PIR Motion Sensor
The PIR motion sensor, also known as a human infrared sensor, is widely used in fields such as anti-theft alarms, visitor notifications, and non-contact switches. Piezoelectric ceramic dielectrics can maintain a polarized state after polarization, known as spontaneous polarization. Spontaneous polarization decreases as temperature increases and drops to zero at the Curie point. Therefore, when this material is exposed to infrared radiation and its temperature rises, the surface charge will decrease, equivalent to releasing some charge, hence the name pyroelectric. The released charge can be converted into a voltage output via an amplifier. This is the working principle of the pyroelectric sensor. When radiation continues to act on the pyroelectric element, causing its surface charge to reach equilibrium, it will no longer release charge. Therefore, the pyroelectric sensor cannot detect constant infrared radiation.
PIR motion sensor sold on Taobao
Functional Features
1. Fully automatic sensing: When a person enters its sensing range, it outputs a high level; when the person leaves the sensing range, it outputs a low level after a delay.
2. Two triggering methods: (jumper selection)
a. Non-repeating trigger mode: After the sensing outputs a high level, once the delay time ends, it will automatically switch from high level to low level;
b. Repeating trigger mode: After the sensing outputs a high level, if a human is active in its sensing range during the delay period, its output will remain high until the person leaves, after which it will delay changing from high level to low level (the sensing module will automatically extend a delay period after each detection of human activity, using the last activity time as the starting point for the delay time).
Note: The sensing module has about one minute of initialization time after power on. Adjusting the distance potentiometer clockwise increases the sensing distance (approximately 7 meters), while counterclockwise decreases it (approximately 3 meters). Adjusting the delay potentiometer clockwise increases the sensing delay (approximately 300 seconds), while counterclockwise decreases it (approximately 5 seconds). The jumper cap in the upper right corner of the left image indicates non-repeating trigger mode when placed on top.
Testing Circuit
Human sensing test circuit
Reference Program
int Sensor = 8; // Receive signal from the sensor
void setup()
{
Serial.begin(115200);
pinMode(sensor, INPUT); // Set as input
}
void loop()
{
int val = digitalRead(Sensor); // Read pin level
if (val==1) // If a person is detected, val will be 1
Serial.println(“If you are, you breathe.”);
else
Serial.println(“No one”);
delay(100);
}
Using the Arduino IDE serial monitor to observe the results, when a person is detected, the output port of the pyroelectric sensor will output a high level.
Science students romanticize, making it seem like humanities students have nothing to do with it.