FT06 Series Fused Terminal Connectors Plug Terminal Block, Fuse Connector, H Type Terminal Block, Lighting Connector Jiangmen Krealux Electrical Appliances Co.,Ltd. , https://www.krealux-online.com
Urban roads are filled with vehicles and pedestrians, creating a bustling yet orderly environment. But how is this harmony achieved? It all comes down to the traffic light system, which serves as a critical command mechanism for urban traffic. As an effective tool for managing traffic flow and increasing road capacity, traffic lights play a vital role in reducing traffic accidents. This paper presents an **intelligent traffic light system** that uses the **STC89C52 microcontroller** as its core, along with **Zigbee wireless communication** for remote control. Traffic officers can adjust the duration of traffic signals from a distance, adapting to different traffic conditions and crowd densities. The system also features a digital display showing the remaining time of each signal, embodying the principles of the Internet of Things (IoT) and offering significant practical value and market potential.
The system is designed with a wireless control approach centered around the STC89C52 microcontroller. It integrates a **Zigbee module** for remote control, allowing traffic police to adjust signal timings from a handheld device. Two **seven-segment digital displays** are used to show the current status of the traffic lights. The system consists of three main components: the **handheld control unit**, the **traffic signal control module**, and the **digital display module**. In real-world scenarios, the distance between the intersection center and the traffic lights typically does not exceed 300 meters, while the Zigbee module can reliably transmit data within 800 meters. By forming a **Mesh network**, the system enhances reliability by enabling nodes to forward data when necessary. This ensures seamless communication between the central control and the traffic lights.
Figure 1 shows the layout of the wireless terminal used in the system.
**2. System Hardware Design**
**2.1. Handheld Device Hardware Design**
The handheld device includes a microcontroller, a liquid crystal display (LCD), a wireless communication module, and a clock control unit. As shown in Figure 2, traffic officers can input desired signal settings and timing through a button interface. The microcontroller processes the input data and sends it via the Zigbee module to the traffic light control unit. The CN3065 chip is used for system calibration and time synchronization, while the CC2430 module handles wireless communication.
Figure 2 illustrates the hardware structure of the wireless handheld device.
**2.2. Traffic Light Control Module Hardware Design**
The traffic light control module is responsible for receiving and processing control commands sent from the handheld device. It uses serial communication to send field data to the city monitoring center, enabling remote control during emergencies. The digital display uses two common-anode seven-segment displays, each capable of showing numbers from 0 to 99. Each pin of the P1 port on the STC89C52 is connected to a 300-ohm resistor before connecting to the display.
Figure 3 shows the hardware design of the traffic light control module.
**3. System Software Design**
**3.1. Handheld Device Software Design**
The software for the handheld device allows traffic officers to input signal IDs and statuses, then sends the control commands via the Zigbee network. The CC2430 module supports the Z-Stack protocol, ensuring compatibility with the Zigbee standard. The handheld device acts as a **Zigbee coordinator**, initiating the network and updating connected nodes. To prevent packet loss, the system uses the **MODBUS protocol** with **CRC-16** for error checking. Once the network is established, the LCD displays a list of controllable signals, and the officer can send commands accordingly.
Figure 4 illustrates the communication flow of the handheld device.
**3.2. Traffic Light Control Module Software Design**
The traffic light control module joins the Zigbee network initiated by the handheld device and receives control commands. When joining the network, it sends its ID and date to the handheld device for time synchronization. If the module is not connected to the network, it defaults to the original control logic.
Figure 5 shows the flowchart of the control module’s operation.
**4. Conclusion**
This paper addresses the real-world need for traffic police to manage traffic lights efficiently. By integrating IoT concepts, the system provides a wireless, handheld solution for remote traffic signal control. Using the Zigbee network, control commands from the handheld device are transmitted to the traffic light modules, meeting the operational needs of traffic officers. The system is low-cost, energy-efficient, and highly reliable, making it suitable for large-scale deployment in smart cities.