Unit 35
Electronics in Agriculture
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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
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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
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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
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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
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Laboratories
Aquaculture
Food distribution
All use automated analysis and ordering
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Maintenance Procedures
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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)
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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)
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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
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