MECHENG 201 Part 2: Electronics, Sensors and Actuators

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MECHENG 201 Part 2: Electronics, Sensors and Actuators par Mind Map: MECHENG 201  Part 2: Electronics, Sensors and Actuators

1. Sensors

1.1. never used by themselves!

1.2. = element that produces a signal relating to the quantity being measured

1.3. Transducer:

1.3.1. = device that converts energy from one form to another

1.4. Absolute & Incremental Sensors

1.4.1. Absolute:

1.4.1.1. detect a unique position - not power dependent

1.4.2. Incremental:

1.4.2.1. measure a relative position - depends on a prior position or last power on/off

1.5. Analog & Digital Sensors

1.5.1. Analogue:

1.5.1.1. continuous output signal or voltage

1.5.1.2. proportional to quantity being measured

1.5.1.2.1. e.g voltage measured by potentiometer is proportional to the angle it is measuring

1.5.1.3. Example: Thermocouple

1.5.1.4. Measurement:

1.5.1.4.1. 1. Linear

1.5.1.4.2. 2. Polynomial

1.5.1.4.3. 3. Exponential

1.5.1.4.4. y = measurement x = sensor output signal

1.5.2. Digital:

1.5.2.1. discrete digital output signal or voltage - step response

1.5.2.2. binary output signal

1.5.2.2.1. Signal conditioning

1.5.2.3. Example: Light Sensor

1.6. Selecting a Sensor:

1.6.1. 1. Nature of measurement required

1.6.1.1. nominal value of variable

1.6.1.2. range of values

1.6.1.3. accuracy required

1.6.1.4. required speed of measurement

1.6.1.5. reliability required

1.6.2. 2. Nature of output required from sensor

1.6.3. 3. Factors of the sensor

1.6.3.1. range

1.6.3.2. accuracy

1.6.3.3. linearity

1.6.3.4. speed of response

1.6.3.5. reliability

1.6.3.6. life

1.6.3.7. power supply requirements

1.6.3.8. cost

1.6.3.9. size

2. Sensors: Examples

2.1. Strain Gauge Pressure Sensor

2.1.1. change in R/R = G.E E = strain G = proportionality factor

2.2. Pressure Sensor

2.2.1. pressure measurements of gases or liquids

2.2.1.1. produces proportional output voltage

2.2.2. can indirectly measure volume or alititude

2.3. Barometric Sensors

2.3.1. detect atmospheric pressure

2.3.2. Tactile Sensors

2.4. Potentiometer

2.4.1. example of an encoder

2.4.2. absolute analog sensor that measures angular position

2.4.2.1. after a few revolutions, it will reset to zero

2.4.2.2. it works like a variable resistor

2.4.2.2.1. turning the shaft changes the resistance

2.5. Radar Sensor

2.5.1. "Radio detection and ranging"

2.5.1.1. emits very small wavelength radio frequency signals

2.5.1.1.1. detect - moving objects (planes) - shape of land

2.5.2. radio waves

2.6. Sonar

2.6.1. "Sound navigation and ranging"

2.6.1.1. generates ultrasonic waves and the receiver captures waves that bounce back from the target

2.6.1.1.1. timer calculates how long it takes for signal to return

2.6.1.1.2. using speed of sound in the air

2.6.1.2. long range poor resolution

2.6.2. sound waves

2.7. Infrared Sensor

2.7.1. accurate, medium range, non contact position measurement

2.7.2. small maximum range better resolution compared to Sonar sensor

2.8. Optical Position Sensor

2.8.1. measure position of a target

2.8.1.1. infrared emitting diode + NPN infrared silicon phototransistor

2.8.1.1.1. used in assembly lines, machine automation, edge detection

3. Sensors: Types

3.1. Types:

3.1.1. Displacement, Position & Proximity Sensors (either contact or non-contact)

3.1.1.1. Displacement Sensors focus on measuring how much the object has moved

3.1.1.2. Position Sensors focus on the position of the object to a reference point

3.1.1.3. Proximity Sensors are position sensors that sense whether the object has moved within a critical distance = give ON/OFF outputs

3.1.2. Velocity & Motion

3.1.2.1. monitor linear and angular velocity and detect motion

3.1.2.1.1. e.g security systems cash machine screens

3.1.3. Force Sensors

3.1.3.1. focus on measuring forces applied on them

3.1.3.1.1. e.g spring balance - displacement is a measure of force

3.1.4. Fluid Pressure & Level

3.1.4.1. Fluid Pressure

3.1.4.1.1. monitors fluid pressure

3.1.4.2. Fluid Level

3.1.4.2.1. Directly

3.1.4.2.2. Indirectly

3.1.4.3. Pressure Sensing Technologies

3.1.4.3.1. Force Collector Types

3.1.4.3.2. Other Types

3.1.5. Environmental Sensors

3.1.5.1. Temperature Sensors

3.1.5.1.1. changes commonly used are - expansion/contraction of solids/liquids/gases - change in resistance of conductors

3.1.5.2. Light Sensors

3.1.5.2.1. measure intensity of light

3.1.5.3. Humidity Sensors

3.1.5.4. Wind Sensors

4. Sensors: Characteristics

4.1. Characteristics

4.1.1. Performance

4.1.1.1. 1. Range

4.1.1.1.1. the limits between which the input can vary

4.1.1.2. 2. Span

4.1.1.2.1. maximum value - minimum value input

4.1.1.3. 3. Error

4.1.1.3.1. Error = measured value - true value

4.1.1.4. 4. Accuracy

4.1.1.4.1. extent to which the value might be wrong

4.1.1.5. 5. Sensitivity

4.1.1.5.1. how much output there is per unit input = output/input

4.1.1.6. 6. Hysteresis Error

4.1.1.6.1. same point being measured, different outputs, due to continuously increasing or decreasing change

4.1.1.7. 7. Repeatability

4.1.1.7.1. ability to give the same output for repeated applications of the same input value

4.1.1.7.2. Repeatability = (max - min values given)/full range x 100%

4.1.1.8. 8. Stability and Drift

4.1.1.8.1. Stability

4.1.1.8.2. Drift

4.1.1.8.3. Zero Drift

4.1.1.9. 9. Dead Band

4.1.1.9.1. Dead Band or Dead Space

4.1.1.9.2. Dead Time

4.1.1.10. 10. Resolution

4.1.1.10.1. the smallest change in the input value that will produce an observable change in output

4.1.1.11. 11. Output Impedance

4.1.1.11.1. electrical output is interfaced with an electronic circuit = there will be output impedance

4.1.1.11.2. having a sensor that reads the output impedance can modify the behavior of the system

4.1.2. Static VS Dynamic

4.1.2.1. Static Characteristics

4.1.2.1.1. values given when steady-state conditions occur

4.1.2.2. Dynamic Characteristics

4.1.2.2.1. behavior of the sensor between the time that the input value changes and the time that the value given by the sensor settles down to steady-state.

4.1.2.3. Response Time

4.1.2.4. Time Constant

4.1.2.5. Rise Time

4.1.2.6. Settling Time

5. Electronics: Filters

5.1. Filters

5.1.1. Signal Processing

5.1.1.1. a device or process that removes some unwanted components or features from a signal

5.1.2. Electronics

5.1.2.1. a circuit designed to pass inputs in a certain frequency range while blocking other inputs

5.1.3. Classes:

5.1.3.1. Linear or Nonlinear

5.1.3.2. Time invariant or Time variant

5.1.3.3. Causal or Not causal

5.1.3.4. Active or Passive

5.1.3.4.1. Active

5.1.3.4.2. Passive

5.1.3.5. Analog or Digital

5.1.3.6. Discrete time (sampled) or Continuous Time

5.1.3.7. Infinite Impulse Response (IIR) or Finite Impulse Response (FIR)

5.1.4. Types:

5.1.4.1. Low-Pass Filter

5.1.4.1.1. "High-cut"

5.1.4.2. High-Pass Filter

5.1.4.2.1. "Low-cut"

5.1.4.3. Band-Pass Filter

5.1.4.3.1. based on a frequency range

5.1.4.4. Band-Stop Filter

5.1.4.4.1. "Band-reject"

6. Sensors: Encoders

6.1. capture position or orientation

6.1.1. Rotary Encoder

6.1.1.1. electro-mechanical device

6.1.1.2. converts angular position/motion to analog/digital signal

6.1.2. Linear Encoder

6.1.2.1. paired with a scale which the encoder reads from

6.1.2.1.1. converts encoded position to analog/digital signal

6.2. Absolute

6.2.1. unambiguous position (doesn't depend on previous position)

6.2.1.1. robust to interruptions

6.3. Incremental

6.3.1. cyclical, ambiguous (counting of cycles)

7. Switches

7.1. Microswitch

7.2. Push Button

7.3. Optical Switch

7.3.1. photo-micro sensor non-contact triggering

7.3.1.1. triggers when object comes between components

8. Electronics: Diodes

8.1. Introduction

8.1.1. Active

8.1.2. Passive

8.1.3. Electro-mechanic

8.2. Diodes

8.2.1. a two-terminal electronic component that conducts primarily in one direction

8.2.1.1. Role: allow current to pass in forward direction, block current in reverse direction

8.2.1.2. Analogous example: Check Valve

8.2.1.3. First Diode: Thermionic Diode

8.2.1.3.1. Edison Effect: when hot, the cathode releases electrons into the vacuum

8.2.1.4. Types:

8.2.1.4.1. Diode

8.2.1.4.2. LED

8.2.1.4.3. Photodiode

8.2.1.4.4. Zener Diode

8.2.1.4.5. Schottky Diode

8.2.1.4.6. Transient-voltage-suppression Diode (TVS)

8.2.1.4.7. Tunnel Diode

8.2.1.4.8. Varicap

8.2.1.5. Ideal Diode:

8.2.1.5.1. Forward Biased

8.2.1.5.2. Reverse Biased

8.2.1.5.3. NO Break down region

8.2.1.6. Real Diode:

8.2.1.6.1. Forward Biased

8.2.1.6.2. Reverse Biased

8.2.1.6.3. Breakdown

8.2.1.7. Other Functions:

8.2.1.7.1. Unidirectional behaviour = Rectification: - convert AC to DC - detect AM radio signals

8.2.1.7.2. - voltage drop is a function of temperature = use as a temperature sensor or voltage reference

8.2.1.7.3. Avalanche Diode: protect circuits from high voltage

8.2.1.7.4. Varactor Diode: tune radio and TV receivers

8.2.1.7.5. Tunnel, Gunn and IMPATT Diode: - generate radio frequency oscillations - create microwave and switching circuits

8.2.1.8. Diode + Inductors:

8.2.1.8.1. current stopped = 0 --> stored energy creates reverse voltage spike (flyback) that can damage switch

8.2.1.9. Diode-Resistor Logic (DRL):

8.2.1.9.1. OR Gate

8.2.1.9.2. AND Gate

8.3. Integrated Circuit

8.3.1. a set of electronic circuits on one small chip (semiconductor material e.g silicon

9. Actuators

9.1. part of the machine that moves or controls something

9.1.1. Types:

9.1.1.1. 1. Mechanical

9.1.1.1.1. conversion of rotary motion to linear motion

9.1.1.2. 2. Electric

9.1.1.3. 3. Electro-mechanic

9.1.1.3.1. like mechanical actuators but control knob/handle is replaced with electric motor

9.1.1.3.2. rotary motion converted to linear displacement

9.1.1.4. 4. Piezoelectric

9.1.1.4.1. very short range of motion

9.1.1.4.2. very high voltages = tiny expansions

9.1.1.5. 5. Hydraulic

9.1.1.5.1. converts hydraulic pressure + flow into torque + angular displacement (rotation)

9.1.1.6. 6. Pneumatic

9.1.1.6.1. air

9.1.1.7. 7. Thermal

9.1.1.7.1. material in actuator changes from solid <--> liquid

9.1.1.7.2. narrow temperature range = precise control

9.1.1.8. 8. Magnetic

9.1.2. Types of Motion:

9.1.2.1. Linear

9.1.2.2. Rotary/Circular

9.1.3. Performance Metrics:

9.1.3.1. Force

9.1.3.2. Speed

9.1.3.3. Operating conditions

9.1.3.4. Durability

9.1.4. Electric Motors

9.1.4.1. DC Motors

9.1.4.1.1. continuous movement, speed of rotation easily controlled

9.1.4.2. AC Motors

9.1.4.2.1. outside Stator/inside Rotor/ Permanent Magnets or electrical windings

9.1.4.3. Stepper Motors

9.1.4.3.1. electromechanical

9.1.4.4. Solenoids

9.1.4.4.1. coil of electrical wire with an armature

9.1.4.4.2. electromagnet and plunger inside coil

9.1.5. Smart Motors:

9.1.5.1. in a Single Servo Model:

9.1.5.1.1. DC Motor

9.1.5.1.2. Reduction Gearhead

9.1.5.1.3. Encoder + Controller + Driver

9.1.5.1.4. Communications

10. Electronics: Microcontrollers and Microprocessors

10.1. Microcontrollers and Microprocessors

10.1.1. Microprocessor

10.1.1.1. heart of a computer CPU complete computation engine

10.1.1.1.1. General/personal purpose use

10.1.1.1.2. Example: Raspberry Pi

10.1.2. Microcontroller

10.1.2.1. MCU small computer on one IC one or more CPUs

10.1.2.1.1. Embedded applications

10.1.2.1.2. Example: Arduino

10.1.2.1.3. Selecting a Microcontroller:

10.1.3. Microprocessor Systems

10.1.3.1. 1. Central Processing Unit (CPU) or Microprocessor

10.1.3.1.1. Roles:

10.1.3.1.2. Parts:

10.1.3.2. 2. Memory

10.1.3.2.1. stores binary data

10.1.3.2.2. Size: depends on number of wires in the address bus

10.1.3.3. 3. Input and Output Interfaces

10.1.3.3.1. transfer of data between the microprocessor and the external world

10.1.3.4. 4. Buses

10.1.3.4.1. Data Bus

10.1.3.4.2. Address Bus

10.1.3.4.3. Control Bus

10.1.4. Microcontroller VS Microprocessor System

10.1.4.1. Microprocessor systems have an external peripheral Microcontrollers have RAM, ROM, EEPROM embedded internally

10.1.4.2. Microcontrollers = all on ONE CHIP Microprocessor Systems = many chips

10.1.4.3. Microcontrollers = cheaper Microprocessor Systems = expensive

10.1.4.4. Microcontrollers = lower processing speed (8 to 50MHz) Microprocessor Systems = high processing speed (>1GHz)

10.1.4.5. Microcontrollers = simpler tasks Microprocessor Systems = more complex tasks

10.1.5. Computer

10.1.5.1. Structure:

10.1.5.1.1. 1. Input devices

10.1.5.1.2. 2. Processor

10.1.5.1.3. 3. Main memory

10.1.5.1.4. 4. Output devices

10.1.5.1.5. 5. Backing storage

10.1.5.2. Classification:

10.1.5.2.1. Structure

10.1.5.2.2. Type

10.1.5.2.3. Size

11. Electronics: 555 Timer

11.1. Timer 555

11.1.1. an integrated circuit used in a variety of timer, pulse generation, and oscillator applications

11.1.1.1. Structure:

11.1.1.1.1. a SR Flip-flop

11.1.1.1.2. 2 comparators (OPAMPS)

11.1.1.1.3. transistor Q1 = switch

11.1.1.2. Modes of Operation:

11.1.1.2.1. 1. Monostable

11.1.1.2.2. 2. Astable

11.1.1.2.3. 3. Bistable

11.1.1.3. Pulse Width Modulation (PWM)

11.1.1.3.1. modulation = changing

11.1.1.3.2. allow the control of power supplied to electrical devices

12. Electronics: OPAMPS

12.1. OPAMP

12.1.1. a high-gain electronic voltage amplifier with a differential input and a single-ended output

12.1.1.1. Used in:

12.1.1.1.1. 1. Signal conditioning

12.1.1.1.2. 2. Filtering

12.1.1.1.3. 3. Perform math operations

12.1.1.2. Symbols:

12.1.1.2.1. V+

12.1.1.2.2. V-

12.1.1.2.3. Vout

12.1.1.2.4. Vs+

12.1.1.2.5. Vs-

12.1.1.3. Structure:

12.1.1.3.1. 20 BJT transistors

12.1.1.3.2. 11 resistors

12.1.1.3.3. 1 capacitor

12.1.1.4. Types:

12.1.1.4.1. Comparator

12.1.1.4.2. Inverting amplifier

12.1.1.4.3. Non-inverting amplifier

12.1.1.4.4. Differential amplifier

12.1.1.4.5. Summing amplifier

12.1.1.4.6. Differentiator

12.1.1.4.7. Integrator

12.1.1.4.8. Instrumentation amplifer

12.1.1.5. Ideal OPAMP:

12.1.1.5.1. Open-loop gain (AOL) = infinite

12.1.1.5.2. zero gain for common mode signal (only has gain when there is a voltage difference)

12.1.1.5.3. infinite input impedence

12.1.1.5.4. zero output impedence

12.1.1.5.5. infinite bandwith

12.1.1.6. Real OPAMP:

12.1.1.6.1. Bandwidth Considerations

12.1.1.6.2. Non Linear Limitations

12.1.1.6.3. Slew Rate

12.1.1.6.4. DC Imperfections

12.1.1.7. Summing Point Constraint

12.1.1.8. Negative Feedback Loop

13. Electronics: Transistors

13.1. Transistor

13.1.1. a semiconductor device used to amplify or switch electronic signals and electronic power

13.1.1.1. made from semiconductor material (silicone) through DOPING

13.1.1.1.1. Triode

13.1.1.1.2. Doping

13.1.1.2. Advantages

13.1.1.2.1. 1. no cathode heater

13.1.1.2.2. 2. very small size and weight

13.1.1.2.3. 3. lots of transistors can be made on one IC

13.1.1.2.4. 4. low operating Voltage

13.1.1.2.5. 5. physically robust

13.1.1.2.6. 6. no maintenance

13.1.1.3. Limitations

13.1.1.3.1. 1. silicon can age and fail

13.1.1.3.2. 2. high power/frequency operation better suited for vacuum tubes where e- can move better

13.1.1.3.3. 3. sensitive to radiation and cosmic rays

13.1.1.4. Types:

13.1.1.4.1. FETS Field-effect Transistors

13.1.1.4.2. BJTS Bipolar junction Transistors

13.1.1.5. Categories:

13.1.1.5.1. Semiconductor Material

13.1.1.5.2. Structure

13.1.1.5.3. Electrical Polarity

13.1.1.5.4. Maximum power rating

13.1.1.5.5. Maximum operating frequency

13.1.1.5.6. Application

13.1.1.5.7. Physical Packaging

13.1.1.5.8. Amplification Factor

13.1.1.6. Operation Modes:

13.1.1.6.1. 1. Saturation

13.1.1.6.2. 2. Cut off

13.1.1.6.3. 3. Active

13.1.1.6.4. 4. Reverse Active

13.1.1.7. Transistor as Switches

13.1.1.7.1. making use of cutoff and saturation states

13.1.1.7.2. Advantages of TRANSISTORS

13.1.1.7.3. Advantages of RELAY SWITCHES (a substitute)