copyright © 2010 delmar, cengage learning. all rights reserved. unit 35 electronics in agriculture

Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.

Unit 35

Electronics in Agriculture


Development

• In 600 BC a Greek philosopher discovered that when you rub a cloth on a piece of amber, it attracts bits of feathers and pith

• Use of electric eels to send shock through the body to cure stiffening

• Archaeologists have discovered pots that suggest the electroplating of jewelry thousands of years ago


Discoveries

• Lodestones attract iron• Laws of attraction• First battery• Lightning is electricity• First electric motor• Telegraph• Telephone• Incandescent lightbulb


Twentieth-Century Discoveries• Superheterodyne receiver• Radio astronomy• Television• Radar• Sonar• Transistor• Direct dialing• Molecular electronics• Satellites• Laser• Computer• Electron microscope


Resistance

• Resistance: (R) tendency of a material to prevent electricity to flow

- Measured in ohms

• Conductance: (G) measure of how well a material allows electricity to pass through

• Formula: R = 1/G or G = 1/R


Resistors

• Devices that offer specific resistance to a current

• Most commonly used component in a circuit

• Two types– fixed: deliver rated resistance within certain tolerances

above or below that rating– variable: have three terminals

• Color coded


Resistive Circuits

• Three types– series circuit

– parallel circuit

– series-parallel circuit


Electrical Meters

• A device that measures the activities of invisible electrons and provides a visual interpretation of these activities

• Analog: has a graduated scale with a pointer

• Digital: provides a direct numerical readout


Inductance

• The ability to draw energy from a source and store it in a magnetic field

• Unit: henry (H)—the amount of inductance required to induce an electromotive force of 1 volt when the current in a conductor changes at the rate of 1 ampere per second

• Inductor: a device that provides inductance


Semiconductors

• Materials with characteristics that fall between insulators and conductors

• Silicon is the most used semiconductor

• Common uses: diodes, transistors, thyristors, and integrated circuits

• Primarily used to control voltage or current for a desired result


Diodes

• Simplest type of semiconductor

• Allow current to flow in one direction only

• Often used for automobile alternators


Transistors

• A three-element, two-junction device used to control electron flow

• Varying the amount of voltage applied can control amplification, switching, and oscillation


Thyristor

• Device used for electronically controlled switches

• Used to apply or remove power from a load

• Often used for things like dimmer lights and motor speed controls


Optoelectric Devices

• Designed to interact with light energy in the infrared, ultraviolet, and visible ranges

• Types– photoconductive cell– photovoltaic cell– photodiode– phototransistor – light-emitting diode


Computers

• Digital computer: automatically processes data using digital techniques

• Digital: using digits

• Digits: numbers 0 to 9

• Runs on the binary system

• Data is stored on hard drives, CDs, DVDs, and flash drives


Uses in the Field

• Electronics are used in the field for land leveling, drainage, irrigation, and construction

• Lasers, sensors, lights, alarms, and digital readouts all assist in these operations


Livestock and Dairy

• Biosensors are used on cattle and other animals to show body temperature, feed requirements, breeding status, and disease problems

• Heat sensors, viscosimeters, robots, and humidistats are also used


Grain and Feed Processing

• Microprocessors monitor and control the grinding, drying, and handling of grains

• Computers determine proportions and control the machinery


Other Areas

• Laboratories

• Aquaculture

• Food distribution

• All use automated analysis and ordering


Maintenance Procedures

• Keep item clean and free of spills or metal objects• Routinely wipe off with a clean, dry cloth• Lubricate as specified• Maintain a cool, dry environment• Read and follow operator’s manual• Do not tamper with devices; always call a

qualified technician when repairs are needed


Important Terms

• Lodestone: magnetized piece of black iron oxide• Resistivity: resistance of a wire• Insulators: materials that do not allow the flow of

electricity• Siemen: unit for measuring conductance• Reciprocal: opposite• Potentiometer: resistor used to control voltage• Rheostat: resistor used to control current


Important Terms (continued)

• Series circuit: provides a single path for current flow• Parallel circuit: provides two or more paths• Series-parallel circuit: combines both circuits• Capacitance: ability of a device to store electrical

energy in an electrostatic field• Capacitor: possesses a specific amount of capacitance• Plates: the conductors



• Dielectric: insulator• Cycle: flow of current through one positive thrust

followed by flow through one negative thrust• Hertz: one cycle per second• Sine wave: wave created by the flow of current

through one cycle• Oscilloscope: test equipment for working on

electronic equipment and circuits• Integrated circuit: miniature electronic circuit


Important Terms (continued)• Photoconductive cell: light-sensitive device• Photovoltaic cell: converts light energy into electrical

energy• Photodiode: used to control current flow• Phototransistor: has three leads• Light-emitting diode: produces light when subjected to

current flow• Power supply: device that provides electricity of the

proper type and amount to circuits



• Rectifier: converts AC to DC• Voltage regulator: controls voltage output• Voltage multiplier: increases DC voltage• Amplifier: electronic circuit used to increase the

amplitude of an electronic signal• Video amplifier: amplifies pictorial information• Oscillator: non-rotating device for producing

alternating current• Filter: converts pulsating DC voltage to smooth

voltage



• Binary system: contains only the digits 0 and 1

• Binary: two parts or components• Chips: tiny electronic circuits• Mainframe: large unit• Microcomputer: self-contained small computer• Minicomputers: intermediate in capacity• Supercomputers: have enormous capacity• Throughput: rate of flow



• Infrared light sensors: detect heat or motion• GPS: Global Positioning System; latest system in

monitoring technology• Claw: cup• Viscosimeters: flow meters• Biosensors: measure processes of the body• Pallet: portable platform for storing or moving

cargo

copyright © 2010 delmar, cengage learning. all rights reserved. unit 35 electronics in agriculture

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