Choosing motors for perfect stall detection
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@bot:
In terms of our applications, it seems that 5 mH is about "average" inductance for us. So, IMO, "low" is below 5 mH, and "high" is above 5.
Awesome. This is the answer i was waiting for. well… now comes the hard part. there are few sellers who offer 5mH nema 17 motors, so the only option will be by order. but.... i guess i can t make a special order for 5 or 10 motors....
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Forget Aliexpress! They may not sell high impedance motors there, but any good seller does. 5mH is not really high; you can find some with 50mH inductance:
high impedance: https://www.omc-stepperonline.com/hybrid-stepper-motor/nema-17-bipolar-18deg-40ncm-566ozin-04a-12v-42x42x39mm-4-wires-17hs15-0404s.html
They even have 2 other intermediate values for that 40-45N.cm torque range.
(Don't know if you can reach the site, I have troubles myself).
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Don't choose very high inductance motors, or you will find that you don't have enough drive voltage to run them as fast as you want to. Use the calculation at https://duet3d.com/wiki/Choosing_stepper_motors#How_to_work_out_the_power_supply_voltage_you_need to check the suitability of your motors before you order them.
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Also, keep in mind moving by hand a motor with a high impedance will generate a high voltage, which can destroy the electronic!
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oh got it. Nice, today I have learned something new
I ll keep you posted with my decision guys. Thank a lot! -
Don't choose very high inductance motors, or you will find that you don't have enough drive voltage to run them as fast as you want to. Use the calculation at https://duet3d.com/wiki/Choosing_stepper_motors#How_to_work_out_the_power_supply_voltage_you_need to check the suitability of your motors before you order them.
I did some calculus with these types of motors:
https://www.aliexpress.com/item/Hot-No-Tax-to-EU-10-PCS-Nema-17-Stepper-Motor-42BYGHW609L20P1-X2-4000g-cm-1/32792872368.html?spm=a2g0s.13010208.99999999.262.rpduqP
I power my duet at 25 V. Making the calculus, I took the conclusion from the point 6 from wiki that the sum of my two back emf is 21.22 so I'm way good under 25V. This means I can easily go for higher inductance motors. The calculus was made for 250mm/s travel speed on a corexy.If I remake the calculus for 5mH inductance motors I'll have a sum of 28.8V witch is a bit bigger than 25V so Maybe I won't achieve a travel speed of 250mm/sec.
With 4mH inductance motors I'll have 25.36V witch is a bit over limit so….Maybe I'll achieve something like 230mm/sec travel speed but also I'll be able I think to implement more easier the stall detections function.
These been said I think the right motors for me will be:
2 phase
1.8 degree/step
current: 1.7A/phase
resistance: 1.5 ohm/phase
inductance: 4mH/phase
holding torque: 40N.cm
I also run my motors at 1A current. I saw that this is the best proportion between noise and power. -
Those sound very much like the motors I use on my delta. I managed to get homing working using stall detect, but I haven't managed to get stall detection during printing working yet. I think it may be something that is difficult to do on a delta.
I have put a spreadsheet to calculate maximum motor speeds before torque is list at https://www.dropbox.com/s/5z66rgjc8gptn5o/StepperMotor.ods?dl=1.
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Those sound very much like the motors I use on my delta. I managed to get homing working using stall detect, but I haven't managed to get stall detection during printing working yet. I think it may be something that is difficult to do on a delta.
I have put a spreadsheet to calculate maximum motor speeds before torque is list at https://www.dropbox.com/s/5z66rgjc8gptn5o/StepperMotor.ods?dl=0.
I have downloaded the sheet on my computer and replaced the values in the yellow boxex but the green ones are not changing. I also can't modify the values directly on the link you have provided.
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Yes you will need to take a copy because Dropbox will quite rightly not let you modify my files. I've changed the ?dl=0 at the end of the link to ?dl=1 so that if you click on it, it will prompt you to download it. I suspect that what you have downloaded may be the HTML rendering of the sheet.
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Yes you will need to take a copy because Dropbox will quite rightly not let you modify my files. I've changed the ?dl=0 at the end of the link to ?dl=1 so that if you click on it, it will prompt you to download it. I suspect that what you have downloaded may be the HTML rendering of the sheet.
Now it will download automatically but when I try to open with Excel 2010 it says that some parts of the sheet are impossible to be read….something like that. After I press ok it opes and when I try to change values it behave the same. Green cell value don't change. Maybe a C++ little program written in CodeBlocks will be more efficent?!
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You could download Libre Office, which is what I used to create it.
I'm hoping to get a Javascript version implemented on either my Escher 3D site or on reprapfirmware.org.
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Thank you for the tool, David. It is very useful and confirmed my previous calculations were correct.
