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Home Security(Burglar) Alarm CIrcuit

2016-02-19 06:05  
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This is a simple Burglar Alarm Circuit (home security) to protect your home/garden from burglary activity. In present contest there is no such place in the world where crime doesn’t exist. This simple circuit can be used to avoid illegal entry inside your home/garden. I prefer this circuit for outdoor purpose with bigger area like your garden or a whole compound of your home.Most of those other burglar alarm circuit is built around magnetic field and works on opening and closing the door. That is, circuit will be closed while door is closed and electricity can pass through the circuit but if someone opens the door circuit will also be opened, no electricity flows and this will triggers the alarm. So this kind of circuits can only be applicable for indoor purpose and that can’t cover the bigger area like compound or garden. But this burglar alarm circuit I am showing here is applicable for this contest since its working principle is different than others (no magnet used).This circuit is built around a Thyristor TYN612 and some other discrete components as in diagram. TYN612  Home Security Alarm The red line in the circuit indicates thin wire as much desiredTYN612    Application Connect thin wire as shown in figure and the two terminals with circuit. Assemble the given circuit in general PCB board and put it inside simple cabinet. Then cover the desired area with the help of thin wire and connect two terminals of wire with terminal ‘a’ and ‘b’ of the circuit. Provide 12v of supply voltage and switch on the circuit. Now if someone tries to enter inside your compound and breaks the wire, the circuit alerts you by producing big sound. Thyristor used here operates the alarm. Thysristor is special kind of diode and also known as silicon controlled rectifier (SCR) which only allows current to flow when a control voltage is applied to its gate terminal. At initial condition the transistor is off since it’s held at ground potential that makes SCR not conducting and horn remains off. But as soon as wire is broken transitor T1 gets positive potential and will be on. This makes SCR on and starts conducting and horn will blow loudly. Once thyristor is turned ON it will not turned off even if the gate voltage is removed so you have to turn off the power to stop the blowing horn.