Stepper Motors
Thus far we have used motors that are relatively imprecise. We say that because the motor runs for a certain time and makes a certain number of revolutions, but this can vary with the battery voltage and the motor's own internal friction and inertia. Moving an arm on a plotter, printer or 3D printer requires precision. We want to know exactly how far a motor has turned so we will know where it sends an arm that can cut, paint, melt plastic, or write.
Stepper motors fulfill this need. To see how steppers are different than brushed motors (the ones we used in the 2D model and the most common hobby motors), watch this video about one kind of brushless motor:
Stepper motors are similar in theory. We energize one set of electromagnets and the permanent magnets inside the motor rotate to align. We can control these motors using the L293 control chip. Watch this example below.
You can experiment with a stepper motor like the one above. Connect it to your motor controller board and step the motor as shown in the diagram below:
Challenge:
A. Use a sketch (Arduino program) to drive the brushless motor in the first video above. You will need to use a different driver..a transistor. See this page for details: Transistor Driver
B. Now use the Arduino to control the step motor. You will need to use the diodes as shown in the 2D plotter model you built: Controlling the Motors with a Microprocessor: Arduino and you will need to use a sequence software sketch that you used for the square shape on the 2D plotter. Software Control of a Microprocessor: Arduino