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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Kaw AreaKaw AreaTechnical SchoolTechnical School
Industrial TechnologyIndustrial Technology
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Kaw AreaKaw AreaTechnical SchoolTechnical School
Richard E. StephensCET Sr.
Richard E. StephensCET Sr.
Electrical ControlElectrical Control
Systems ISystems I
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P ower P oint ® P resentation P ower P oint ® P resentation
Chapter 11Chapter 11Control DevicesControl Devices
Industrial Pushbuttons � Selector Switches �
Joysticks � Limit Switches � Foot Switches � Daylight
Switches � Pressure Switches � Temperature
Switches � Flow Switches � Smoke/Gas Switches �
Level Switches � Wind Metering � Automated
Systems � Troubleshooting Control Devices �
Smart (Intelligent) Input Devices
Industrial Pushbuttons � Selector Switches �
Joysticks � Limit Switches � Foot Switches � Daylight
Switches � Pressure Switches � Temperature
Switches � Flow Switches � Smoke/Gas Switches �
Level Switches � Wind Metering � Automated
Systems � Troubleshooting Control Devices �
Smart (Intelligent) Input Devices
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
An industrial pushbutton consists of a legend plate,
an operator, and one or more contact blocks
(electrical contacts).
An industrial pushbutton consists of a legend plate,
an operator, and one or more contact blocks
(electrical contacts).
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
An operator is the device that is pressed, pulled, or
rotated by the individual operating the circuit.
An operator is the device that is pressed, pulled, or
rotated by the individual operating the circuit.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Contact blocks include
normally open (NO), normally
closed (NC), or both NO and
NC contacts.
Contact blocks include
normally open (NO), normally
closed (NC), or both NO and
NC contacts.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A pushbutton station is an
enclosure that protects the
pushbutton, contact block,
and wiring from dust, dirt,
water, and corrosive fluids.
A pushbutton station is an
enclosure that protects the
pushbutton, contact block,
and wiring from dust, dirt,
water, and corrosive fluids.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A two-position selector switch allows the operator to
select one of two circuit conditions.
A two-position selector switch allows the operator to
select one of two circuit conditions.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A three-position selector switch allows the operator to
select one of three circuit conditions.
A three-position selector switch allows the operator to
select one of three circuit conditions.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Contact position on a
selector switch may be
illustrated using truth
tables (target tables) or
solid lines, dashed lines,
and a series of small
circles.
Contact position on a
selector switch may be
illustrated using truth
tables (target tables) or
solid lines, dashed lines,
and a series of small
circles.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A joystick is used to
control many different
circuit operations from
one location.
A joystick is used to
control many different
circuit operations from
one location.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Limit switches are used
to convert a mechanical
motion into an electrical
signal.
Limit switches are used
to convert a mechanical
motion into an electrical
signal.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Arcing or welding of the
contacts may occur from a
possible short circuit if the
contacts are connected to
opposite polarity.
Arcing or welding of the
contacts may occur from a
possible short circuit if the
contacts are connected to
opposite polarity.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A relay, contactor, or motor
starter must be used to
interface the limit switch with
the load if the load current
exceeds the contact rating.
A relay, contactor, or motor
starter must be used to
interface the limit switch with
the load if the load current
exceeds the contact rating.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
An actuator is the part of a
limit switch that transfers
the mechanical force of
the moving part to the
electrical contacts.
An actuator is the part of a
limit switch that transfers
the mechanical force of
the moving part to the
electrical contacts.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Limit switches should not
be operated beyond the
manufacturer¶s
recommended travel
specifications.
Limit switches should not
be operated beyond the
manufacturer¶s
recommended travel
specifications.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A cam-operated limit switch
must be installed to prevent
severe impact and allow a
slow release of the lever.
A cam-operated limit switch
must be installed to prevent
severe impact and allow a
slow release of the lever.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Limit switches using
push-roller actuators
must not be operated
beyond their travel limit.
Limit switches using
push-roller actuators
must not be operated
beyond their travel limit.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Limit switches should be
mounted to avoid
accidental activation,
accumulated materials,
and excessive heat.
Limit switches should be
mounted to avoid
accidental activation,
accumulated materials,
and excessive heat.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A foot switch is used to
allow hands-free control or
an additional control point.
A foot switch is used to
allow hands-free control or
an additional control point.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A daylight switch is a switch that automatically turns
lamps ON at dusk and OFF at dawn.
A daylight switch is a switch that automatically turns
lamps ON at dusk and OFF at dawn.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A pressure switch is a
control switch that detects
a set amount of force and
activates electrical
contacts when the setamount of force is
reached.
A pressure switch is a
control switch that detects
a set amount of force and
activates electrical
contacts when the setamount of force is
reached.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Deadband is the amount
of pressure that must be
removed before the
switch contacts reset for
another cycle after thesetpoint has been
reached and the switch
has been actuated.
Deadband is the amount
of pressure that must be
removed before the
switch contacts reset for
another cycle after thesetpoint has been
reached and the switch
has been actuated.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Pressure switches are
used to maintain a
predetermined pressure
in a tank or reservoir, or
sequence the return of pneumatic or hydraulic
cylinders.
Pressure switches are
used to maintain a
predetermined pressure
in a tank or reservoir, or
sequence the return of pneumatic or hydraulic
cylinders.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A low-range pressure switch may be used with a
metal tubing arrangement in a fluidic sensor to
determine the presence of a material in process.
A low-range pressure switch may be used with a
metal tubing arrangement in a fluidic sensor to
determine the presence of a material in process.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
In a heating system, heat is
produced when the
temperature switch contacts
cool and close.
In a heating system, heat is
produced when the
temperature switch contacts
cool and close.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
In a cooling system, cool air is
produced when the temperature
switch contacts heat and close.
In a cooling system, cool air is
produced when the temperature
switch contacts heat and close.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
The different sensors used
to activate electrical
contacts in response to
temperature changes
include bimetallic, capillarytube, thermistor, and
thermocouple.
The different sensors used
to activate electrical
contacts in response to
temperature changes
include bimetallic, capillarytube, thermistor, and
thermocouple.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Thermistors are
available that monitor
the temperature of
liquid, air, or a surface
temperature.
Thermistors are
available that monitor
the temperature of
liquid, air, or a surface
temperature.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A flow switch is a control switch that detects the
movement of a fluid.
A flow switch is a control switch that detects the
movement of a fluid.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Both NO and NC electrical
contacts are used with flow
switches.
Both NO and NC electrical
contacts are used with flow
switches.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A flow switch may be
used to determine if
sufficient air is flowing
across the heating
elements of an electricheater.
A flow switch may be
used to determine if
sufficient air is flowing
across the heating
elements of an electricheater.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A flow switch may be used to advance a clogged filter
when restricted airflow is sensed.
A flow switch may be used to advance a clogged filter
when restricted airflow is sensed.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A flow switch may be used to
advance a clogged filter when
restricted airflow is sensed.
A flow switch may be used to
advance a clogged filter when
restricted airflow is sensed.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A smoke switch (smoke detector)
is a switch that detects a set
amount of smoke caused by
smoldering or burning material
and activates a set of electricalcontacts. A gas switch (gas
detector) is a switch that detects
a set amount of a specified gas
and activates a set of electricalcontacts.
A smoke switch (smoke detector)
is a switch that detects a set
amount of smoke caused by
smoldering or burning material
and activates a set of electricalcontacts. A gas switch (gas
detector) is a switch that detects
a set amount of a specified gas
and activates a set of electricalcontacts.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A mechanical level switch
uses a float, which moves up
and down at the level of the
liquid and activates electrical
contacts at a set height.
A mechanical level switch
uses a float, which moves up
and down at the level of the
liquid and activates electrical
contacts at a set height.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A magnetic level switch uses a magnetically operated
reed switch and a moving magnet to detect the level
of a liquid.
A magnetic level switch uses a magnetically operated
reed switch and a moving magnet to detect the level
of a liquid.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A conductive probe level
switch uses liquid to
complete the electrical
path between two
conductive probes.
A conductive probe level
switch uses liquid to
complete the electrical
path between two
conductive probes.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A capacitive level switch
detects the dielectric variation
when the product is in contact
with the probe and when the
product is not in contact withthe probe.
A capacitive level switch
detects the dielectric variation
when the product is in contact
with the probe and when the
product is not in contact withthe probe.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Optical level switches use a
photoelectric beam to sense the
liquid.
Optical level switches use a
photoelectric beam to sense the
liquid.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Level switches detect and respond to
the level of a material in a tank.
Level switches detect and respond to
the level of a material in a tank.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
The distance controlled
in one-level control is
small. Any distance may
be controlled in two-level
control.
The distance controlled
in one-level control is
small. Any distance may
be controlled in two-level
control.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A temperature and level
control may be combined to
control the temperature and
level of a fluid.
A temperature and level
control may be combined to
control the temperature and
level of a fluid.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
In a solar heating system, the circulation pump is
activated by the temperature differential between T1
and T2.
In a solar heating system, the circulation pump is
activated by the temperature differential between T1
and T2.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A wiring diagram is used to properly install the control
circuit of the solar heating system.
A wiring diagram is used to properly install the control
circuit of the solar heating system.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
An air pollution detector uses a logic module and an
air pollution sensor to measure the pollutants in the
air and compare them to a set level.
An air pollution detector uses a logic module and an
air pollution sensor to measure the pollutants in the
air and compare them to a set level.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Windmills are used to harness the wind to generate
power.
Windmills are used to harness the wind to generate
power.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Anemometer and wind
velocity relay
specifications are given
in manufacturer data
sheets.
Anemometer and wind
velocity relay
specifications are given
in manufacturer data
sheets.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A wind vane and a wind
direction relay are used
to control the yawing
function of a windmill.
A wind vane and a wind
direction relay are used
to control the yawing
function of a windmill.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Contact protection may be
added when switching large DC
and AC inductive loads to
prevent or reduce arcing at the
switch contacts.
Contact protection may be
added when switching large DC
and AC inductive loads to
prevent or reduce arcing at the
switch contacts.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A pressure relief valve may be
added to a circuit to protect a
pressure switch from excessive
pressure.
A pressure relief valve may be
added to a circuit to protect a
pressure switch from excessive
pressure.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Allow a distance of at least
three pipe inside diameters
(ID) on each side of the flow
switch when mounting a flow
switch.
Allow a distance of at least
three pipe inside diameters
(ID) on each side of the flow
switch when mounting a flow
switch.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A DMM set to measure voltage is
used to test the operation of a switch.
A DMM set to measure voltage is
used to test the operation of a switch.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A DMM set to measure
voltage is used to measure
the voltage into and out of a
two-wire solid-state switch.
A DMM set to measure
voltage is used to measure
the voltage into and out of a
two-wire solid-state switch.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A DMM set to measure
voltage is used to measure
the voltage into and out of a
three-wire solid-state switch.
A DMM set to measure
voltage is used to measure
the voltage into and out of a
three-wire solid-state switch.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
Hard wiring requires a
large number of control
wires to interconnect a
system.
Hard wiring requires a
large number of control
wires to interconnect a
system.
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Chapter 11 ² Control DevicesChapter 11 ² Control Devices
A smart device uses a
communication protocol
that allows individual
devices to communicate
with each other over asingle cable.
A smart device uses a
communication protocol
that allows individual
devices to communicate
with each other over asingle cable.