Circuit panel

Description

               Circuit showing a Burglar Alarm.Here we have used a ldr and a switching transistor for making this circuit
.When the light coming towards the ldr during the period the ldr have low resistance so the buzzer will on.When the light going away the ldr during the period the ldr have high resistance so the transistor will off.Here you need a 12 volt power supply

 Components Required

      Resistor

                   10 k(preset)

      Transistor


                   BC 548

       LDR


        Buzzer



Source by : http://www.electronics-circuits.in/2012/03/burglar-alarm-ldr-bc-548.html

BURGLAR ALARM USING IC TIMER 555/556 ELECTRONIC DIAGRAM

In this figure is design circuit for modular burglar alarm circuit. This circuit features automatic Exit and Entry delays and a timed Bell Cut-off. It has provision for both normally-closed and normally-open contacts, and a 24-hour Personal Attack/Tamper zone. This circuit is connected permanently to the 12-volt supply and its operation is “enabled” by opening SW1. By using the expansion modules, you can add as many zones as you require; some or all of which may be the inertia (shock) sensor type.

All the green LEDs should be lighting before you open SW1. You then have up to about a minute to leave the building. As you do so, the Buzzer will sound. It should stop sounding when you shut the door behind you. This indicates that the Exit/Entry loop has been successfully restored within the time allowed. When you re-enter the building you have up to about a minute to move SW1 to the off position.

If SW1 is not switched off in time, the relay will energize and sound the main bell. It will ring for up to about 40 minutes. But it can be turned off at any time by SW1.However, it’s much easier to find a fault when the alarm is divided into zones and the control panel can remember which zone has caused the activation.