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Intelligent traffic light control system based on ultrasonic counting
With the rapid development of the economy, the number of vehicles on the road has significantly increased, leading to growing pressure on urban traffic systems. To manage traffic flow and enhance road capacity, traffic lights have proven effective in reducing accidents. However, traditional traffic lights operate on fixed-time control, which is not adaptive to real-time changes in traffic volume. This often results in inefficiencies, such as unnecessary waiting times or traffic congestion at intersections. In order to address these issues, this paper introduces a smart traffic light control system that uses ultrasonic counting technology for real-time monitoring of vehicle flow, allowing more flexible and practical adjustments.
The system consists of several key modules: a microcontroller unit (MCU), power management, ultrasonic vehicle detection, infrared remote control, traffic light groups, and an Ethernet interface. The overall block diagram of the system is illustrated in Figure 1. Each intersection is equipped with ultrasonic sensors to detect vehicle presence. The MCU processes the data and controls the traffic lights accordingly. In special situations, such as emergencies, manual control by traffic officers is still required. However, due to the distance from the control box, it is inconvenient for officers to manage traffic lights manually. To solve this problem, an infrared remote control module was designed, enabling traffic officers to control the system from any location near the intersection.
An Ethernet interface is also included, allowing remote monitoring and control of the traffic system. This feature supports networked transportation management and enhances the efficiency of traffic control. The chosen MCU, the MSP430F449, manages signal detection, data processing, and controls the four light groups across 16 monitoring devices.
For vehicle detection, ultrasonic sensors are installed on straight and left-turn lanes. Two sets of sensors are placed per direction: one close to the stop line (module group 1) to count vehicles exiting the lane, and another 80–100 meters away (module group 2) to count vehicles entering. The difference between these two readings provides the number of vehicles currently in the lane, which helps determine the optimal timing for traffic light changes.
The ultrasonic ranging principle involves emitting a pulse and measuring the time it takes for the echo to return. Using the formula D = t × v / 2, where v is the speed of sound, the distance to an object can be calculated. This principle is applied to count vehicles by detecting changes in the measured distance when a car passes under the sensor.
The HC-SR04 ultrasonic module is used for this purpose. Its timing diagram shows how the trigger and echo signals interact with the MCU. By analyzing the pulse width, the system can determine the presence of vehicles and adjust the traffic light timing accordingly.
Signal interaction between the ultrasonic module and the MSP430 is crucial. The trigger signal is sent from the MCU to the module, and the echo signal is received back. Through the capture function of the timers in the MSP430, accurate timing of the echo pulses is achieved, allowing the system to count vehicles effectively.
Error analysis is an important part of the system design. Ranging errors due to temperature variations are minimized by focusing on significant changes in pulse width rather than fixed distances. Additionally, mixed lane driving may cause minor inaccuracies, but these are considered negligible due to their low frequency.
The infrared remote control module uses PT2262 and PT2272 chips for encoding and decoding signals, allowing remote operation of the system. A relay-based drive circuit is used to control the high-power traffic lights, ensuring safe and efficient operation.
In terms of software design, the system includes both automated and manual control modules. The main program flow chart illustrates how the system cycles through different intersections, adjusting green light durations based on detected vehicle counts. When congestion exceeds a threshold, manual intervention by traffic officers becomes necessary to ensure smooth traffic flow.
Overall, the proposed intelligent traffic light control system offers a cost-effective, reliable, and scalable solution for improving urban traffic management. It demonstrates practical value and potential for future integration into smart city infrastructure.