ej501 t2 logical sensor and actuator

8/10/2019 EJ501 T2 Logical Sensor and Actuator

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SENSOR


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Logical Sensor

Sensors allow a PLC to detect the state of a process.

Logical sensors can only detect a state that is either true orfalse. Examples of physical phenomena that are typically

detected are listed below :

inductive proximity - is a metal object nearby?

capacitive proximity - is a dielectric object nearby?

optical presence - is an object breaking a light beam

or reflecting light?mechanical contact - is an object touching a switch?


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Types of Logical Sensor

Contact Switches

Contact switches areavailable as normallyopen and normallyclosed. Their housings

are reinforced so thatthey can take repeatedmechanical forces. Door Contact Switches


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Proximity

Sensors allow

a PLC to detectthe state of a

process


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Photo Optics

Optical sensors require both a

light source (emitter) and

detector.


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Photo Optics

Emitters will produce lightbeams in the visible and

invisible spectrums usingLEDs and laser diodes.Detectors are typically builtwith photodiodes orphototransistors.

The emitter and detector arepositioned so that an objectwill block or reflect a beamwhen present.


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Capacitive

Capacitive sensors are able to detectmost materials at distances up to a fewcentimeters. Recall the basic relationshipfor capacitance.


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Capacitive

In the sensor the area

of the plates and

distance betweenthem is fixed. But, the

dielectric constant of

the space around them

will vary as different

materials are brought

near the sensor.


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5. Inductive

Inductive sensors use currentsinduced by magnetic fields to

detect nearby metal objects.

The inductive sensor uses acoil (an inductor) to generate ahigh frequency magnetic field.

If there is a metal object nearthe changing magnetic field,current will flow in the object.



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5. InductiveThis resulting current flow sets up a new magnetic field that

opposes the original magnetic field.

The net effect is that it changes the inductance of the coil in theinductive sensor. By measuring the inductance the sensor candetermine when a metal have been brought nearby.

These sensors will detect any metals, when detecting multipletypes of metal multiple sensors are often used.



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6.

Ultrasonic

An ultrasonic sensor emits a sound above the normal

hearing threshold of 16KHz. The time that is required for the

sound to travel to the target and reflect back is proportional

to the distance to the target.



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6. Ultrasonic

The two common types of sensors are;

electrostatic - uses capacitive

effects. It has longer ranges and

wider bandwidth, but is more

sensitive to factors such as

humidity.

piezoelectric - based on charge

displacement during strain in

crystal lattices. These are rugged

and inexpensive.

These sensors can be very effective for

applications such as fluid levels in tanks and

crude distance measurement.



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Logical Sensor and Switches Wiring

(sourcing and sinking)


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ACTUATORS


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ACTUATORS

Solenoid


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ACTUATORS

Valves


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Cylinder

ACTUATORS


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Cylinder

ACTUATORS


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Cylinder

ACTUATORS


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Motor

ACTUATORS


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Hydraulic

ACTUATORS


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Electro -Hydraulic

The word electro-hydraulic has two meanings

for two highly different operations. It can

stand for an electrical control device that

makes precise adjustments in a hydraulic

system.

Also, it can mean a chemical reaction that is

created by firing short, powerful electricalimpulses into or directly beneath the surface

of a body of liquid.

ACTUATORS

Electro hydraulic servo valve


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Electro -Hydraulic

Perhaps the most well-known electrohydraulic

device is an automobile's power steeringunit

also called an electrohydraulic actuator.

The unit combines high power with a high degree

of accuracy to adjust for the minute movements

of the steering wheel in a vehicle.

This type of technology, where electrical

components are used to increase the accuracy of

hydraulic movements, can be applied to almost

any situation where hydraulics is used.

ACTUATORS
http://www.wisegeek.com/what-is-power-steering.htmhttp://www.wisegeek.com/what-is-power-steering.htm


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Pneumatic

ACTUATORS


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Electro - Pneumatic

The electro-pneumatic action is a control system for pipe organs,

whereby air pressure, controlled by an electric current and

operated by the keys of an organ console, opens and closes valveswithin wind chests, allowing the pipes to speak.

This system also allows the console to be physically detached from

the organ itself.

The only connection was via an electrical cable from the console

to the relay, with some early organ consoles utilizing a separate

wind supply to operate combination

pistons.

ACTUATORS


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ej501 t2 logical sensor and actuator

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