Simple Air Puff Controlled LED Circuit

The “Simple Air Puff Controlled LED Circuit” is a cool and easy electronic project that lets you turn off an LED just by blowing air at it.

This neat feature can be used in different areas like touchless controls, fun gadgets and interactive displays.

The main part of this circuit is a electret microphone which can hear the sound made by your puff of air.

When it picks up that sound it triggers a transistor that switches off the LED.

Also this circuit runs on a small power source like a 3V battery.

Circuit Working:

Parts List:

In the above circuit diagram electret microphone is really good at picking up soft sounds like a gentle breath.

When it does this, it creates a small alternating current AC signal.

This signal travels through a capacitor C1 and then it gets boosted by a transistor Q1 BC547.

After the signal is amplified it goes through a diode D1 and then it gets stored in another capacitor C2.

The voltage that builds up in C2 makes another transistor Q2 BC547 work, which then turns on Q3 a BC557 transistor.

When Q3 is activated it switches off LED1 cutting off its power.

To turn the LED back on there is a push button switch S1 included in the setup.

Formulas with Calculations:

To design a Simple Air Puff Controlled LED Circuit you should use the following formulas with calculations for better understanding:

Microphone Biasing Voltage Calculation:

The bias voltage for the microphone is determined using the voltage divider formula:

V_bias = (Vcc × R1) / (R1 + R2)

where,

Vcc = 3V
R1 = 10k
R2 = 1M

V_bias = (3V × 10k) / (10k + 1M)
V_bias = 0.03V

Capacitor Time Constant Calculation:

The time constant (τ) of the circuit, which affects the pulse duration is given by:

τ = R × C

where,

R4 = 4.7k
C2 = 10µF

τ = 4.7k × 10µF
τ = 47ms

LED Current Calculation:

The LED current can be calculated using ohms law:

I_LED = (Vcc – V_LED) / R6

where,

Vcc = 3V
V_LED = 2V for a LED1
R6 = 100Ω

I_LED = (3V – 2V) / 100Ω
I_LED = 10mA

This ensures safe operation of the LED

How to Build:

To build a Simple Air Puff Controlled LED Circuit follow the below mentioned steps:

• Gather all the components as mentioned in the above circuit diagram:
• Connect resistor R1 and electret MIC in series from positive supply to GND.
• Connect base of transistor Q1 to negative of capacitor C1 and positive of C1 connect between resistor R1 and electret mic
• Connect collector of transistor Q1 to positive supply through resistor R3.
• Connect emitter of transistor Q1 to GND.
• Connect one end of resistor R2 between base of transistor Q1 and cathode of capacitor C1 and other end to collector of Q1 and resistor R3.
• Connect diode D1 between the collector of Q1 and emitter of Q2.
• Connect capacitor C2 parallel to diode D1
• Connect collector of transistor Q2 to base of transistor Q3 and to positive supply through capacitor C3.
• Connect emitter of transistor Q2 to one end of resistor R4 and other end of R4 connect to GND.
• Connect base of transistor Q2 to collector of Q3 and one end of resistor R5 and other end of R4 resistor connect to GND.
• Connect emitter of transistor Q3 to positive supply,
• Connect collector of transistor Q3 between one end of S1 switch and anode of LED1.
• Connect S1 switch one end from positive supply and other end to anode of LED1 and other end of LED1 to one end of resistor R6 and other end of R6 to GND.
• Connect the positive supply of the circuit to 3V battery and connect the negative of 3V battery to GND.

Conclusion:

This “Simple Air Puff Controlled LED Circuit” circuit lets you control things without using your hands, thanks to a basic design that uses a transistor.

It is a great project for people just starting out in electronics and you can change it up for different uses like making sound activated gadgets.

The math behind it helps pick the best parts for everything to work well.

References:

Sip-and-puff controller’s system design