Design and Implementation of Master-slave Distributed Solar Wireless Signal System

1 Introduction

With the rapid development of the global economy, the problem of energy shortage has increasingly become the focus of attention in all walks of life. New energy sources such as solar energy and wind energy are being widely used in various fields, and the proportion of the proportion is gradually increasing. As a new achievement in the application of solar energy in the field of traffic management, Jerry Solar's wireless signal system came into being. This system solves two important problems: First, due to the application of solar power technology, no need for mains power supply, more energy-saving and more environmentally friendly; second, due to the combination of wireless communication technology and solar power technology, the system is realized. Distributed control, no cable connection is required between the extensions of the system, thus eliminating a series of engineering costs such as buried pipe and wiring, which greatly reduces the overall cost of the signal control system, and saves time, effort and money. . It is foreseeable that Jerry Solar's wireless signal system, which is born in the trend of the times, will bring a new model to the transformation of traffic signal control systems.

The generation of solar wireless signal systems has undergone a process of exploration and innovation. At the beginning of the project, there are no mature precedents at home and abroad. The wireless communication technology used in the early wireless signal systems is relatively backward: the communication error rate is high, the communication distance is limited, the reliability of communication is difficult to guarantee, and more importantly, there is no The wireless signal system combined with the solar power supply technology cannot really take advantage of its wireless power because it requires power leads, and there is no comparative advantage of energy saving and environmental protection. After fully understanding the system and experimenting with a variety of wireless technologies, we have selected wireless communication components to communicate with wireless communication protocols in several scenarios, based on mature solar power technology. The wireless design together realizes the design of a distributed control system without cable connection. After many on-site verification tests and continuous improvement, the solar wireless signal system realizes the self-organization, self-detection and self-recovery functions of wireless communication, realizes the charge and discharge control and protection functions of the solar power supply system, and realizes the wireless distribution of the system. Design goals for highly reliable control. The features and design ideas of this system will be described in detail below.

2 system composition and characteristics

2.1 System composition

The whole system consists of signal control equipment and solar power equipment distributed in four directions. The four directions are controlled by one master and three slaves (the number of slaves can be selected according to the actual intersection). The host direction equipment is solar power equipment, main engine and control box, and solar signal light; the slave direction equipment is solar power equipment, slave machine, and solar signal light. The system composition diagram is shown in Figure 1.

System composition diagram

2.2 System features

The system has undergone several innovative designs, and its main design features include:

The whole system adopts the master-slave distributed architecture design. One master and multiple slaves, the number of slaves is optional between 0-3. The master and the slave respectively control multiple sets of semaphores in different directions. Each extension adopts solar energy independent power supply, and wireless control between the master and slave machines. No cable connection is required between the extensions, which greatly saves engineering costs.

The system uses solar distributed power supply technology. The solar power sub-system realizes the charge and discharge control function between the solar panel, the battery and the load, and has the functions of undervoltage protection, overcharge protection, hysteresis start, hysteresis charging and the like. Effectively extend battery life and improve reliability. Due to the use of solar power, the mains supply is no longer needed, and the system is both energy efficient and environmentally friendly.

The master and slave are controlled by wireless communication technology. The wireless communication component with high reliability, high anti-interference and self-reset function is combined with the perfect communication protocol to realize the wireless control of the system.

The system wireless communication protocol adopts the scheme of sending and answering combined with periodic inspection, and has a variety of communication fault diagnosis and correction capabilities, including: packet error retransmission, watchdog time limit reset, message head and tail self-recovery design, Self-diagnosis recovery design such as system time-limited reset can effectively shield external signal interference such as lightning strikes and radio.

The system has self-organizing, self-detecting, and self-recovery functions. When the host or slave experiences power failure, communication failure, control failure, etc., the system can automatically enter the yellow flash state. When the solar power is restored or the fault is removed, the system can automatically resume normal operation.

The whole system adopts power-saving design. After the master-slave machine starts, it enters the power-saving mode, and the signal light also adopts energy-saving LED design.

The man-machine interface with patented technology is convenient and quick to operate. Users do not need to refer to the instruction manual to complete various settings according to the menu prompts.

3 System software and hardware design summary

3.1 Design Outline of Wireless Communication Protocol

The design of wireless communication protocol is an important part of system design. In the design of this system, we have adopted many measures to ensure the protocol is strict, safe and reliable, and realize self-organization, self-detection and self-recovery functions. The design points are as follows:

Asynchronous serial communication baud rate 9600bps, 1 start bit, 8 data bits, 1 stop bit, odd parity;

After the power-on verification is turned on, the verification signal is sent to all the slaves;

The scheme sends the running plan to all the slaves;

Fault diagnosis and handling of various accidental and short-term communication failures;

The school hours and inspections are used to answer the time of each slave, and at the same time, the inspection is carried out to deal with long-term faults.

3.2 System Host Design Summary

3.2.1 Host hardware design

The solar wireless signal system host is mainly composed of the following parts:

MCU, the main control chip, using Winbond's W78E516B;

CPLD interface control chip, using ALTERA products;

Wireless communication module ISM band, no need to apply, transmission power 50mW, communication distance 200 meters;

The panel display and the light state output are realized by DC drive technology;

Peripheral circuits include storage, clock, keyboard, serial port, power supply, and so on.

3.2.2 Host Software Design

The host software consists of the main program and four interrupt programs:

The main program completes system initialization, LCD display, watchdog service, keyboard processing, and communication processing.

Interrupt service program: serial port transceiver interrupt program, keyboard interrupt program, 500ms timer interrupt program, 1 second interrupt service program.

3.3 System Slave Design Summary

The slave hardware consists of a single chip microcomputer, a wireless communication module, a lamp driving circuit, a watchdog chip, and a power supply.

The slave software includes the main program and the interrupt service program. The main program completes initialization, communication control, light state control, watchdog service, and the like. The interrupt service routines include: serial port interrupt service routine and 500ms timer interrupt.

3.4 Solar Power Subsystem Design Summary

The solar power system design mainly considers the following design elements:

The maximum power of the power load;

The maximum discharge time of the battery in cloudy days;

The maximum charging time for the solar panel to fully charge the battery;

Average daily sunshine time;

Local latitude

The solar power control circuit must have hysteretic start and hysteresis charging.

4 Summary

The Jerry Solar Wireless Signal System, which uses solar power and wireless communication technology to achieve distributed control, is an innovative product. Compared with the previous system, the system adopts the scheme to send and respond to the wireless communication protocol, and uses a variety of self-diagnosis and recovery design methods to make it better in terms of lightning protection, anti-interference ability, system self-organization and self-recovery. Performance; especially the system combines solar power technology to make it more energy-efficient and environmentally friendly, in line with the direction of the national energy policy; the system completely eliminates the cable connection between the extensions, completely eliminating the materials and labor costs of the buried pipelines and cables. The overall cost of the system is much lower than the mains system, thus saving time, effort and money! Overall, the system is a practical, cost-effective product, has been applied in Bulgaria, Nigeria and other countries and countries, and has received a good price. I believe that with the increase of market awareness, solar wireless signal system will have more application space!

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