Radar & Active Infrared Sensor for Automatic Doors

The automatic door opening systems are used in commercial buildings, shopping malls, theatres, etc. These systems are used to open the door when a person comes near to the entrance of the door and closes it after he moves away from the door or after entering into the door. There are various kinds of sensors are available in the market to make such types of systems such as Radar sensors, PIR sensors, Infrared sensors, and Laser sensors, etc. This project uses a PIR sensor to open or close the door automatically which senses the infrared energy produced by the human body. When someone approaches the door, the IR energy sensed by the PIR sensor changes and activates the sensor to open and close the door automatically. Further, the signal sent to the microcontroller to control the door.
You might have seen Automatic Door Opener Systems at shopping malls, cinemas, hospitals etc. where, as soon as a person approaches the door (at about 2 or 3 feet), the door automatically slides open. And after some time (about 5 to 10 seconds), the door closes by sliding in the reverse direction.
Such Automatic Door Opener Systems are very useful as you do not need a person to standby the door and open it whenever a guest comes. Also, since the doors are opened and closed only when a person approaches the door, there is significantly less loss of air conditioning.
An Active Infrared Detector always consists of one transmitter and at least two receiver chips with high-quality optical systems. The scanning range is set by means of a mechanical micro-speed unit by changing the angle between the transmitter and receiver. This optical procedure is called triangulation or optical differential measurement.
Active Infrared Detectors are static—they only detect persons and objects if they break the beam. The detection area consists of spots, and depends to a large extent, on the optical center-to- center distances of the transmitter and receiver lenses. Several beams can be combined in a modular system to form a larger area.
Passive Infrared Sensors function in a similar way to infrared cameras used to detect heat loss from buildings. The infrared-sensitive sensor forms a heat image of the defined area to be monitored. After an initial set-up time of approximately 20 seconds, the measured infrared image is saved. The sensor switches if the heat image changes as a result of movement. Two conditions must be fulfilled here:
1. There must be a temperature difference of +/- 1.8 F between the object to be detected and the background.
2. The object to be detected must move at a rate of at least 4 inches per second.
The system is ideal for detecting people only if— There is always a difference of at least 1.8 F between the surface temperature of a clothed person and the surrounding environment. For reasons of a physical nature, this technology should only be used to detect living beings as it's not always possible to guarantee that the difference in temperature between items such as shopping carts or vehicles, and that of the surrounding environment will be great enough.
Microwave
Functional Principles: Microwaves are electromagnetic waves such as those emitted by a radio transmitter but with a much higher frequency (> 1GHz). Thanks to the variable antenna, the microwaves emitted by the transmitter can be directed without any difficulty and are reflected back to the receiver via the floor, walls and other surfaces.
If there is no movement in the monitored zone, the transmitter and receiver frequency remain the same—the zone is clear. People and objects, however, activate the motion detector as they move through the monitored zone. The emitted and received frequencies are no longer identical. The difference between the frequencies is evaluated and transferred via relay or electronic contacts in the form of a switching pulse. The microwave power used is perfectly safe for humans and animals.