This circuit is operated using a 12V battery. The battery voltage is regulated using the Zener diode, which produces a constant voltage. Initially as current flows through the RTD, it gets heated up and its temperature increases, thereby increasing its resistance. Now as current is constant, the voltage across the resistance also tends to increase. When this voltage is applied to the trigger pin of the timer, it fails to trigger the timer and the LED is in off condition. Now as air flows over the RTD, it starts cooling. This reduces the temperature of the device. As the temperature reduces, the resistance also reduces and so does the voltage across the device. As this voltage reduces below a certain point, the timer gets triggered and the LED starts blinking. As voltage falls further, indicating fall of temperature, the LED starts glowing with full intensity. This indicates the flow the air.

1. .
KARNATAK LAW SOCIETY’S
GOGTE INSTITUTE OF TECHNOLOGY
UDYAMBAG, BELAGAVI-590008
(An Autonomous Institution under Visvesvaraya Technological University, Belagavi)
(APPROVED BY AICTE, NEW DELHI)
Course Activity Report
on
“Air detector”
Submitted in the partial fulfillment for the academic requirement of
3rd Semester B.E.
in
Computer Science Engineering
Submitted by
Durgesh Pandey (2GI19CS040)
Abhi Gawade (2GI19CS043)
Harsh Mahindrakar (2GI19CS048)
Hussain Malik Rehan (2GI19CS051)
Under the guidance of
Prof. Vidya Kulkarni
2020 – 2021

2. TeamMembers Details:
S. No. USN Student Name
1 2GI19CS040 Durgesh Pandey
2 2GI19CS043 Abhijeet Gawade
3 2GI9CS048 Harsh Mahindra kar
4 2GI19CS51 Hussain Malik Rehan
Marks Allocation:
Batch No.: 8
1. Seminar Title: Marks
Range
USN
2GI19CS040 2GI19CS043 2GI19CS048 2GI19CS051
2. Abstract (PO2) 0-2
3. Application of the topic to
the course (PO2)
0-3
4. Literature survey and its
findings (PO2)
0-4
5. Methodology, Results and
Conclusion
(PO1, PO3, PO4)
0-6
6. Report and Oral
presentation skill (PO9,
PO10)
0-5
Total 20
Signature of Staff

3. INTRODUCTION :
Explicit airflow detection is essential in many applications. High power-
density electronics are liable to overheat and self- destruct when cooling
fan failures go unnoticed. Clean-room air-handling systems with
undetected dirty, blocked air filters can ruin process yield. Laboratory
fume hoods can contain volatile solvents or toxic reagents, making
adequate air turn-over critical to safety.
In these and similar scenarios, the consequences of undetected airflow
interruption can range from the merely expensive to the frankly
dangerous. Therefore, it becomes necessary to use some reliable means
for airflow detection. This is a design for detecting air flow. It can be also
used to check whether there is air flow in a given space.
Air flow detection is often necessary in many applications or systems
where it is necessary to detect the presence of air to have a descriptive
picture of the proper functioning of the systems. For example, we need air
flow detection in engines to get an estimate about the amount of fuel to be
added to the engine, we need air flow detection to check the amount of
contamination or the transfer of contamination using chemical media like
air. For high power density electronic devices, we need air flow detection
to ensure the devices from getting over heated.

4. THEORY :
Voltage Regulator using Zener Diode:
Zener diode is a simple PN junction diode operated in reverse bias condition. It
basically works on the principle of breakdown – Avalanche and Zener. Zener
breakdown occurs at a reverse bias voltage between 2V to 8V, when highly strong
electric field intensity causes the electrons to break free from the atoms and form
free electron hole pairs. The avalanche breakdown occurs above 8V, when high
speed charge carriers cause disrupt of covalent bond due to collision, leading to
formation of free electrons.
As can be seen by the characteristics, for a large variation in current through the
diode, the voltage across the diode remains very small or constant. This unique
feature is utilized in many applications byusing Zener diodeas the voltage regulator.
Resistance Temperature Detector:
A resistance temperature detector or RTD is a metal resistor whose resistance
changes with temperature. It is based on the fact that in metals, as temperature
increases, the lattice vibrations increases. These vibrations cause collision among
the electrons. As collisions increase, the energy of the electrons decrease, causing a
decrease in the flow of free electrons, leading to low conductivity. Thus, with
increase in temperature, the resistance increases. An RTD is constructed basically
using platinum. At 0 degree Celsius, resistance of an RTD is about 100 Ohms.

5. 555 Timer Multivibrator:
Multivibrator circuit is used to produce pulsed output signal. It is triggered when a
low level signal is applied to the trigger pin of the IC. The 555 timer IC is an 8 pin
IC and the timing of the output signal is given by T=1.1 RC. To get detailed
information about 555 timer IC.
COMPONENTS :
 CIRCUIT V1 = 12 V
 R1 = 38 Ohms
 D1= 4.7 V Zener diode, 1N4732
 R2 = 100 Ohms
 Rx = HEL-700 platinum RTD
 R3 = 10K
 C2 = 1uF
 C1= 0.01 uF
 LED = 5V, Green LED
 IC = 555 Timer

6. CIRCUIT DIAGRAM :
EXPLANATION :
This circuit is operated using a 12V battery. The battery voltage is regulated
using the Zener diode, which produces a constant voltage. Initially as current flows
through the RTD, it gets heated up and its temperature increases, thereby increasing
its resistance. Now as current is constant, the voltage across theresistance also tends
to increase. When this voltage is applied to the trigger pin of the timer, it fails to
trigger the timer and the LED is in off condition. Now as air flows over the RTD, it
starts cooling. This reduces the temperature of the device. As the temperature
reduces, the resistance also reduces and so does the voltage across the device. As
this voltage reduces below a certain point, the timer gets triggered and the LED starts
blinking. As voltage falls further, indicating fall of temperature, the LED starts
glowing with full intensity. This indicates the flow the air.

7. PIN DIAGRAM :

8. Applications of Air Flow Detector Circuit:
 This circuit can beused to detectthe flow ofair in areas like carengine, where
it is required to estimate the amount of fuel needed by the engine.
 Apart from being used as an air flow detector, this circuit can also find its
application as a temperature detector circuit.
 With slight modifications, this circuit can be used to control loads like a fan,
based on temperature sensing.
Limitations of Air Flow Detector Circuit:
1. Since Zener diode is being used, the efficiency of the circuit is affected.
This is because loss in series resistor causes a decline in efficiency in
case of heavy loads.
2. The resistance temperature detector used is expensive and easily
affected by shockand vibration.
CONCLUSION :
Thus, the circuit can give a visual indication of the rate of air flow.
It can be also used to check whether there is air flow in a given space.
The filament of an incandescent bulb is the sensing part of the circuit.
When there is no air flow the resistance of the filament will be high
Thus the air flow is been detected and as an output the
LED indicates.

9. REFERENCE
 http://www.wikipedia.org/ WIKIPEDIA.
 http://electronicsforu.com.asp ELECTRONIC FOR YOU.
 http://www.circuit-projects.com/ CIRCUIT PROJECT.
 http://www.aaroncake.net AARON CAKE.
 http://electroschematics.com/ ELECCTRON SCHEMATICS.