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Interfacing LabView with Stepper Motors via pulse modulation

Hi all,

 

I had a question regarding stepper motor actuation via pulse modulation.  I already have the program (attached) which controls the motors with pulse/direction control determined from an input file (attached).  The waveform appears to indicate the input file is being read correctly but the motors themselves are not responding.

 

I'm using 2 devices, BNC-2110 and an SC-2345 board though the SC board is strictly used as a timer/counter source.  Attached to the BNC-2110 are two lines indicating motor spin direction, those are attached in port0/line0 and port0/line1.  Additionally the BNC has two lines for the pulse modulation output indicating the step rate for the motors, those are attach to port1/line2 and port1/line3.  Then a ground grom the stepper board is attached to the D GND on the BNC and because of the length of wire I've run a capacitor in parallel to port1/line2 and port1/line3 to another D GND on the BNC. 

 

Can anybody see what I might be missing?  Any help would be much appreciated.

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Message 1 of 6
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Hi Jihen,

Hi Jihen,

 

 

Hi Jihen,

 

 

 

Hi Jihen,

 

 

 

 

 

Which DAQ card is connected to the BNC-2110? It is unlikely that the DAQ card will be able to source enough current to power a motor through the digital lines without some external circuit. The maximum current on Port 0 for a PCI-6221 for example is 24mA. This information can be found in the NI 622x Specifications. Please post the specifications for the stepper motor.

Hi Jihen,

 

 

 

 

 

Which DAQ card is connected to the BNC-2110? It is unlikely that the DAQ card will be able to source enough current to power a motor through the digital lines without some external circuit. The maximum current on Port 0 for a PCI-6221 for example is 24mA. This information can be found in the NI 622x Specifications. Please post the specifications for the stepper motor.

 

In either case, it is not recommended to use DAQ cards for motor control. For the reasons, please see this forum thread: Controlling 3 stepper motor with labview using usb6218

 

Hi Jihen,

 

 

 

 

 

Which DAQ card is connected to the BNC-2110? It is unlikely that the DAQ card will be able to source enough current to power a motor through the digital lines without some external circuit. The maximum current on Port 0 for a PCI-6221 for example is 24mA. This information can be found in the NI 622x Specifications. Please post the specifications for the stepper motor.

 

In either case, it is not recommended to use DAQ cards for motor control. For the reasons, please see this forum thread: Controlling 3 stepper motor with labview using usb6218

 

 

Thanks,

Steven K.
National Instruments
Software Engineer
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Hi,

 

The DAQ cards are both NI PCI-6251.  I should also clear up my title, I'm strictly using the the BNC for step and direction.  The stepper board card and motors have an independent power source. 

 

I'm beginning to wonder if it's a grounding issue.  The stepper board card/motors are powered by laptop power adapters connected to the wall outlet.  Now although the two are independent I have connected to ground of the stepper board directly to the ground of the BNC. 

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Can you probe the signal coming out of the DAQ card with an oscilloscope to see if the output is what you expect?

 

Thanks,

Steven K.
National Instruments
Software Engineer
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I used an oscilloscope and found the problem, I had the devices switched.  Thanks for all the help and sorry if I took too much of your time.

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No problem at all. Thats what we are here for. I'm glad you were able to find the solution.

Steven K.
National Instruments
Software Engineer
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