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Proximity Sensors


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Description about some basic proximity sensors

Published in: Engineering
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Proximity Sensors

  1. 1. Proximity sensor Koustubh Chakraborty B.Tech 3rd year (ECE) Roll No- 18700312067
  2. 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. 3. Definition  Detection occurs when object approaches within detection range  All sensors performing non contact sensing are included in proximity sensors
  4. 4. Proximity Sensors Inductive Capacitive Ultrasonic Optical Reflective Direct Retro Reflective Polarized Reflection with reflector Thru Beam Types of Proximity Sensors
  5. 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. 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. 7. Components & Working Principle
  8. 8. Components & Working Principle  Output Circuit • Output of circuit changes due to change in oscillation
  9. 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. 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. 11. Components & Working Principle  Main Components  Plate  Oscillator  Threshold Detector Output Circuit Continued…
  13. 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. 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. 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. 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.
  18. 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. 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. 20.  Thru Beam type  Emitter and receiver housed separately  Object is detected when light beam is disrupted  Allows the longest range
  21. 21. THRU BEAM TYPE
  22. 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. 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
  26. 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
  28. 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. 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. 30. REFRENCES  ature/documents/ca/c116-ca502_-en-p.pdf    01&mid=01/01  ml  php  itysensors.htm  2041221/12041223/Retroreflective-and-Polarized- Retroreflective.html
  31. 31. Thank You!