CN102200763A - Grain status monitoring system based on fieldbus - Google Patents

Abstract

A grain situation monitoring system belongs to the fields of electrical and electronic technology, computer technology and automation, and specifically relates to a grain situation monitoring system based on a CAN field bus. The invention comprises a management center computer (1), an RS-232 conversion CAN bus module (2), a field bus (3), several CAN field bus control terminals (4), several temperature sensors (5), and several humidity sensors (6), several contactors (7). The management center computer (1) completes the dynamic real-time display and accurate control of the monitoring interface, and the CAN field bus control terminal (4) collects temperature, humidity and contactor (7) signals and transmits them to the management center computer (1) through the field bus (3). The invention has good real-time control performance, vivid and accurate monitoring interface, simple and efficient circuit, strong anti-interference ability, fewer cables, convenient application and low cost.

Description

A Grain Situation Monitoring System Based on Fieldbus

Technical field

The invention belongs to the fields of electric and electronic technology, computer technology and automation, and specifically relates to a field bus-based grain situation monitoring system.

Background technique

Food is a necessity for human survival. Every year, a large amount of new grain is harvested and some old grain is backlogged. If a large amount of food is wasted due to improper storage, it will cause huge economic losses. Food security is very important. The safety of grain in the storage process is mainly manifested in the change of grain temperature and moisture. Once the grain is damp, its metabolism will speed up and produce respiratory heat. Changes, you can grasp the food situation. Therefore, the safe storage of grain has always been a major problem that plagues grain management units. It is imperative to improve the conditions of grain storage, improve the level of grain storage technology, and promote the progress of grain storage technology. The measures taken in the past were to dry the grain manually, ventilate it, and spray chemicals to prevent insect damage caused by improper storage, which consumed a lot of manpower and financial resources. However, the effect was not good, and the phenomenon of mold and deterioration still existed. With the development of electronic technology and computer technology, electronics and computers are widely used to measure, control and manage the grain situation, but there are still many unsatisfactory problems, such as poor anti-interference performance, loss of transmitted data, and the interface of the upper computer is not vivid, etc. Aiming at these situations, a fieldbus-based grain monitoring system is proposed, which can reduce grain loss and increase farmers' income.

Fieldbus control system technology is a brand-new industrial control technology developed abroad in the mid-1980s. Fieldbus (fieldbus) is a system used in the production site to realize two-way serial multi-node digital communication between computerized measurement and control equipment, also known as the underlying control network of open, digital, and multipoint communication. Integration of network and control system. With the continuous enhancement of microprocessor and computer functions and the reduction of prices, computers and computer network systems are developing and expanding rapidly. The field bus can realize the information integration of the whole enterprise, implement comprehensive automation, form the bottom layer network of the factory, complete the multi-point digital communication between the field automation equipment, and realize the information exchange between the bottom field equipment and the production site and the outside world. Because adopting the field bus will make the control system structure simple, the system installation cost will be reduced and easy to maintain, the field bus technology is being paid more and more attention by people. At present, there are hundreds of fieldbuses that have appeared in the world, and the typical ones that have a certain influence and occupy a certain market share mainly include Foundation Fieldbus (FF), CAN, PROFIBUS, Lonworks, and HART. CAN (Controller Area Network Controller Local Area Network) bus was originally a serial data communication multi-host local area network designed by Germany's BOSCH company for vehicle monitoring and control systems.

Contents of the invention

The purpose of the present invention is to propose a grain situation monitoring system based on the field bus to solve the grain situation monitoring problem, the technical solution is as follows: a grain situation monitoring system based on the field bus, the system includes: a management center computer (1) , RS-232 conversion CAN bus module (2) field bus (3), several CAN field bus control terminals (4), several temperature sensors (5), several humidity sensors (6), several contactors (7 ).

Described management center computer (1) adopts PCI bus industrial control machine, installs industrial control configuration software on management center computer (1), designs various grain situation monitoring interface, simultaneously management center computer (1) will also pass field bus (3) Communicate with each CAN field bus control terminal (4) to monitor the grain situation in real time. Because the PCI bus industrial controller does not have a CAN bus but has an RS-232 interface, the RS-232 conversion CAN bus module (2) is selected for connection with the field bus (3). Described field bus (3) selects CAN field bus for use, and CAN field bus is a kind of popularization rate very high field bus (fieldbus), direct communication distance can reach 10km farthest, rate is below 5Kbps, and communication speed can reach 1Mbps at the most, at this moment The longest communication distance is 40m, the number of nodes can reach 110 at present, and the communication medium can be twisted pair, coaxial cable or optical fiber. Described CAN fieldbus control terminal (4) adopts MCU intelligent terminal, is responsible for temperature and humidity measurement and ventilator is controlled, sends information to management center computer (1), receives the control information of management center computer (1), The used CAN field bus control terminal (4) is determined according to the grain storage enterprise and monitoring system. Described temperature sensor (5) selects the novel single-bus digital temperature sensor chip DS18B20 that U.S. DALLAS company produces for use, and it has simple structure, does not need external component, adopts an I/O data line to be able to supply power and can transmit data again, and can be controlled by User-settable temperature alarm limit feature. DS18B20 is widely used in temperature control systems that require temperature control, such as food storage, cold storage, grain storage, and greenhouses. Therefore, DS18B20 is used, and it has two power supply methods: direct power supply and parasitic power supply. The direct power supply method is used here. The humidity sensor (6) selects the HIH-4000-1 chip produced by Honeywell (Honeywell), which is a monolithic integrated circuit with laser adjustment and interchangeable capacitive changes. Its output voltage and RH value Linear relationship, high precision, fast response time, small drift. Under standard operating voltage (Dc5V) and standard room temperature (25°C), as the RH value ranges from 0 to 100%, the corresponding output voltage ranges from 0.196 to 3.190V. The measuring humidity range is 0~100%RH, the accuracy is ±3.5%RH, and the working temperature range is -40~+85℃. Contactor (7) selects common AC contactor (7) for use and gets final product.

The CAN field bus control terminal (4) comprises an MCU single-chip microcomputer 2-1, a CAN bus circuit 2-2, a driving circuit 2-3, a single bus circuit terminal 2-4, and a humidity signal conditioning circuit 2-5. MCU microcontroller 2-1 selects Atmel's AT89C51CC01 microcontroller. AT89C51CC0x series microcontroller is a member of the MCS-51 microcontroller family. The core of the controller is the 51 series microcontroller, which uses a powerful 80C51 instruction set and successfully includes Philips The PeliCAN function of the semiconductor SJA1000CAN controller, the fully static core provides an extended power-saving mode, the oscillator can be stopped and resumed without losing data, and the improved 1:1 internal time divider achieves a 500ns instruction cycle at a 12MHz external clock frequency , AT89C51CC01 itself has its own CAN bus controller, so no additional CAN bus controller is needed. The CAN bus circuit 2-2 is the communication interface between the management center computer (1) and the CAN field bus control terminal (4), the drive circuit 2-3 plays a role of power amplification and isolation, and the single bus circuit terminal 2- 4 play the role of connecting the CAN field bus control terminal (4) and the temperature sensor (5), the humidity signal conditioning circuit 2-5 adjusts the 0.96-3.90V voltage signal of the humidity sensor (6) into a 0.00-5.00V voltage signal, So that the MCU microcontroller 2-1A/D converter can receive the signal.

The CAN bus circuit 2-2 includes a photocoupler 3-1, a CAN bus transceiver 3-2, a lightning protection tube 3-3, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a capacitor C1, and a capacitor C2. The optocoupler 3-1 selects a high-speed optocoupler isolation 6N137 chip. Here, two 6N137 chips are used. The TXDC pin of the MCU microcontroller 2-1 is connected to the IN pin of a 6N137 chip through a resistor R1. The RXDC of the MCU microcontroller 2-1 The pin is connected to the OUT pin of another 6N137 chip, the CAN bus transceiver 3-2 uses the TJA1050 chip, the OUT pin of one 6N137 chip is connected to the pin TXD of the TJA1050 chip, and the IN pin of the other 6N137 chip is connected to the pin of the TJA1050 chip through the resistor R2 Pin RXD, the CANH pin of the TJA1050 chip is connected to the CAN bus node through the resistor R3, the capacitor C1, and the lightning protection tube 3-3, and the CANL pin of the TJA1050 chip is connected to the CAN bus node through the resistor R4, the capacitor C2, and the lightning protection tube 3-3. CAN bus nodes are connected.

Described single bus circuit terminal 2-4 comprises single bus 4-1, single bus connection terminal 4-2, MCU single-chip microcomputer 2-1P0 mouth 8 pin interfaces 4-3, MCU single-chip microcomputer 2-1P2 mouth 8 pin interfaces 4-4. Single bus 4-1 is a proprietary technology of DALLAS company. Single bus, as the name suggests, has only one data line, which uses a single signal line to transmit both clock and data, and the data transmission is bidirectional. It can collect temperature data on site, and directly convert the measured temperature data into digital output as a serial digital signal output, which is easy to connect with a microcontroller. It has the advantages of saving I/O port line resources, simple structure, low cost, and convenient bus expansion and maintenance. Described single-bus connection terminal 4-2 is temperature sensor (5) and CAN field bus control terminal (4) connection node, MCU single-chip microcomputer 2-1P0 mouth 8 pin interfaces 4-3 and MCU single-chip microcomputer 2-1P2 mouth 8 The pin interface 4-4 is connected to the single-bus terminal 4-2, and the single-bus terminal 4-2 has 16 terminals in total, and each input terminal is respectively connected to 8 temperature sensors, and the maximum here is 16×8=128 Temperature measurement points, as for how many temperature measurement points are needed, it depends on the situation.

The beneficial effects of the present invention are:

1. The real-time control performance is good, and the monitoring interface is vivid and accurate.

2. The circuit is simple and efficient, and has strong anti-interference ability.

3. Less cables, easy to use and low cost.

Description of drawings

Fig. 1 is a schematic diagram of the system structure of the present invention.

Fig. 2 is a schematic diagram of the structure and working connection of the CAN field bus control terminal of the present invention.

Fig. 3 is a schematic structural diagram of the CAN bus circuit of the present invention.

Fig. 4 is a schematic diagram of the terminal structure of the single bus circuit of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific implementation.

The first step: as shown in Figure 1, install industrial control configuration software on the management center computer (1), design various grain monitoring interfaces, and the management center computer (1) will communicate with each other through the field bus (3) simultaneously. The CAN field bus controls the terminal (4) to communicate, and sets various parameters of the grain situation.

Second step: as shown in Fig. 1 and Fig. 2, each CAN field bus control terminal (4), collects temperature, humidity and contactor (7) signal and transmits to management center computer (1) by field bus (3), The management center computer (1) can dynamically display various grain situation monitoring interfaces in real time, and at the same time, the management center computer (1) sends instructions to each CAN field bus control terminal (4) through the field bus (3). Step 3: The management center computer (1) can query real-time and historical data, print reports, and process alarms as required.

Claims (4)

1. A grain situation monitoring system based on Fieldbus, characterized in that: comprising management center computer (1), RS-232 conversion CAN bus module (2) Fieldbus (3), several CAN Fieldbus control terminals (4) , several temperature sensors (5), several humidity sensors (6), several contactors (7) seven parts. 2. a kind of grain situation monitoring system based on field bus as claimed in claim 1, is characterized in that: described CAN field bus control terminal (4) comprises MCU single-chip microcomputer 2-1, CAN bus circuit 2-2, drive circuit 2 -3. Composed of single bus circuit terminals 2-4 and humidity signal conditioning circuit 2-5. MCU microcontroller 2-1 selects Atmel's AT89C51CC01 microcontroller. AT89C51CC0x series microcontroller is a member of the MCS-51 microcontroller family. The core of the controller is the 51 series microcontroller, which uses a powerful 80C51 instruction set and successfully includes Philips The PeliCAN function of the semiconductor SJA1000CAN controller, the fully static core provides an extended power-saving mode, the oscillator can be stopped and resumed without losing data, and the improved 1:1 internal time divider achieves a 500ns instruction cycle at a 12MHz external clock frequency , AT89C51CC01 itself has its own CAN bus controller, so no additional CAN bus controller is needed. The CAN bus circuit 2-2 is the communication interface between the management center computer (1) and the CAN field bus control terminal (4), the drive circuit 2-3 plays a role of power amplification and isolation, and the single bus circuit terminal 2- 4 play the role of connecting the CAN field bus control terminal (4) and the temperature sensor (5), the humidity signal conditioning circuit 2-5 adjusts the 0.96-3.90V voltage signal of the humidity sensor (6) into a 0.00-5.00V voltage signal, So that the MCU2-1A/D converter can receive the signal. 3. CAN bus circuit 2-2 as claimed in claim 2 is characterized in that: described CAN bus circuit 2-2 comprises optocoupler 3-1, CAN bus transceiver 3-2, lightning protection tube 3- 3. Resistor R1, resistor R2, resistor R3, resistor R4, capacitor C1, capacitor C2. The optocoupler 3-1 selects a high-speed optocoupler isolation 6N137 chip. Here, two 6N137 chips are used. The TXDC pin of the MCU microcontroller 2-1 is connected to the IN pin of a 6N137 chip through a resistor R1. The RXDC of the MCU microcontroller 2-1 The pin is connected to the OUT pin of another 6N137 chip, the CAN bus transceiver 3-2 uses the TJA1050 chip, the OUT pin of one 6N137 chip is connected to the pin TXD of the TJA1050 chip, and the IN pin of the other 6N137 chip is connected to the pin of the TJA1050 chip through the resistor R2 Pin RXD, the CANH pin of the TJA1050 chip is connected to the CAN bus node through the resistor R3, the capacitor C1, and the lightning protection tube 3-3, and the CANL pin of the TJA1050 chip is connected to the CAN bus node through the resistor R4, the capacitor C2, and the lightning protection tube 3-3. CAN bus nodes are connected. 4. single-bus circuit terminal 2-4 as claimed in claim 2, is characterized in that: described single-bus circuit terminal 2-4 comprises single-bus 4-1, single-bus connection terminal 4-2, MCU single-chip microcomputer P0 mouth 8 8 pin interfaces 4-3, MCU microcontroller P2 port 8 pin interfaces 4-4. Single bus 4-1 is a proprietary technology of DALLAS company. Single bus, as the name suggests, has only one data line, which uses a single signal line to transmit both clock and data, and the data transmission is bidirectional. It can collect temperature data on site, and directly convert the measured temperature data into digital output as a serial digital signal output, which is easy to connect with a microcontroller. It has the advantages of saving I/O port line resources, simple structure, low cost, and convenient for bus expansion and maintenance. Described single-bus connection terminal 4-2 is temperature sensor (5) and CAN fieldbus control terminal (4) connection node, MCU single-chip microcomputer P0 mouth 8 pin interfaces 4-3 and MCU single-chip microcomputer P2 mouth 8 pin interfaces 4 -4 is connected to the single-bus terminal 4-2, the single-bus terminal 4-2 has 16 terminals in total, and each input terminal is respectively connected to 8 temperature sensors, where the maximum is 16×8=128 temperature measurement points, As for how many temperature measurement points are needed, it depends on the situation.

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