Design and hardware structure analysis of traffic signal control machine

Signal machine hardware structure analysis

Taking the four-phase traffic control of the ordinary intersection as an example, the signal machine must realize the effective traffic control of the motor vehicles and pedestrians at the intersection through the red, yellow and green lights. It needs 7 signal lights: the left turn of the motor vehicle, go straight Turn right to the green light, go straight to prohibit red light, yellow light, pedestrian red light, pedestrian green light, so the traffic signal control machine needs to provide 4*7=28 signal output channels in four directions.

Straight in each direction of the cross, left turn to different lane entrance traffic flow through the buried detection coil for data acquisition, a total of 8 red data, so 8 input channels are required. In addition, the signal machine must implement the trunk and regional coordinated control, as well as the data exchange with the host computer, and must have a communication interface.

All of the conventional logic devices and signal detections used in the system, such as latches and decoders, can be implemented with a single CPLD (EPM7032).

In order not to occupy more MCU I/O port, the output control of 2B signal light is realized by bus mode. Four 74LS377 latches are used, and ULN2803 chip is used as output drive. The actual intersection signal light is output through the power drive module.

In order to ensure that the signal output corresponds to the intersection red, it is necessary to take out the green conflict light position that may be generated. For its detection, the CPLD is used to implement the logic analysis circuit. When there is a green conflict, an alarm is generated after the interruption, and the yellow flash control is started.

Clock circuit

The clock circuit provides real-time time to the signal meter, and the signal machine can automatically execute the operation plan set in the preset time table according to the current time, so it is very important to provide accurate time.

Communication module

The communication module uses m to realize the transmission of data between the MCU and the host computer and the network control of the signal machine. The standard RS232 port is used to connect the MCDEM.

To realize the remote communication capability, before communication, it is necessary to coordinate the communication format between the host computer and the single-chip microcomputer, and adopt a mutually consistent communication protocol. Signal machine

Receive the timing data transmitted by the host computer. Or upload the matching color data to the upper computer backup. By means of the communication network host computer, the signals of multiple intersections can be controlled to form a "wire control" or "face control" system.

Traffic signal control machine

Vehicle detection module

Through the ground-sensing coil detection interface buried in the lane, go straight in each direction, turn left to enter the traffic data of different lane entrances, collect 8 sets of data, and strobe and detect by 74LS138 decoder, that is, which way to strobe, the road The induction oscillation circuit works to send the detection data to the microcontroller.