Breadboard Adapter for Lego Mindstorms to control bipolar stepper motor


#1

All, I am bit of a novice and I am trying to design and build a very slow moving camera platform for astrophotography. Before I start buying some of the components, I want to understand whether my idea will work. I want to control with microstepping a strong bi-polar stepper motor using a pololu motor driver. I want to use the EV3 via the Breadboard Adapter for Lego Mindstorms to act as micro controller. Did anyone try this? I see lots of reference of using the lego motors in other systems and making new sensors for the EV3, but I have difficulty finding any references for my project.

The questions I have are:

  1. will this work
  2. do I need any special EV3 program blocks or can I use standard motor blocks (will the EV3 recognize these?)
  3. are there other EV3 program blocks I can use to directly communicate with the motor driver via the I2C protocol.

Thanks a lot for your help.


#2

Hey Jeroen,

Do you have a diagram for a specific part you’re trying to use? I guess the devil is in the details on this sort of project!

It sounds like an awesome project!


#3

Hi John, thanks for coming back so quickly. Yes indeed an awesome project. Basically I am aiming to build this: http://www.amazon.com/iOptron-3302B-SkyTracker-Camera-Mount/dp/B00EFRN1GE for a fraction of the costs and enjoying the project time with my son whilst building and using it!

I am aiming to drive one of these motors (undecided):
https://www.pololu.com/product/2267 Nema 17, 200 step, 1.7 amp per phase
https://www.sparkfun.com/products/10846 Nema 17, 400 step, 1.7 amp per phase
https://www.sparkfun.com/products/10847 Nema 23, 200 step, 2 amp per phase

using a vertical shaft worm gear with a gear ratio of 30:1, 120:1 180:1 or 360:1 (again to be decided depending on motor power and internal friction…working that)

To get basically to one revolution per astronomical day. The motor will be running somewhere between 4 and 12 minutes per revolution. So micro stepping is important and smooth operation is everything as a jerking motion will spoil the pictures!

As motor driver I am looking at the following options (see hook up schemes attached). The choice will be determined by whether we think we can get this to work. I can also chicken out and not risk it and just buy an arduino, but that is the last resort.
adafruit TB6612FNG
Big_easy_driver_HookupFixed available via spark fun
Pololu DRV 8825

and the EV3 connected up via the dexter break out board. At the moment I am thinking of using the 4.3V line to power the motor board, have a separate 12 V motor supply and I am hoping that I can use the SCL and SDA ports as the 2 interface boards as per the simplified connection schemes attached to this post for step and dir.

So would this all work and would the EV3 see this as a motor or do I need to build a dedicated I/O block.

As you can see I did my research but I am really reaching the limit of my understanding of electronics here…thanks for the effort and help.