PIC Motor Control and Serial Port Example

Introduction

In this application, we will use a PIC 18F4431 microcontroller to implement a closed-loop lead-lag compensator that controls the velocity of a motor with an encoder. This example will cover the use of:

• interrupts
• reading encoders
• pulse-width modulation
• USART (Universal Synchronous Asynchronous Receiver/Transmitter)

Every 20 milli-seconds, the PIC will sample the encoder and run the feedback control loop. The output from the control loop is then sent to the motor to try to match the motor's speed with the target speed. To set the target speed, commands are sent from a PC's serial port to the USART on the PIC. The PIC will also print the target speed and actual speed of the motor to the terminal window of the PC.

Project Files

Download the MPLAB project here.

This was compiled using MPLAB 7.6 and C18 3.12 (student version). If MPLAB has problems finding files or does not compile, it may be because the directories on your computer are set up differently. In this case, create a new project following these instructions, and copy in the source files.

Wiring Diagram

File:C18 tutorial Motor controller wiring.png

Wiring Diagram for the motor velocity controller example

Wiring Diagram for the motor velocity controller example(PowerPoint)

DE9 Female Connector Wiring

Breadboard Layout

HyperTerminal

Open HyperTerminal by going to Start>All Programs>Accessories>Communications>HyperTerminal. When it prompts you for a name for the connector, you can give it any arbitrary name.