust the driver to increase the torque if it isn't enough.
I'm experimenting with this one as the small round Nema14 is stalling occasionally. The difference in torque between those two isn't as much as i expected though...
I'm always searching for a compact, lightweight and very low backlash geared stepper but i haven't find anything yet, the Nema17pg27 is just too big and heavy for me...
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I would think the torque is a bit lesss than a Nema14. I havent had time to measure anything, its just sitting on the bench after being prototyped. But I do know of a company that is using it on their refractor telescopes.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
This is my build of myFocuserPro2 controller, i made a full version with rotary encoder.
I use it with a Nema 14 to focus my lenses, here is an example with my Samyang 135mm f2
And with a smaller round Nema 14 to drive my Altair Astro 102EDT.
I attached the motor to the fine focus shaft using a rigid coupler. I had to raise the current @0.28Amps (datasheet states that peak is 0.5A @ 8.5V) but now it has no problem holding and moving the focuser with 2.5kg of weight when pointing at zenith.
I know that using a geared motor to the coarse focus shaft is prefferable but these motors are big and the gearbox induces backlash that i want to avoid.
Is there any option for a geared stepper much more compact (especially shorter) than eg Nema17-pg27 and with zero backlash?
Once more, many, many thanks to Robert for his amazing project!
That is really cool, an excellent build. I see you even put in the diodes for reshapping the stepper waveforms. Very nice. And that solid bracket, looks very professional.
I have yet to find a geared Nema14 which might be suitable. I am lately thinking that the NEMA14 0.9 degree microstepped using gear/pulley/belt is a viable alternative.
Thanks for the pictures, really awesome!
Regards
Robert
Author myFocuserPro2
Thank you very much Robert!
Both motors are 0.9degree motors
https://www.omc-stepperonline.com/hybrid-stepper-motor/nema-14-bipolar-09deg-11ncm-1558ozin-04a-10v-35x35x28mm-4-wires-14hm11-0404s.html?mfp=149-step-angle%5B0.9%5D
https://www.omc-stepperonline.com/hybrid-stepper-motor/round-nema-14-bipolar-09deg-5ncm-708ozin-05a-85v-%CF%8636x12mm-4-wires-14hr05-0504s.html?mfp=149-step-angle%5B0.9%5D
I'm using the square one at 1/16 microstepping mode to focus my lenses and the round one at full steps to focus my apo. These configurations give me enough torque and steps in the cfz.
The bracket is a simple 5mm thick aluminium L bracket which i shaped with a little of cutting, drilling, etc.
I'm already collecting the parts needed for the SQM meter project...
Best Regards,
Stamatis
Hi Stamatis
I have been playing with both of those NEMA14 motors - great minds think alike. I have them on the bench at present with some new protoype focusers.
Be interested in your assessment, is there any noticeable backlash?
Also that big ring gear you have Samyang 135mm f2, care to share any information on that - like gear ratio, purchase or built?
Regards
Robert
Last edit: brownrb 2018-11-26
No backlash at all Robert.
I haven't yet tested the apo's focuser under the stars though, but my digital calipers show no perceptible backlash.
The weather here in Athens is not very cooperative, lots of clouds the past 2-3weeks and the near future predictions are not good too.
The big ring and the small gear are follow focus gears which i bought from ebay
https://www.ebay.com/itm/Cinematics-follow-focus-gear-ring-70-80mm-adjustable-for-dslr-lens-focusing-red/270969443852?hash=item3f1709960c:g:~V8AAOSwdDpZcdC6:rk:1:pf:1&frcectupt=true
https://www.ebay.com/itm/Fotga-Standard-38T-43T-65T-0-8mm-Pitch-Gear-for-DP3000-DP500IIS-Follow-Focus/352456160617?hash=item5210063569:g:wdEAAOSw8Ehb61zZ:rk:12:pf:0
If i remember correctly the ratio between those two is approximately 1:4...
I loved Athens, all of Greece actually. My family holidayed there for a month, we hired a car and drove aound, epidavros, nafplio, tiryns [birthplace of Hercules], olympia, sparta, corinth, mycanae, mystras, Monastry of Ousis Loukas, the monastries, cape sounion, delphi, diros and glyfatha caves [great pottery shop] etc, great wine and great food and great people, was a most excellent time had by all. This was 2001
Always wanted to return. Loved the restuarants down in Plaka, frequented them daily whilst in Athens.
Its one place I recommend everyone goes to at least once in their lifetime.
Thanks for the info, I had not seen the ring gears on ebay, looks real interesting. The quality is good?
Cheers
Robert
You have to come again Robert, you have an excuse as there are at least x3 places you have to visit when in Greece, for example Aegean and Ionian islands, Macedonia, Crete etc...
Seriously, that was a very big trip, you have gone to places where i haven't! I'm glad you liked my country.
A lot of things have changed since 2001 but fortunately the beauty remained the same.
Regarding the gears, i think it is the best solution for lens focusing.
I have tried the belt-pulley method but i was never quite happy, i had to put a lot of tension to the belt to minimize backlash and prevent it from slipping and if the lens' support isn't good there will be tilt somewhere in the train.
The quality is very good, stiff enough and the teeth engage perfectly, i think you should give it a try...
Cheers,
Stamatis
I never made the islands, but still have very fond memories of the mainland.
I think we were very fortuante that our first real holiday was in Greece. Kind a fitting.
I have a belt system on my canon f2 usm lens and yes, there is a bit of backlash, so am tempted now to try the tooth syste - thanks for posting, most appreciated
Regards
Robert
Hello again!
I have a (small?) problem with my controller and i cannot find out what is wrong...
One of the phases is not drawing current, i put the multimeter in line with the blue cable and i don't get any reading. Everything seems fine with the other phase though... The result is that when everything is connected and i turn the knob the motor moves erratically. Until recently everything was fine.
I replaced the driver with a new one since my first thought was that the drv probably got fried somehow but nothing changed.
Any thoughts?
Stamatis
If the motor is stuttering then its a wiring issue where one of the wires isno longer making contact.
I would unplug the stepper and check resistance on pins 1 and 2, then on pins 3 and 4. There should be anywhere from 5 - 30 ohms, Pair one is wired to pins 1 and 2. Pair 2 to pins 3 and 4.
If there is an open circuit then open the connector and check if the wires have come unsoldered.
Its unusual for a stepper motor to go faulty especially the type of stepper and how its being driven in this project. Any damage such as unplugging a stepper motor with 12V on is more than likely to blow up the drv8825 chip, not the stepper.
Measuring current is pretty much useless with steppers in this project we are using chopped waveforms (basically pwm signals to the motor).
There is a support video I can send you a link, I am not atthe right location right now but will be later today and will post it then, in the time being, check the wiring from drv8825 to connector, from connect to stepper using a resistance meter AND WITH POWER OFF.
Regards
robert
https://www.dropbox.com/s/ks3cwabbg2cxcou/Stepper%20Motor%20Issues-01.mp4?dl=0
Thanks a lot Robert!
It seems that i had two issues happening simultaneously, firstly a non stable connection between two cables and secondly a broken multimeter. It was a very cheap one (5€ or so) and i had it for several years so that was a very good excuse to buy a good new Mastech!
Everything is fine now.
I use the multimeter as a reference Robert, just to know how i have to adjust the driver to increase the torque if it isn't enough.
I'm experimenting with this one as the small round Nema14 is stalling occasionally. The difference in torque between those two isn't as much as i expected though...
I'm always searching for a compact, lightweight and very low backlash geared stepper but i haven't find anything yet, the Nema17pg27 is just too big and heavy for me...
https://www.ebay.com/itm/GM12-15BY-DC5-12V-2-phase-4-wire-Permanent-Magnet-Stepper-Gear-Motor-Metal-Gear/163265164855
low power, works off 5v, very small, super geared, I got the 1:210 motor - more torque than the 28BYJ motors
Do you think it has enough torque to drive the coarse focus shaft Robert?
And what about its backlash?
I cannot find any specs about these motors...
I would think the torque is a bit lesss than a Nema14. I havent had time to measure anything, its just sitting on the bench after being prototyped. But I do know of a company that is using it on their refractor telescopes.