Q1: What are Ultrasonic transducers?
Explain the construction of
receiver and transmitter of ultrasonic sensors.
Ultrasonic transducers are devices that convert electrical energy into
high-frequency sound waves (ultrasound) and vice versa. They are the core
components of ultrasonic sensors.
Construction of Receiver and Transmitter:
Transmitter:
Piezoelectric crystal: A thin slice of a material like quartz or
lead zirconate titanate (PZT) is used.
Backing material: A material like tungsten or steel is attached
to the back of the crystal to dampen vibrations and improve
efficiency.
Electrical connection: A thin wire is attached to the crystal to
provide an electrical connection.
Receiver:
Piezoelectric crystal: Similar to the transmitter, it uses a
piezoelectric crystal to convert sound waves back into electrical
signals.
Matching layer: A thin layer of material is placed in front of the
crystal to improve the transfer of sound energy from the air to
the crystal.
Electrical connection: A thin wire is attached to the crystal for
electrical connection.
Q2: What are the classification of switches? Explain the working of
the following switches:
Classification of Switches:
Mechanical Switches:
Toggle switches: Simple ON/OFF switches.
Push-button switches: Momentary contact switches.
Rotary switches: Select from multiple positions.
Limit switches: Detect the end of travel.
Mercury switches: Tilt-activated switches.
Reed switches: Magnetically activated switches.
Electronic Switches:
Transistors: Control current flow electronically.
MOSFETs: Field-effect transistors for high-power applications.
Relays: Use an electromagnetic coil to switch contacts.
Working of Specific Switches:
1. Limit Switches:
A mechanical switch that opens or closes when a moving part
reaches a certain limit.
Used in conveyor belts, elevators, and other machinery to
prevent overtravel.
2. Mercury Switches:
A small glass tube containing mercury that conducts
electricity when tilted.
Used in thermostats, tilt sensors, and other applications where
a small tilt is needed to trigger a switch.
3. Reed Switches:
A small glass capsule containing two flexible metal reeds that
close when a magnetic field is applied.
Used in security systems, proximity sensors, and other
applications where magnetic activation is desired.
Q3: What are proximity detectors? Explain their types.
Proximity detectors are sensors that detect the presence of an object
without physical contact.
Types of Proximity Detectors:
Inductive: Detect metallic objects based on changes in magnetic field.
Capacitive: Detect changes in capacitance caused by the presence of
an object.
Photoelectric: Use light beams to detect objects.
Ultrasonic: Use sound waves to detect objects.
Q4: What is a potentiometer? How can we use it to measure angular
position?
A potentiometer is a variable resistor with a sliding contact that can be
moved along a resistive track.
Measuring Angular Position:
Connect the potentiometer to a voltage source.
Attach the sliding contact to a rotating shaft.
As the shaft rotates, the resistance between the contact and one end
of the track changes proportionally.
Measure the voltage across the potentiometer to determine the
angular position.
Q5: What is Digital Optical Encoder? Explain in detail.
A digital optical encoder is a sensor that converts the angular position of a
rotating shaft into a digital signal.
Construction and Working:
Disc with alternating patterns: A disc with alternating light and
dark patterns is attached to the rotating shaft.
Light source and detector: A light source shines on the disc, and a
detector senses the light passing through the patterns.
Photodiodes: Photodiodes convert the light signals into electrical
pulses.
Digital signal processing: The electrical pulses are processed to
generate a digital signal representing the shaft's position.
Q6: What is an absolute encoder? Explain its construction and
working.
An absolute encoder provides a unique digital code for each position of the
shaft, regardless of the starting position.
Construction and Working:
Coded disc: A disc with multiple concentric tracks, each with a unique
binary code.
Light source and detectors: Light sources and detectors are
positioned to read the codes on each track.
Digital signal processing: The codes from each track are combined
to generate a unique absolute position code.
Q7: What is an incremental encoder? Explain its construction and
working.
An incremental encoder measures the change in position of the shaft
relative to a starting point.
Construction and Working:
Disc with alternating patterns: A disc with alternating light and
dark patterns is attached to the rotating shaft.
Light source and detectors: A light source shines on the disc, and
two detectors are positioned to sense the light passing through the
patterns.
Quadrature output: The two detectors generate two square wave
signals that are 90 degrees out of phase.
Counting and direction: By counting the pulses and determining the
phase relationship, the direction and distance of rotation can be
calculated.
Q8: Draw an Incremental encoder having a resolution of nearly 6°.
Resolution: Each pattern corresponds to a 6° rotation, giving a resolution of
approximately 6°.
Q9: Draw an 8-bit Absolute encoder and what will be its resolution.
Resolution: With 8 bits, there are 28 = 256 possible positions. For a full 360°
360
rotation, the resolution is ≈ 1.4°.
256
Q10: Draw an 8-bit Absolute gray encoder and what will be its
resolution.
Resolution: Same as the 8-bit absolute encoder, approximately 1.4°.
Q11: If LSB of the 8-bit Absolute gray encoder is used as an
Incremental encoder, then what will be its resolution? Draw that
Incremental encoder.
Resolution: The LSB of an 8-bit encoder represents the smallest change in
position, which is 1.4°.
Resolution: 1.4°.
Feel free to ask if you have any more questions or want further clarification
on any of the topics!
