Smooth stepper motor velocity profiles

[barddya]

Hi hrh1818

what if one uses a stepper motor shield. Would that work?

Barddya

[Nathan_B.]

If the stepper motor shield handles all the stepper motor timing and such and you simply communicate with it via I2C or something (and it can do 4 steppers) then yeah.

[hrh1818]

Your Question.

"what if one uses a stepper motor shield. Would that work?"

The version 2 of the Adafruit Motor Shield can drive two stepper motors and uses I2C to interface an Arduino board with the shield.  In addition the shield is stackable.  You can stack up to 32 shields and drive as many as 64 stepper motors. See:

<http://www.adafruit.com/products/1438>

However, the supplied software is designed to run on an Arduino board.  If you need to use LIFA or LINX with a version 2 Adafruit Motor Shield then you need to examine the source code to extract the appropriate I2C commands.  This is not a trivial task. 

I had forgotten about the version 2 Adafruit Motor Shield when I wrote yesterday you can only use 1 stepper motor with LIFA.   Nathan jogged my memory when he mentioned I2C.  With respect to other brands of stepper motor shields most are not compatible with LIFA.

hrh1818

[hrh1818]

Hello cterill,

What hardware and software are you using to interface Labview to 4 stepper motors and to run the stepper motors simultaneously?

hrh1818

[cterrill]

hrh1818, here is a photo of my setup. Ignore the 5th power supply and extra stepper motor, those are for a different application. I know for a fact that this setup runs all 4 stepper motors. I don't know much about the software, since I inherited this project, but I'm reluctant to mess with what's on the Arduino, if anything, since I remember the guy who had the project before me having a lot of trouble with it.

It is worth mentioning, however, that just running my current setup with all 4 motors running on the standard trapezoidal profiles seems to cause some variation in the loop timing. The period of the motion has a range of about 100 ms (standard duration of the loop is around 6.5 seconds), which makes taking phase locked images for PIV (this is for fluid mechanics research) samples difficult. Would switching to Arduino fix or attenuate this? Would Arduino allow me to take force data from a DAQ and plot it against the time of the motion?

edit: I'm on LabVIEW 2012

[cterrill]

Also, Nathan_B., I'm working on implementing your method now. The reason I've been using the Wait Until Steps Complete function is that if I don't, the motor essentially skips to the final speed and travels only a step or two (some amount that is imperceptible to my eye) at each of the speeds before the last one.

[Nathan_B.]

I understand why you were using it, it is necessary as you found out.

Are all four of your steppers running at the same time?

[cterrill]

All four motors run at the same time, yes. I'm not sure if they necessarily receive commands at the same time, but they are all in motion at the same time.