Circuit panel

This Photodiode based Alarm can be used to give a warning alarm when someone passes through a protected area. The circuit is kept standby through a laser beam or IR beam focused on to the Photodiode. When the beam path breaks, alarm will be triggered. The circuit uses a PN Photodiode in the reverse bias mode to detect light intensity. In the presence of Laser / IR rays, the Photodiode conducts and provides base bias to T1. The NPN transistor T1 conducts and takes the reset pin 4 of IC1 to ground potential. IC1 is wired as an Astable oscillator using the components R3, VR1 and C3. The Astable operates only when its resent pin becomes high. When the Laser / IR beam breaks, current thorough the Photodiode ceases and T1 turns off. The collector voltage of T1 then goes high and enables IC1. The output pulses from IC1 drives the speaker and alarm tone will be generated.

Photo-Diode Alarm Circuit diagram

IR Transmitter Circuit diagram
A simple IR transmitter circuit is given which uses Continuous IR rays. The transmitter can emit IR rays up to 5 meters if the IR LEDs are enclosed in black tubes.

R1  100K 1/2W 1% Resistor
R2, R4  10K 1/2W 1% Resistor
R3 1  Meg 1/2W 1% Resistor
C1, C3  0.1uF Ceramic Disc Capacitor
C2  0.01uF Ceramic Disc Capacitor
IC1  4001UBE Quad 2-i/p NOR Gate
Q1  MPSA14 Low Power NPN Transistor
SIREN  Micro piezo siren 12V DC 150mA, 110dB @ 1M
LOOP  See “Notes”

The loop can be any kind of hookup wire, with a most resistance of about 90K. Using very skinny wire (40AWG, for example) will make an awfully sensitive travel wire, but will shorten the distance it will also be strung due to the high resistance.

 The siren can be changed with a relay to power external load

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

Circuit diagram :

The front wheel of the bicycle is kept unlocked, so that the reed  switch closes momentarily when the wheel turns. This  triggers the 555, which in turn activates the window alarm. The circuit around the 555 takes very little current and can  be powered by the batteries in the window alarm.  There  is just enough room  left inside the enclosure of the window  alarm to mount the time-switch inside it.

The result is a very cheap, compact device, with only a single cable going to the reed switch on the front wheel. And the noise this thing produces is just unbelievable! After about one minute the noise stops and the alarm goes back into standby mode. The bicycle alarm should be mounted in an inconspicuous place, such as underneath the saddle, inside a (large) front light, in the battery compartment, etc.

Hopefully the alarm scares any potential thief away, or at least it makes other members of the public aware that something isnt quite right.


Caution. The installation and use of this circuit may be subject to legal restrictions in your country, state or area.

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.