Proximity sensors are sensors that can detect nearby objects without physical contact. They work by emitting electromagnetic fields or beams and detecting changes in the fields or returned signals. Common types include capacitive, inductive, ultrasonic, and photoelectric sensors. Proximity sensors are used in applications like parking sensors, aviation safety systems, engine sensors, conveyor systems, and automatic doors. They allow contactless object detection and adaptive control systems.

2. What are proximity sensors?
 A proximity sensor is a sensor able to detect the
presence of nearby objects without any physical
contact.
 Most likely a plate of glass or plastic separates the
two. Although you are likely to touch the separating
element, there is no physical contact with the sensor.
 Proximity sensing technology enables adaptive
controls, alleviates isolation issues, improves overall
application robustness, generates almost unlimited
design flexibility and fosters new functionalities.

3. TYPES OF PROXIMITY SENSORS
 Capacitive
 Capacitive displacement sensor
 Doppler effect (sensor based on effect)
 Eddy-current
 Inductive
 Laser range finder
 Magnetic, including Magnetic proximity fuse
 Passive optical (such as charge-coupled devices)
 Passive thermal infrared
 Photocell (reflective)
 Radar
 Reflection of ionising radiation
 Sonar (typically active or passive)
 Ultrasonic sensor(sonar which runs in air)

4. LASER RANGE FINDER
 A laser rangefinder is a rangefinder which uses
a laser beam to determine the distance to an object.The
most common form of laser rangefinder operates on
the time of flight principle by sending a laser pulse in a
narrow beam towards the object and measuring the time
taken by the pulse to be reflected off the target and
returned to the sender.

5. Working
 A proximity sensor often emits an electromagnetic field
or a beam of electromagnetic radiation (infrared, for
instance), and looks for changes in the field or return
signal.The object being sensed is often referred to as the
proximity sensor's target. Different proximity sensor
targets demand different sensors. For example,
a capacitive or photoelectric sensor might be suitable for
a plastic target; an inductive proximity sensor always
requires a metal target.

6.  The maximum distance that this sensor can detect is
defined "nominal range". Some sensors have
adjustments of the nominal range or means to report a
graduated detection distance.
 Proximity sensors can have a high reliability and long
functional life because of the absence of mechanical
parts and lack of physical contact between sensor and
the sensed object.

7. Working

9. PROXIMITY SENSING
TECHNOLOGIES
Common Sensing Technologies
Technology Detection Mode Advantages Disadvantages
Inductive Metal
Induced
electromagnetic
currents
 Operates in harsh
conditions
 Rapid response
time
 Short range
 Detects only
movement
 Difficult array
setups
Ultrasonic Virtually all objects Sound wave echo
 Long range
 Measure distance
 Cost
 Dead zone
 No idea of
size/shape
Photoelectric Solid objects
Reflection or
absorption of light
different to
background
 Medium range
 Possibility of
interference
 Cost
 Pb in
fog/smoke/nontransp
arent materials
 Simple array

10. Applications
 Parking sensors, systems mounted on car bumpers that sense distance to
nearby cars for parking
 Ground proximity warning system for aviation safety
 Vibration measurements of rotating shafts in machinery
 Top dead centre (TDC)/camshaft sensor in reciprocating engines
 Sheet break sensing in paper machine.
 Anti-aircraft warfare
 Roller coasters
 Conveyor systems
 Beverage and food can making lines
 Mobile devices
 Touch screens that come in close proximity to the face
 Attenuating radio power in close proximity to the body, in order to
reduce radiation exposure

11. Proximity Sensors in smartphones
The proximity sensor is common on most smart-
phones, the ones that have a touch screen. This is
because the primary function of a proximity sensor is to
disable accidental touch events. The most common
scenario being- The ear coming in contact with the
screen and generating touch events, while on a call.
If a proximity sensor close to the speaker,
then it will detect any object in the vicinity of
the speaker. If any object is present (ex.
user's ear), then the touch events can be
assumed to be accidental & ignored.

12. Parking sensors
 Parking sensors are proximity sensors for road vehicles designed to
alert the driver to obstacles while parking.
 These systems feature ultrasonic proximity detectors to measure
the distances to nearby objects via sensors located in the front
and/or rear bumper fascias or visually minimized within adjacent
grills or recesses.
 The sensors emit acoustic pulses, with a control unit measuring the
return interval of each reflected signal and calculating object
distances.The system in turns warns the driver with acoustic tones,
the frequency indicating object distance, with faster tones
indicating closer proximity and a continuous tone indicating a
minimal pre-defined distance. Systems may also include visual aids,
such as LED or LCD readouts to indicate object distance. A vehicle
may include a vehicle pictogram on the car's infotainment screen,
with a representation of the nearby objects as coloured blocks.

13. Automatic Door Openers
 One of the most common applications for presence detection is the automatic
door.Typically, as you approach a door you are detected by an optical sensor, or
your weight closes a contact in the floor.
 The electric field sensor can be integrated into the floor and can detect the
presence of a person through different substances (wood, tile, carpet, etc.).There
are no moving parts and the sensor is impervious to rust and virtually
indestructible, making it a suitable replacement technology for the mechanical
pressure sensor.The physical nature of the electrode ensures a well defined and
limited sensing area, unlike that of an optical solution where you need to define a
volume and sensitivity threshold.
 Alternatively, proximity sensors can be embedded in the wall or other object to be
activated only by voluntary movement.This also allows the door to be opened
without any physical contact.
 Optimizing access control can also lead to benefits in energy consumption.
Minimizing the time a doorway remains open ensures the shortest possible
exchange between hot or cold outside air with the conditioned air in the building.