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Contactless doorbell using 555 timer IC

500.00

Availability: In Stock

Circuit Design:

  1. 555 Timer Connections:
    • Connect the VCC pin (pin 8) of the 555 timer to the positive supply voltage (e.g., 9V).
    • Connect the GND pin (pin 1) of the 555 timer to the ground (0V) of the circuit.
  2. Monostable Mode Connections:
    • Connect the trigger input (pin 2) to the output of the ultrasonic sensor.
    • Connect the threshold input (pin 6) to the discharge pin (pin 7).
    • Connect the discharge pin (pin 7) to the capacitor side of a resistor-capacitor series.
  3. Resistor and Capacitor Values:
    • Connect a resistor (e.g., 10kΩ) from the trigger input (pin 2) to the positive supply voltage.
    • Connect a capacitor (e.g., 10μF) from the trigger input (pin 2) to the ground.
    • Connect the other end of the capacitor to the discharge pin (pin 7).
  4. Transistor Driver:
    • Connect the collector of an NPN transistor (e.g., 2N3904) to the output pin (pin 3) of the 555 timer.
    • Connect the emitter of the transistor to the ground (0V).
    • Connect the base of the transistor through a resistor (e.g., 330Ω) to the output pin (pin 3) of the 555 timer.
  5. Buzzer or Speaker:
    • Connect the positive terminal of the buzzer or speaker to the collector of the transistor.
    • Connect the negative terminal of the buzzer or speaker to the ground (0V).
  6. Ultrasonic Sensor:
    • Connect the VCC and GND pins of the ultrasonic sensor to the positive supply voltage and ground, respectively.
    • Connect the trigger and echo pins of the ultrasonic sensor to two digital pins of a microcontroller (if using one) or directly to the trigger input of the 555 timer and the trigger input of the 555 timer.

Working Principle:

  • The ultrasonic sensor detects movement or proximity.
  • When movement is detected, the sensor triggers the 555 timer in monostable mode.
  • The 555 timer produces a pulse, turning on the transistor and activating the buzzer or speaker.
  • The capacitor determines the duration of the alert, which can be adjusted using the resistor and capacitor values.

Product Description

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