Proximity sensors detect nearby objects without physical contact, commonly used in smartphones and industrial applications. They include various types such as inductive, capacitive, magnetic, and photoelectric sensors, each with unique detection methods and applications. These sensors facilitate automation by recognizing the presence or distance of objects through electromagnetic fields, capacitance changes, or light beams.

1. Proximity Sensor
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2. Proximity sensor
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o A proximity sensor is a sensor able to detect the presence of
nearby objects without any physical contact. A proximity
sensor often emits an electromagnetic field or a beam of
electromagnetic radiation (infrared, for instance), and looks for
changes in the field.
 The maximum distance that this sensor can detect is defined
"nominal range". Some sensors have adjustments of the nominal
range.
 Proximity sensors are commonly used on smartphones to detect (and skip) accidental
touchscreen taps when held to the ear during a call.
 They are also used in machine vibration monitoring to measure the variation in
distance between a shaft and its support bearing. This is common in large
steam turbines, compressors, and motors that use sleeve-type bearings.

3. Proximity Sensors - Applications
• Detects Aluminum Components
• Inspects High-speed Table Movement
• Detects Bottle Caps
• Detects Aluminum Caps
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4. • Detects the Height of Liquid in a Pipe
• Detects Instruction Sheets in Paper Boxes
• Provides Long-distance Detection of Aluminum
• Liquid Level Control of Various Pipes and Liquid
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5. Types of Proximity sensor
 Inductive Proximity sensor
 Capacitive Proximity sensor
 Photoelectric Proximity sensor
 Magnetic Proximity sensor
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6. INDUCTIVE PROXIMITY SENSOR
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7. PT
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Magnetic
field
o An inductive proximity sensor is an electronic proximity sensor, which detects
metallic objects without touching them.
 The sensor consists of an induction loop.
 Electric current generates a magnetic field, which collapses generating a current that
falls asymptotically toward zero from its initial trans when the input electricity ceases.
 The inductance of the loop changes according to the material inside it and since metals
are much more effective inductors than other materials the presence of metal increases
the current flowing through the loop.
 This change can be detected by sensing circuitry, which can signal to some other device
whenever metal is detected.

8. CONSTRUCTION
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9. Sensor Head
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 Consists of closed-loop op-amp configuration
 Has a tank circuit connected to the non-inverting input head
 One branch of the tank contains a capacitor and the other branch an
inductor
 Once power applied, resonance develops in the tank and oscillators will
produce a frequency(100Hz to 1MHz)
 Filtered rectifier which converts the AC signal into a DC voltage level
Oscillator
 The coil of the tank inductor is wound around a ferrite core
 An electromagnetic field continually expands and contracts
around the coil
 Shape of the core causes the flux lines to bundle together
Unshielded sensor, which directs the flux lines to the front and
side the sensor head.

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Evaluation Unit
 The function of the output is to drive a load ON or
OFF. It's consists of an NPA current sinking
transistor or a current sourcing device
Output Stage
 Output of the demodulator connected to a Schmitt trigger input
 Produces two voltages
 If demodulator decreases to certain amplitude, it causes the
trigger output to quickly to a low voltage level

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Eddy currents are electric currents induced within conductors by a
changing magnetic field in the conductor
 These circulating eddies of current have inductance and thus
induce magnetic fields.
Eddy current
 Whenever a metal object enters this magnetic field,
the moving flux lines induce small Eddy currents on
the object’s surface

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 Inductive sensors are ideal for environments in which
grease or dirt builds up on the sensor or target because
the magnetic field is not affected by these conditions.
• Power is needed to make these currents flow, energy is drained from the oscillator circuit,
causing its amplitude to decrease.
• A trigger circuit inside the sensor detects the change in amplitude and causes the sensor
output to switch on.
• when the metal target moves out of the magnetic field, the oscillator regenerates and the
sensor output switches back to its normal off state

13. APPLICATION
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Application 1: Determination of position
with the use of two inductive sensors.
Application 2: Interrogation of a
camshaft gear with inductive
sensors

14. Capacitive Sensor
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15. Capacitive Sensor:
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 Capacitive sensors can directly sense a variety of things—motion,
chemical composition, electric field—and, indirectly, sense many
other variables which can be converted into motion or dielectric
constant, such as pressure, acceleration, fluid level, and fluid
composition. They are built with conductive sensing electrodes in
a dielectric, with excitation voltages on the order of five volts and
detection circuits which turn a capacitance variation into a voltage,
frequency, or pulse width variation. The range of application of
capacitive sensors is extraordinary.

16. Circuit:
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Note: For proper operation, circuit ground must be connected via a small value, high
voltage-rating capacitor to one side of the mains supply socket. The "Live" side is the
right one.

17. Capacitive proximity sensors working principle
Capacitive sensors are used for non-contact detection of metallic objects & non-metallic
objects(liquid, plastic, wooden materials and soon). Capacitive proximity sensors use the
variation of capacitance between the sensor and the object being detected. When the
object Is at a preset distance from the sensitive side of the sensor, an electronic circuit
inside the sensor begins to oscillate. The rise or fall of such oscillation is identified by at
threshold circuit that changes the output of the sensor.
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18. Applications
 Capacitive touch sensors are used in many devices such as laptop track pads,
digital audio players, computer displays, mobile phones, mobile devices and
others.
 More and more design engineers are selecting capacitive sensors for the
versatility, reliability and robustness and cost reduction over mechanical
switches.
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19. Magnetic sensors
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20. What is magnetic proximity switch:
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Magnetic sensors are actuated by the presence of a permanent magnet. Their operating
principle is based on the use of reed contacts,
which consist of two low reluctance Ferro-magnetic reeds enclosed in glass bulbs
containing inert gas. The reciprocal attraction of
both reeds in the presence of a magnetic field, due to magnetic induction, establishes an
electrical contact.

21. Circuit Diagram
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 When a magnet is reached in proximity of S1 it closes to give a negative trigger at pin 2
of IC1.The output of IC1 goes high.
 time determines by R2 and C2.This clocks the IC2 wired as a toggle flip flop. The
output (pin 1 ) of IC2 goes high and the transistor.
 Q1 is biased to ON. The relay is activated and so do the equipment connected to the
relay. The LED D1 glows when IC1 is triggered.
 Here is the circuit diagram of a magnetic
proximity switch that finds a lot of
applications in many fields.
 The circuit is based on a magnetic reed
switch(S1) as the proximity sensor. A
monostable multivibrator based on NE555
(IC1) and a toggle flip flop based on
CD4013 (IC2) does the rest of the circuit.

22. Magnetic sensors compared to traditional mechanical switches have the
following advantage:
• Contacts are well protected against dust, oxidization and corrosion due to the hermetic glass bulb
and inert gas; contacts are activated by means of a magnetic field rather than mechanical parts
• Special surface treatment of contacts assures long contact life
• Maintenance free
• Easy operation
• Reduced size
• Reed sensors can withstand higher voltage than typical Hall devices.
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Advantage

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Photoelectric Sensor

24.  A photoelectric sensor, or photo eye, is a device used to detect the distance,
absence, or presence of an object by using a light transmitter, often infrared , and a
photoelectric receiver. They are used extensively in industrial manufacturing.
• Types: There are three different functional Photoelectric Sensor
1. opposed (through beam),
2. retro-reflective
3. proximity-sensing (diffused).
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25. Detection configuration and features 25
Type
Detection configuration Features Model
Through beam
Detection occurs when the target crosses the beam between
transmitter and receiver
*Long-detecting distance
*Stable detection
*Opaque objects are detectable regardless of shape, color
or material
*Powerful beam
LV,LX2,PZ-M,PZ2,PS,PW,PJ,PJ‐S,PQ
and FS,FS2,FS-L units
Retro-reflective
Detection occurs when the target crosses the beam between
sensor head and reflector.
*Reflector allows for installation in a limited space
*Simple wiring
*Easily-adjustable optical axis
*Opaque objects are detectable regardless of shape, color, or
material
PZ-M,PZ2,PW and LV,FS units
Diffuse-reflective
Detection occurs when the light beam is reflected by the
target and received by the sensor
*Space-saving
*Adjustment of optical axis not required
*Reflective transparent objects are detectable
*Color differentiation possible
PZ2,PS,PW, and FS,FS2 units
Focused-beam reflective
Detection occurs when the beam spot is reflected by the
target and received by the sensor
*Minute objects detectable
*Target markings detectable
LV and FS,FS2,FS-L units

26. Type Detection configuration Features Model
Small-spot definite reflective
The transmitting and receiving portions are constructed at an
angle allowing detection within the limited area where the
optical axes intersect
*Effect of target background minimal
*Low hysteresis
*Slight height differences detectable
PS, and FS,FS2,LV units
(Internal lens units)
Fixed-distance
Detects the target at a specific distance according to the angle
of the reflected light beam
*Unaffected by highly reflective target background
*Stable detection of targets of colors and materials with
varying reflectance
*Highly accurate detection of minute objects
PZ-V,PZ-M
Luster recognition
When the light beam hits a target, the beam reflects differently
according to the luster of the target. The sensor detects the
difference in luster based on how the beam reflects (specular or
diffusive) light
*Detection is not affected by target color.
*Transparent targets can be detected.
PI-G
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27. Thank You All 
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