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What's the Difference Between Optical and Capacitive Encoders?

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Nov
14
by Eric Rice

We offer different incremental encoder options for our stepper motors. Encoders are used to provide feedback to the motor drive or controller and improve overall performance of the step motor system. The following provides a summary of those encoder options.

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Can I Operate a Step Motor at Full Current all the Time?

Oct
29
by Jeff Kordik

If you read our article Why Do Step Motors Get Hot? you may have wondered "What does this mean to me?” Step motor losses are important because the energy lost in the motor results in heat. Any motor has a thermal constant that can be used to compute how hot the motor will get for a given level of energy dissipation. Once the windings exceed 130°C, the insulation on the motor windings will melt and it’s game over.

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How Can You Calculate Step Motor Trajectories?

Oct
28
by Jeff Kordik

Step motor motion is conceptually simple: Just rotate the stator field and the rotor will follow, so long as you don’t expect it to violate the laws of physics.  An easy but unpleasant way to violate said laws is to ask for more acceleration than the motor can achieve.  So how does one perform step motor trajectory calculations? As we learned in the post Dynamic Torque & Step Motor Sizing, maximum acceleration is determined by torque divided by inertia.

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How Does Holding Torque Differ From Pullout Torque?

Oct
28
by Jeff Kordik

The first thing many new users ask about step motors is: "what's the difference between holding torque and pullout torque?". Which one matters to me (as Herb Tarlek might say)? If you apply a constant current to one winding of a step motor, torque is produced according to this formula:

torque_eqn

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Why Do Step Motors Get Hot?

Oct
28
by Jeff Kordik

In our post Step Motor Heating we looked at step motor losses over a wide range of speeds and power supply voltages. Now, we deepen our examination. Step motors waste power in two ways: copper losses that result from the electrical resistance of the stator coils and iron losses from magnetic hysteresis and eddy currents. In both cases, this lost power results in the motor heating.

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What is Step Motor Stack Length?

Oct
28
by Jeff Kordik

In our post What Do NEMA Sizes Mean?, we examined the NEMA frame sizes in which step motors are made. Larger frame sizes produce more torque. But this is not a one dimensional process: within a given frame size, the motor length can vary and that also affects torque. Because step motors require expensive tooling in order to be produced economically, a fixed rotor length is chosen, as is the stator that surrounds it.

How Does A Step Motor Work?

Oct
28
by Jeff Kordik

Though it's long been rumored that step motors are driven by tiny hamsters on wheels contained inside, I can assure you that this is not only untrue, but also promulgated by unscrupulous pneumatic actuator salesmen.  So how does a step motor work? In reality, step motors operate by electromagnetism.  Specifically, a permanent magnet rotor such as the one shown below is attracted to electromagnets that reside in the stator.

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What do NEMA sizes mean?

Oct
28
by Jeff Kordik

Step motors are categorized by frame size, such as "size 11" or "size 23".  Ever wonder how that came to be or what it means?  The National Electrical Manufacturers Association sets standards for many electrical products, including step motors.  Generally speaking, "size 11" mean the mounting face of the motor is 1.1 inches square.

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How Do You Mount A Step Motor?

Oct
28
by Jeff Kordik

If you are new to step motors, you may be wondering how to mount one in your application. You’ll need to be concerned with three things: piloting the motor, fastening it to the mounting surface, and coupling the shaft to your load.

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What Is A Unipolar Step Motor Drive?

Oct
28
by Jeff Kordik
What is a unipolar step motor driver? How does a unipolar driver compare to a bipolar step motor driver? When step motors first became popular as a simple, inexpensive means to control position and speed, the transistors required to drive them were very expensive. What, transistors expensive? Don’t they put, like, a billion of them on a chip?
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