AUTOMATIC AIRFLOW DETECTOR ELECTRONIC DIAGRAM Sensor used in this circuit is a bulb filament. If there is no airflow, the filament resistance would give low value. On the other hand, if there is airflow, the filament resistance would varies. The variation of the resistance is caused by the heat difference between filament. It also effects to the voltage variation passing through that filament. That voltage difference will be processed by LM339 op-amp and displayed by the LED. Parts list : LED1 : LED 5mm IC1 volt regulator : LM7805 Polar Capacitor C1 : 47 uF/15V Resistor R1 : 100 ohm Resistor R2 : 470 ohm Resistor R3 : 10k ohm Potensiometer R4 : 100k ohm Resistor R5 : 1k ohm IC2 op-amp : LM339 Bulb filament Power supply/battery 12V