PIR Sensor Burglar Alarm System Circuit using 555 Timer IC
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Many times, we have busy with our work at our house, office. That time an unknown person can be entering our property and stole our valuable items. In this blog tutorial, we will make a simple PIR Sensor Burglar Alarm System. This is a small portable low-cost device, which can be used at our house, office, building, locker, etc. When an unknown person comes in front of this device, then it detects motion and starts sounding. Basically, a burglar alarm system is an intruder alert system used to prevent theft/robbery and protect property and valuable items.
The PIR Sensor Burglar Alarm System is built based on a simple concept and it has few key components. The key components are the PIR motion sensor, Transistor BC547, NE555 Timer IC, and Buzzer. The PIR sensor is used to detect motion. When the PIR Sensor detects any human body movement, its OUTPUT pin becomes HIGH. Then this High output will go to the BC547 Transistor. Then the transistor will connect the trigger pin of the NE555 timer IC to the ground. Now the timer IC produces output, which turns on the buzzer.
Block Diagram of PIR Sensor Burglar Alarm System
|NE555 Timer IC||1|
|BC547 Transistor (T1)||1|
|HC-SR501 PIR Sensor Module||1|
|220 ohm Resistor (R1)||1|
|10K ohm Resistor (R2)||1|
|47K ohm Resistor (R3)||1|
|150 ohm Resistor (R4)||1|
|100 uF Capacitor (C1)||1|
|0.01uF Capacitor (C2)||1|
|Slide Switch (SW1)||1|
|9V Power Supply||1|
|Connecting Wire||As required in the circuit diagram|
PIR Sensor Burglar Alarm System Circuit Diagram
Working Principle of PIR Sensor Burglar Alarm System
When the PIR Sensor detects any human body movement, its OUTPUT pin becomes HIGH (Vcc) and when it does not detect any human body movement, its OUTPUT pin becomes LOW (Ground). Here the BC547 Transistor work as a switch. When the voltage is applied at the base terminal of it, it is turn ON and otherwise, it is off. In this circuit, the 555 timer IC is configured in monostable mode, so when it gets a LOW (Ground) trigger pulse at its trigger pin, then the IC OUTPUT becomes High.
For More Details:
PIR sensor detect motion
When anyone passes in front of the sensor, then the sensor provides high output voltage. This output voltage goes to the base terminal of the BC547 Transistor, then the transistor is turn ON. In this condition, the NE555 Timer IC trigger (Pin 2) is connected to the ground through the transistor and gets a LOW (Ground) trigger pulse. So, the Timer IC Provides output voltage, which goes to the Buzzer. Then the buzzer is turn ON and produces loud sounds.
PIR sensor does not detect motion
When the PIR sensor does not detect any motion, then the sensor provides low (0) output voltage. This output voltage is not sufficient to turn ON the BC547 Transistor, it means the transistor is OFF. In this condition, NE555 Timer IC trigger (Pin 2) does not get a LOW (Ground) trigger pulse. So, the Timer IC does not provide an output voltage. So, the buzzer is also OFF.