In this tutorial, we are going to make a “PIR Burglar Alarm Circuit”.
As nowadays security is a real concern, a burglar alarm is a device that alerts us when intrusion and unauthorized entry are detected and it is very useful to protect our living space, house, and office from theft. Here we design a burglar alarm circuit by using a PIR sensor and three-siren sound generator IC UM3561. PIR sensor (Passive Infrared sensor) is widely used in motion detection applications and security-based applications. Thus, the system could be effectively used for detecting trespassing, theft, intrusion, burglars, or any form of unlawful entry inside a restricted area or zone. When an unknown person comes in front of this device, then it detects motion and provides a sound alert against unauthorized entry or movements.
Hardware Required
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | IC | UM3561 | 1 |
| 2. | PIR Sensor | – | 1 |
| 3. | Zener Diode | 5.1V | 1 |
| 4. | Resistor | 560Ω,100K, 10K | 1, 1, 1 |
| 5. | NPN Transistor | BC547 | 1 |
| 6. | Variable Resistor | 100K | 1 |
| 7. | Speaker | 8Ω | 1 |
| 8. | Connecting Wires | – | – |
| 9. | Battery | 9V | 1 |
Circuit Diagram
PIR Sensor
A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) light radiating from objects in its field of view. They are most often used in PIR-based motion detectors. It comes with a breakout board that gives you options to control triggers, sensitivity adjustments, and time delay adjustments. It uses only three pins one is Vcc (+5V) and GND power pins then the Output pin. It gives High during IR presence (3.3V) else Low output (0) depends on the IR detection.
Working Explanation
The main part of this circuit is the PIR sensor, which is used here to detect the human body movement, whenever there is any movement, the voltage at the output pin changes. It detects the change in heat(Infrared (IR) light radiation emitted) from a person or object and gives logical output signal whenever such detection occurs. The UM3561 is responsible to detect and generate siren sounds, it can generate four types of sound: Police Siren, Ambulance siren, Fire brigade siren, and machine-gun sound. It is an 8-pin IC and only requires an external resistor to work. It has inbuilt oscillators and circuitry to produce the sounds. UM3561 works in the range of 3-5 volts, a voltage higher than 5V can damage the IC. So, if we are using it with another circuit or using a high-voltage source, a Zener diode must be connected to protect the IC. The output generated by the IC is not sufficient to drive an 8ohm small speaker. Hence to amplify the output of the IC, a transistor must be used at the output (PIN 3).
Now when we provide a power supply to this circuit, a 5.1V Zener diode which we have placed across the battery provides a regulated power supply to the PIR sensor. Here the output of the PIR sensor (3.3V) Is connected to the Vdd pin 5 of UM3561. Whenever the PIR sensor detects motion then the UM3561 gets supplied and starts to give a siren sound through the speaker.
Applications
This is a small portable low-cost device, which can be used at our house, office, building, locker, etc.
