張思遠(yuǎn)

Abstract：To provide people waiting on the bus stop the information about the number of passengers on the bus traffic and distance between the site and the running bus. Design a set of intelligent bus stop system. This system counts up the number of the people gets on the bus and the people getting out of the bus to add up the people on the bus by infrared sensor and uses the hall sensor to measure the distance of having driven. Then， send data via GPRS. Finally display on the corresponding bus stop.

Keywords：passenger statistics；distance measurement；wireless communication

As the rapid development of city， the city also faces many problems， such as traffic congestion. The bus has the advantageous of great transport power and economic convenience. It is efficient to decrease urban traffic pressure. Some cities have installed intelligent bus stop， only individual roads of rare cities have installed and it is reported that the intelligent bus stop cost more and is difficult to carry out. Meanwhile the bus stop only provides some simple query functions and dont make a whole lot of sense. For this case， a kind of intelligent bus stop is designed. Compared with existing intelligent bus stop， it is at low cost and easy to popularize. It can provide message of traffic and bus arrival time.

1 Whole design plan

The system calculates the present number of people on bus through the infrared sensors. The real time monitoring （the speed and latitude） of bus which is read on GPS module will be displayed on bus stop through GPRS and DTU.

2 Hardware design

The system mainly contains sending unit and receiving unit. The sending unit contains traffic statistics module， distance measure module and GPS module.

2.1 Design of traffic statistics module

This module is made up with infrared sensor. The number is calculated with recorded the number of high pulses. The infrared receiving phototube 1 and infrared emission phototube 1 are installed on the door for getting in to get the number of passengers of getting in.

2.2 Design of distance measure module

The hall sensor is installed on the shaft. When the bus moving， a number of pulses which are generated by hall sensor for one cycle of shaft are send to MSP430. MSP430 counts the number of received signal and calculate the distance with the radius of wheel. The counting value is cleaned when the bus arrive a bus stop. Then the distance to next stop can be calculated with the distance data of two bus stops that are stored in MSP430.

2.3 Design of wireless transmission module

GPRS and DTU are wireless data terminals of the internet of things. The function of long distance wireless data transmission is depended on GPRS. GPRS and DTU module provides interface of RS232/RS485， so it can communicate with MSP430 and is convenience to use. Transmission is far and the coverage is great.

3 Design of software

3.1 Design of the GPS program

GPS receiver is depended on standard specification of NMEA-0183 agreement. Information of speed and location， and so on， are send to MSP430 by serial port. MSP430 decodes the received string and only get the information about latitude， longitude and speed of $GPRMC.

3.2 Design of GPRS program for receive and transmission

The information received by transmitter is send to DTU （where the information is into packets） through serial port， and then the packets are sent to internet by GPRS. At last， datacenter servers that own fixed public IP address and port number receive the data. The information is forwarded to corresponding bus stop by servers and is displayed.

4 Conclusion

The hardware of this system is designed reasonably. Every function module works normally. The statistics for the number of passengers is accurate and the real-time information is provided to passengers. It is a effective measure to improve the city traffic. Meanwhile low cost and easy to popularize. So it has use value.

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