After completing these tutorials it’s hard not to notice automated mechanical devices usually taken for granted, printers, for instance. The servo element used in #8, followed by the motor used in #9 and #10 demonstrates an important difference between them. A servo is for simple repeat motions like an elbow. A motor, on the other hand, can be programmed to spin for a specified number of revolutions; stop, continue, or, as in #10, reverse direction. In a printer, the servo might be used to feed sheets of paper from the paper tray. Motors would be used to carry the sheets through the various inking operations. By mastering these two operations almost unlimited opportunities for employment in mechanical automation are possible! Tutorial 9 demonstrates what can be done with code for automation, but #10 adds user controls to the motor turning program. The experimenter sits back and watches #9 do its thing. In #10, the experimenter can reverse motor rotation by pushing a button, and control speed with a potentiometer. After performing circuit 10, I thought about how easy it is to change DC motor direction by changing voltage polarity. Why automate? A crude schematic would involve DC power and a pair of contacts. Mount the motor for convenience and touch the power wires to the motor contacts, reversing order to reverse motor direction, but consider how much easier that can be done with a button. Pushing the button in the circuit I built is a novel experience. Pushing the button changes motor direction, not simply on/off, like a typical button. In other words, on is clockwise, off is counterclockwise. The potentiometer acts as a variable on/off switch. Zero volts causes the motor to stop. I hope to develop an experiment combining a temperature sensor with a cooling fan. Either, or both, starts up the fan at a specified temperature, or increases and decreases speed with temperature change. After completing the rest of the tutorials in this series I will be back for advice. https://learn.sparkfun.com/tutorials/ex … er-kit/all