Air Puff Controlled LED Circuit is fun and easy project to make.
We we blow air the LED turns OFF.
It is used in no-touch controls, fun devices and displays.
Main part is electret mic which hears our puff.
Mic triggers transistor and transistor turns OFF the LED.
It works with small power like 3V battery.
Circuit Working:
Parts List:
| Component | Value/Type | 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 |
Electret mic in circuit hears soft sounds like light breath.
Signal goes through capacitor C1 and then is boosted by transistor Q1 BC547.
Boosted signal passes to diode D1 and is stored in capacitor C2.
C2 voltage makes transistor Q2 BC547 work which turns on Q3 BC557 transistor.
Q3 turns OFF the LED1 by cutting power.
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
This keeps LED safe and working right.
How to Build:
To build a Air Puff Controlled LED Circuit follow the below mentioned steps:
- Take resistor R1 and mic and connect in series from +3V to GND.
- Capacitor C1 positive side goes between R1 and mic.
- Negative side goes to base of transistor Q1.
- Q1 collector goes to +3V through resistor R3.
- Q1 emitter goes to GND.
- Resistor R2 one end goes between base of Q1 and cathode of C1.
- Other end goes to collector of Q1 same point with R3.
- Diode D1 goes between collector of Q1 and emitter of Q2.
- Capacitor C2 is parallel with diode D1.
- Q2 collector connects to base of Q3 and also to +3V through capacitor C3.
- Q2 emitter goes to one end of R4
- Other end of R4 goes to GND.
- 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.
- Q3 collector connects to one side of switch S1 and anode of LED1.
- S1 one end connects to +3V and other end goes to anode of LED1.
- Cathode of LED1 goes to one end of R6 and other end of R6 to GND.
- Connect 3V battery positive to positive supply and negative to GND.
Conclusion:
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.
It is good for beginners where we can change it to make sound devices too.
The above steps help choose right parts so the circuit works well.