I'm struggling trying to get my 28BYJ-48 motor tuned for peak torque and
would like to know if anyone has figured out what the delay setting should
be for peak torque? I'm using the 12V version that I have rewired for
bipolar operation and am using the DRV8825 driver. It's working it's just
very close to stalling in my tests with the scope on its end, worst case
weight scenario.
Also on the motor tab there is a window "PB Steps" what does that control
or do?
PB steps is for use with the push buttons only.
The 28BYJ motors only have a fraction of the torque that a nema motor has, and much less of that again when compared to a nema planetary geared motor. Even after any mod or 12V it still is a fraction of power compared to what one can get out of a NEMA
The delay setting only controls speed, not torque,
In one of the videos I showed the used of a small geared motor 5V, gearbox of 1:298 from memory
GM12-15BY which is much more powerful than 28byj motors. https://www.ebay.com/itm/125533410198
How does one increase torque
use geared motors
run off 12V
use toothed gears and a belt: eg: 20T on motor to 60T on focuser shaft = increase of 3x
Regards
Robert
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Well I have everything working much better today. I dug into all of your code in the libraries and such and made a few changes to delays and motor speed delay, I also increased the power supply to 24V since the bipolar mod uses the whole coil not, not half at a time. It works MUCH better, just crude test with a kitchen scale I am able to push 1.7Kg before stalling on a crayford focuser on the Skywatcher ED80, happy now, although I have numerous other larger PG steppers on the way.
Also want to mention a discrepancy between the user manual and the code in myBoards.cpp. The manual states "In the firmware, Medium speed is set to 2x the Step Delay value and Slow speed is set to 2.5x the Step Delay value."
The code is as below and you can see SLOW is actually 3x, not 2.5x. I changed one of the variables in line 1 to sdelay / 2 and it works 100%. FYI.
Many thanks, I will update the documentation. Good to hear it is working. How is the motor temperature when using 24V? Is the 24V going into the controller now instead of 12V ?
Regards
Robert
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Yes it's all working fine now, I have yet to actually use it on sky objects as we are currently under a blanket of clouds, rain and soon snow, 2 weeks now.
While I was testing full runs, focus in/out max, 3.5 turns on the Crayford, the motor did get warm but not uncomfortably hot, and when it stopped moving immediately began cooling as I am not using coil power to hold it. Yes I'm putting 24V straight into the controller and using a 7809 as I didn't have a 7808 in stock. The DRV8825 runs cool as well.
Looking forward using this soon.
Thank you.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I'm struggling trying to get my 28BYJ-48 motor tuned for peak torque and
would like to know if anyone has figured out what the delay setting should
be for peak torque? I'm using the 12V version that I have rewired for
bipolar operation and am using the DRV8825 driver. It's working it's just
very close to stalling in my tests with the scope on its end, worst case
weight scenario.
Also on the motor tab there is a window "PB Steps" what does that control
or do?
Thanks!
Last edit: PaulW 2024-11-03
PB steps is for use with the push buttons only.
The 28BYJ motors only have a fraction of the torque that a nema motor has, and much less of that again when compared to a nema planetary geared motor. Even after any mod or 12V it still is a fraction of power compared to what one can get out of a NEMA
The delay setting only controls speed, not torque,
In one of the videos I showed the used of a small geared motor 5V, gearbox of 1:298 from memory
GM12-15BY which is much more powerful than 28byj motors.
https://www.ebay.com/itm/125533410198
How does one increase torque
use geared motors
run off 12V
use toothed gears and a belt: eg: 20T on motor to 60T on focuser shaft = increase of 3x
Regards
Robert
Thanks Robert,
Well I have everything working much better today. I dug into all of your code in the libraries and such and made a few changes to delays and motor speed delay, I also increased the power supply to 24V since the bipolar mod uses the whole coil not, not half at a time. It works MUCH better, just crude test with a kitchen scale I am able to push 1.7Kg before stalling on a crayford focuser on the Skywatcher ED80, happy now, although I have numerous other larger PG steppers on the way.
Also want to mention a discrepancy between the user manual and the code in myBoards.cpp. The manual states "In the firmware, Medium speed is set to 2x the Step Delay value and Slow speed is set to 2.5x the Step Delay value."
The code is as below and you can see SLOW is actually 3x, not 2.5x. I changed one of the variables in line 1 to sdelay / 2 and it works 100%. FYI.
Hi Paul
Many thanks, I will update the documentation. Good to hear it is working. How is the motor temperature when using 24V? Is the 24V going into the controller now instead of 12V ?
Regards
Robert
Hello Robert,
Yes it's all working fine now, I have yet to actually use it on sky objects as we are currently under a blanket of clouds, rain and soon snow, 2 weeks now.
While I was testing full runs, focus in/out max, 3.5 turns on the Crayford, the motor did get warm but not uncomfortably hot, and when it stopped moving immediately began cooling as I am not using coil power to hold it. Yes I'm putting 24V straight into the controller and using a 7809 as I didn't have a 7808 in stock. The DRV8825 runs cool as well.
Looking forward using this soon.
Thank you.