This is a simple and useful electronic mini project for the beginners. In this project, we are going to detect the flow of air present or not. Air flow detector circuit is used for the detection of the flow of air. This circuit can be used for the visual indication of the rate of air flow. This circuit can also be used for detecting the presence of air flow in the given space or not.
In this mini project about detecting the rate of air flow, we will require following components:
- IC 7805
- Capacitor: 47uF (15V)
- Resistors: R1 = 100 Ohm, R2 = 470 Ohm, R3 = 10K, R4 = 100K, R5 = 1K
- 12V DC power supply
- OP-AMP LM339
- The filament of an incandescent bulb as a sensing element. (See this video for extracting filament from bulb: https://www.youtube.com/watch?v=X5E1n0uLepM)
As mentioned earlier, we are going to detect the rate of air flow with help of visual indication using LED. In this project, we are using filament of an incandescent bulb as a sensing element of our circuit.
When the intensity of the air flow is minimum or if there is no airflow, the resistance of the filament of the incandescent bulb will be low. Similarly, when the air flow is maximum the resistance of the filament will be high. This is because filament of incandescent bulb has a negative temperature of a coefficient. That is when the temperature of the filament increases the resistance decreases and vice versa.
Now in our case when there is maximum air flow the heat will be decreased due to that air flow and its resistance increases. This difference in resistance will produce a different voltage drop across the filament of an incandescent bulb. This difference in the resistance will be picked up by the opamp (LM339) and it will produce variations in the output. That is the output will be proportional to the airflow.
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