Capacitance operated alarm to foil purse snatchers
The described circuit functions as a simple touch-sensitive alarm system. It consists of two primary touch plates (1) that, when pressed together, create a closed circuit, thereby preventing the alarm from sounding. The alarm system is designed to remain inactive as long as the plates are in contact. However, should the user release the plates for a duration exceeding 30 seconds, the circuit will trigger the alarm, activating a battery-operated bicycle horn.
To enhance functionality, the circuit includes a switch that allows for manual disabling of the alarm system. This feature provides flexibility for the user, enabling them to deactivate the alarm without needing to maintain contact between the touch plates (2). The choice of a bicycle horn as the alarm sound source is advantageous due to its loudness and clear audibility, making it suitable for alerting individuals in various environments.
The power supply for this circuit is derived from a battery, ensuring portability and ease of installation. The design can be further optimized by incorporating a resistor-capacitor (RC) timing circuit to ensure a precise 30-second delay before the alarm activates, thereby preventing false alarms from brief interruptions. Additionally, the implementation of LED indicators could provide visual feedback regarding the status of the alarm system, indicating whether it is active, inactive, or in the process of timing out.
Overall, this circuit offers a straightforward yet effective solution for a touch-sensitive alarm system, suitable for various applications where security and alertness are paramount.As long as touch plates (1) are touched together, the alarm is off. If not held for about 30 seconds, the alarm goes off. The circuit can be disabled with switch or by touching the plates (2) The alarm is battery operated by a bicycle horn. 🔗 External reference
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