PIR (HC-SR501) Sensor with the Arduino

How PIR Motion Sensor Works?

If you didn’t realize, all gadgets with a temperature above Absolute Zero (zero Kelvin / -273.15 °C) emit warmth electricity within the form of infrared radiation, inclusive of human our bodies. The hotter an object is, the more radiation it emits.

PIR sensor is mainly designed to discover such ranges of infrared radiation. It essentially consists of  principal elements: A Pyroelectric Sensor and A special lens known as Fresnel lens which focuses the infrared indicators onto the pyroelectric sensor

A Pyroelectric Sensor without a doubt has  rectangular slots in it product of a material that permits the infrared radiation to bypass. Behind these, are  separate infrared sensor electrodes, one chargeable for generating a high quality output and the other a poor output. The reason for that is that we are seeking out a exchange in IR tiers and now not ambient IR tiers. The two electrodes are wired up in order that they cancel every other out. If one half of sees greater or much less IR radiation than the alternative, the output will swing high or low.

When the sensor is idle, i.E. There is no movement across the sensor; both slots stumble on the same amount of infrared radiation, ensuing in a zero output sign.

But when a heat body like a human or animal passes through; it first intercepts one 1/2 of the PIR sensor, which reasons a positive differential trade among the two halves. When the warm body leaves the sensing place, the opposite happens, wherein the sensor generates a terrible differential change. The corresponding pulse of alerts consequences in the sensor placing its output pin high.

HC-SR501 PIR Motion Detector

For most of our Arduino initiatives that need to stumble on while someone has left or entered the location, or has approached, HC-SR501 PIR sensors are a awesome preference. They are low electricity and coffee fee, quite rugged, have a wide lens variety, smooth to interface with and are insanely famous among hobbyists.

HC-SR501 PIR sensor has 3 output pins VCC, Output and Ground as shown inside the diagram under. It has a integrated voltage regulator so it may be powered by using any DC voltage from 4.5 to twelve volts, commonly 5V is used. Other than this, there are a couple alternatives you have got along with your PIR. Let’s test them out.

There are two potentiometers at the board to regulate a couple of parameters:

• Sensitivity– This units the most distance that motion can be detected. It levels from three meters to about 7 meters. The topology of your room can have an effect on the actual variety you achieve.
• Time– This units how lengthy that the output will stay HIGH after detection. At minimum it's miles three seconds, at most it's far 300 seconds or 5 mins.Finally the board has a jumper (on some fashions the jumper isn't soldered in). It has two settings:
• H– This is the Hold/Repeat/Retriggering In this function the HC-SR501 will continue to output a HIGH sign as long because it maintains to discover motion.

Making HC-SR501 PIR Sensor greater flexible

The HC-SR501 circuit board has solder pads for two additional components. These are usually categorized as ‘RT’ and ‘RL’. Note that on a few forums the labels may be covered by using the “dome” lens at the aspect contrary the additives.

• RT– This is supposed for a thermistor or temperature-sensitive resistor. Adding this lets in the HC-SR501 to be used in intense temperatures, it also will increase the accuracy of the detector to some degree.
• RL– This connection is for a Light Dependant Resistor (LDR) or Photoresistor. By adding this element the HC-SR501 will simplest operate in darkness, a common software for movement-sensitive lights structures.The additional additives may be soldered at once to the board or extended to remote locations the usage of wires and connectors.

HC-SR501 PIR Sensor Pinout

The HC-SR501 has a 3-pin connector that interfaces it to the outdoor world. The connections are as follows:

• VCC is the energy supply for HC-SR501 PIR sensor which we connect the 5V pin on the Arduino.

• Output pin is a three.3V TTL good judgment output. LOW suggests no motion is detected, HIGH way a few movement has been detected.
• GND must be connected to the floor of Arduino.

ARDUINO CODE 

//define the pins
int LED = 4;
int PIR = 7;
int Buzzer = 2;

void setup() {
  //define the LED and Buzzer pin as output
  pinMode(LED, OUTPUT);
  pinMode(Buzzer, OUTPUT);
  //define the sensor pin as input
  pinMode(PIR, INPUT);
}

void loop() {
  //using the digitalRead function we will read the signal of the sensor
  int value = digitalRead(PIR);
  //if its high or if an any object is detected it will activate the LED and Buzzer
  if (value == HIGH){
    digitalWrite(LED, HIGH);
    digitalWrite(Buzzer, HIGH);
  }
  else {
    digitalWrite(LED, LOW);
    digitalWrite(Buzzer, LOW);
  }
}