Automatic doors are able to detect persons, and open at the appropriate time, through the use of automatic sensors. There are many types of sensors that are used on automatic doors.
Motion detectors, or optical sensors, are the most common types of sensors used on automatic doors. These sensors detect movement and are installed on the sides of the doors. Once movement is detected, the doors open. Another common type of sensors used for automatic doors are pressure sensors. These sensors are placed in a large area in front of the door and they sense pressure, which causes the doors to open. Pressure sensors can also be used as secondary or back-up sensors for motion detectors. When used in this manner, the door remains open when pressure is sensed, even if motion is not detected. This keeps doors that are controlled by motion sensors from closing on someone. Infrared sensors are also used for automatic doors. When a warmer temperature is sensed, such as that in a human, these sensors trigger the automatic doors to open. Automatic doors have become a popular feature in places such as airports and detention facilities. Along with the capabilities of opening automatically comes the capability of closing off the doors, keeping them from opening when the need arises.