Road lighting solution based on wireless communication M2M module

The structure of the road lighting system based on the Internet of Things is shown in Figure 1. By embedding a wireless communication module in each street lamp, they can form a self-network, receive commands from the control center and feed back the status of the street lamp to the control center. The HG-2 control box uses ZigBee technology to communicate with all street lamps on the roads under its jurisdiction, and uses GPRS to communicate with the control center. According to the instructions of the control center or the time and daylight intensity, it issues control commands to each street lamp (street lamp on, off, illumination (power size), etc.), and automatically adjusts the power balance of the entire road. The control center consists of a server, a large-screen display, and the CenterView central control system software platform. The CenterView central control system software platform adopts a 3D design, and can observe and control the lighting conditions of the entire city, a street, a road, and even a street lamp from a bird's-eye view through zoom transformation. Mobile computing tools (laptops, PDAs, mobile phones) and street lamp maintenance vehicles can also perform remote telemetry and remote control through the control center.



3 Wireless communication module

The MCU of the wireless communication module is Freesclae's MC13213. MC13213 uses SiP technology to integrate the MC9S08GT main control MCU and MC1320x RF transceiver in a 9×9mm LGA package. As shown in Figure 2. The



wireless communication module uses ZigBee technology and IEEE802.15.4 protocol. The communication coverage radius can reach 150m. It can form a self-organized network and communicate with any street light node within its coverage. In addition to realizing the interconnection of street lights, it also has the functions of adjusting the power output of the electronic ballast (30%~100%) to achieve energy saving and green lighting, detecting the current, voltage, power factor of the power supply line, and the working status of each lamp. When a fault occurs (such as lamp damage, lamp pole collision, and human damage), it can send an alarm to the monitoring center and relevant departments in real time.

The wireless communication module is also designed to be rainproof, moisture-proof, lightning-proof, and electromagnetic interference-proof, and fully considers easy installation, simple maintenance, and recoverability (connecting two wires to achieve street lamp-level wireless control, and removing the two wires to restore to the original state). It can be embedded in different positions of street lamps (bottom of the lamp pole, inside the lamp pole, inside the lampshade).

3.2 Communication protocol

The communication protocol of the wireless communication module is as follows: the lighting is numbered in sequence according to the road section, and the "hand-in-hand" communication between nodes is realized through command forwarding and status return. Command forwarding mechanism: Each node uses a bitmap structure to record which frames have been forwarded (the bitmap can represent up to 256 frames). If a node receives a command frame, it determines whether the frame has been forwarded by the node. If so, the frame is discarded (the node only forwards the received command frame and does not modify the content of the frame), thereby ensuring that a line is controlled at the fastest speed and effectively preventing a node failure from affecting the operation of the entire line; Status return mechanism: After the command frame is sent to the designated node, the designated node receives the command and immediately returns the status; Forwarding rules: Only when the node number is smaller than the target node number will it be forwarded, and the status return process is the opposite.

3.3 Connection with central monitoring

A transmission communication link consists of several ZigBee nodes, and a cluster node is set in the middle of these nodes (one road can set one or more cluster nodes), which communicates with the control center in GPRS mode (command acceptance and status return). The cluster node uses Freescale's 32-bit CodeFire series MCF52223 chip as the control unit, GTM900B (Huawei GPRS communication module) and EM770W (Huawei WCDMA 3G communication module) as long-distance wireless communication modules. The MCF5222x series is built with the commonly used V2ColdFire core, with a performance of up to 76MIPS (Dhrystone2.1) at a frequency of 80MHz. The interface functions include: 1 MiniUSB interface, supporting USBOTG function, 3 2-wire serial ports, 1 microphone input interface, 1 HEADSET input/output interface, 1 HANDSET input/output interface, 1 8Ω/16Ω speaker output interface, 1 132*96 dot matrix LED, 1 5*5 keypad, supporting RTC, ADC, PIT＆GPT, PWM, etc.; GTM900B and EM770W complete long-distance GPRS communication.

4 Control Center Software Design

The software design platform of the control center is Windows 2003, the development tool is Microsoft Visual Studio 2005, and the database uses SQL Server 2005. After obtaining the location, shape and other characteristic information of streets, buildings and street lights, a 3D virtual city with street lights as the main body is designed. The lighting effect of the road is dynamically displayed on the large screen of the control center, and the lighting conditions of the entire city, streets and even each street light can be observed through geometric transformations such as translation, zooming in and out. The software mainly has 5 functional modules: system settings, intelligent control, power calculation, fault handling and emergency plan. There are 4 types of regional settings in the system settings: city, district, street and electric control box; the street light settings include the location, model, production unit, construction unit, maintenance person, installation date, cleaning and maintenance date, etc. of the street light; the lighting mode settings include full on, full off, odd-numbered street lights on, odd-numbered street lights off, even-numbered street lights on, even-numbered street lights off, 1/3 street lights on, 1/3 street lights off, 1/4 street lights on, 1/4 street lights off, intelligent control and other 11 control modes; the time period setting can set the lighting mode for different time periods according to different cities and seasons; intelligent control has two aspects: for sections where electronic street lights are installed, the lighting brightness of the street lights is intelligently adjusted by real-time sampling of ambient light intensity according to seasonal changes and weather conditions; at night, especially late at night When it is detected that the traffic of cars and pedestrians is very scarce, the road lighting brightness is appropriately reduced without affecting the reliability of identification to save power consumption; power accounting can count and calculate the power consumption of cities, districts, streets, electric control boxes and even each street lamp; fault handling is to quickly generate a fault report after reporting to the monitoring center in the first time for situations such as lamp damage, power failure, phase failure, overcurrent, overvoltage, three-phase imbalance and human damage; another function of fault handling is to count the lighting rate, fault rate, and efficiency of each fault handling (average repair time) by road section and time period (year, quarter, month); emergency plans are formulated for some emergencies. In special circumstances, appropriate road lighting is provided as much as possible to ensure the safety of people's lives and property. Figure 3 is one of the operating interfaces of the control center software.



5 Practical Applications

Since May 2009, the road lighting system of the Internet of Things has been installed and tested in a national industrial park. The installation environment is 100 street lights on both sides of the same road. The 100 street lights on the left side of the road use wireless sensor intelligent control, which adds a total cost of RMB 24,600.00. The 100 street lights on the right side of the road use conventional control methods (the lights are turned on at odd and even intervals after midnight from 18:30 to 6:30). The test results are shown



in Table 1. As can be seen from Table 1, the intelligent control of the Internet of Things saves 15,925 degrees of electricity in 91 days through actual testing. Generally, the entire investment can be recovered within half a year after the product is put into use. The following factors can reduce power consumption: the adjustment of the opening and closing time. The control method of the street lights on the right side of the road is to set the opening and closing time according to the season (timing control) and it is full-power on and full-power off. The control method of the street lights on the right side of the road is to automatically control the opening and closing time according to the ambient light intensity and the season. When turned on, due to the strong ambient light on the road surface, the street lights work in a fill light mode, gradually increasing the lighting intensity, and the street light off control is similar; late night control mode, due to the reduction of corporate and residential electricity load at night, the low-voltage power grid voltage increases, the street lights under conventional control mode (right side of the road) are abnormally bright and dazzling, often causing excessive lighting, which not only greatly increases power consumption, but also causes the actual service life of lamps and electrical appliances to decline rapidly, greatly increasing the maintenance volume and maintenance costs. In the late night control mode (left side of the road), the use of reduced power lighting not only reduces power consumption, but also improves the quality of road lighting and visual comfort, and extends the actual service life of lamps and electrical appliances; intelligent control of road lighting, for special sections with schools, densely populated communities, road bends, accident-prone areas, etc., the lighting brightness is appropriately increased, and the lighting brightness is appropriately reduced for other sections.

After adopting the intelligent street light control of the Internet of Things, the automatic fault detection and alarm have the advantages of good real-time performance and strong reliability, which greatly shortens the time and labor intensity of regular manual inspections.



6 Conclusion

Advanced road lighting can not only enhance the image of the city, improve transportation efficiency, reduce traffic accidents, but also save a lot of public electricity consumption. However, for most cities, due to the lack of necessary infrastructure (street light level communication link), advanced control methods cannot be implemented. The emergence and application of the Internet of Things (IoT) effectively solves the above problems. Based on the wireless sensor network, this paper selects the MC13213 chip of Freesclae Company and designs an embedded wireless communication module to enable each street light on the entire road to connect to the Internet autonomously. Using the MCF52223 chip of Freescale Company, MG323 and EM770W of Huawei Company as remote communication modules, the telemetry and remote control of street lights are realized, which has a high practical application value for saving public resources and building digital and economical cities.