How does it work?

Airflow detector is circuit that can give a visual indication of the rate of airflow. It can be also used to check whether there is an airflow in a given space or area. In order to operate a filament of an incandescent bulb is used as the sensing part of the airflow detector circuit. If on a given space there is no airflow the resistance of the filament will be low. And when there is an airflow the resistance drops, because of the the movement of the air, it will remove some of the heat generated in the filament. These variations in the resistance will produce variation of voltage across the filament. 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. The filament L1 can be made by removing the glass of a 40W incandescent bulb. The circuit can be powered from a 12 V DC power supply.

During the making of the airflow detector, I encountered some difficulties and problems. One of them is the potentiometer was not connected properly in the circuit. Potentiometer plays an important role in the airflow detector since it will be used to vary how much airflow would be read. So always check the connections of the layout so that there would be no problems such as short circuit or open circuit connection.

SCHEMATIC /LAYOUT/ ACTUAL CIRCUITS