LCD-LED Display

Puff to OFF LED Circuit

This article will guide you through the process of constructing an electronic circuit capable of activating and deactivating a burst of air. Candles have been a part of various celebrations, decorations, and specific occasions for centuries. In today’s world, electronics play a pivotal role in enhancing the visual appeal of candles. We previously introduced a straightforward circuit that extinguishes an LED with a gentle puff of air.


  • Puff to Off LED Circuit Working Principle:
  • Puff to Off LED Circuit Diagram:
    • Puff to Off LED Circuit Description:
    • Puff to Off LEDs Circuit Simulation Video:
    • Puff to Off LED Circuit Working:
    • Puff to OFF LEDs Project Output Video:
    • Puff to Off LED Circuit Applications:

Puff to Off LED Circuit Working Principle:

The circuit’s fundamental premise is to use a puff to turn off the LED. The puff delivered to the microphone is turned into a very low voltage. To turn off the led, this voltage is amplified and applied to the circuit.

Puff to Off LED Circuit Diagram:

Puff to OFF LED

Puff to Off LEDs Circuit Diagram

Circuit Components:

  • Electret condenser mic
  • Light Emitting Diode
  • BC 550 (NPN )transistor
  • BC 337 (NPN )transistor
  • BC 327 (PNP )transistor

Puff to Off LED Circuit Description:

Mic, LED, transistors, resistors, and capacitors are the key components of the suggested circuit.

An electret condenser microphone (MIC) is utilized to detect the puff of air. This type of condenser microphone converts acoustic signals into electrical signals and is highly sensitive to sound. It functions as a transducer by converting the analog signal into an electrical one. The electret microphone operates on the principle of electrostatic induction, with its positive terminal connected to capacitor C1 and the negative terminal linked to ground. The MIC is connected to the transistor through capacitor C1, which serves as a high-pass filter to prevent unwanted device shutdown.

The circuit incorporates a red LED with a cutoff voltage of 1.7 volts. Unlike regular LEDs that dissipate energy as heat, light-emitting diodes (LEDs) emit energy in the form of light. LEDs can handle voltages up to 3 volts, and exceeding this value can damage them. The LED’s positive terminal is connected to the latching pair and a push button, while the negative terminal is linked to ground through a 100-ohm resistor.

Both PNP and NPN transistors are utilized in the circuit. The BC550 transistor is an NPN transistor that starts in an open-circuit state and conducts from emitter to collector only when the base reaches its cutoff voltage. These transistors amplify the incoming signal from the MIC, which is then received by the latching pair. The BC327 transistor is a PNP transistor that conducts between its emitter and collector when no voltage is applied to them. Applying a cutoff voltage to the base causes the emitter and collector to cease conducting. The BC337 transistor’s collector is connected to the base of the PNP BC337 transistor, and these two transistors work together as a latching pair responsible for turning off the LED. A 4.7kohm resistor connects the emitter of the BC337 transistor to ground, while a 10kohm resistor connects the base to ground.

To couple the output of transistor Q1 with the latching pair, a signal diode is connected in parallel with a 10uF capacitor C2. The diode and C2 shape the positive pulse that resets the latching pair. A 1Mohm resistor connects from capacitor C1 to the signal diode.

Puff to Off LEDs Circuit Simulation Video:

Puff to Off LED Circuit Working:

  • To begin, connect the components as shown in the circuit diagram.
  • As indicated, connect a 5v battery.
  • S1 (push button) is now pressed.
  • The latching pair of transistors Q2 and Q3 is activated.
  • As a result, the LED begins to shine.
  • The analogue sound signal is transformed into a voltage signal at the MIC’s output when you puff on it.
  • The transistor Q1 amplifies this voltage.
  • The latching pair receives the enhanced signal.
  • As a result, the transistor’s base receives the requisite voltage, and the PNP transistor ceases to conduct.
  • As a result, the LED stops glowing.
  • To switch it back on, press the push button once more.

Puff to OFF LEDs Project Output Video:

Puff to Off LED Circuit Applications:

  • It’s possible to use this as a candle.
  • The circuit can be used to decorate a church or for special occasions. Get a sense of how the LED Christmas Lights Circuit works.
  • This circuit is used in stained glass lights and lanterns.
  • This can be used in a variety of arts and crafts projects.
  • This circuit is used in model railroading accessories.
  • This can be used in frightening lighting and haunted dwellings.
  • This can be utilised in car novelty items.

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