I built the DRV8825 M-MT-F-BT-12 focuser, with oled screen, temperature sensor, and buttons.
I'll add led lights later. The motor is a Nema17 400 steps 1.67A stepper.
The firmware I use, is the myFP2_DRV8825_294 firmware. It's working well, but there are little inaccuracies/problems in there.
First of all, I would like to use the focuser with 16/48 gear, but I couldn't find the following lines in the firmware:
// #define STEPSPERREVOLUTION 200 // NEMA17 motor, if half stepping multiply by 2
In my case, 200 would be changed to 9600 . (1/8 microsteps /3200/ and 1:3 gear ratio 3200x3)
Can you tell me, how can I set up the rate accurately?
Secondly, if I control it from PC, the motor's turnover rate is just okay (fast setting),
but if I'm trying to use the buttons, it'll become slow and sometimes get stuck (That happens when the screen changes). The spin stops immediately, for a sec, and then continues where it was left off. This time the step counter is stopping too (i see in oled screen), so the focuser stay accurate, but the spin isn't as smooth as it should be
Is there any solution for these problems?
Thanks for your help,
Sanya Reményi
Last edit: Sanya Reményi 2020-04-28
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Why did you do this?
Did you not read the pdf and all the warnings about stepper motor current and selection of stepper motors? the warnings are there for a reason.
This from the FAQ pdf
I WANT TO USE MY 2A STEPPER MOTOR. WHAT LIMITS ARE THERE ON STEPPER
MOTOR CURRENTS?
You cannot. Stepper coil current should be less than 0.6A per coil. If you have a stepper motor that has a higher
rating than 0.6A you need to look at something like the ST6128 driver board. Using a stepper motor with a
higher current on a DRV8825 or EASYDRIVER board will cause permanent damage.
and from pg28 of pdf
If you decide not to use the recommended motors suggested here, then make sure that the current rating
(*2) of your stepper motor does NOT exceed that of the driver board you have selected. For example, if you selected a 1.4A stepper motor, then the current draw when both coils are energized is 2.8A, which exceeds most of the driver boards listed here
and pg 39 of pdf
If your stepper motor is rated at 1A or above, it cannot be supported due to the high current and you will need to buy a suitable stepper motor – the recommend stepper motor is the NEMA17-PG27
and pg 40 of pdf
Example
I purchased a NEMA stepper motor from eBay which has a rated coil current of 1.6A. Which option should I chose? Sorry – None. The maximum current will be 3.2A (there are two coils in a NEMA stepper motor) and no driver board above will supply that much current.
It is best to use the recommended NEMA stepper motors for this project which all have a current rating of 400mA.
The pauses are normal. the arduino is NOT a multitasking computer chip and can only do one thing at a time. So if its busy updating the display, it cannot move the motor. Steps are not lost. This is mentioned multiple times and in the FAQ. If you want the display then this the tradeoff.
See pg 9 of FAQ
PUSH BUTTONS TOO SLOW
Buttons are NOT used to go long distances winding the focuser in and out. Its not designed to do that. Again this is covered in the pdf. Speed is always going to be slow with the push buttons. Again, read the pdf and FAQ. The focuser is designed primarily to work with an autofocusing program. Instead of the push buttons try jogging.If you want manual control using the push buttons then disable the display. You can't have everything all at the same time and expect nothing to be impacted.
Infrared controller is much better option than push buttons
The steps per revolution setting is only valid for l293d shield and uln2003 motors. Its meaningless and not used for other driver chips. For your build its meaningless and will make no difference.
Robert
Last edit: brownrb 2020-04-29
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
in response to your issue, I have made some changes to the next firmware release v295. This should minimise the pauses during push button moves if an extra option is enabled. the downside [there is always one] is that the display is only updated 5s after a move is completed. So don't watch the display when moving! [after all one should be looking through the eyepiece?]
If you wish to test this, please email me direct and we can talk about how best to do this.
in the latest PDF-134 to be uploaded today these new changes are outlined. See pg61 and pg88 for more information
regards
Robert
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hi Robert,
I built the DRV8825 M-MT-F-BT-12 focuser, with oled screen, temperature sensor, and buttons.
I'll add led lights later. The motor is a Nema17 400 steps 1.67A stepper.
The firmware I use, is the myFP2_DRV8825_294 firmware. It's working well, but there are little inaccuracies/problems in there.
First of all, I would like to use the focuser with 16/48 gear, but I couldn't find the following lines in the firmware:
// #define STEPSPERREVOLUTION 200 // NEMA17 motor, if half stepping multiply by 2
In my case, 200 would be changed to 9600 . (1/8 microsteps /3200/ and 1:3 gear ratio 3200x3)
Can you tell me, how can I set up the rate accurately?
Secondly, if I control it from PC, the motor's turnover rate is just okay (fast setting),
but if I'm trying to use the buttons, it'll become slow and sometimes get stuck (That happens when the screen changes). The spin stops immediately, for a sec, and then continues where it was left off. This time the step counter is stopping too (i see in oled screen), so the focuser stay accurate, but the spin isn't as smooth as it should be
Is there any solution for these problems?
Thanks for your help,
Sanya Reményi
Last edit: Sanya Reményi 2020-04-28
"The motor is a Nema17 400 steps 1.67A stepper."
Why did you do this?
Did you not read the pdf and all the warnings about stepper motor current and selection of stepper motors? the warnings are there for a reason.
This from the FAQ pdf
I WANT TO USE MY 2A STEPPER MOTOR. WHAT LIMITS ARE THERE ON STEPPER
MOTOR CURRENTS?
You cannot. Stepper coil current should be less than 0.6A per coil. If you have a stepper motor that has a higher
rating than 0.6A you need to look at something like the ST6128 driver board. Using a stepper motor with a
higher current on a DRV8825 or EASYDRIVER board will cause permanent damage.
and from pg28 of pdf
If you decide not to use the recommended motors suggested here, then make sure that the current rating
(*2) of your stepper motor does NOT exceed that of the driver board you have selected. For example, if you selected a 1.4A stepper motor, then the current draw when both coils are energized is 2.8A, which exceeds most of the driver boards listed here
and pg 39 of pdf
If your stepper motor is rated at 1A or above, it cannot be supported due to the high current and you will need to buy a suitable stepper motor – the recommend stepper motor is the NEMA17-PG27
and pg 40 of pdf
Example
I purchased a NEMA stepper motor from eBay which has a rated coil current of 1.6A. Which option should I chose? Sorry – None. The maximum current will be 3.2A (there are two coils in a NEMA stepper motor) and no driver board above will supply that much current.
It is best to use the recommended NEMA stepper motors for this project which all have a current rating of 400mA.
The pauses are normal. the arduino is NOT a multitasking computer chip and can only do one thing at a time. So if its busy updating the display, it cannot move the motor. Steps are not lost. This is mentioned multiple times and in the FAQ. If you want the display then this the tradeoff.
See pg 9 of FAQ
PUSH BUTTONS TOO SLOW
Buttons are NOT used to go long distances winding the focuser in and out. Its not designed to do that. Again this is covered in the pdf. Speed is always going to be slow with the push buttons. Again, read the pdf and FAQ. The focuser is designed primarily to work with an autofocusing program. Instead of the push buttons try jogging.If you want manual control using the push buttons then disable the display. You can't have everything all at the same time and expect nothing to be impacted.
Infrared controller is much better option than push buttons
The steps per revolution setting is only valid for l293d shield and uln2003 motors. Its meaningless and not used for other driver chips. For your build its meaningless and will make no difference.
Robert
Last edit: brownrb 2020-04-29
Hi Sanya
To show that I do listen...
in response to your issue, I have made some changes to the next firmware release v295. This should minimise the pauses during push button moves if an extra option is enabled. the downside [there is always one] is that the display is only updated 5s after a move is completed. So don't watch the display when moving! [after all one should be looking through the eyepiece?]
If you wish to test this, please email me direct and we can talk about how best to do this.
in the latest PDF-134 to be uploaded today these new changes are outlined. See pg61 and pg88 for more information
regards
Robert
Thanks for the answers, I will apply by email
regards
Sanya