Page 804 - Mechatronics with Experiments

790 MECHATRONICS
4. Experiment with different PWM duty cycles and PWM frequencies. Try to feel the
net force generated as a function of PWM duty cycle while holding the solenoid at a
fixed mid position.
5. (Optional) Obtain a proportional single stage valve with two proportional solenoids,
spool position sensor, and centering spring. Connect two PWM output pins from
the PIC microcontroller to drive two transistors to control two solenoids. Under
software control, control either one of the solenoids proportionally under software
control. Verify the spool position change as function of the solenoid (number 1 or
number 2) and the magnitude of the command signal sent to the solenoids by the PIC
microcontroller.

11.10 EXPERIMENT 10: STEPPER MOTOR MOTION
CONTROL USING A PIC MICROCONTROLLER

Objective
Design a complete system for motion control of a stepper motor using the PIC microcon-
troller and a step motor controller integrated circuit (IC). Write software to control
1. magnitude of speed,
2. direction of speed,
3. run the motor in full-step mode and half-step mode.

Components

Item Quantity Part No. Supplier
EDE1200 IC (translator chip) 1 141532 www.jameco.com
Stepper Motor 1 151861 www.jameco.com
Potentiometer (200 Ω) 1 181972 www.jameco.com
DIP Switch 1 38818 www.jameco.com
PIC Demo Board/connectors 1 set DM163022 or www.microchipdirect.com
DV164006
ULN2003A - Transistor array 1 60K7049 www.newark.com
IN4744 - Zener diode 1 36185 www.jameco.com
Resonator: AWCR 4.00 MD 1 13J2002 www.newark.com

Theory

Stepper Motor A stepper motor rotates one step per change in the energized state of
its stator windings. The stepper motor used in the experiment is a unipolar, 2-phase (center
tapped), 7.5 degrees/step, 5 VDC stepper motor.

EDE1200 Unipolar Stepper Motor IC and ULN2003A Driver EDE1200
is an integrated circuit (IC) logic chip (also called the translator) for a unipolar step
motor. The actual current control in the motor phases is done by another high current
driver, which is ULN2003A chip in this case. EDE1200 accepts 5 V logic level signals
and generates output commands which define how the current in each phase should be
controlled. EDE1200 provides four TTL level output signals. These TTL-level output
signals control the sequence of the amplifier drive circuit, which generally consists of