Getting Started

Chapter 7: Microcontroller Interrupts and Timers

et’s modify the LED PWM software a little and use it to control the speed of a

stroy the Butterfly when messing with this circuit. I
actually managed to burn up both the optoisolator and the power transistor when
fooling with this design so, at least for me, this is not overkill. Since this is not an
electronics text, we won’t learn anything about how the circuit works. Just follow
the illustrations and you shouldn’t have any problems.

Pulse Width Modulation - Motor Speed Control

L

motor. But first, Let’s design and build the hardware. We’ll use parts from the
JAMECO parts list: a 9v motor, a 9v battery, a 9v battery connector, a 4N28
optoisolator, a TIP115 power transistor, a 330 Ohm resistor, and a 2.2K Ohm
resistor. I’ve included the optoisolator for the simple reason that it helps lessen the
possibility that we’ll de

Figure 18: Motor Speed Control Schematic and Parts........................................