Portland Community College | Portland, Oregon

Upon completion of the course students should be able to:

• Identify types of sensors used in a mechatronic system and describe and probe the behavior of their inputs and outputs.
• Identify faulty power amps through probing.
• Describe important safety precautions with regard to motors.
• Describe components, mechanisms, characteristics, and common failure modes of DC motors.
• Troubleshoot DC motors at the system/board level.

The course will include instructor delivered lectures and demonstrations stressing key topics in the course. Students will also reinforce and practice concepts learned in a laboratory setting.

Assessment of student performance in this course will be in the form of homework, quizzes, exams, in-class lab performance and lab reports.

Signal Conditioning

Section 1         Explain types of signal conditioning needed for sensors: signal amplification, filtering, impedance isolation

Op-amp

1                 Know circuit connection, amplification factor, equivalent input and output impedance of four types of op-amp circuits: Voltage follower, inverting op-amp, non-inverting op-amp, and differential op-amp.

2                 Explain how op-amps can be used to achieve signal amplification and the transformation from high impedance to low impedance signals. Know that op-amps are typically not used for power amplification of actuators.

3                 Be able to design a suitable op-amp circuit based on the amplification, impedance isolation, and polarity need of the application.

Sensors

Section 1         Position sensors

1                 Know how a potentiometer can be used to measure position.

2                 Know how to design an interface circuit between a potentiometer and a controller.

3                 Know the advantages and issues of using a potentiometer as a position sensor.

4                 Know how an absolute optical encoder can be used to measure position

5                 Know what determines its resolution

6                 Know how to design an interface circuit between an absolute encoder and a controller.

7                 Know the advantages and issues of using an absolute encoder as a position sensor.

8                 Know how an incremental optical encoder can be used to measure position

9                 Know what determines its resolution

10              Know how to design an interface circuit between an incremental encoder and a controller to extract both step and direction information.

11              Know the advantages and issues of using an incremental encoder as a position sensor.

Optical sensors

1                 Know how light can create a change in resistance of voltage in photo-resistor, photo-diode, photo-transistor, and photovoltaic cell.

2                 Know how to design an interface circuit to transform resistance changes in a photo-sensor into a voltage signal.

Temperature sensor

1                 Know common types of temperature sensors

2                 Know how a thermal couple sensor can be used to measure temperature

3                 Know its advantages and limitations

4                 Know how to correlate between voltage output and temperature measured using tables or graphs.

Sensor lab

1                 Be able to assemble the above sensors, their interface circuits and a PC as a controller together to measure the intended physical parameter in a laboratory setting.

Power transistors

1                 Know that power transistors can be used to amplify current enough to drive actuators, modify their power, or turn them on and off.

2                 Know that transistors are used to amplify current. Be able to determine base current from base voltage, Ice from Ib.

3                 Know how to bias the base voltage using a voltage divider circuit.

4                 Know A,B,C classes of operation of power transistors and their advantages and disadvantages.

5                 Know that power transistors need proper heat dissipation.

6                 Be able to choose a suitable power transistor for the specific application from a table based on Ic, Vce, amplification factor and power rating.

DC motors

Section 1         Theory of operation

1                 Explain how DC motors can turn and keep on turning

2                 Understand the quantitative relation between speed, CEMF, armature current and torque.

Section 2         Series-wound DC motors:

1                 Understand what a series-wound DC motor is

2                 Understand characteristics of its speed vs. torque relation and thus its advantages and disadvantages.

Section 3         Shut-wound DC motors:

1                 Understand what a shut-wound DC motor is

2                 Understand characteristics of its speed vs. torque relation and thus its advantages and disadvantages.

Section 4         Permanent-magnet motors

1                 Understand what a PM DC motor is

2                 Understand qualitatively and quantitatively characteristics of its speed vs. torque relation and thus its advantages and disadvantages.

3                 Be able to predict its performance based on the speed vs. torque relation.

Section 5         DC motor control circuits

1                 Understand how to control motor direction and stoppage using circuits.

2                 Understand how to use analog drive to achieve motor speed control. Be able to do so in a laboratory setting.

3                 Understand how to use pulse-width-modulation to achieve motor speed control. Be able to do so in a laboratory setting.