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Just so I get this right about stepper drivers . . .

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(@voltage)
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I have a project using a NEMA 23 stepper (with reduction 4:1) that is BiPolar 4 wire hookup, and the spec sheet says Rated Current/Phase 2.8A with a 3.2V rating. I am using a Stepperonline DM542T Digital Driver that is capable of 42.A Peak and 3.0A RMS. I am running with a 36V Regulated Meanwell PS that puts out 5.9A. So I set up the driver to the closest (2.84A Peak) to match my motor. Then I watched Bill's video on large steppers and got confused on a few things. Do we set up the driver to "Peak Amps" or "RMS" and seeing it is a BiPolar motor do I really need to double the amps (2.8 x 2 = 5.6A) for the correct setup? I have more questions but I want to clear up the PEAK vs RMS and the total amps needed for the correct setup first.

Thanks,

Voltage

Thanks,
Voltage


   
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(@voltage)
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Oops. Typo. That should be 4.2A Peak in this sentence above. I can't edit it as I guess there is a time window for that be done.

 

I am using a Stepperonline DM542T Digital Driver that is capable of 42.A Peak and 3.0A RMS.

Thanks,
Voltage


   
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(@voltage)
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Ok, So I found this info and after all my research I hope I found the holy grail. 😋 

Simplest to connect are 4-wire motors. Inside the stepper motor are two coils, each coil having a wire connected to each end. The wire and coil pairs are called a phase.

So that if true makes good sense based on matching drivers to higher amp steppers without having to double the driver output current thinking I have 2 phases.

EDIT ADDED: I think I am still confused and mainly with whether I need to use a driver setting of 5.6 Amps for a stepper that lists the output as 2.8 Amps/phase.

The other question still remains. Do you use the PEAK or the RMS setting from the driver chart for correctly selecting the amps?

Thanks,
Voltage


   
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(@voltage)
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Ok, so here is where I found some great info and if it is all correct, I am golden. Please comment if it look correct to you when it comes to amp settings and digital drivers.

https://tinyurl.com/3ecj9sur

Thanks,
Voltage


   
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MadMisha
(@madmisha)
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@voltage

My understanding is that most of the world uses RMS for stepper motors but Chinese manufactures do not always do that nor do they annotate it. The safest option would be to use that rating as peak. If you have issues then switch it over.

 

Edit: I just reread what you wrote. If it does in fact state that it is current per phase then that is RMS!

Stepper Motors and Drivers Explained Here

 


   
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(@voltage)
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Posted by: @madmisha

@voltage

My understanding is that most of the world uses RMS for stepper motors but Chinese manufactures do not always do that nor do they annotate it. The safest option would be to use that rating as peak. If you have issues then switch it over.

 

Edit: I just reread what you wrote. If it does in fact state that it is current per phase then that is RMS!

Stepper Motors and Drivers Explained Here

 

madmisha, So does that mean if the datasheet says 2.8Amp/phase that I just set the driver to 2.8 RMS (or as close as possible) and that is the correct way to set it. I went back and watched Bill's video on driving large stepper motors and read all of the comments on YouTube and many people were also confused on this 2.8 or 5.6 amp question. And not many answers were given. I guess the meaning of phase id the real question on a bipolar stepper. Some places say one thing and others say another. But based on looking at drivers manufactured it seems like if the specs says the stepper is rated at 2.8 Amp/Phase then you go with the 2.8 Amp RMS setting.

 

Thanks,
Voltage


   
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MadMisha
(@madmisha)
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Posted by: @voltage

So does that mean if the datasheet says 2.8Amp/phase that I just set the driver to 2.8 RMS (or as close as possible) and that is the correct way to set it.

Yes. As close to but not over.

Amps/phase is the max amount of current each winding can take before burning out(Peak for that winding). RMS will be the rating if both phases are powered. Average current, RMS current and current/phase will all be the same. The peak current will be 1.41 times higher.

 

That article I posted is old but it helped me understand it better.


   
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(@voltage)
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Posted by: @madmisha
Posted by: @voltage

So does that mean if the datasheet says 2.8Amp/phase that I just set the driver to 2.8 RMS (or as close as possible) and that is the correct way to set it.

Yes. As close to but not over.

Amps/phase is the max amount of current each winding can take before burning out(Peak for that winding). RMS will be the rating if both phases are powered. Average current, RMS current and current/phase will all be the same. The peak current will be 1.41 times higher.

 

That article I posted is old but it helped me understand it better.

MadMisha, I guess I missed the link on the article you added thinking it was my link quoted. 🙄 Now that I read the article you sent it makes perfect sense although without that article I can see why it would/could be confusing. I was confused because in my research there is a lot of confusion on that topic. Now I can rest easy and quit dreaming about the answer. 😋 Thanks for clearing that up. If you get a chance to watch Bill's video on setting up a big stepper here, see if you think I missed something or not as that is when I started worrying about it.

https://tinyurl.com/43f58vty

Edit: At 2:30 into the video Bill mentions the 4.2 Amp stepper he is using and says that the "Power Supply" needs to be able to handle twice that amount of Amps due to the possibility/reality that "Both" coils are energized at the same time thereby drawing 8.4 Amps. I think that is what got me into trouble and then I started researching and found on the internet two opposing views on almost every forum where I read related questions and replies. My bad. 😟 Doh!

 

p.s. I am not trying to make any trouble but I just want to see if the video may have left an opening for more questions. I think Bill's Youtube channel and this site are awesome. 😎 

Thanks,
Voltage


   
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MadMisha
(@madmisha)
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@voltage

So that has to do with micro-stepping. It will not actually be exactly double. It will be 41%(that 1.4 times figure I mentioned above). It's not double because if you are producing a sinusoidal wave on each phase, they should never exactly match up but will get closer to matching. But rough back of the hand calculation, double is an easy figure. It also accounts for losses because the driver needs power too.

But when Bill mentions it, he is referring to the current needed to drive the controller as a whole(supply current/voltage). You are selecting the current per phase on your driver. Your driver will need double the current supplied to it(roughly).

Here is some further reading that might help. It is referring to the total current here.

Peak vs RMS for Stepper Motor Drivers

If you look at his video at about 21:06 in, you can see that sw1 and 2 are on and 3 is off. At 11:54 you can see that is the selection for 4.28REF and 5.14Peak. That would be the setting for 4.2(slightly over but probably ok). I am not sure if REF is RMS but that seems logical to me.


   
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(@voltage)
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Posted by: @madmisha

@voltage

So that has to do with micro-stepping. It will not actually be exactly double. It will be 41%(that 1.4 times figure I mentioned above). It's not double because if you are producing a sinusoidal wave on each phase, they should never exactly match up but will get closer to matching. But rough back of the hand calculation, double is an easy figure. It also accounts for losses because the driver needs power too.

But when Bill mentions it, he is referring to the current needed to drive the controller as a whole(supply current/voltage). You are selecting the current per phase on your driver. Your driver will need double the current supplied to it(roughly).

Here is some further reading that might help. It is referring to the total current here.

Peak vs RMS for Stepper Motor Drivers

If you look at his video at about 21:06 in, you can see that sw1 and 2 are on and 3 is off. At 11:54 you can see that is the selection for 4.28REF and 5.14Peak. That would be the setting for 4.2(slightly over but probably ok). I am not sure if REF is RMS but that seems logical to me.

madmisha,

Thanks for all the help clearing this up. It makes sense but somewhere I got tripped up and was thinking about it wrong. This happened originally with some plans I got that were in a sense wrong, and then the internet as a whole with varying opposing views. Add the lack of clarity in the documentation and it starts to create some important questions. Enter me. 😋 I kind of thought the stepper driver took care of the black box magic, and it does. But the power supply is just as, or even more important. My current parts for my project (before I even knew of Bill's video or webpage) include a Nema 23 2.85A stepper. a 36V 5.9A power supply, and a DM542T stepper driver. So in retrospect I did a good job picking the parts.

On my original journey into my first stepper project where I bought some plans, the power supply chosen by the designer was way under powered and that is likely what led to me playing with arduino code etc to try to fix it. I fixed some of the issues but not the lack of power. Now I can probably put in a better power supply and fix it, and likely will. But now am am so interested in this stepper motor stuff I am going to have some more fun with it. Thanks for all your help clearing this up. It's funny I didn't find the same info online as you linked to as I always bookmark everything and those links were not already there. Now I have to sort through and delete the bad info links. 😜 

 

Thanks,
Voltage


   
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