PIR SECURITY ALARM | amazing mj
In this tutorial we make PIR(passive infra red) sensor based security system, PIR is basically measures infrared light emitted from the object that generate heat and therefor IR radiation on its field of view.
The sensor is actually split in to two halves each half is made of IR sensitive material. When sensor is ideal each half receives same amount of IR radiation. When warm body of human or animal passes by it first intersepts the first half, it create positive differential charges between two halves. When the body leave sensing zone it intercepts second half of the sensor. Which create negative differential charge between two halves. These differential charges create pluse so as to detect not the rediation itself but change in the condition that occurs when target enter its field. These changes in the amount of IR radiation on the element it turns changes the voltage generated which are measure by amplifier. Output of sensor is normally low and goes high if any human or animal body sensed.
Components required :-
The PIR sensor is the heart of the project. We run this project on dc 12v supply. The diode D2 is use for circuit protection. The supply is filtered by the capacitor C3. This supply is further regulated by the IC 7805. When any living thing comes in contact with the PIR sensor then it gives a high signal. This signal is given to the IC 555 through transistor Q1 (BC547) the transistor is used as a not gate to activate the IC 555.
The IC 555 is used in a monostable mode which detects the high signal of the PIR and activates the relay through transistor Q2 (BC547). The activation time period of IC 555 depends on the RC constant (VR1 and C2). The potentiometer is used as a variable resistor for adjusting the time period. You can connect any alarm or a buzzer across the relay but in the video i connect LED bulb as security purpose. The Red LED is used to indicate the output of the circuit. The diode D1 is used as free Wheel diode for circuit protection from back EMF.
The IC 555 is used in a monostable mode which detects the high signal of the PIR and activates the relay through transistor Q2 (BC547). The activation time period of IC 555 depends on the RC constant (VR1 and C2). The potentiometer is used as a variable resistor for adjusting the time period. You can connect any alarm or a buzzer across the relay but in the video i connect LED bulb as security purpose. The Red LED is used to indicate the output of the circuit. The diode D1 is used as free Wheel diode for circuit protection from back EMF.
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