My notes on intelligent charging pile development (II): overview of system hardware circuit design

2. My intelligent charging pile Development Notes （ Two ）： Overview of system hardware circuit design

2 System hardware circuit design

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​ Due to charging control for both , One is TTL UART Interface of the electric control board , One is RS485 Controlled circuit breaker , A choice . By default TTL UART Interface's DCP mode .

​ 4G The data traffic of network module is large , Adopt support DMA Of UART 1 Interface . Dianchuan control board 1, Dianchuan control board 2 And MCU There is also more interactive data , Adopt support DMA Of UART2 UART3 Interface .

Which mode does the power on automatic detection belong to . namely UART2 UART3 All connected to the Dianchuan control board , That is to say, at present TTL UART Interface's DCP mode . here , The debugging serial port in this mode adopts MCU UART4 As DEBUG, The UART Not supported by default DMA receive , Therefore, the UART. otherwise , Use RS485 Charging control of circuit breaker , namely UART2 UART3 Belong to idle UART, Use UART3 As a debug serial port .

    if(dc1_exist == 1 && dc2_exist ==1)
    {
        debug_uart_id = PRINTF_UART_ID_4;
    }
    else
    {

        debug_uart_id = PRINTF_UART_ID_1;
    }

be based on STM32F103VET6 and 4G The hardware structure of the intelligent charging pile of the module is shown in the figure 2 Shown . Gateway control system adopts STM32F103VET6 Microcontrollers and EC20 modular , The microcontroller is 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 also equipped with a charging control board 、DS18B20 Temperature measurement module 、NTC Inter board temperature measurement module 、 Digital tube display module 、PCM Voice file broadcast module 、 Power module .

chart 2 System hardware structure

Fig.2 System hardware structure

2.1 Charging control board

STM32F103CET6 The main controller passes 2 road TTL、UART Communicate with the charging control board . 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 STM32F103VET6 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 .

2.1.1 5V–3.3V Level conversion circuit

Dianchuan board is 5V level ,MCU yes 3.3V, Both use UART Communication requires level conversion .

2.1.2 The electric board is connected to the detection circuit

The picture on the left shows that the interfaces of the board are ,GND,TX,RX,5V Power Supply , The corresponding network LABEL yes GND DC2_TX RC2_RX +5V_DC2, Among them +5V_DC2 It is the battery board that produces

When the Dianchuan board is connected MCU Behind the core control board , The reverse circuit of the triode on the right works , here DC2 The level is low

When the electric board is not connected MCU Behind the core control board , The reverse circuit of the triode on the right is not working , here DC2 Pull up the resistor , The level is high

MCU Judge whether there is control board access according to this

2.2 4G Communication module

​ EC20 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 . System USES STM32F103VET6 Master controller ,EC20 Module and main controller UART2 Connect , With RS485 The protocol realizes the master 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 .

2.2.1 1.8V–3.3V Level conversion circuit

4G Module is 1.8V level ,MCU yes 3.3V, Both use UART Communication requires level conversion .

2.2.2 mobile phone SIM Data communication flow card access circuit

2.2.2 Move far 4G module miniPCIE Interface circuit

2.3 Temperature measurement module

​ The temperature measurement module is divided into DS18B20 Temperature measurement module and NTC Inter board temperature measurement module .STM32F103VET6 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 ,STM32F103VET6 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 STM32F103VET6 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 PCM Voice file broadcast module

STM43F103VET6 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

STM32F103VET6 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 .

2.6 System power supply Sketch Map

2.7 RS485 Circuit breaker module