EAS 199A Lecture 10:     24, 25 October 2012

10. DC Motor control, Soldering the DC motor leads

Class meeting on 24, 25 October 2012

Learning Objectives

1. Be able to safely solder extension leads onto the DC motor
2. Be able to use a potentiometer to control the speed of the DC motor from the Sparkfun kit

Notes and Supplemental Files

1. Review DC motor circuits PDF slides and 3-up notes before class.
2. Controlling the speed of a DC motor slides or 3up notes
3. Review Soldering instructions Powerpoint before class.
4. Soldering extension leads onto the DC motor slides or 3up notes

Flyback Diode

The Wikipedia article on flyback diodes explains how the flyback diode prevents unwanted reverse current surges when a circuit containing an inductive load (like a motor) is interrupted.

Wiring of Diode and Transistor

The manual for the Sparkfun Inventor's Kit calls for a 10k resistor to connect the Arduino motor pin to the base (middle pin) of the transistor. I found that the voltage drop between the digital output pin and the base was too great, which meant that the transistor did not change state and allow current to flow from the 5V supply to ground. The circuit did work when a 330 ohm resistor was used instead.

Historical article on the Transistor

The modernmechanix.com site has [a short article from the 1953 Scientific American with the title Transistor -- mighty mite of electronics