ESD Module 6-8

Solar Cells, Transduces, Acoustic.

Photovoltaic Effect

Is the basic physical process by which a solar cell converts sunlight into electricity.

Sunlight

It contains photons or "packets" of energy sufficient to create electron-hole pairs in the n and p regions.

Silicon

The most common material in use today in the full range of bulk and thin-film solar cells.

single-crystal

This silicon structure has an atomic lattice that is uniform, perfectly ordered, and of the highest purity.

Polycrystalline

This silicon solar cells are manufactured in a different, cheaper process but have lower levels of efficiency (9%-14%).

thin-film technology

had a broad impact on the cost and range of application of solar cells.

amorphous silicon (a-Si)

A compound and is currently the most extensively used thin-film material.

gallium arsenide (GaAs)

It is commonly used in bulk solar cells because of its high rate of absorption and higher energy conversion rate in the range 20%-30%

cadmium telluride (CdTe)

Has a very high light absorption level and is less expensive to manufacture with the same conversion efficiency as silicon.

copper indium diseelenide (CIS)

It is used in leading-edge research with conversion levels approaching 18% with high absorption and conversion rates.

Light Intensity

The third factor of major importance in the design of solar cells

Infrared-emitting diodes

are solid-state gallium arsenide devices that emit a beam of radiant flux when forward-biased.

Transducers

are devices that can change one form of energy to another, e.g., a resistance thermometer converts temperature into electrical resistance, or a thermocouple converts temperature into voltage.

Wave Transducers

convert AC or DC into acoustic or electromagnetic (EM) waves.

Wave Transducers

They can also convert these waves into AC or DC signals.

Dynamic Transducer

comprises a coil and magnet that translates mechanical vibration into varying electrical current or vice-versa.

Electrostatic Transducer

Takes advantage of the forces produced by electric fields. Two metal plates, one flexible and the other rigid, are placed parallel to each other and close together.

electrostatic pickup

It is where incoming sound waves vibrate the flexible plate, producing small, rapid changes in the spacing, and therefore, the capacitance, between the plates.

electrostatic emitter

It is where fluctuating currents in the transformer produce changes in the voltage between the plates.

Piezoelectric transducers

consists of a slab-like crystal of quartz or ceramic material sandwiched between two metal plates.

infrared-emitting diode (IRED)

The most common IR transmitting transducer

displacement transducer

measures a distance or angle traversed, or the distance or angle separating two points.

displacement transducer

Can convert an electrical signal into mechanical movement over a certain distance or angle.

Displacement Transducers

A device that measures or produces movement in a straight line constitutes a linear displacement transducer

angular displacement transducer

It measures or produces movement through an angle

joystick

can produce movement or control variable quantities in two dimensions.

mouse

is a peripheral device commonly used with personal computers.

trackball

resembles an inverted mouse, or a two-dimensional joystick without the lever.

eraser-head pointer

is a rubber button approximately five millimeters (5 mm) in diameter, usually placed in the center of a computer keyboard

touch pad

is a sensitive plate approximately the size and shape of a credit card.

5. touch pad

Pointing and Control Devices

Electric Motor

converts electrical energy into angular (and in some cases linear) mechanical energy.

Motors

can operate from either AC or DC, and range in size from tiny devices used in microscopic robots to huge machines that pull passenger trains. I

Stepper Motor

turns in small increments, rather than continuously. The step angle , or extent of each turn, varies depending on the particular motor.

selsyn

is an indicating device that shows the direction in which an object points.

selsyn

consists of a transmitting unit and a receiving (or indicator) unit.

synchro

is a two-way selsyn that can control certain mechanical devices and also display their status

Electric Generator

Is constructed in much the same way as an AC motor, although it functions in the opposite sense.

Optical Encoder

also called an optical shaft encoder, offers an alternative to mechanical switches or gear driven devices that wear out with time.

chopping wheel

An optical encoder comprises two LEDs, two photodetectors, and a device

sensor

It employs one or more transducers to detect or measure parameters, such as temperature, humidity, barometric pressure, pressure, texture, proximity, and the presence of certain substances.

Capacitive Pressure Sensor

Two metal plates, separated by a layer of compressible dielectric foam, create a variable capacitor that we connect in parallel with an inductor.

body capacitance

If such a mass comes near the transducer, the capacitance can change even if direct mechanical contact does not occur.

Elastomer

is a flexible substance resembling rubber or plastic that can be used to detect the presence or absence of mechanical pressure.

Elastomer

We use this when we want to avoid the effects of body capacitance

Back-Pressure Sensor

Detects and measures the torque that the motor exerts at any given instant in time.

end effectors

Robotics engineers use back-pressure sensors to limit the forces applied by robot grippers, arms, drills, hammers

Capacitive Proximity Sensor

It uses an RF oscillator, a frequency detector, and a metal plate connected into the oscillator

Photoelectric Proximity Sensor

contains a light-beam generator, a photodetector, a frequency sensitive amplifier, and a microcomputer, interconnected

Texture sensing

It is the ability of a machine to determine whether an object has a shiny surface or a rough (matte) surface.

Texture Sensor

It contains a laser and several light-sensitive receptors.

Location Systems

In this section, we'll examine a few medium-range and long-range applications of transducers and sensors.

Radar

This term derives from the words radio detection and ranging.

target

distance to a reflecting object

compass directions

The transmitting antenna rotates in a horizontal plane at constant angular speed, allowing observation in all azimuth bearings

azimuth bearings

are indicated in degrees clockwise from true north, and are marked around the perimeter of the screen.

radar horizon

Its range is near the maximum for the display

Doppler radar

Some radar sets can detect changes in the frequency of the returned pulse, thereby allowing measurement of wind speeds in hurricanes and tornadoes, or the speeds and acceleration rates of approaching and receding targets

Sonar

It is a medium-range method of proximity sensing. The acronym derives from the words sonic navigation and ranging.

Signal Comparison

A machine or vessel can find its geographic position by comparing the signals from two fixed stations at known positions

triangulation

A process where navigators of aircraft and oceangoing vessels physically plotted diagrams on paper maps using a pen, a straightedged ruler, and a drafting compass.

Radio Direction Finding (RDF)

This equipment aboard a mobile vehicle facilitates determining the location of an RF transmitter

Navigation

involves the use of location devices over a continuous period, thereby deriving a function of position versus time.

Navigational Methods

We can use this technique to determine whether or not a vessel follows its prescribed course.

Fluxgate Magnetometer

This system employs sensitive magnetic receptors and a microcomputer to detect the presence of, and changes in, an artificially generated magnetic field.

Epipolar Navigation

works by evaluating how an image changes as viewed from a single, moving perspective.

Loran

This acronym derives from the words long-range navigation

Loran

is one of the oldest electronic navigation schemes.

Global Positioning System (GPS)

comprises a network of radiolocation and radionavigation units that operate on a worldwide basis.

Global Positioning System (GPS)

The system employs several satellites, and allows determination of latitude, longitude, and altitude.

Sound

is simply an airborne version of vibration. The air which carries sound is a mixture of gases.

Acoustics

It is the science of sound waves.

bass

Musicians divide the AF range into three broad, vaguely defined parts

Treble

consists of the audio frequencies higher than midrange.

acoustic waveform

determines the timbre (sometimes erroneously called "tone").

baffles

a listener, a speaker, and three sound reflectors

loudness

also called volume

Phase

allows you to perceive the direction from which a sound arrives

Decibels

are also used in acoustics to express relative sound power.

antinodes

distort the original sound

nodes

At certain other frequencies, the waves might mix in phase opposition, yielding acoustic nulls is called?

Linearity and dynamic range

Two (2) of the most important technical considerations

Linearity

In acoustics, it is the extent to which the output waveform of an amplifier constitutes a faithful reproduction of the input waveform.

dual-trace oscilloscope

an oscilloscope that lets you observe two waveforms at the same time

Dynamic Range

the ratio of the maximum power output to the minimum power output that the system can deliver while maintaining acceptable performance with low distortion

Dolby

A scheme that can minimize the effects of background noise in analog recording.

audiophile

assembles a complex system over a period of time.

tuner

is a radio receiver capable of receiving signals in the standard AM broadcast band (535 to 1605 kHz) and/or the standard FM broadcast band (88 to 108 MHz).

tuner

can provide enough power to drive a headset, but it usually takes an externa

Amplifier

delivers medium or high audio power to a set of speakers.

Speakers

are rated according to the audio power they can handle

Headsets

are rated according to how well they reproduce sound.

woofer

reproduces bass frequencies.

midrange speaker

handles medium and, sometimes, treble (high) audio frequencies

tweeter

is designed especially for enhanced treble reproduction.

Balance Control

allows adjustment of the left-channel volume versus the right-channel volume

Tone Control

With this, you can adjust the amplitude-versus-frequency characteristic of a hi-fi sound system

Tone Control

consists of a single knob or slide device.

Audio Mixer

eliminates the problems involved with connecting multiple devices to a single channel.

Graphic Equalizer

allows for adjustment of the relative loudness of audio signals at various frequencies so that you can fine-tune the amplitude-versus-frequency output characteristic of hi-fi sound equipment.