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Switches & Relays
Osman Glercan
16169230356
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What is switch?
A switch is an electrical component that
can break an electrical circuit
Switches are highly varied based on theirintended utility.
A pair of contacts is said to be "closed"
when current can flow one to the other.
The termspole and throware also used to
describe switch contact variations.
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Some of Switch Types
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Electronics specification and
abbreviation SPST: Single pole, single throw SPDT: Single pole, double throw
SPCO SPTT, c.o. : Similar to SPDT.Some suppliers use SPCO/SPTTfor
switches with a stable off position in the
centre and SPDTfor those without
DPST: Double pole, single throw
DPDT: Double pole, double throw
DPCO: Double pole changeover
orDouble pole, centre off
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Dimmer Switches
Any standard single-pole switchcan be replaced with a dimmer,as long as the switch is of
adequate size.D
immerswitches have larger bodies thatstandard switches. They alsogenerate a small amount of heatthat must dissipate. For thesereasons, dimmers should not beinstalled in undersized electricalboxes or in boxes that arecrowded with circuit wires.Always follow themanufacturers specifications forinstallation.
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Double Switch
Separate-circuit wiring
Four black wires areattached to the
switch Feed wires from thepower source areattached to the sideof switch that has a
connecting tab, andthe connecting tab isremoved
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Pilot-light Switches
A pilot-light switch has abuilt-in bulb that glowswhen power flowsthrough the switch to alight fixture or appliance
Pilot- light switchesoften are installed for
convenience if a lightfixture or appliancecannot be seen fromthe switch location
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Timer Switches
Timer switches havean electricallypowered control dialthat can be set to turnlights on and offautomatically onceeach day
They are commonlyused to controloutdoor light fixtures
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Time-delay Switches
A time-delay switch hasa spring-driven dial thatis wound by hand
The dial can be set toturn off a light fixtureafter a delay rangingfrom I to 60 minutes
Time-delay switchesoften are used forexhaust fans, electricspace heaters, ventfans, and heat lamps
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Automatic Switches
An automatic switch
uses a narrow infrared
beam to detectmovement When a hand passes
within a few inches ofthe beam, an electronic
signal turns the switchon or off
Some automaticswitches have a manualdimming feature
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Automatic Switches
Automatic switches can
be installed wherever a
standard single-pole
switch is used Automatic switches are
especially convenient for
children and persons with
disabilities.
Automatic switchesrequire no neutral wireconnections
For this reason, anautomatic switch can beinstalled in a switch boxcontaining either one ortwo cables
The wire leads on theswitch are connected tohot circuit wires with wireconnectors
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Motion-sensor Security Switches
A motion-sensor switchuses a wide-angle infra-red beam to detectmovement over a largearea
Turns on a light fixtureautomatically
A time-delay featureturns off lights aftermovement stops
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Motion-sensor Security Switches
Most motion-sensorswitches have anoverride feature thatallows the switch to beoperated manually
Better switches includeadjustable sensitivitycontrol and a
Variable time-delayshutoff control.
Motion-sensor switchesrequire no neutral wireconnections
They can be installed inswitch boxes containingeither one or two cables
The wire leads on theswitch are connected to
hot circuit wires with wireconnectors
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Programmable Switches
Programmable
switches represent
the latest in switchdesign
They have digital
controls and
Can provide four on-off cycles each day
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ContactorsContactors
Contactors are relays that switch high
current loads a.k.a magnetic starters
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Contactors
A Contactoris a control devicethat uses a small controlcurrent to energize or de-energize the load connectedto it.
Abouts:
A contactor has a frame,plunger, and a solenoid coil.
The action of the plunger isused to close (or open) setsof contacts.
A contactor does not include
overload protection. The closing of the contacts
allows electrical devices to becontrolled from remotelocations.
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Relay Timers
ON Delay
OFF Delay
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Wired ON Delay
1. Energy appliedto power rails
X1 X2OFF
NC
NO
ON
1
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Wired ON Delay - NCTO
1. Energy applied topower rails
2. Start PB is pressed- Coil is energized
- Holding contact close- Timer contact stays
closed, lamp stays on.
- Count begins (5 sec)
2
X1 X2ON
NC
NC
ON
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Wired ON Delay - NCTO
3. Timer count ends- Coil is still energized
- Timer contact open
- lamp goes off.
4. Timer contacts remainopen until the coil is de-energized3
X1 X2ON
NO
NC
OFF
The Normally Closed contact will take 5 seconds To Open when the coil is energized.
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ON Delay - NOTC
1. Power is applied
to rails
X1 X2
The Normally Open contact will take 5 seconds To Close when the coil is energized.
OFF
NO OFF
1
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ON Delay - NOTC
2. Start PB is pressed
Coil energizes
Holding contacts
close
Timer contacts stay
open
Lamp stays off
Counter starts to
count (5 sec)
X1 X2
The Normally Open contact will take 5 seconds To Close when the coil is energized.
ON
NC
OFF
2
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ON Delay - NOTC
3. Counter finishes count
Coil stays energized
Timer contacts close
Lamp goes on
4. Timer contacts will
open when relay coil
is de-energized.
X1 X2
The Normally Open contact will take 5 seconds To Close when the coil is energized.
ON
NC
ON
3
NC
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OFF Delay - NCTC
1. Power is applied to
rails
2. Coil is off, contacts are
closed, lamp is on
The timer contacts will close 5 seconds after the coil is de-energized
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OFF Delay - NCTC
3. Start PB is pressed
4. Timer contacts open
5. Counter will start to
count only when coil is
de-energized.
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OFF Delay - NOTO
1. Power is applied to
rails
2. Coil is off, contacts are
closed, lamp is on
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OFF Delay - NOTO
3. Start is pressed.
4. Contacts close, lamp on
5. Counter only starts when
coil is de-energize