Microchip Technology PICDEM Mechatronics Demo Board DM163029 DM163029 User Manual
Product codes
DM163029
PICDEM
TM
Mechatronics Demo Board User’s Guide
DS51557C-page 32
©
2006 Microchip Technology Inc.
2.3.6
Project 6: Brushed DC Speed Control with Back EMF Feedback
Project 5 uses an optical encoder to provide motor speed feedback. In this project,
another form of speed measurement will be explored, Back Electromotive Force (Back
EMF). You may be aware that a Brushed DC motor, when turned by hand, will produce
voltage at its leads, becoming a generator. When a Brushed DC motor is being driven,
and then the drive voltage is removed for a brief amount of time, the voltage generated
by the inertia of the motor will be proportional to its speed. This voltage is the Back EMF.
another form of speed measurement will be explored, Back Electromotive Force (Back
EMF). You may be aware that a Brushed DC motor, when turned by hand, will produce
voltage at its leads, becoming a generator. When a Brushed DC motor is being driven,
and then the drive voltage is removed for a brief amount of time, the voltage generated
by the inertia of the motor will be proportional to its speed. This voltage is the Back EMF.
Objectives
1.
Effectively read Back EMF using the on-board Analog-to-Digital Converter.
2.
Interpret the Back EMF into a speed for the motor.
Applicable Technical Documents
Low-Cost Bidirectional Brushed DC Motor Control Using the PIC16F684 Application
Note, AN893 (DS00893)
Note, AN893 (DS00893)
Jumper Configuration
• RD7 (J10) to P1 (J1)
• CCP2 (J10) to N2 (J1)
• AN0 (J13) to POT1 (J4)
• AN1 (J13) to BACK EMF (J16)
• Attach the motor leads to DRIVE1 (P9) and DRIVE2 (P10).
• J2 and J3 should be unpopulated.
• Connect the right and center pins of JP8 using a shunt.