I am working on the final assembly and I am currently testing the current for the Nema17pg27. When I set the current at 245mA, the motor heats up pretty much, so after one hour I am not comfortable holding it in my hand. If I listen to it closely, I can hear a hissing sound.
If I drop the current to 210mA, I can hear the sound changing and I can feel as if some of the steps are skipped. The sound and operation are perfect above 245mA, but the heating is the problem.
I am now testing it at 230mA and it still gets hot, to around 42 degrees Celsius. Robert, have you perhaps measured the temperature of your stepper motor?
Miloš
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Hi Milos
Sometimes this is due to a faulty DRV8825 chip. I had one which also maked the hissing sound and yes the stepper motor got hot with that driver chip. But no, all the others do not get hot (only the little BYJ38 motors got hot).
If you do the math, 230mA, 12V chopped, then the power is about 3 watts, meaning it cannot get hot. http://www.rapidtables.com/calc/electric/ohms-law-calculator.htm
When setting the current, you have set it to full steps, coil power on, placed the multimeter is series with one of the stepper coils, then turned on 12V?
You can turn coil power off with the PG27. It does not really need to be on with the PG27. I would set it to full steps and turn coil power off.
In terms of the OLED versions, they are running pretty close to max memory, so yes, it could be possible that it freezes after 8 hours. It is either an arduino memory issue that gets worse with use or a usb comms issue. I suspect the former but also know windows can cause issues.
Have you checked that the power management of the usb ports is disabled in Windows? This will drop the connection.
If you are running for long periods (like hours) you should enable the update (temp timer) so that the focuser is regularly polled to keep the comms alive.
And a last resort if running with the log file so when it does fail to respond, at least the log file will see what was going on at the time comms wise at the time it happened.
Regards
Robert
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yes, I used full steps, coil power on, and the multimeter in series with one of the stepper coils.
You are right, 3 watts should not cause the motor to get hot like that.
I actually tested the hardware without connecting the USB cable. So it was running for 8 hours without the USB cable.
I didn't implement the Dallas temperature sensor this time since I don't need it. Do you think that removing a bit of the code related to the temperature sensor would increase the stability? I really want to use it with the OLED screen.
Or perhaps I could try to upload the sketch into a Teensy 3.2 to see if it will work.
What do you think?
Miloš
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It seems that the RE code is now not working. No reactions from the switch or rotation on the rotary encoder. I uploaded the old code and it is working.
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About the stepper motor getting hot – I have just checked the datasheet, it says that the max. temperature rise is 80 degrees C while the motor is still (2 phases energized). I can see many comments online about Nema17 and about stepper motors in general that it is normal that they get hot. So, since the coil power can be turned off with the PG27, I'll continue testing it with the old sketch, and if we fix the problem with the Arduino freezing after a longer period, then I'll have a perfectly working system. I already do have one PCB that was built according to your Frizing files and it is working perfectly (the stepper motor gets hot on it too).
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Hi Milos
Awesome. The reduced memory footprint of the smaller code looks like it was the way to go.
It is a really big ask for an embedded system to run a long time especially with serial comms without experiencing issues so well done.
Regards
Robert
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I am using a NEMA17-PG27 with DRV8825. I set the current to 245mA first with the coil power method, and the motor ran hot, I measured it with the temperature probe and it was around 39-40°C. But I used the wrong firmware for the Rev4 PCB, as Robert pointed out.
I changed to the right FW for my build and I reclibrated the DRV8825 as well. Now it is 25°C after 1 hours with 21°C ambient temperature with coil power on.
I don't know how does the waveform of the motor current looks like, but maybe it should be measured with a True RMS multimeter to get accurate results?
I used the Ilimit = 2 * Vref (DC) method to recalibrate the DRV8825: https://youtu.be/zTML-MK6obM
But to be honest, I only have to turn the calbration potmeter of the DRV8825 maybe around 10-15° to get the desired current which doesn't allow too much precision.
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Hello,
I am working on the final assembly and I am currently testing the current for the Nema17pg27. When I set the current at 245mA, the motor heats up pretty much, so after one hour I am not comfortable holding it in my hand. If I listen to it closely, I can hear a hissing sound.
If I drop the current to 210mA, I can hear the sound changing and I can feel as if some of the steps are skipped. The sound and operation are perfect above 245mA, but the heating is the problem.
I am now testing it at 230mA and it still gets hot, to around 42 degrees Celsius. Robert, have you perhaps measured the temperature of your stepper motor?
Miloš
Also, my Arduino freezes after several hours of operation (for example 8 hours). How can I identify the problem?
Miloš
Focuserv255_DRV8825_HW203_OLED_RE_F
Hi Milos
Sometimes this is due to a faulty DRV8825 chip. I had one which also maked the hissing sound and yes the stepper motor got hot with that driver chip. But no, all the others do not get hot (only the little BYJ38 motors got hot).
If you do the math, 230mA, 12V chopped, then the power is about 3 watts, meaning it cannot get hot.
http://www.rapidtables.com/calc/electric/ohms-law-calculator.htm
When setting the current, you have set it to full steps, coil power on, placed the multimeter is series with one of the stepper coils, then turned on 12V?
You can turn coil power off with the PG27. It does not really need to be on with the PG27. I would set it to full steps and turn coil power off.
In terms of the OLED versions, they are running pretty close to max memory, so yes, it could be possible that it freezes after 8 hours. It is either an arduino memory issue that gets worse with use or a usb comms issue. I suspect the former but also know windows can cause issues.
Have you checked that the power management of the usb ports is disabled in Windows? This will drop the connection.
If you are running for long periods (like hours) you should enable the update (temp timer) so that the focuser is regularly polled to keep the comms alive.
And a last resort if running with the log file so when it does fail to respond, at least the log file will see what was going on at the time comms wise at the time it happened.
Regards
Robert
Hi Robert,
yes, I used full steps, coil power on, and the multimeter in series with one of the stepper coils.
You are right, 3 watts should not cause the motor to get hot like that.
I actually tested the hardware without connecting the USB cable. So it was running for 8 hours without the USB cable.
I didn't implement the Dallas temperature sensor this time since I don't need it. Do you think that removing a bit of the code related to the temperature sensor would increase the stability? I really want to use it with the OLED screen.
Or perhaps I could try to upload the sketch into a Teensy 3.2 to see if it will work.
What do you think?
Miloš
Hi Milos
I deleted all the temperature stuff and got it down to 64% on a Nano.
Last edit: brownrb 2017-09-14
Wow, that's great, I'll test it immediately.
It seems that the RE code is now not working. No reactions from the switch or rotation on the rotary encoder. I uploaded the old code and it is working.
About the stepper motor getting hot – I have just checked the datasheet, it says that the max. temperature rise is 80 degrees C while the motor is still (2 phases energized). I can see many comments online about Nema17 and about stepper motors in general that it is normal that they get hot. So, since the coil power can be turned off with the PG27, I'll continue testing it with the old sketch, and if we fix the problem with the Arduino freezing after a longer period, then I'll have a perfectly working system. I already do have one PCB that was built according to your Frizing files and it is working perfectly (the stepper motor gets hot on it too).
Yes my mistake. the version I uploaded does not support RE
Try this.
I'll start testing right away! Thank you so much Robert!
After around 8 hours it all seems great!
Hi Milos
Awesome. The reduced memory footprint of the smaller code looks like it was the way to go.
It is a really big ask for an embedded system to run a long time especially with serial comms without experiencing issues so well done.
Regards
Robert
I am using a NEMA17-PG27 with DRV8825. I set the current to 245mA first with the coil power method, and the motor ran hot, I measured it with the temperature probe and it was around 39-40°C. But I used the wrong firmware for the Rev4 PCB, as Robert pointed out.
I changed to the right FW for my build and I reclibrated the DRV8825 as well. Now it is 25°C after 1 hours with 21°C ambient temperature with coil power on.
I don't know how does the waveform of the motor current looks like, but maybe it should be measured with a True RMS multimeter to get accurate results?
I used the Ilimit = 2 * Vref (DC) method to recalibrate the DRV8825: https://youtu.be/zTML-MK6obM
But to be honest, I only have to turn the calbration potmeter of the DRV8825 maybe around 10-15° to get the desired current which doesn't allow too much precision.