What kind of cFP can I use to control a stepper motor

[Jimmy89]

Hi everybody !

I want to control stepper motors (like to control the opening and closing of a valve) or a variator.

so, my question is :

     - what kind of cFP can I use to do this ?

If you can help me ... 🙂

Thx in advance

Jim

[Eric A.]

Hi Jim,
There are several modules you could use to control a stepper motor.  There are some things that must be considered first.  Most stepper motors use a control that moves the motor based on two bits that are provided by another controller.  There is usually a step bit and a direction bit that determine the motion of the motor.  In this case the 2 bits would be provided by the FieldPoint.  You can use a cFP-PG-522 to output pulses to your stepper motor controller.  This module can provide a finite or continuous number of pulses and the duty cycle can also be adjusted.

[kellis.wiseman]

For any future users to read this post, here is a bit more detail about how you can set this up: 

You can use a Compact FieldPoint system to control a stepper motor. At a minimum, stepper motors require either step and direction or clockwise steps and counter-clockwise steps. You can use a cFP-PG-522 to generate a finite pulse train for step control. For direction selection, you simply need a digital output line, which you can get from a Digital Output FieldPoint Module.

 
While there is no example that I am aware of that specifically addresses stepper motor position control using a Compact FieldPoint system, the NI Example Finder does include a good pulse generation example that you could use as a starting point for step control. The example is called Pulse Generation.vi and can be found by opening LabVIEW, clicking Help » Find Examples » Hardware Input and Output » FieldPoint » Advanced. As you can see in this example, control rate simply refers to the loop rate you specify in software. The amount of code you include in your control loop will determine the minimum loop rate that you can specify. For most stepper motor applications, you will not run into a control loop rate problem. 
The cFP-PG-522 module has a maximum output frequency of 5 kHz. Once you know the number of steps per revolution for your stepper motor, you can use this value to calculate the maximum velocity, in revolutions/second, at which you could control your stepper motor. For example, a stepper motor with 200 steps per revolution could be controlled up to 25 revolutions/second (5,000/200), assuming the motor is physically capable of spinning this fast. 

If you plan to operate your motor in a closed loop control mode, you will also need a cFP-QUAD-510 module than can read in the quadrature encoder measurements. Please also keep in mind that the Compact FieldPoint system only interacts with the stepper motor indirectly. You send your step and direction signals (or clockwise step and counter-clockwise step) to a stepper drive that actually connects to the stepper motor. Look at the specifications page for your particular motor to see the stepper drive National Instruments recommends. For example, for a NEMA17, you will need the P70530 Stepper Drive, 20-75 VDC powered. 

Hope this helps! 

~kgarrett