Stepper Motor Controller

  
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I`ve managed to complete the first phase of my motion-controlled photography rig: setting up a pair of bipolar stepper motor controllers. This is the most important non-mechanical part of the project, as without control of motors there can be no awesome-tastic motion. I went over some preliminary planning in my first MoCo-related post, but
Stepper Motor Controller - schematic

I`ll go through my list of materials again as well as the general process of building and operating the controller in this post. And if you need a refresher on stepper motors well blah. To start out, I purchased an L298N dual full bridge motor driver. Another option would be to use an SN7544 H-Bridge, as demonstrated on the Arduino site. However, I couldn`t find a wiring schematic for that particular implementation that included back-EMF protection diodes. Regardless, both IC`s are designed to power inductive loads (like a motor) and allow you to do bi-directional rotation on a DC motor, or control a stepper motor. The only problem with the L298N is that it comes in a 15-lead Multiwatt package, aka something you can`t plug into a breadboard. Sparkfun sells a breakout board for $3 intended specifically for this IC but that costs more than the chip itself, so I opted to skip it and work out my own ridiculous wiring methodology. The L298N functions basically as such: It has 4 inputs and 4 outputs. Each input corresponds to an output, and by powering these pins in a specific sequence, you can advance a stepper motor (see Wikipedia picture below). There are variations on the 1-2-3-4 stepping scheme, like 12-23-34-41, that increase torque by engaging more coils of the motor but they complicate the wiring and also the control. Apparently one drawback is that it does not guarantee absolute position as well as the 1-2-3-4 scheme...



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