Pump control - Uni or Bi polar stepper motor

I am working on a robot that includes several annular gear pumps. We are using the MZR 2521,

manual: (please see section 5.5)
http://www.micropump.com/support_documents/manual_mzr-xx21.pdf

product page:
http://www.micropump.com/product_detail.aspx?ProductID=62

In the description they say that you can run the pump as if it were a stepper motor. This seems like it could be done perfectly with an Arduino, but I was not sure whether to treat it like a Unipolar or Bipolar stepper motor as the setup for each is quite different. Does anyone have any thoughts as to which it might be? Thanks so much.

It says your pump can be purchased with either a brushed DC motor, brushless DC motor, or a stepper motor. Are you certain you have the stepper version?

If you are certain it's a stepper version then the only option available to you is a bipolar driver.

We are planning to purchase it with the stepper motor. Do you see any cons to buying it with the stepper motor? We are looking for the simplest method to control it without losing an precision.

Between the brushed DC motor, brushless DC motor, and stepper motor the stepper motor is the best choice. The other two options won't give you any precision in control. Well, the brushless DC motor might but you'd be building your own motor driver which is not a simple task...

This A4988-based driver for bipolar steppers is very popular (especially with RepRap-style machines) and should work well for you. You can find plenty of examples on the web, but the gist of it is that every time you toggle the "STEP" pin high it will rotate your pump motor 15 degrees.

On the driver board there's a small potentiometer which needs to be adjusted to 250ma current per this pump's maximum current. See the instructions for details. If you drive the motor with too much current it will overheat (feel the motor with your fingers to make sure it doesn't). A 5V supply should be OK, but if you can't get it to spin quickly enough you can use up to a 35V supply.

The AccelStepper library will make interfacing with the driver pretty straightforward.

The specs look a bit odd, claims a 12.5k ohm winding resistance and a current-per-phase of 0.25A,
suspect the winding resistance is 12.5 ohm, not 12.5k (otherwise it would need 3000V supply!).

Any standard bipolar chopper driver that can be set to 0.25A should work fine.

MarkT:
The specs look a bit odd, claims a 12.5k ohm winding resistance and a current-per-phase of 0.25A,
suspect the winding resistance is 12.5 ohm, not 12.5k (otherwise it would need 3000V supply!).

If you google the motor itself you can find the correct resistance. Yeah it's a typo :wink:

Could I use this H-bridge as well?

Ben1234:
Could I use this H-bridge as well?
https://www.sparkfun.com/products/315

Possibly, but I wouldn't recommend it. That chip has around 2V voltage drop, so you will need to use a higher voltage supply with it to allow for that, and it will get hot.

The H bridge would be used with the brushed DC motor option. It would not offer the precision of RPM that the stepper motor option provides.

...well, if you like doing things the hard way, you could use a couple of those and build your own stepper driver but it would be a complex, inefficient, pain in the butt. The A4988 driver is without a doubt the better solution.