The Air Puff Controlled LED Circuit is a fun and easy project to build and when we blow air onto the microphone, the circuit turns the LED OFF.
This circuit is useful for no-touch controls, interactive devices, demonstration projects, and display applications.
Main part is electret mic which hears our puff and then mic triggers transistor and transistor turns OFF the LED.
Furthermore, the circuit works with small power like 3V battery.
Circuit Working:
Parts List:
| Components | Values | Quantity |
|---|---|---|
| Resistors (All resistors are 1/4 watt unless specified) | 1M | 1 |
| 1k | 1 | |
| 4.7k | 1 | |
| 100Ω | 1 | |
| 10k | 2 | |
| Capacitors | Ceramic 100nF | 1 |
| Electrolytic 10µF 25V | 1 | |
| Electrolytic 1µF 25V | 1 | |
| Semiconductors | Transistors NPN BC547 | 2 |
| Transistor PNP BC557 | 1 | |
| Electret Microphone | 1 | |
| Diode 1N4148 | 1 | |
| LED Any color 5mm 20mA | 1 | |
| Push Button Switch | 1 | |
| Battery 3V | 1 |
The electret microphone detects soft sounds, such as a light breath and generates a small AC signal, then capacitor C1 passes the signal to transistor Q1 BC547, which amplifies it.
The amplified signal then passes through diode D1, which charges capacitor C2 and as the voltage across C2 rises, it drives transistor Q2 BC547, which in turn switches on transistor Q3 BC557.
After that, Q3 turns OFF the LED1 by cutting power and hence, to turn LED ON again, then press push button S1.
Formulas with Calculations:
To make the Simple Air Puff LED Circuit use these formulas for better understanding:
1. Microphone Bias Voltage:
V_bias = (Vcc × R1) / (R1 + R2)
where,
Vcc = 3V, R1 = 10k, R2 = 1M
V_bias = (3 × 10k) / (10k + 1M)
V_bias = 0.03V
2. Time Constant for pulse length:
τ = R × C
where,
R4 = 4.7k, C2 = 10µF
τ = 4.7k × 10µF = 47ms
3. LED Current:
I_LED = (Vcc – V_LED) / R6
where,
Vcc = 3V, V_LED = 2V, R6 = 100Ω
I_LED = (3 – 2) / 100 = 10mA
Therefore, this keeps LED safe and working right.
How to Build:
To build a Air Puff Controlled LED Circuit follow the below mentioned steps:
- First, take resistor R1 and mic and connect in series from +3V to GND and then capacitor C1 positive side goes between R1 and mic and negative side goes to base of transistor Q1.
- Then Q1 collector goes to +3V through resistor R3 and Q1 emitter goes to GND.
- After that, resistor R2 one end goes between base of Q1 and cathode of C1 and other end goes to collector of Q1 same point with R3.
- Now diode D1 goes between collector of Q1 and emitter of Q2 and capacitor C2 is parallel with diode D1.
- Next, Q2 collector connects to base of Q3 and also to +3V through capacitor C3, Q2 emitter goes to one end of R and other end of R4 goes to GND.
- Further, Q2 base connects to collector of Q3 and one side of resistor R5, other end of R5 goes to GND with R4, Q3 emitter connects to +3V and then Q3 collector connects to one side of switch S1 and anode of LED1.
- Also, S1 one end connects to +3V and other end goes to anode of LED1 and cathode of LED1 goes to one end of R6 and other end of R6 to GND.
- Finally, connect 3V battery positive to positive supply and negative to GND.
Conclusion:
To conclude, this Air Puff Controlled LED Circuit lets us control things without hands and with just blow air, it uses simple parts like mic and transistor.
Moreover, the circuit is good for beginners where we can change it to make sound devices too and also the above steps help choose right parts so the circuit works well.