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 and stepper motors.
• Troubleshoot DC and stepper motor control circuits at the system/board level.

The course will include instructor delivered lectures and demonstrations stressing key topics in the course. In preparation for the lecture portion of the course, students will be expected to complete all reading and homework assignments. 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.

Stepper Motors

Section 1         Theory of operation

1                 Explain how stepper motors can take discrete steps

2                 Explain its advantages and disadvantages

3                 Understand the different characteristics and features of the speed vs. torque curve.

4                 Distinguish between slewing and single-stepping modes

Section 2         Excitation modes

1                 Understand excitation sequence of a two-phase vs. four-phase motor.

Section 3         How to achieve finer step size:

1                 Understand how finer step size can be achieved by multi-pole rotors, by multi-stack rotors, by variable-reluctance stepper motors, and by hybrid stepper motors.

Section 4         Stepper motor driver circuit

1                 Understand how 4-phase stepper motor control circuit works

2                 Understand how 2-phase stepper motor control circuit works

3                 Be able to control a stepper motor with a stepper motor control circuit connected to a PC in a laboratory setting.