BACK_EMF_PM_MOTOR_SPEED_CONTROL

Published:2009/7/3 3:09:00 Author:May | From:SeekIC

The use of power MOSFETs allows a direct interface between logic and motor power, which permits circuit simplicity as well as high efficiency. This speed control circuit can be packaged on a 22-pin, double-sided, 3.5 x 4-in. pc board. A 12 V control supply and a TRW BL11, 30V motor are used; with minor changes other motor and control voltages can be accommodated. For example, a single 24V rail could supply both control and motor voltages. Motor and control voltages are kept separate here because CMOS logic is used to start, stop, reverse and oscillate the motor with a variable delay between motor reversals. Motor speed is established by potentiometer R2, which applies a corresponding dc voltage to the + input of comparator U1, whose output is then applied to TMOS device MTP8P08 (Q1). Zener diode D1 limits the drive to Q1. The output of Q1 drives the permanent magnet motor. Back emf is obtained from the motor via the network consisting of R8, R9, R10, C2, C3 and D3; it is applied to-input of comparator U1.



Reprinted Url Of This Article:
http://www.seekic.com/circuit_diagram/Control_Circuit/BACK_EMF_PM_MOTOR_SPEED_CONTROL.html

Print this Page | Comments | Reading(3)