Objectives
A. Develop software routines that control Stepper Motors, small permanent magnet DC motors, and Servos.
B. Understand how an H-bridge can be used to control DC motors and Stepper Motors.

Results
Conclusions
Team
Name Program Signature

Name Program Signature

Name Program Signature

Observations/Measurements
A. Questions for the DC Motor Procedures:
1. What is a use of an Optical Isolator (Optoisolator)?
2. Use Ohmmeter to measure resistance for DC motor used in this Lab.
3. In Activity 1, explain how you turned the DC motor “on” and “off.”

4. In Activity 1, explain how you chose the speed of DC motor.
5. Explain the load and no-load RPM in DC motor.

6. Connect a DC motor leads to +5V and Ground and measure the current usage on current meter. Examine loaded and no-load current usage. Give your conclusion.
7. Explain the PWM technique.

8. What is the disadvantage of using a group of instructions (instead of PWM feature of HCS12) in controlling the speed of the DC motor?

B. Questions for the Stepper Motor Procedures:

1. What is a step angle? Define steps per revolution. What is a step angle for the stepper motor that you used in this Lab? How many steps per revolution do you have for your stepper motor?

Skip since we don’t have step motors included in the lab kit.
2. If a given stepper motor has a step angle of 5 degrees, find the number of steps per
revolution. (You still need to answer this.)
3. Give the four sequences for counter clockwise if it starts with 10011001 (binary).
(You still need to answer this.)
4. Using assembly (or C), show a simple program to generate the four step sequences if the initial step is 0011 (binary). (You still need to answer this.)

5. Give the number of times the four step sequence must be applied to a stepper motor to
make a 100 degree move if the motor has a 5 degree step angle. Also, fill in the
characteristics for your motor below.

Skip since we don’t have step motors included in the lab kit.
Step angle ______________ Degree of movement per 4 step sequence ________

Steps per revolution _____ Number of rotor teeth ______________

Questions for Servo Procedures:
1. Describe apparent speed of the motor as a function of the pulse width used in PWM control.
Please refer this link to find your answer.
http://www.parallax.com/product/900-00008
Continuous servo is controlled by PWM for its CW or CCW speed.
2. How did the rotation angle of the servo depend on the pulse width of the input signal?
Please refer this link to find your answer.
http://learn.parallax.com/KickStart/900-00005
Standard servo rotates to an angle between 0 ~ 180 degree with a PWM signal.

3. Did you use an H-bridge? Why or why not?
(You still need to answer this.)

4. Compare the frequencies of pulse trains that you can obtain with a loop program with pulse frequencies from the PWM generator.
(You still need to answer this but using a pseudo-code is fine.)
5. Compare the pulse trains controlling the servo to the pulse trains controlling the DC motor.
(You still need to answer this.)

Show a picture captured from your oscilloscope with the Tower PWM channel (either PP1 or PP3) to have 50% duty cycle waveform with about 1300Hz in the frequency, such as this example below.

(Show your frequency measurement on the scope image.)

Show the code you used to create the waveform shown above.
Mini Project:

Use your mini lab and Tower system to create a simple DC motor control system.
• Use the SW4 to start the motor or stop (toggle function.)
• Use the SW2 to control CW or CCW. (toggle mode)
• Use the POT to control motor speed.
Please watch the video demo in the iConnect lecture for a reference.
Take a few photos for your work. For instance, take one photo for CW, one photo for CCW, one for high speed (80% duty cycle) and one for low speed (20%) and one for showing power on and the other showing power off. Also, take a photo to show you wiring and connection to the mini lab tool box.
Your LCD interface is to be designed similar to the photo below.