Air Flow Detectors

Published:2013/7/29 20:18:00 Author:muriel | Keyword: Air Flow Detectors | From:SeekIC

This simple circuit uses an incandescent lamp to detect airflow. With the filament exposed to air, a constant current source is used to slightly heat the filament. As it is heated, the resistance increases. As air flows over the filament it cools down, thus lowering it's resistance. A comparator is used to detect this difference and light an LED. With a few changes, the circuit can be connected to a meter or ADC to provide an estimation on the amount of air flow. Parts:R1 100 Ohm 1/4W ResistorR2 470 Ohm 1/4W ResistorR3 10k 1/4W ResistorR4 100K 1/4W ResistorR5 1K 1/4W ResistorC1 47uF Electrolytic CapacitorU1 78L05 Voltage RegulatorU2 LM339 Op AmpL1 #47 Incandescent lamp with glass removed (See Notes )D1 LEDMISC Board, Wire, Sockets for ICs, etc. Notes:1. The glass will have to be removed from L1 without breaking the filament. Wrap the glass in masking tape and it in a vise. Slowly crank down until the glass breaks, then remove the bulb and carefully peel back the tape. If the filament has broken, you will need another lamp.



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