Design of the automatic detection system for the number of people based on the ultrasonic ranging array

In order to accurately detect the number of people in construction hoists, stadiums, libraries, exhibition halls and so on, a kind of automatic detection system based on the ultrasonic ranging array was designed. A ranging array composed by multiple ultrasonic modules was set above the entrance of the place to be monitored. The micro controller coordinated the time division multiplexing of all the ultrasonic modules. According to the average width of human body, the ranging array was divided into a certain amount of units. When someone passes the entrance, the average distance measured by the ultrasonic modules in the unit above the person will be changed, so the number of people who pass the entrance can be calculated according to the number of changed units. In addition, the direction of the person can be identified according to the change order of the outer and inner ultrasonic modules in one unit. The experimental results show that the system is able to achieve accurate detection of the number of people who pass the entrance side by side in the same direction or in opposite directions, so it can meet the requirements of use.