Bidirectional Visitors Counter (BVC) is a system used to count visitors entering and leaving a room. The bidirectional word means the counting of both types, ie, entering and exiting. When a person enters the room, the count increases and when a person leaves the room that counts is decremented. Bidirectional counters are designed according to the demands in real time. The design becomes tedious for one door systems where all visitors enter and exit through a single channel.
Principle of bidirectional tour counter circuit
The circuit operates according to the principle of IR detection. Infrared or simply IR sensors are devices that work with infrared light source and a photo detector like a photo diode or a photo transistor that act as transmitter and receiver respectively. In this project, we have used an IR LED as the infrared transmitter and a photodiode as an infrared receiver. Two sets of infrared sensors consisting of an IR LED and a photodiode are placed at two ends of the entrance of a room.
The output of each sensor is fed to the microcontroller. In normal operation, the infrared LED light would not fall on the photo diode as it is a reflective infrared type sensor. The sensor output would be a LOW logic signal in this case. In case of any interruption (due to anyone crossing the path), the photo diode would start to receive IR light and start to drive. As a result, the sensor output would be a HIGH logic signal. The low to high transition for each pair of sensors is detected by the microcontroller and, as a result, the count will increase or decrease.