Proa

The NAND gates use CMOS 4011 chip, a low power component that is suitable for this battery-operated circuit. You can see that this chip is supplied by a 5V voltage coming from an LM7805L regulator. You might wonder what the purpose of this regulation is, since the power supply come from a  9V battery and the CMOS gates can handle the voltage of 3-15 Volt. The main purpose of the regulator is to keep a constant voltage source for the reference oscillator frequency stability, since the frequency is affected by the power supply voltage variation as the battery voltage drops in the long time of usage.

This circuit uses parts as follows :

•     U1: CD4011
•     U2: LM389
•     U3: 78L05
•     R1: 2.2k 5%
•     P2: 4.7k lin.
•     R3: 330k 5%
•     R4: 270k 5%
•     R5: 1k 5%
•     C1: 390pF (NPO)
•     C2,C3,C4: 10nF
•     C5: 10uF 16v electrolytic
•     C6,C8: 220 uF 16v electrolytic
•     C7: 100uf 16v electrolytic
•     C9: 100nF ceramic
•     P1: 4.7k log
•     L1: 22cm in diameter with 14 turns AWG 26
•     K1: SPDT toggle switch
•     J1= Headphone jack 1/4 or 1/8 inch
•     Other parts: 9v battery connector, speaker or headphones

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