Design of Intelligent Street Light Control System Based on LED Cold Light Source

0 Preface

The current huge energy consumption and the resulting energy shortages and price increases have made saving energy a very urgent task. The National/Eleventh Five-Year Plan No. 0 proposes / to save resources as a basic national policy 0, and for the first time proposes a target of reducing energy consumption per unit of GDP by about 20% during the 11th Five-Year Plan period. The former Ministry of Construction clearly stated in the 5/11-50 Green Lighting Project Planning Outline 6 that the cumulative power saving should reach 25% from 2006 to 2010.

As a new type of green light source, LED cold light source has the characteristics of energy saving, environmental protection and long life, which is the development trend of future lighting. At the beginning of 2009, the Ministry of Science and Technology of China launched the Ten City Wanhao 0 Semiconductor Lighting Application Demonstration City Program, which covers 21 domestically developed cities such as Beijing, Shanghai, Shenzhen and Wuhan. The implementation of this plan will effectively guide the healthy and rapid development of semiconductor lighting applications in China.

This topic is an intelligent street lamp energy-saving control system based on LED cold light source road lighting, which effectively solves the existing road lighting management system. It is difficult to feedback street lamp status information, no timely switch lights, and basically no power saving effect. problem.

1 LED Technology Overview

LED (Light Emitting Diode) is a solid-state semiconductor device that directly converts electricity into light [1]. LED light source has the characteristics of high energy saving, environmental protection, long life, small size, strong applicability, high stability, short response time, etc. It can be widely used in various indications, displays, decorations, backlights, general lighting and cities. Night scenes and other fields [2]. Although the price is more expensive than existing lighting equipment, it is still considered an ideal substitute.

In terms of energy saving, the LED has DC drive, ultra-low power consumption (single tube < 0. 1 W), etc. Compared with the traditional light source, the LED light source is close to the point source, single-phase illumination, good light distribution, and high light efficiency utilization. In terms of average illumination, a 50 W LED can be as bright as a 100 W high-pressure sodium lamp, which is even higher in terms of illumination. The same lighting effect is more than 50% energy saving than traditional light sources (taking practical applications as an example).
The LED light source is a solid cold light source, epoxy resin package, and there is no loose part in the lamp body, and there are no shortcomings such as filament light-emitting, heat deposition and the like. When the luminous flux is attenuated to 70%, its lifetime reaches 50 000 h, and the life of high-pressure sodium lamps is 10 000 to 20 000 h. It has better environmental benefits, pure luminescent color, no ultraviolet and infrared radiation, no mercury, no pollution, and waste can be easily recycled. Cold light source, safe to touch, is a typical green lighting source.

2 street lamp energy-saving control system overall structure

Considering the requirements of cost, monitoring range, control point setting, and capacity expansion, a combination of wireless communication and power carrier communication is adopted in this design.

The specific scheme is as follows: The entire monitoring system consists of a monitoring terminal, a centralized controller, a street light controller, and a street light. The upper computer of the system, that is, the monitoring terminal is placed in the urban street lamp management department, and the centralized controller is installed in the range of a single distribution transformer. The street lamp controller is installed on each street lamp to facilitate single lamp control. GPRS communication is adopted between the main control room and the centralized controller. The GPRS communication method is easy to realize high-speed data transmission, long-time online, and low-cost method of charging by traffic, with less hardware investment and relatively lower geographical requirements [ 3]. The power line carrier communication technology is adopted between the centralized controller and the street lamp controller. The biggest advantage of adopting the power carrier technology is that the detection of each lamp can be easily realized without laying the communication cable, and the cost of the channel construction is reduced. . The structure of the entire system is shown in Figure 1.

3 communication implementation

The whole system adopts a hierarchical communication mechanism, one level is the communication between the monitoring terminal and the centralized controller, and the other level is the communication between the centralized controller and the street lamp controller.

The communication between the monitoring terminal and the centralized controller adopts GPRS. The centralized controller monitors and manages all street lights in the jurisdiction, and uses power line carrier communication with the street light controller. The centralized controller can work independently, switch lights according to the preset scheme, and collect relevant information of each street lamp controller in the scope under the jurisdiction. Whenever one information collection of all street lamps is completed, the centralized controller will just collect the information. The information of each street lamp controller monitoring the street lamp is quickly fed back to the monitoring terminal. When the centralized controller receives the command of the monitoring terminal, the command issued by the monitoring terminal is parsed and sent to the street lamp controller through the power line carrier communication to perform the relevant actions. The street light controller is always in the standby mode, which cyclically collects the current and status information of all the lamps of the lamp post, and once receiving the command corresponding to the local address, performs the corresponding action and feeds back the execution result to the centralized controller. Through these two levels of communication, the inspection cycle of the entire monitoring system can be greatly shortened.

3. 1 street lamp controller communicates with centralized controller

In order to facilitate the design and debugging of the system's hardware and software modules, as well as subsequent system debugging, fault analysis and system upgrade, the design uses a dual CPU structure. The two CPUs are PL3105 (relevant for carrier transceiver) and Acer. STC12C5404AD (other control). The STC12C5404AD microcontroller is a high-speed, wide-voltage, low-power, enhanced 8051 core microcontroller [4]. Because the real-time performance required in the design is not high, serial communication is directly used here. The RXD and TXD of PL3105 are directly connected with RXD and TXD of STC12C5404AD. By programming the microcontroller to start the program, it is initialized and set up according to the communication protocol. Various actions. The voltage and current acquisition circuits respectively sense the AC voltage and current through the HCT218 and HPT304 precision miniature voltage transformers, and then exchange the corresponding voltage values through I2V interchange. The street lamp controller is a single lamp operation, and the street lamp under the same transformer operation is a local area, and a plurality of power line carrier modules are connected on the same phase line. In the master-slave communication mode, the modules work separately. Its hardware block diagram is shown in Figure 2.

3. 1. 1 power line carrier module

Power Line Communication (PLC) is a general term for communication methods that use power line carriers to transmit information [526]. It has many advantages [ 729] : such as a wide range of applications, low implementation costs, permanent online and so on.

The PL3105 chip used in the power line carrier module is a single-chip system chip (SoC) developed for automatic meter reading, intelligent information appliances and remote monitoring systems [10]. The 8051 instruction-compatible high-speed microprocessor is easy to develop. The embedded carrier communication control unit has the powerful function of remote communication on the low-voltage power line. The CPU controls the carrier communication through the configuration register. Convenient; the spread spectrum communication unit has the advantages of strong resistance to in-band co-channel interference and high sensitivity.

3. 1. 2 Implementation of routing algorithm

The router is an interconnecting component of the network layer. It provides a richer and more flexible network interconnection function than the bridge. It is one of the most widely used network interconnection components. The routing algorithm is a function that implements routing by software.

Since the reliable communication distance of the general power carrier chip is about 500 m, which far exceeds the maximum communication distance in practical applications, the routing protocol layer is added to the street lamp controller designed in this design, and the physical layer design with superior performance is adopted. And a complete network communication protocol to ensure reliable network communication performance. As long as the equipment on the power line of the same jurisdiction is integrated into the chip and related communication modules, it can become an intelligent control product that can be controlled by the power line.

The routing action consists of two basic elements: path finding and forwarding. Path finding is the best path to determine the destination, and the path information varies depending on the routing algorithm used. The routing algorithm populates the routing table based on a lot of information, and maintains and updates its routing table by exchanging routing information. The routing update information usually contains all or part of the routing table. By analyzing the information from other routers, the router can establish a new network. Topology. In some complex and large-scale projects, dynamic routing algorithms are used to adapt to changes in the network environment by analyzing received routing update information. If the information indicates a change in the network, the routing software recalculates the route and issues new routing updates. This information infiltrates the network, causing the router to recalculate and make corresponding changes to the routing table, and supplement it with static routes where appropriate to keep the system stable. In view of the small scale of some projects, the hardware of the carrier network is very fixed, and relatively less data is transmitted. Therefore, it is also possible to use only the static routing table algorithm, which makes the algorithm easier to design and works well. Forwarding means transmitting information packets along the best path of path finding.

The operation process of the routing action mainly includes the following points:

(1) Receive and decompose data packets. When the router receives the data packet, it first verifies its legitimacy, and then separates the header, the message, and the check byte. Then select the operation according to the different headers.

(2) Process the packet. When a valid message is received, the router must decide whether the data is forwarded locally or forwarded. When IP broadcast or multicast, it may also be a mixed case. The judgment of these situations is mainly handled according to the following three rules:
When there is a source routing option in the IP destination address, it is sent to the next site according to the corresponding entry in the routing table, without local commit.
When an address in the IP destination address matches a port address of the router, a local commit is made.
When the IP destination address is a broadcast address, or a multicast address that is both forwarded and committed locally, two operations are performed simultaneously.

(3) Forward addressing. The router first looks in the routing table to see if it knows how to send the packet to the next station (router or host). If the router does not know how to send the packet, it usually discards the packet; otherwise, it will be grouped according to the corresponding entry in the routing table. Send to the next site. If the destination network is directly connected to the router, the router will send the packet directly to the corresponding port.

(4) Forward verification. Before forwarding, the router should perform some verification work on the data packet, and the forwarding can only be performed when the verification is correct. Otherwise, the data packet is discarded and the broadcast source of the data packet is re-requested. The verification here is divided into two parts: one is the verification of IP, to see if the target IP of the received packet meets the requirements; the second is the verification of the specific data, and whether the data obtained by the verification is incorrect.

3. 2 street lamp energy saving control system software implementation

3. 2. 1 centralized controller

The main program structure is divided into two parts: one is the initialization segment, and the other is the loop body. In order to facilitate debugging and maintenance, a multi-module organization structure is adopted in this design. Each task is a sub-function. In the main program loop body, the task modules are called one by one. The execution of these module functions depends on whether the condition flags are satisfied. The main program flow chart is shown in Figure 3.

To prevent each task from preempting clock resources and causing time conflicts, take the following measures:

(1) Different time schedules are given depending on the task. For example, LCD display swipe processing only needs 1 s call once; button processing is called once for 10 ms; device patrol is called once according to device number 5 min, and the timing processing program flow chart is shown in Figure 4~ Figure 6.

(2) In order to avoid the timely processing of other tasks due to the long execution of some tasks, one task can be divided into multiple time slices. For example: In the button processing program, when the button is closed for the first time, it takes 10 ms delay time to debounce, but if the 10 ms delay program is used in the program, it will affect the execution of other programs. Therefore, the 10 ms waiting time should be given to other tasks.

(3) For tasks with higher real-time requirements, you can put the sub-function directly into the interrupt function to execute. For functions that are not very real-time, you can first set the flag in the interrupt function, and then let the background program perform specific functions according to the flag.

3. 2. 2 street light controller

The data acquisition adopts the program control mode, and collects the real-time power according to the host computer command. In order to facilitate the monitoring of the working state of the street light, in the microcontroller
The reference voltage is stored in the E2PROM. When the voltage collected by the HPT 304 precision miniature voltage mutual inductance enters the MCU A/D conversion, it is compared with the reference voltage. When it is less than or greater than a certain value, the communication fault code is set, and according to the communication. The protocol is sent by the power line carrier module to the centralized controller alarm, and its program flow chart is shown in Figure 7.

The PL3105 and the centralized controller communicate with each other through the power line. For the user, the power line carrier module establishes a transparent data transmission channel for the customer, and the user can directly connect the master and slave devices as a cable, and the reliability of the user communication is determined by the user. The communication protocol is guaranteed.

Since the working range of the LED is large, its light output is proportional to the operating current, so the current can be reduced by dimming. LED dimming can also be obtained by pulse width adjustment. By adjusting the duty cycle and operating frequency of the voltage, the luminous intensity of the LED can be effectively adjusted.

Combined with this feature of the LED light source, PWM dimming is used to reduce resource waste and source pollution. This design uses Macrotec's STC12C5404AD microcontroller, in addition to its built-in AD, because it has four programmable counter arrays (PCA) / PWM, convenient to achieve adjustable PWM signal output. The implementation of dimming is controlled by the centralized controller. When the set time is reached, the controller sends a signal to the street lamp controller through the power line. After the command is decoded, the internal control register of the STC12C5404AD is set to start the programmable counter array (PCA). /PWM operation, output adjustable PWM, to achieve dimming function.

4 Conclusion

As an energy-saving and environmentally-friendly green lighting source, LED will play an increasingly important role in the development of road lighting in the future. This paper combines the characteristics of LED lamps to design intelligent street lamp energy-saving control system, which is energy-saving, efficient and user-friendly. .

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About the Author:

Lu Yunpeng, born in 1956, Zhengzhou, Henan, professor, department head. The main research direction is information acquisition and processing technology.
Ji Xiao's daughter, born in 1984, Zhangjiakou, Hebei, master's degree. The main research direction is smart instruments.
Li Hongchao, born in 1985, Zhengzhou, Henan, master's degree. The main research direction is smart instruments. 

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