The document discusses PIR sensors and how they work, explaining that PIR sensors can detect infrared radiation from warm bodies like humans and animals moving in their field of view, causing a change in voltage that signals motion. It also describes common applications of PIR sensors in security alarms, motion-activated lighting, and more. The key components of a PIR sensor are a pyroelectric sensor and fresnel lens that focus infrared signals onto the sensor to detect changes from motion.

1. PIR SENSOR
• PIR sensors allow you to sense motion . Generally, PIR sensor can detect
animal/human movement. PIR is made of a pyro electric sensor, which is
able to detect different levels of infrared radiation.
• A Passive Infrared sensor is an electronic sensor that measures infrared
light radiating from objects. Term “passive” means that sensor is not using
any energy for detecting purposes, it just works by detecting the energy
given off by the other objects.
• PIR sensors are mostly used in PIR-based motion detectors. Also, it used
in security alarms and automatic lighting applications.
• The most widely used infrared detector is a pyroelectric detector.
• It uses as a sensor for converting human infrared radiation into electrical
signal. The detector itself does not emit any energy but passively receives
it.Pyro electric detectors are thermal detectors: Temperature fluctuations
produce a charge change on the surface of pyroelectric crystals, which
produces a corresponding electrical signal.

2. PIR SENSOR

4. • How does a PIR sensor work?
• All objects, including the human body, at temperatures above
absolute zero emit heat energy in the form of infrared
radiation. The hotter an object is, the more radiation it emits.
This radiation is not visible to the human eye because it is
emitted at infrared wavelengths. The PIR sensor is specifically
designed to detect such levels of infrared radiation.
• A PIR sensor consists of two main parts:
• A pyroelectric sensor, which you can see in the image below
as a round metal with a rectangular crystal in the center.
• A special lens called a fresnel lens which Focuses the infrared
signals on the pyroelectric sensor.

6. The Pyroelectric Sensor
• A pyroelectric sensor consists of a window with two
rectangular slots and is made of a material (typically
coated silicon) that allows infrared radiation to pass
through. Behind the window, there are two separate
infrared sensor electrodes, one responsible for
producing the positive output and the other for
producing the negative output.
• The two electrodes are wired such that they cancel
each other out. This is because we are looking for
changes in IR levels and not ambient IR levels. That’s
why when one half sees more or less IR radiation than
the other, we get the output.

7. Working
• When ever it detects change in infrared radiation it produces
digital output signal.
• When there is no movement around the sensor, both slots
detect the same amount of infrared radiation, resulting in a
zero output signal.
• But when a warm body like a human or an animal passes by, it
first intercepts half of the sensor. This causes a positive
differential change between the two halves.
• When the warm body intercepts the other half of the sensor
(leaves the sensing region), the opposite happens, and the
sensor produces a negative differential change.
• By reading this change in voltage, motion is detected.

10. PIR in Lighting application
• When Unoccupied
• When a space is unoccupied, the
pyroelectric sensor does not detect any change in
temperature and would remain idle.
• When Occupied
• When the human or animal body gets into the
sensors range, the infrared signal difference
between these two pyroelectric sensors will
trigger the lights to turn on.

13. Technical specification

16. Applications of PIR Sensor
• PIR sensors are used in thermal sensing
applications, such as security and motion
detection. They are commonly used in security
alarms, motion detection alarms, and
automatic lighting applications.

17. Ultrasonic sensor
• An ultrasonic sensor is an electronic device that measures the
distance of a target object by emitting ultrasonic sound waves,
and converts the reflected sound into an electrical signal.
Ultrasonic waves travel faster than the speed of audible sound
(i.e. the sound that humans can hear).
• Ultrasonic sensors have two main components: the transmitter
(which emits the sound using piezoelectric crystals) and the
receiver (which encounters the sound after it has travelled to
and from the target).

18. How the HC-SR04 Ultrasonic Distance
Sensor Works?
• It emits an ultrasound at 40 000 Hz which travels through the air and if
there is an object or obstacle on its path. It will bounce back to the
module. Considering the travel time and the speed of the sound you can
calculate the distance.
• In order to generate the ultrasound we need to set the Trig pin on a High
State for 10 µs. That will send out an 8 cycle ultrasonic burst which will
travel at the speed of sound. The Echo pins goes high right away after that
8 cycle ultrasonic burst is sent, and it starts listening or waiting for that
wave to be reflected from an object.

19. • It all starts when the trigger pin
is set HIGH for 10µs. In
response, the sensor transmits
an ultrasonic burst of eight
pulses at 40 kHz. This 8-pulse
pattern is specially designed so
that the receiver can
distinguish the transmitted
pulses from ambient ultrasonic
noise.
• These eight ultrasonic pulses
travel through the air away
from the transmitter.
Meanwhile the echo pin goes
HIGH to initiate the echo-back
signal.
• If those pulses are not
reflected back, the echo signal
times out and goes low after
38ms (38 milliseconds). Thus a
pulse of 38ms indicates no
obstruction within the range
of the sensor.
• IF OBJECT(obstruction) IS
NOT PRESENT

20. • If those pulses are reflected
back, the echo pin goes low
as soon as the signal is
received. This generates a
pulse on the echo pin
whose width varies from
150 µs to 25 ms depending
on the time taken to receive
the signal.
• IF OBJECT(obstruction)
IS PRESENT

21. • Let us take an example to make it more clear. Suppose we have an object
in front of the sensor at an unknown distance and we receive a pulse of
500µs width on the echo pin. Now let’s calculate how far the object is
from the sensor. For this we will use the below equation.
• Distance = Speed x Time
• Here we have the value of time i.e. 500 µs and we know the speed. Of
course it’s the speed of sound! It is 340 m/s. To calculate the distance we
need to convert the speed of sound into cm/µs. It is 0.034 cm/μs. With
that information we can now calculate the distance!
• Distance = 0.034 cm/µs x 500 µs
• But we’re not done yet! Remember that the echo pulse indicates the time
it takes for the signal to be sent and reflected back. So to get the distance,
you have to divide your result by two.
• Distance = (0.034 cm/µs x 500 µs) / 2
• Distance = 8.5 cm
• Now we know that the object is 8.5 cm away from the sensor.

23. Distance=(speed of sound x time)/2

24. Ultrasonic Sensor HC SR 04

25. HC-SR04 Hardware Overview
• An HC-SR04 ultrasonic distance sensor actually consists of
two ultrasonic transducers.
• One acts as a transmitter that converts the electrical signal into 40
KHz ultrasonic sound pulses. The other acts as a receiver and
listens for the transmitted pulses.
• When the receiver receives these pulses, it produces an output
pulse whose width is proportional to the distance of the object in
front.
• This sensor provides excellent non-contact range detection between
2 cm to 400 cm (~13 feet) with an accuracy of 3 mm.

28. Applications
• They can be found in automobile self-parking technology and anti-
collision safety systems. Ultrasonic sensors are also used in robotic
obstacle detection systems, as well as manufacturing technology.
• They are used within food and beverage to measure liquid level
in bottles,
• Ultrasonic sensors are also used in robotic obstacle detection
systems,

29. OBSTACLE DETECTION

30. Water level detection

31. SENSOR AND ACTUATOR
• A sensor transforms interesting, useful energy into
electrical data. By contrast, an actuator transforms
electrical data into interesting, useful energy. Our
smartphones are full of transducers — the camera
and microphone are sensors whereas the speakers
and screen are actuators.

32. Sensor:
• Sensor is a device used for the conversion of physical
events or characteristics into the electrical signals.
• This is a hardware device that takes the input from
environment and gives to the system by converting
it.For example, a thermometer takes the
temperature as physical characteristic and then
converts it into electrical signals for the system.
• Sensors pick physical gestures from their
environment and convert them into electrical signals-
while actuators pick the system's electrical signals to
convert them into physical gestures (heat, sound,
electricity, etc.).

34. Actuator:
• Actuator is a device that converts the electrical
signals into the physical events or characteristics.
• It takes the input from the system and gives output
to the environment.
For example, motors and heaters are some of the
commonly used actuators.