PIR sensors are widely used in motion detection projects now a days. Since my today's tutorial is about interfacing of PIR sensor with Arduino micro controller. Before going to that it is necessary that we should first understand the construction and working principle of PIR sensor. So i am going to divide my tutorial into different blocks and i will describe PIR sensor from its construction to practical applications. So first of all, lets see the construction and operating principle of PIR sensor.
The construction of PIR sensor is very simple and easy to understand. In the bottom or you can say in the core of the PIR sensor we have a set of sensors which are made of pyro-electric materials. The properties of this material is that when this material is exposed to heat then, it generates energy. Different methods are used to to measure this energy generated by PIR sensor. On the top of the PIR sensor and above the internal sensors we have a small screen through which infrared radiations enters into sensor. When these radiations falls on the pyro-electric material then it generates energy. Generally the size of this sensor is very small and it is available in the form of thin film in market. Many other materials are also used in collaboration with pyro-electric material like galliam nitrite and cesium nitrate and all these materials take the form of an small integrated circuit.
The modern studies in the field of quantum physics tells us the fact each and every object when it is placed at a temperature above absolute zero, emits some energy in the form of heat and this heat energy is in fact the form of infrared radiations. So an other question comes into mind that why our eyes can't see these waves? It is because that these waves have infrared wavelengths and his wavelength is invisible to human eyes. if you want to detect these waves then, you have to design a proper electronic circuit.
If you see closely the name of PIR sensor which is Passive Infrared Sensor. Passive elements are those elements that don't generate their own voltages or energy. They just only measures things. So we can say that this sensor is a passive infrared sensor and it doesn't generate anything by itself. It is only capable to measure the rediations emitted by other objects around it. It measures those raditions and do some desired calculations on them.
The pin configuration of a PIR sensor is shown in the image given above. Since we have to interface the PIR sensor with Arduino micro controller. The image showing the interfacing of PIR sensor with Arduino is shown below as:
#define pirPin 2 int calibrationTime = 30; long unsigned int lowIn; long unsigned int pause = 5000; boolean lockLow = true; boolean takeLowTime; int PIRValue = 0; void setup() { Serial.begin(9600); pinMode(pirPin, INPUT); } void loop() { PIRSensor(); } void PIRSensor() { if(digitalRead(pirPin) == HIGH) { if(lockLow) { PIRValue = 1; lockLow = false; Serial.println("Motion detected."); delay(50); } takeLowTime = true; } if(digitalRead(pirPin) == LOW) { if(takeLowTime){lowIn = millis();takeLowTime = false;} if(!lockLow && millis() - lowIn > pause) { PIRValue = 0; lockLow = true; Serial.println("Motion ended."); delay(50); } } }
PIR sensors possess a no of applications and due to their low cost and much advanced features they are the main focus of different projects being made now a days. Some of their features and practical applications are listed below as:
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