How does a PIR sensor work?

A Passive Infrared (PIR) sensors is specifically designed to detect changes in infrared radiation within their field of view. Passive infrared radiation can be emitted from certain objects or warm-blooded creatures such as humans and pets.

How are PIR sensors used in Home Automation?

PIR sensors can be a great addition to a Home Automation setup, due to their low-cost, energy efficiency and ease of installation.

Motion-Activated Lighting — PIR sensors are frequently used to control lighting systems in homes. By installing PIR sensors in various rooms or outdoor spaces, you can automate the activation of lights when motion is detected. This is particularly useful for areas like hallways, cupboards, and entryways where hands-free operation is desired.

Occupancy Sensing — PIR sensors can also be used to monitor occupancy within specific areas of the home. By detecting movement, PIR sensors can trigger actions such as adjusting thermostat settings, turning on fans or air purifiers, or activating music or ambient lighting to create a welcoming atmosphere when someone enters a room.

Security and Intrusion Detection — PIR sensors can be used to trigger alarms, send notifications, or activate cameras and recording devices when motion is detected in sensitive areas or during specific times, providing enhanced security and peace of mind.

Energy Management — PIR sensors can contribute to energy efficiency by ensuring that lighting and climate control systems or thermostats are only active when needed. By automating the operation of lights, heating, and cooling based on occupancy, PIR sensors help reduce energy consumption and lower utility costs.

How does a PIR sensor work under the hood?

At the heart of a PIR sensor lies a pyroelectric sensor, which is capable of detecting infrared radiation. This sensor is divided into two halves, with each half covered by a special material that generates an electric charge when exposed to infrared radiation. When an object moves within the sensor's field of view, the infrared radiation emitted by the object causes a temperature difference between the two halves of the sensor.

As a result, one half of the sensor experiences a change in temperature before the other. This temperature difference generates a voltage difference between the two halves, which is then detected and interpreted by the sensor's electronics. This change in voltage signals the presence of motion, triggering the sensor to activate and send a signal to your home automation system.