Burglar Alarm Powered By Battery

The burglar alarm circuit design was based on the operation of CMOS 4001 where a high output would only result if both the inputs to the gate are low.

• Burglar Alarm – one way of preventing break in’s into one’s property, not only to protect the possessions but the occupants as well; can prevent the havoc and disruption caused by theft and break-in’s
• CMOS 4001 – a quad 2-input NOR gate integrated circuit, generally characterized by small fluctuation in voltage supply, very high impedance, outputs that can sink and source, one output can drive up to 50 inputs, high speed gate propagation time, high frequency, and low power consumption
• Zone – refers to an alarm control panel’s input from a protective circuit which divides the alarm system into separate independent areas of protection based on function which may include medical, fire, intrusion, or critical condition monitoring.

The basic operation of the alarm occurs with the interruption of electric current to a relay cause by deenergizing of the relay and making the relay contacts to operate the alarm indicator. The circuit is applicable to a single zone which can consist of a single point of contact. An alarm panel’s zone inputs are closed circuit where it begins at the alarm control and terminate on a single pair of wires. As the alarm gets activated, it causes the siren to run up to 20 minutes then it switches off. The power requirement for this circuit can be as high as 15 V but 9 V battery will do for as long as the buzzer, siren and relay will fit the supply input.

This zone alarm consists of siren cut-off timers as well as modifiable entry and exit delay which can also be applicable to other normally open and normally closed switches that contains input devices such as magnetic reed contacts, pressure mats, foil tapes, inertia sensors and passive infrared detectors. The alarm will operate with any type of two-way switch. The buzzer will sound if the alarm is switched on wherein the loop is in open stage. On the other hand, as the switch turns off, the loop becomes a closed circuit again.

As an example of its application to a secured door, the buzzer will sound as the door is opened and will stop sounding when the door is closed. The affirmation of a closed loop depends on the value set on resistor R3, while the setting on resistor R4 will determine the amount of delay when the siren will sound if the buzzer have not confirmed a closed loop. When the siren sounds, it will switch off and remain switched off depending on the setting on resistor R5 for the amount of time that the siren will sound. Even if the siren stops to sound but the buzzer is still running, this is an indication that the alarm has been activated.

A burglar alarm system helps detect unauthorized entry onto a company’s premises. The system sends a signal to a central monitoring center when activated. The monitoring centers provide 24/7 service and will alert the local police to dispatch authorities to the scene. It is a proven fact that the risk of burglary is significantly reduced after a burglar alarm is installed.

Source:www.zen22142.zen.co.uk/Circuits/Alarm/boto.htm