Smart & Connected Life Smart Home IP Motion Sensors in Home Automation Systems by Ron Fritz Writer Ron Fritz is former Lifewire writer and a computer technology writer with over 15 years of experience with information technology and home automation products. our editorial process Ron Fritz Updated on December 10, 2019 Gary Ombler/Getty Images Smart Home Your Best Year Ever: College Tech Tips Amazon Appliances & Lighting Google Tweet Share Email Using motion detectors as sensors allow a home automation system to make specific events happen automatically. Motion detectors can trigger a light to come on automatically, a camera to begin recording, or an alarm to sound. Motion detectors can become the eyes of your home automation system. How Motion Detectors Work Most modern motion detectors are PIR (Passive Infrared) sensors. This means the detector doesn’t sense motion but instead measures infrared light (heat), or changes in heat level. PIR detectors measure the ambient heat level of a room, and when they sense that level changing quickly, the detector interprets this as motion. How quickly the light has to change is configurable, referred to as the sensitivity of the detector. Motion detectors work best when a warm body sweeps across the front of them such as someone walking by. PIR detectors are less sensitive to slow motion or an object approaching them. The typical sensing range for a PIR motion detector is between 25 and 35 feet (8 to 11 meters) from the sensor. Shortcomings of PIR Detectors PIR detectors measure heat and therefore can interpret any sudden changes in heat as motion. This can include sudden sunbeams (opening the curtains), nearby AC and heating units, and fireplaces. If you find your motion detector is giving too many false alarms, check its location for possible interference from these sources. Home Automation Motion Detectors Motion Detectors are a ubiquitous component of home automation systems and come available in virtually every home automation technology. Motion detectors are commonly used to turn on lights in a room, adjust thermostat temperatures, or notify security systems of a break-in. Many motion detectors are wireless and are designed for the popular wireless home automation technologies like INSTEON, Z-Wave, and ZigBee. Wireless motion detectors provide the added convenience of installing in places where electrical power is unavailable. That capability makes these devices essential for many home automation systems. Prices for wireless motion detectors typically run between $25-$40 USD.