Panic Alarm Circuit

This alarm system utilizes a loud police siren to deter potential intruders. Activated by a single clap, the circuit triggers the alarm for three minutes, which is adequate to alert nearby residents. The design incorporates a sensitive clap switch with a timer function. The integrated circuit IC1 acts as a sensitive inverting amplifier, amplifying sound signals received from a condenser microphone. A variable resistor, VR1, adjusts the microphone's sensitivity, while resistors R1 and VR2 set the amplifier's gain. When properly calibrated, the circuit can detect sounds from a distance of five meters or more. Upon detecting a clap, the microphone transmits AC signals that pass through capacitor C1, allowing IC1 to amplify the signal, which subsequently activates transistor T1. When T1 conducts, it grounds the trigger pin of the monostable timer IC2, initiating the timer. With the specified values of resistors R5 and capacitor C2, the output of IC2 remains high for three minutes, supplying power to the ROM IC UM3561, which generates the police siren sound due to its pin 6 being unconnected. Resistor R8 controls the frequency of oscillation for IC3, and the siren signals are amplified by transistor T2, allowing the alarm tone to be emitted through a speaker. A zener diode ZD provides a regulated supply of 3.1 volts to IC3.

The alarm circuit is designed for simplicity and effectiveness in sound detection and response. The use of a condenser microphone ensures high sensitivity to sound, making it capable of detecting claps from a significant distance. The inverting amplifier configuration of IC1 enhances the sound signals, allowing for reliable activation of the alarm system. The variable resistors enable fine-tuning of the system's sensitivity and gain, ensuring optimal performance in various environments.

The monostable timer IC2 is crucial for determining the duration of the alarm. By selecting appropriate resistor and capacitor values, the circuit can maintain a high output for a specified time, in this case, three minutes. This feature is essential for providing a sufficient alert period to notify neighbors without causing undue disturbance.

The integration of the UM3561 ROM IC allows for the generation of a realistic police siren sound, which is effective in deterring intruders. The unconnected pin 6 of the IC ensures that the siren sound is produced continuously while the circuit is powered. The amplification stage provided by T2 ensures that the alarm tone is audible over a considerable distance.

The zener diode ZD plays a vital role in maintaining a stable voltage supply to the oscillating circuit, ensuring reliable operation of the siren generator. Overall, this alarm circuit is a practical solution for enhancing security through sound-based deterrence, combining sensitivity, reliability, and effectiveness in a compact design.This Alarm will help you with its loud Police siren to abort the attempt of intrusion. With a single clap, the circuit generates the alarm for three minutes and then goes off. This is sufficient to catch the attention of neighbours. The circuit is a sensitive Clap switch with timer action. IC1 is designed as a sensitive inverting amplifier to amplify the sound signals from the condenser mic. Variable resistor VR1 set the sensitivity of mic and resistor R1 and VR2 set the gain of the amplifier. If the sensitivity of mic and amplifier is suitably adjusted, the circuit can detect the sound from a distance of 5meters or more.

When the mic detects clap sound, the ac signals pass through C1and IC1 amplifies the signal. This triggers T1. When T1 conducts, the trigger pin of the Monostable Timer IC2 will be grounded and the timer triggers. With the given values of R5 and C2, output of IC2 remains high for three minutes. This high output provides power to the ROM IC UM3561. It generates the Police Siren since its pin6 remains unconnected. Resistor R8 determines the frequency of oscillation of IC3. The siren signals are amplified by T2 and the alarm tone can be heard through the speaker. Zener diode ZD gives 3. 1 volt regulated supply to IC3. 🔗 External reference