You have a private area, right? If you have this motion detector alarm circuit. It will reduce your worries. Imagine a big bear is coming to the behind of your house. Then, the siren alert. The big bear is shocked and runs away. You and your family are safe. Is it great?
I know you like me show simple circuits. You can do easy.
This circuit is a piece of cake for you.
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How it works
The basic principle, when a human or warm-blooded animal comes to a radius of about 3 to 5 meters. This circuit detects infrared radiation from theirs and sends an alarm.
When a signal from an Infrared PIR Sensor module comes to the circuit. It is a 3V peak voltage. Then, this voltage flows to the base of Q1 through R1-current limiting for the transistor.
Now Q1 runs, the current can flow from the 12V to a relay coil. The RY1 pulls contact C to NC. Next, the siren alert with a lot of louder.
In the same time, LED glows up. Because some currents from the emitter of Q1 flows to LED. And R2 limits current to LED1.
We want to use an inexpensive circuit. So, we use C1 and D1 use delay time of siren alert for 20 seconds.
The S1-switch on-off the relay circuit. When you want to close a siren. Also, you can use a remote control instead of S1.
When PIR Sensor runs, it will give a very short signal. We need to keep this voltage with a capacitor. And Diode-D1 protect a discharge voltage of C1, not reverse to PIR sensor. And in a signal of the output of the PIR sensor is AC form with negative voltage. So, diode rectifier to positive only can come to the trigger the transistor.
It is good. Now we have a smart module. It has a delay time mode inside. But it may be expensive a little.
We should use a good power supply at 12V. Although, the module has regulated supply inside. But some one may not have it. The battery 12V is a good choice.
What is a PIR sensor?
Some called Human Detector module. PIR stands for Passive infrared. It is one type of electronic device. It detects infrared radiation from an object. Through the optical integration device into a “Pyro Electric” inside. They will convert the heat energy from infrared radiation into electrical energy. Although, a little Infrared, PIR also can detect infrared and temperature waves.
The manufacturer creates a PIR Motion Sensor module. They are a type of sensor device that is used to detect infrared radiation from human or animal movements. Makes we can use a PIR sensor in many applications. For example, To detect the movement of an organism or detect intrusion in security work.
Cr: Impage by Gowoops
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How to build the circuit
I try to make this circuit as easy as possible. Everything may not be as good as a hundred percent. Many friends test this circuit. It works well.
Hassan bassari said.
I have made this circuit successfully for my 4th-semester mini project…
Please note the following to make it work…
- Do not use the capacitor C1… as it delays the relay to activate
- Use a 6v relay for better performance
- It is better if we use a 12v 1A rectifier for input voltage
- Q1: BC337, 0.6A 50V NPN transistor
- D1: 1N4148, 75V 150mA Diode
- D2: 1N4007, 1000V 1A Diode
- R1: 1.2K to 2.2K, 0.25W Resistor
- R1: 1K, 0.25W Resistor
- LED1: LED, Red 3mm LED
- C1; 220uF 25V, Electrolytic capacitor
- RY1: Relay, 6V to 9V coil
- PIR-Sensor: Infrared PIR Human Motion Sensor Detector Modules
- Siren 12V
- 12V DC power supply at more 1A. For example 12V battery or AC adapter.
- Universal PCB and more parts
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