C11 Control Devices

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Chapter 11 ² Control DevicesChapter 11 ² Control Devices

Kaw AreaKaw AreaTechnical SchoolTechnical School

Industrial TechnologyIndustrial Technology




Kaw AreaKaw AreaTechnical SchoolTechnical School

Richard E. StephensCET Sr.

Richard E. StephensCET Sr.

Electrical ControlElectrical Control

Systems ISystems I



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




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).




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.




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.




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.




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.




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.




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.




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.




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.




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.




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.




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.




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.




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.




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.




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.




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.




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.




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.






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.




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.




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.




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.




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.




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.




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.




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.




Both NO and NC electrical

contacts are used with flow

switches.

Both NO and NC electrical

contacts are used with flow

switches.




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.




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.




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.




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.




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.




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.




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.




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.




Optical level switches use a

photoelectric beam to sense the

liquid.

Optical level switches use a

photoelectric beam to sense the

liquid.




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.




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.




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.




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.




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.




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.




Windmills are used to harness the wind to generate

power.

Windmills are used to harness the wind to generate

power.




Anemometer and wind

velocity relay

specifications are given

in manufacturer data

sheets.

Anemometer and wind

velocity relay

specifications are given

in manufacturer data

sheets.




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.






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.




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.




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.




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.




A DMM set to measure

voltage is used to measure

the voltage into and out of a

two-wire solid-state switch.




two-wire solid-state switch.







three-wire solid-state switch.




three-wire solid-state switch.




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.




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.




Smart devices may be

connected using screw

connectors or quick

connectors.

Smart devices may be

connected using screw

connectors or quick

connectors.

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C11 Control Devices