Photoelectric sensors detect objects using light. They have a light emitter and receiver - when light is interrupted by an object, the receiver detects the change and outputs an electrical signal. There are different types of photoelectric sensors including through-beam, retroreflective, and proximity sensors. Through-beam sensors detect when a light beam between an emitter and receiver is blocked. Retroreflective sensors bounce light back from a reflector to the receiver. Proximity sensors detect when light is reflected off an object and into the receiver.

1. PHOTO ELECTRIC SENSORS
SENSOR TECHNOLOGY
WORKING PRINCIPLE AND APPLICATIONS

2. PHOTOELECTRIC SENSORS
• Photoelectric Sensors detect objects, changes in surface conditions, and
other items through a variety of optical properties.
• A Photoelectric Sensor consists primarily of an Emitter for emitting light
and a Receiver for receiving light.
• When emitted light is interrupted or reflected by the sensing object, it
changes the amount of light that arrives at the Receiver. The Receiver
detects this change and converts it to an electrical output.
• The light source for the majority of Photoelectric Sensors is infrared or
visible light (generally red, or green/blue for identifying colors).
Photoelectric Sensors are classified as shown in the figure below. (See
Classification.)

7. PHOTO ELECTRIC SENSOR VS ULTRA SONIC
SENSOR

8. PHOTOELECTRIC SENSOR VS PROXIMITY SENSOR
• The sensor uses light to detect an object without physical contact.
• Proximity sensor utilizes an electromagnetic field to detect an object
contact. After that, it changes this data into an electrical signal.

9. PHOTO ELECTRIC VS PROXIMITY SENSOR

10. PHOTOELECTRIC VS PROXIMITY SENSORS

11. INTRODUCTION
• A photoelectric sensor is a device used to determine the
distance, absence, or presence of an object by using a light
transmitter, often infrared, and a photoelectric receiver.
• They are largely used in industrial manufacturing. There are
three different useful types: opposed (through-beam), retro-
reflective, and proximity-sensing (diffused).

12. TYPES OF PHOTO SENSORS
• A self-contained photoelectric sensor contains the optics, along
with the electronics. It requires only a power source.
• The sensor performs its own modulation,
demodulation, amplification, and output switching.
• Some self-contained sensors provide such options as built-in
control timers or counters. Because of technological progress,
self-contained photoelectric sensors have become increasingly
smaller.
.

13. • When space is restricted or the environment too hostile even for
remote sensors, fibre optics may be used. Fibre optics are
passive mechanical sensing components.
• They may be used with either remote or self-contained sensors.
• They have no electrical circuitry and no moving parts, and can
safely pipe light into and out of hostile environments

14. • Remote photoelectric sensors used for remote sensing contain
only the optical components of a sensor.
• The circuitry for power input, amplification, and output switching
is located elsewhere, typically in a control panel.
• This allows the sensor, itself, to be very small. Also, the controls
for the sensor are more accessible, since they may be bigger.

15. SENSING MODES
• A through-beam arrangement consists of a receiver located
within the line-of-sight of the transmitter.
• In this mode, an object is detected when the light beam is
blocked from getting to the receiver from the transmitter.
• A retroreflective arrangement places the transmitter and
receiver at the same location and uses a reflector to bounce the
inverted light beam back from the transmitter to the receiver.
• An object is sensed when the beam is interrupted and fails to
reach the receiver.

16. • A proximity-sensing (diffused) arrangement is one in which the
transmitted radiation must reflect off the object in order to reach the
receiver.
• In this mode, an object is detected when the receiver sees the
transmitted source rather than when it fails to see it.
• As in retro-reflective sensors, diffuse sensor emitters and receivers
are located in the same housing. But the target acts as the reflector
so that detection of light is reflected off the disturbance object.
• The emitter sends out a beam of light (most often a pulsed infrared,
visible red, or laser) that diffuses in all directions, filling a detection
area. The target then enters the area and deflects part of the beam
back to the receiver.
• Detection occurs and output is turned on or off when sufficient light
falls on the receiver.

17. • Some photo-eyes have two different operational types, light
operate and dark operate.
• The light operates photo eyes become operational when the
receiver "receives" the transmitter signal.
• Dark operate photo eyes become operational when the receiver
"does not receive" the transmitter signal.
• The detecting range of a photoelectric sensor is its "field of
view", or the maximum distance from which the sensor can
retrieve information, minus the minimum distance.
• A minimum detectable object is the smallest object the sensor
can detect. More accurate sensors can often have minimum
detectable objects of minuscule size.