Description about some basic proximity sensors

1. Proximity sensor
Koustubh
Chakraborty
B.Tech 3rd year
(ECE)
Roll No-
18700312067

2. Contents:
1. Definition
2. Types of Proximity Sensors
3. Inductive Proximity Sensors
4. Capacitive Proximity Sensors
5. Ultrasonic Proximity Sensors
6. Optical Proximity Sensors
7. Conclusion
8. Reference

3. Definition
 Detection occurs when object approaches
within detection range
 All sensors performing non contact sensing
are included in proximity sensors

4. Proximity
Sensors
Inductive
Capacitive
Ultrasonic
Optical
Reflective
Direct
Retro
Reflective
Polarized
Reflection with
reflector
Thru Beam
Types of Proximity Sensors

5. Inductive Proximity Sensors
 Detects Metallic objects without physical
contact
 A coil and high frequency oscillator is used
 Operating distance depends on
 Coil’s size
 Target’s shape, size, material

6. Components & Working Principle
 Main components & their work
 Coil
• Generates high frequency magnetic field in front of
face
• Metallic target absorbs some magnetic energy
Oscillator
• Oscillation circuit is affected by the absorption of
energy
Detector
• Change in oscillation is detected with threshold
circuit
Continued…

7. Components & Working Principle

8. Components & Working Principle
 Output Circuit
• Output of circuit changes due to change
in oscillation

9.  Advantages
• Accurate
• High switching rate
• Works in harsh environmental condition
 Disadvantages
• Detects only metallic target
 Applications
• Metal detectors
• Car washes
ADVANTAGES AND APPLICATIONS

10. Capacitive Proximity Sensors
 Detects metallic objects as well as non-metallic
objects(liquid, plastic, wooden material etc)
 Uses variation of capacitance between sensor
and object
 Distance down to 1 micro inch can be
measured
 All targets having dielectric constant more
than air can be detected

11. Components & Working Principle
 Main Components
 Plate
 Oscillator
 Threshold Detector
Output Circuit
Continued…

12. CAPACITIVE PROXIMITY SENSOR

13.  Working Principle
 Plate acts as one plate of capacitor
 Other plate being the target
 Air is dielectric medium
 Change in capacitance initiates oscillation
 This is identified by threshold circuit which
switches the output

14.  Advantages
• Metallic & non-metallic targets
• High speed
• Good stability
• Low cost and power consumption
 Disadvantages
• Affected by temperature and humidity
• Less accurate
• Difficult to design
Applications
• Mobile Phones
• Laptop track pads and more
ADVANTAGES AND APPLICATIONS

15. Ultrasonic Proximity Sensors
 Uses ultrasonic sound wave for detection
 Used frequency is higher than audible range
 Can measure distances very accurately
 Provides good sensing for large objects with
hard surface

16.  Ultrasonic Sensors Working Principle
 Quartz-crystal transducer generates
ultrasonic sound wave
 Emitter transmits the sound wave
 Waves strike objects within the field of
detection
 Movement disrupts the sound wave
 Reflected back to the system’s receiver.

17. ULTRASONIC PROXIMITY SENSORS

18.  Advantages
• Not affected by atmospheric dust, snow, rain etc.
• Sensing distance more than capacitive and inductive Sensors
• Works in adverse condition
 Disadvantages
• Difficult to sense from soft, curved, thin or small objects
 Applications
• Ultrasonic thru beam sensors in bottle counting machine
• Vehicle detection in barrier system
ADVANTAGES AND APPLICATIONS

19. Optical Proximity Sensors
 Senses any object within 10 meters range
 Uses an LED in either infrared or visible light
spectrum to transmit
 Photodiode detects the light generated
 Generally light sources pulse the infra-red light
on and off at a fixed frequency.
 Sensor detects object when it disrupts light beam
 Two types- Reflective type And Thru beam type

20.  Thru Beam type
 Emitter and receiver housed separately
 Object is detected when light beam is
disrupted
 Allows the longest range

21. THRU BEAM TYPE

22.  Reflective type
 Emitter and receiver are housed together
 Object is detected by means of reflection
 Three types
1. Direct reflection
2. Reflection with reflector
3. Polarized reflection with reflector

23. 1. Direct reflection
 Light reflected off the object is detected
 Surface and colour determines the sensing distance
2. Reflection with reflector (Retro Reflective)
 A reflector is needed
 Disruption of the light beam between Sensor and
reflector is detected
 Rays emitted are almost totally reflected towards the
receiver so longer sensing distance is allowed

24. DIRECT REFLECTION

25. REFLECTION WITH REFLECTOR

26. 3. Polarized Reflector
 Contain polarizing filters in front of the
emitter and receiver
 Filters are 90° out of phase with each other
 Polarized light if reflected off an object,
remains polarized
 Polarized light if reflected off a
depolarizing reflector, it is depolarized
 Receiver can only detect reflected light that
has been depolarized

27. POLARIZED REFLECTION WITH
REFLECTOR

28.  Advantages
• Effective in dusty environments
• Focused beam
• Higher sensing distance
• Immune from interference
 Disadvantages
• Expensive
 Applications
• Lift door mechanisms
• Components positioning sensing
• Security & safety
•Counting objects in conveyer belts
ADVANTAGES AND APPLICATIONS

29. Conclusion
 Machine tools, woodworking machines,
packaging machines and other types of machinery.
 Further applications are automatic door units
such as garage doors or doors inside buildings,
elevator doors or doors inside railway coaches.
 The building and automotive sector are further
industries using high volumes of proximity
sensors.

30. REFRENCES
 http://literature.rockwellautomation.com/idc/groups/liter
ature/documents/ca/c116-ca502_-en-p.pdf
 http://en.wikipedia.org/wiki/Proximity_sensor
 http://www.fargocontrols.com/sensors.html
 http://www.autonics.co.in/products/products_2.php?big=
01&mid=01/01
 http://www.ia.omron.com/support/guide/41/overview.ht
ml
 http://www.sensorcentral.com/photoelectric/proximity01.
php
 http://www.engineershandbook.com/Components/proxim
itysensors.htm
 http://www.ab.com/en/epub/catalogs/12772/6543185/1
2041221/12041223/Retroreflective-and-Polarized-
Retroreflective.html

31. Thank You!