Automatic doors have contributed to the most efficient movement in common areas that require some form of separation. When talking about automatic doors, the sliding doors in an industrial building, shopping mall, grocery store, or the garage door in the home come to mind. Understanding how automatic sliding doors work is made easier by breaking them down into common components. There is the triggering technology, the opening and closing mechanism, and any safety overrides applicable to the specific type of automatic door.
The common triggering technologies for automatic doors are motion sensors, pressure sensors, infrared sensors and remote controls.
• Motion sensors can use microwave motion such as Doppler effect radar, or ultrasonic technology to detect any motion in the area and trigger an appropriate event such as the door opening or closing.
• Pressure sensors use various technologies to detect strain on a surface. These often involve using a diaphragm and cavity. Displacement or strain is detected using strain gauges, capacitors or inductance. In most cases, pressure on the sensor sends the open signal and removal of that pressure sends the close signal.
• Passive infrared (PIR) sensors measure infrared light radiating off of people, animals or objects. The principle here is that all objects emit some heat in the form of radiation. The PIR detects the emitted or reflected radiation from an object and sends the appropriate signal to the door opening mechanism.
• Garage door remote controls use radio signals that usually operate at 315 MHz The user pushes the remote control button that sends a signal to the radio receiver. Upon receiving the signal, the receiver activates the garage door motor to open or close the garage door.
Most automatic doors have common mechanical components. There is a door engine or motor that turns a cog in one direction or another depending on the open or close event being triggered. That cog drives a rubber belt and pulley system on which the door is attached. The belt can only go in two directions; that cause the door to either open or close. The doors rest on rollers in tracks allowing them to slide easily when opening or closing.
As with most automatic systems safety is a concern, so often multiple sensors are installed. Sensors are used to detect if an object is in the doorway and if so, will prevent the door from closing. Garage doors also have various handles that can be used when the automatic system does not work.…