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.
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.
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).
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.
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).
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.
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