Controlling Stepper Motors with NI myDAQ

kristielNational Instruments

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This month at Studica in Canada we are happy to have the help of two COOP students from Rick Hansen Secondary School in Mississauga. These two students will be tackling projects using National Instruments products, Fischertechnik, and many of our other exciting tools. They will be exploring Automation, Control mechanism, and Renewable Energy in the next few weeks. Watch out for their blogs about their exciting projects. Here is the first one – “Controlling Stepper Motors with the use of NI MyDAQ”.

Here at Studica Systems in Mississauga Ontario, we are working on control and testing of stepper motors with the use of an NI MyDAQ and NI LabVIEW. Our Co-op Students, Kamran and Denisan, will be experimenting and studying the use and theory behind stepper motors and the use of NI MyDAQ. Used together the stepper motor and NI MyDAQ perform very well.

What is a Stepper Motor?
A stepper motor is similar to a DC motor however rather than rotating continuously it rotates in small controlled steps.

There are two main types of stepper motors:
1. Uni-Polar: In a uni-polar stepper the windings are connected by a center tap between the two windings. The current flow is unidirectional with only half the current on each center tap.
2. Bi-Polar: A bi-directional stepper motor has each winding brought out individually with bi-directional current flow throughout the entire winding.

For the purpose of this blog we are going to be working with a uni-polar stepper motor. There will be many phases throughout this project.

Phase 1: For phase 1 we had originally planned to use dedicated stepper motor control chips such as the LS297 to provide the frequency along with the 555 timer. The LS297 when wired correctly generates the correct sequence to rotate the stepper motor continuously in a clockwise motion, however due to some difficulty and a lack of components we could not continue to work with this; we may however revisit this approach at a later time utilizing a bipolar configuration rather than a uni-polar configuration. We then decided to use the UCN4204b however we were having many issues with this chip as well.

We had used the MyDAQ to test it for various issues and found that we wouldn’t be able to use it because for some reason the current wasn’t able to flow through to all the windings on our stepper motor. As a last approach we decided to have the inputs of our stepper motor circuit connected directly to the MyDAQ which we would use to provide the digital outputs for the stepper sequence. After hooking everything together we manually applied the high’s and low’s to make sure that the stepper was working.

After verifying that everything was working fine we began to use LabVIEW to create a Virtual Instrument that would automatically feed the sequence we would program to the stepper. 

Watch our video of these activities regarding the controlling stepper motors incorporating the MyDAQ…

Skills Required:
Basic use of Labview, the understanding of the NI MyDAQ, and the research involved to understand a stepper motor. Using all of these skills we were able to use LabView to control the NI myDAQ that sent signals to the stepper motor. Hope you enjoyed reading this blog and watching the video.

We are looking forward to assembling some fischertechnik products and implementing the control features of the myDAQ and LabVIEW into these models. Stay Tuned!

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