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
Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.
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
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Discoveries
• Lodestones attract iron• Laws of attraction• First battery• Lightning is electricity• First electric motor• Telegraph• Telephone• Incandescent lightbulb
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Twentieth-Century Discoveries• Superheterodyne receiver• Radio astronomy• Television• Radar• Sonar• Transistor• Direct dialing• Molecular electronics• Satellites• Laser• Computer• Electron microscope
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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
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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
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Resistive Circuits
• Three types– series circuit
– parallel circuit
– series-parallel circuit
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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
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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
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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
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Diodes
• Simplest type of semiconductor
• Allow current to flow in one direction only
• Often used for automobile alternators
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Transistors
• A three-element, two-junction device used to control electron flow
• Varying the amount of voltage applied can control amplification, switching, and oscillation
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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
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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
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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
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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
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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
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Grain and Feed Processing
• Microprocessors monitor and control the grinding, drying, and handling of grains
• Computers determine proportions and control the machinery
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Other Areas
• Laboratories
• Aquaculture
• Food distribution
• All use automated analysis and ordering
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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
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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
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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
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Important Terms (continued)
• 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
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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
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Important Terms (continued)
• 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
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Important Terms (continued)
• 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
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Important Terms (continued)
• 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