Presented by:
Pooja S Kulkarni

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Sensors
List of sensors:
 Photo sensors
 Motion sensors
 Pressure sensors
 Temperature sensors
 Proximity switches
 Passive sensors:
Infrared Radiation:
 Infrared radiation exists in the electromagnetic spectrum at a wavelength that is longer than visible light.
 Objects that generate heat also generate infrared radiation and can be detected.
 Radiation is strongest at a wavelength of 9.4um.
Passive sensors:
 Pyroelectric Sensors:
◦ The pyroelectric sensor is made of a crystalline material that generates a surface electric charge when exposed to heat in the form of infrared radiation.
◦ When the amount of radiation striking the crystal changes, the amount of charge also changes and can then be measured with a sensitive FET device built into the sensor.
Active Sensors:
 Inductive Proximity Sensors
 Inductive proximity sensors operate under the electrical principle of inductance.
 An inductive proximity sensor has four components; The coil, oscillator, detection circuit and output circuit.
Capacitive Proximity Sensors
 Capacitive proximity sensors are similar to inductive proximity sensors.
 The main difference between the two types is that capacitive proximity sensors produce an electrostatic field instead of an electromagnetic field.
 Capacitive proximity switches will sense metal as well as nonmetallic materials such as paper, glass, liquids, and cloth.
Photo sensors:
 These sensors use light sensitive elements to detect objects and are made up of an emitter (light source) and a receiver. Four types of photoelectric sensors are available.
 Direct Reflection –
◦ emitter and receiver are housed together and use the light reflected directly off the object for detection.
◦ In the use of these photocells, it is important to bear in mind the color and the type of surface of the object.
Reflection with Reflector –
 emitter and receiver are housed together and requires a reflector.
 An object is detected when it interrupts the light beam between the sensor and reflector.
 These photocells allow longer sensing distances, as the rays emitted are almost totally reflected towards the receiver.
 Polarized Reflection with Reflector - similar to Reflection with Reflector, these photocells use an anti-reflex device.
 Thru Beam - emitter and receiver are housed separately and detect an object when it interrupts the light beam between the emitter
and receiver. These photocells allow for the longest distances.