4 in 1 burglar alarm pcb


Posted on Feb 5, 2014

I n this circuit, the alarm will be switched on under the following four different conditions: 1. When light falls on LDR1 (at the entry to the premises). 2. When light falling on LDR2 is obstructed. 3. When door switches are opened or a wire is broken. 4. When a handle is touched. The light dependent resistor LDR1 should be placed in darkness nea


4 in 1 burglar alarm pcb
Click here to download the full size of the above Circuit.

r the door lock or handle etc. If an intruder flashes his torch, its light will fall on LDR1, reducing the voltage drop across it and so also the voltage applied to trigger 1 (pin 6) of IC1. Thus transistor T2 will get forward biased and relay RL1 energise and operate the alarm. Sensitivity of LDR1 can be adjusted by varying preset VR1. LDR2 may be placed on one side of a corridor such that the beam of light from a light source always falls on it. When an intruder passes through the corridor, his shadow falls on LDR2. As a result voltage drop across LDR2 increases and pin 8 of IC1 goes low while output pin 9 of IC1 goes high. Transistor T2 gets switched on and the relay operates to set the alarm. The sensitivity of LDR2 can be adjusted by varying potentiometer VR2. A long but very thin wire may be connected between the points A and B or C and D across a window or a door. This long wire may even be used to lock or tie something. If anyone cuts or breaks this wire, the alarm will be switched on as pin 8 or 6 will go low. In place of the wire between points A and B or C and D door switches can be connected. These switches should be fixed on the door in such a way that when the door is closed the switch gets closed and when the door is open the switch remains open. If the switches or wire, are not used between these points, the points should be shorted. With the help of a wire, connect the touch point (P) with the handle of a...




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    IR 4 channels remote control with PIC12F629
    Simulated inductor
    Two-Transistor Sine-Wave Oscillator
    Audio Triangle Square Wave Generator Using Op-Amp
    spooky arduino projects 4 and musical arduino
    2-to-1 Multiplexer
    Improving the MICOR Receiver for 435-450 MHz
    100V output with shunt regulation
    NONPRECISE PHANTASTRON VARIABLE DELAY
    Audio Response with the FT8900 Yaesu MH-48A6J
    Effective Load Resistance
    Guitar noise circuit diagram



    Top