Development of intelligent charging pile (I): overview of the overall design of the system

According to the statistics of relevant associations ,2021 In the year , The cumulative sales of domestic passenger cars reached 2014.6 Thousands of cars , Year-on-year growth 4.4%. In the Middle East: , Retail sales of new energy passenger vehicles reached 298.9 Thousands of cars , Year-on-year growth 169.1%. so to speak 2021 The growth point of the whole year , Mainly in the field of new energy vehicles . The rapid growth of new energy vehicles , It also drives the rapid development of charging pile enterprises .2021 year , Charging pile business also ushered in explosive growth , Last year, the company's shipment of intelligent charging piles has exceeded 4 Ten thousand units , It is expected that this year will impact 10 The integer of 10000 units is off .

​ With the rapid economic development of our country , Battery cars have become one of the main means of transportation for people . However , The traditional coin operated charging pile not only makes the user experience very poor , There are still many potential safety hazards . The rapid development of Internet of things technology , It is guiding a profound change in the information society . The number of domestic battery cars is even more amazing , The charging pile business of battery cars has a broad market prospect . The safety hazard of charging the battery car at home is great , Such as personal injury caused by fire after entering the elevator , It also promotes people's attention to charging safety .

​ meanwhile 3G Communication base station , Move Telecom and other operators have also closed down , Also prompted 4G The intelligent charging pile of network communication is developing more rapidly .

​ This paper introduces a kind of 4G Intelligent charging pile , The cost of this scheme is low 、 Small volume , Suitable for installation in various public places . The gateway of the charging point system passes through the server 4G The network communicates directly , The management party can directly carry out reasonable and timely maintenance and adjustment of the charging pile through the data feedback of the server , It improves the maintenance efficiency of the charging pile and plays a role in preventing fire to a certain extent . Users can use the socket to charge through wechat applet , Make the user experience better while ensuring the safety of funds .

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1 Overall design of the system

​ The overall design of the system is shown in the figure 1 Shown , It mainly includes intelligent charging pile , Cloud platform services , client . Between intelligent charging piles and cloud services 4G signal communication , The communication between client and cloud service through Wan can be 4G It can also be WIFI. Considering the user's use cost, the client directly uses wechat applet . Smart charging includes 4G Communication module 、 Main controller 、 Data collection 、 Display module 、 Voice module and charging board control module .

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​ chart 1 Overall system diagram

​ Fig.1 Overall system diagram

​ The customer directly scans the QR code on the charging pile through wechat applet （ One machine, one yard ） after , Select an idle charging socket according to the prompt , You can start charging after submitting your order online . Customers can also check the charging status of the socket at any time on their mobile phones , And you can end charging at any time .

​ Intelligent charging pile includes 4G The module moves away EC200, Main controller MCU STM32F103VE, The charging board is like the charging control board of Dianchuan , Its core control MCU STM8S105S4T6C.EC200 The module passes through 4G The network communicates with ECS , Transmit the data packets sent by the cloud service to the main controller STM32F103VE, Main controller STM32F103VE First analyze the data packet , Then issue the parsed command , The charging board will respond relatively to the commands of the main controller . Main controller STM32F103VE The collected data will be packaged through EC200 Upload the module to the server . Besides , The main controller can also drive the ten channel nixie tube display and PCM Voice file broadcast , It improves the user experience in terms of audio-visual .

​ The charging board controls ten relay switches to provide charging interface for users , If something unexpected happens, the system will respond automatically , Send voice alarm and power off the hardware .

2 Overall design of system hardware

be based on STM32F103VE and 4G The hardware structure of the intelligent charging pile of the module is shown in the figure 2 Shown . The gateway control system of intelligent charging pile adopts GD32F103VE Microcontrollers and EC200 modular .GD MCU It's based on Cortex-M3 ARM Kernel 32 Bit microprocessor , The microcontroller integrates many modules , Including abundant hardware resources such as memory and communication unit [5]. In addition, the system is externally connected to the charging control board 、DS18B20 Temperature measurement module 、NTC Inter board temperature measurement module 、 Digital tube display module 、PCM Voice file broadcast module 、 Power module .EC200 It is moving far and low cost 4G modular .

​ chart 2 System hardware structure

​ Fig.2 System hardware structure

2.1 Charging control board

Charging control panel and MCU STM32F103VE 2 road TTL Level UART signal communication . The charging control panel uses STM8S105 Control the ten way relay for the controller , The relay adopts JQC-3FF Subminiature high-power relay . The charging control board realizes the intelligent control of the charging socket through the relay , The charging control board will collect charging power and charging power data and transmit them to STM32F103VE Main controller . The board is also equipped with AP8022H The chip protects the charging board from overcurrent 、 Over temperature protection and under voltage protection .AP8022H Pulse width modulation controller and 800V High avalanche capability, intelligent power MOSFET.AP8022H The chip also has a built-in high-voltage starting module , Ensure that the system can start quickly .

2.2 4G Communication module

EC200 It's mobile communications LTE Cat4 All Netcom wireless communication module , collocation SIM Card execution 4G module MQTT Protocol communication , Support maximum downlink rate 150Mbps And maximum uplink rate 50Mbps, Support AT Command operation and FOTA Remote upgrade .EC200 Module and main controller UART Connect , Realize the main control chip and 4G Data communication between modules .

Here the 4G The reason for the module is to consider our 2G、3G Network services are gradually shutting down , Major operators gradually do not provide 2G、3G Network services , also 4G Communication speed ratio 2G、3G fast , It is more suitable for complex logical business . In order to make the intelligent charging pile operate longer in the future and facilitate remote maintenance , Here the 4G The module is more cost-effective .

2.3 Temperature measurement module

The temperature measurement module is divided into DS18B20 Temperature measurement module and NTC Inter board temperature measurement module .STM32F103VE And DS18B20 The temperature measurement module uses 1-Wire Bus protocol for communication , And pass 4.7KΩ The pull-up resistance of is DS18B20 Provide 3.3V voltage . The temperature detection range of the temperature sensor is -55℃ to +125℃, And the temperature range exceeds -10℃ to 85℃ Besides, it also has ±0.5℃ The accuracy of the .DS18B20 The sensor provides 9-Bit To 12-Bit Degree Celsius measurement accuracy ,GD32F103VE Main controller and DS18B20 Cooperation can realize the alarm function of triggering the alarm at excessive temperature and low temperature . An alarm causes the main controller control socket to be powered off , It plays a certain role in preventing fire .NTC Inter board temperature measurement module coordination GD32F103VE Of ADC_IN9 To achieve , basis NTC Characteristics of thermistor , Convert the collected data into temperature in the main controller , So as to monitor the temperature of the charging board , It is used to prevent the chip from working under abnormal temperature and causing system failure .

DS18B20 The temperature measurement module is mainly used for the environmental temperature measurement of the charging station , Cooperate with smoke sensor and micro spark sensor to send voice alarm after detecting abnormal environmental conditions .

2.4 Audio broadcasting module

GD32F103VE built-in 3 A synchronous standard timer . Each timer has a 16 Bit counter 、 One 16 Bit prescaler and 4 Independent PWM passageway . and PCM Voice file usage 16kHz Sampling frequency of ,8BIT Quantization coding of , Its broadcast module only needs one way PWM Channels and 1 A timer can complete the voice broadcast function . When there is PCM When voice files need to be broadcast , With 16kHz Play data at a rate , Data into PWM Duty cycle to control the audio signal , Through the output of filter circuit and audio power amplifier, it is amplified and output to speakers for audio playback [6].

The content of voice broadcast mainly includes charging status broadcast , Such as “X(1-10) Charging started on the th ”、“X(1-10) The charging is completed ” etc. , Let users hear the broadcast content and understand the status of the socket . In case of accidents such as socket fire , Voice broadcast can give an alarm at the first time to remind people to pay attention to safety and control the situation .

2.5 Digital tube display module

GD32F103VE The main controller passes GPIO and SPI Two ways TA6932 Chip to control . Between the main controller and the nixie tube module 8 Root line , among 2 The root is power line and ground wire , rest 6 Root and master controller SPI3_SCK、SPI3_MOSI、PD3、PD4、PD5、PD6 Connect .TA6932 The chip receives the data of the main controller through the serial interface, and then checks each LED Drive , Each chip drives 5 road LED Display .

The nixie tube module mainly displays the remaining charging time of the corresponding socket ( In minutes ), Users can intuitively see the remaining service time of the socket .