proximity sensors
TRANSCRIPT
Proximity sensorKoustubh ChakrabortyB.Tech 3rd year (ECE)Roll No- 18700312067
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
Definition
Detection occurs when object approaches within detection range
All sensors performing non contact sensing are included in proximity sensors
Proximity Sensors
Inductive
Capacitive
Ultrasonic
Optical
Reflective
Direct
Retro Reflective
Polarized Reflection with
reflectorThru Beam
Types of Proximity Sensors
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
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…
Components & Working Principle
Components & Working Principle
Output Circuit• Output of circuit changes due to change in oscillation
Advantages
• Accurate• High switching rate• Works in harsh environmental condition
Disadvantages
• Detects only metallic target
Applications
• Metal detectors• Car washes
ADVANTAGES AND APPLICATIONS
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
Components & Working Principle Main Components
Plate
Oscillator
Threshold Detector
Output Circuit
Continued…
CAPACITIVE PROXIMITY SENSOR
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
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
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
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.
ULTRASONIC PROXIMITY SENSORS
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
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
Thru Beam type
Emitter and receiver housed separately
Object is detected when light beam is disrupted
Allows the longest range
THRU BEAM TYPE
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
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
DIRECT REFLECTION
REFLECTION WITH REFLECTOR
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
POLARIZED REFLECTION WITH REFLECTOR
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
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.
REFRENCES http://literature.rockwellautomation.com/idc/groups/
literature/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.html http://www.sensorcentral.com/photoelectric/
proximity01.php http://www.engineershandbook.com/Components/
proximitysensors.htm http://www.ab.com/en/epub/catalogs/
12772/6543185/12041221/12041223/Retroreflective-and-Polarized-Retroreflective.html
Thank You!