Switches, Relays, And
Transcript of Switches, Relays, And
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Switches, Relays, andPower-Control Semiconductors
ISMAIL, S ST.,MT
Ps.LISTRIK
2010
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OBJECTIVES Understand mechanical switch types,
configurations, and terms. Describe the types and operation of
electromechanical relays. Understand the characteristics of solid-state
relays and the advantages anddisadvantages of solid-state relayscompared with electromechanical relays.
Comprehend the operation of powertransistors and power amplifiers, calculatetransistor circuit currents, and select areplacement power transistor
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INTRODUCTION
An important ability of almost allcontrol systems is to regulate the
flow of electrical power becauseelectricity is usually the link betweenthe controller and the actuator
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Three classifications of components :
Electromechanical devices such as
switches and relays, Power transistors and field effect
transistors
A group of semiconductor devices called
thyristors
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SWITCHES A mechanical switch is a device that
can open or close, thereby allowing a
current to flow or not
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Toggle Switches
Probably the most common switchtype is the toggle switch.
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Athree-position switch: on±off±on
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A slide switch
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Push-B
utton Switches
Push-button switches are almostalways the momentary type pressuremust be maintained to keep the switchactivated
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Push-button switches and Limit
switches
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Other Switch Types
A limit switch is a push-buttonswitch mounted in such a position
that it is activated by physical contactwith some movable object
An example is a car door switch, whichsenses whether or not the door is closed
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A DIP switch is a set of small SPSTswitches built into a unit shaped like
an integrated circuit (IC) (DIP standsfor dual in-line package).
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Rotary switch operation
The rotary switch is constructed of switch wafers mounted along a
single shaft
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A thumbwheel switch (ten-decimalposition)
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A membrane switch
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RELAY
S
Electromechanical Relays
The electromechanical relay (EMR)
is a device that uses anelectromagnet to provide the force toclose (or open) switch contacts, inother words, an electrically powered
switch
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An electromagnetic relay
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A selection of relays
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A reed relay The reed relay is unique because the small
reed like contacts are encapsulated in a smallsealed glass tube that is evacuated or filledwith an inert gas like dry nitrogen
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Solid-State Relays A solid-state relay (SSR) is a purely solid-
state device that has replaced the EMR in manyapplications, particularly for turning on and off
AC loads such as motors
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SSR circu
it A block diagram of the interior of an
SSR