MINI PROJECTAIR FLOW DETECTOR

NAME REG NO.:-RUKMI SARMAH 12-1-4-010G.LAVANYA SWETHA 12-1-4-019P.JUHITHA 12-1-4-001

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-roomair-handling systems with undetected dirty, blockedair 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

BASIC IDEA

• This 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 a incandescent bulb is the sensing part of the circuit.

• A constant current source is used to slightly heat the filament. The heated filament has a high resistance. (H=(I^2) (RT))

HOW IT WORKS When there is no air flow

the resistance of the filament will be high.

When there is air flow the resistance drops , because the moving air will remove some of the heat generated in the filament.

We know that heat generated is directly proportional to resistance.

• So, with the flow of air, resistance across the filament varies.

• This variations in the resistance will produce variation of voltage across the filament (OHM’S LAW).

• These variations will be picked up by the opamp (LM339) and the brightness of the LED at its output will be varied proportionally to the airflow.

Circuit diagram

Component required:-S NO. TOTAL QTY DISCRIPTIONR1 1 100 Ohm 1/4W Resistor

R2 1 470 Ohm 1/4W Resistor

R3 1 10k 1/4W Resistor

R4 1 100K 1/4W Resistor

R5 1 1K 1/4W Resistor

C1 1 47uF Electrolytic Capacitor

IC1 1 7805 IC

IC2 1 LM339 IC

L1 1 filament

D1 1 LEDMISC1Board, Wire, Sockets for ICs, etc.

• The filament L1 can be made by removing the glass of a 40W incandescent bulb.

• Caution,We do not touch the filaments of incandescent lamps by hand.• The circuit can be powered from a 12 V DC

power supply.• In case the filament is not available, we can use

different resistances to denote the change in resistance across the filament.

GETTING FILAMENT FROM A BULB

• The glass will have to be removed from L1 without breaking the filament. We wrap the glass in masking tape. We slowly crank down until the glass breaks, then remove the bulb and carefully peel back the tape. If the filament has broken, we need another lamp.

IC 7805

7805 is a voltage regulator integrated circuit. It is a member of 78xx series of fixed linear voltage regulator ICs. The voltage source in a circuit may have fluctuations and would not give the fixed voltage output. The voltage regulator IC maintains the output voltage at a constant value. The xx in 78xx indicates the fixed output voltage it is designed to provide. 7805 provides +5V regulated power supply. Capacitors of suitable values can be connected at input and output pins depending upon the respective voltage levels.

PIN DIAGRAM OF IC 7805

IC LM339

LM339 is a comparator IC with four inbuilt comparators. A comparator is a simple circuit that moves signals between the analog and digital worlds. It compares two input voltage levels and gives digital output to indicate the larger one. The two input pins are termed as inverting (V-) and non-inverting (V+). The output pin goes high when voltage at V+ is greater than that at V-, and vice versa. In common applications, one of the pins is provided with a reference voltage and the other one receives analog input from a sensor or any external device. If inverting pin (V-) is set as reference, then V+ must exceed this reference to result in high output. For inverted logic, the reference is set at V+ pin.

PIN DIAGRAM OF LM339

• So as we vary the resistances, the brightness of LED varies.

• When the resistance is high, i.e there is no air flow, the LED doesn’t glow.

• When resistance is low i.e when air flow is there the LED glows

• As we don’t get low resistance in the laboratory, we use a short circuit with a wire to denote low resistance.

Live circuit

INDUSTRIAL APPLICATION:-

• Industrial gas flow measurement

• Detection of air leakage in pressurized air systems

• Air intake of combustion engines

MORE APPLICATIONS IN MEDICAL SCIENCE

• Spirometers : A spirometer is an apparatus for measuring the volume of air inspired and expired by the lungs. A spirometer measures ventilation, the movement of air into and out of the lungs.

FUTURE SCOPE

• Wind energy farms• Vacuum detector

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.

REFERENCES

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.