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This reliable and easy-to-operate electronic security system can be used in banks, factories, commercial establishments, houses, etc. The system comprises a monitoring sys-tem and several sensing zones. Each sensing zone is provided with a closed-loop switch known as sense switch. Sense switches are fixed on the doors of premises under security and connected to the monitoring system. As long as the doors are closed, sense switches are also closed. The monitoring system can be installed at a convenient central place for easy operation. Fig. 1: Monitoring circuit along with the alarm circuit Fig. 1 shows the monitoring circuit only for zone 1 along with the common alarm circuit. For other zones, the monitoring circuit is identical, with only the prefixes of components changing as per zone number. Encircled points A, B, and C of each zone monitoring circuit need to be joined to the corresponding points of the alarm circuit (upper half of Fig. 1). When zone 1 sensing switch S11, zone...

Most thefts happen after midnight hours when people enter the second phase of sleep called ‘paradoxical’ sleep. Here is an energy-saving circuit that causes the thieves to abort the theft attempt by lighting up the possible sites of intrusion (such as kitchen or backyard of your house) at around 1:00 am. It automatically resets in the morning. The circuit is fully automatic and uses a CMOS IC CD 4060 to get the desired time delay. Light-dependent resistor LDR1 controls reset pin 12 of IC1 for its automatic action. During day time, the low resistance of LDR1 makes pin 12 of IC1 ‘high,’ so it doesn’t oscillate. After sunset, the high resistance of LDR1 makes pin 12 of IC1 ‘low’ and it starts oscillating, which is indicated by the fashing of LED2 connected to pin 7 of IC1. The values of oscillator components (resistors R1 and R2 and capacitor C4) are chosen such that output pin 3 of IC1 goes ‘high’ after seven hours, i.e., around 1 am. Midnight Security Light Circuit Diagram: This high ou...

Most thefts happen after midnight hours when people enter the second phase of sleep called ‘paradoxical’ sleep. Here is an energy-saving circuit that causes the thieves to abort the theft attempt by lighting up the possible sites of intrusion (such as kitchen or backyard of your house) at around 1:00 am. It automatically resets in the morning. The circuit is fully automatic and uses a CMOS IC CD 4060 to get the desired time delay. Light -dependent resistor LDR1 controls reset pin 12 of IC1 for its automatic action. During day time, the low resistance of LDR1 makes pin 12 of IC1 ‘high,’ so it doesn’t oscillate. After sunset, the high resistance of LDR1 makes pin 12 of IC1 ‘low’ and it starts oscillating, which is indicated by the fashing of LED2 connected to pin 7 of IC1. The values of oscillator components (resistors R1 and R2 and capacitor C4) are chosen such that output pin 3 of IC1 goes ‘high’ after seven hours, i.e., around 1 am. This high output drives triac 1 (BT136) throu...