Simple Air Flow Detection Circuit

A basic electrical circuit that detects the existence or intensity of air flow is known as a simple air flow detection circuit.

These circuits are frequently used to monitor air flow in appliances and DIY projects.

Here, we are constructing a very basic circuit to find the existence of air movement.

Here, we are detecting the presence of air using a basic AC broken filament bulb and a few inexpensive parts.

This is a really intriguing project that requires very few parts, all of which are readily available.

Circuit Working:

Parts List:

This circuit uses a small broken filament bulb as its main tool, acting as a detective for air movement.

The filament is unique in that it reacts to heat in the opposite way to most materials decreasing in resistance to electricity as temperatures rise.

The filament heats up a little when the circuit is turned on and there is no airflow indicating low resistance.

However, the filament cools down when air passes by it like a little air conditioner.

The resistance of the filament increases as it cools.

The circuit can decipher this shift in resistance like a hidden code.

This code is read by an op amp IC1 LM358, a specialized semiconductor and converted into a signal.

Much like a judge in a competition the op amp is configured to compare this signal to a predetermined point.

In the event that the airflow surpasses the predetermined resistance, the op amp functions as a referee and indicates a victory by activating an LED1.

This LED1 indicates that there is airflow by acting as a triumph light.

You may fine tune the circuits sensitivity by altering the amount of airflow required to activate the LED1 using a preset VR1.

A 12V battery powers the circuit itself.

The circuit has a push button and a little fan to replicate airflow for testing purposes.

To watch the LED light up, though you may also blow on the filament yourself.

Formulas:

We may list the essential elements and general formula for designing a basic air flow detecting circuit as follows:

Calculating the Threshold Voltage:

The preset P may be used to establish the threshold voltage Vth at the non inverting input of the LM358.

At the non inverting input, the voltage is as follows if the preset is set to R ohms total resistance:

V_th​ = P / P+R​ * V_cc​

where,

• P is the preset resistance.
• The resistance between the preset and ground is represented by R.
• The supply voltage, for example is Vcc.

Using the listed components, this formula offers a fundamental structure for creating an air flow detecting circuit.

Depending on the demands of a particular application and the surrounding circumstances, adjustments could be required.

How to Build:

To build a Simple Air Flow Detection Circuit you need to follow the below mentioned steps:

• Assemble all the components as shown in above circuit diagram.
• Connect pin 1 of IC1 LM358 to ground through resistor R3 and LED1.
• Connect pin 2 of IC1 LM358 to one end of the broken filament bulb and other end of the bulb to ground.
• Connect pin 3 of IC1 LM358 to first leg of VR1 preset, second leg of preset to positive supply through resistor R4 and third leg of preset to ground.
• Connect pin 4 of IC1 LM358 to ground.
• Connect pin 8 of IC1 LM358 to positive supply.
• Connect input pin of IC2 7805 to positive end of DC fan, and other negative end to ground through push button.
• Connect ground pin of IC2 7805 to pin 2 of IC1 LM358.
• Connect output pin of IC2 7805 through two resistors R1 and R2 to pin 2 of IC1 LM358.
• Connect capacitor C1 from IC2 7805 input supply pin to ground.

Safety Measures:

• Initially, when testing the circuit, use a low voltage power source.
• Keep an eye out for any strange odors or smoke emanating from the circuit, since these might be signs of a failing component.
• Seek advice from someone with circuit construction knowledge if you are not comfortable with electronics.
• By taking these precautions, you may reduce the possibility of mishaps when constructing and testing your air flow detecting circuit.

Conclusion:

This simple air flow detecting circuit creates a visible indicator of airflow by utilizing the temperature sensitivity of a broken filament bulb .

The circuit detects changes in resistance and when airflow is present, it activates an LED.

It is a clever method of detecting air movement with widely available electrical parts.

While constructing and experimenting with this circuit, keep in mind that safety comes first.

References:

Simple Air flow detector circuit

Air flow detector