Microstepping with motor shield rev3

Hello everybody, I'm implementing a motorized focuser for my telescope and I'm trying to get the smooter and vibration free possible solution. I am using both Arduino uno and Motor Shield rev 3 and also using this stepper motor: http://www.kysanelectronics.com/Products/datasheet_display.php?recordID=7850

I wonder whether is possible to pilot it in mocrostepping way, I really did not find anything regarding so any suggestion is appreciated. In case motor shield or motor are not compliant would you please suggest me other items? Thanks in advance, Giovanni.

Hi ggkids,

I'm assuming your telescope is outside, so you may want to control your telescope using batteries.

Using the stepper you mentioned above draws far too much current. In my opinion you are better off buying a nema17 stepper from Sparkfun or Adafruit, 12V .4A 200 steps.

If you are going to use an Arduino UNO R3 to control everything, then you'll need to piggy back that with an Adafruit motor shield V2. You cannot drive a decent stepper directly from an Arduino, the outputs can't handle the current draw.

See here to get you started https://learn.adafruit.com/adafruit-motor-shield-v2-for-arduino/using-stepper-motors. Microstep is slow and very smooth.

Good luck

Ken

edit: should have read your post more carefully, I see you are using an Arduino and Adafruit motor shield.

Once you have installed the Adafruit motor shield software, under their example sketches, there's one called motor test. This is a good starting point.

Hi Ken, Thanks for your reply! I'm not afraid about power consuption because I have 220V power plug near my mount. I also use a motor drive but not that from Adafruit: I'm using the Arduino one called Motor Shield rev 3. On this type of shield I wonder how to drive my stepper in microstepping. At the moment I managed to drive it in half step mode but I'm not sure micro is possible nor any code I found about it. I hope someone will have some good trips or code fragment to reach my goal. Thanks in advance! Cheers, Giovanni

The simplest way to do microstepping is to use a specialized stepper motor driver. A Pololu A4988 or Pololu DRV8825 should work fine with your 1.5 amp motor.

A motor shield is a poor choice for controlling a stepper motor.

See stepper motor basics.

...R

That motor requires a chopper drive anyway, its a low impedance bipolar motor intended for current control. DRV8825 will just about handle the 1.5A. Chopper driver chips normally support several levels of microstepping. H-bridge motor drivers don't.

Better to ask before buying the motor really, with your speed and torque requirments - steppers are wholey different from DC motors. You may not need the ability to drive the motor at 1000's of rpm which this kind of stepper is all about...

MarkT: That motor requires a chopper drive anyway, its a low impedance bipolar motor intended for current control. DRV8825 will just about handle the 1.5A. Chopper driver chips normally support several levels of microstepping. H-bridge motor drivers don't.

Better to ask before buying the motor really, with your speed and torque requirments - steppers are wholey different from DC motors. You may not need the ability to drive the motor at 1000's of rpm which this kind of stepper is all about...

Sorry, I didn't get if a DVR8825 is good enought to drive my motor...I won't sure use at high rpm.

Thanks, Giovanni.

ggkids: I didn't get if a DVR8825 is good enought to drive my motor...

Yes.

...R

Dear all, I come back to this topic after some weeks because I have the components and time to go on in this project. As you know I'm goint to use this stepper: http://www.kysanelectronics.com/Products/datasheet_display.php?recordID=7850 From the DRV8825 docs I see I have to set the onboard trim to the rated current of the stepper; unfortunatelly the sheet on the link I copied does not have any "rated current" but only a "current per phase". What value should I use for the DRV setting?

Thanks in advance, Giovanni.

Robin2: The simplest way to do microstepping is to use a specialized stepper motor driver. A Pololu A4988 or Pololu DRV8825 should work fine with your 1.5 amp motor.

A motor shield is a poor choice for controlling a stepper motor.

See stepper motor basics.

...R

Definitely go for the DRV8825, it can take more current. It will still be very hot at 1.5A, but should just about cope. Set maximum microstepping for smoothest operation.

ggkids: unfortunatelly the sheet on the link I copied does not have any "rated current" but only a "current per phase". What value should I use for the DRV setting?

Thanks in advance, Giovanni.

Same thing.