Siemens S7-200 SMART series PLC in the edible fungus laboratory...

A good production environment is the key to the successful cultivation of edible fungi. The cultivation environment of edible fungi includes air cleanliness, air temperature, humidity, PH value, light, carbon dioxide concentration, air pressure, etc. The edible fungus cultivation control system controls fans and compressors. , Heaters, humidifiers, air valves and other equipment to accurately manage the entire process of edible fungus cultivation and production, and improve the efficiency of edible fungus cultivation.

The project is located in Zibo City, Shandong Province, and the cultivated product is shiitake mushrooms. The main process flow: cooling of the culture material, inoculation, mycelium culture, and fruiting.

Pre-cooling of the culture material: The initial cooling of the culture material is carried out through outdoor low-temperature air.

Cooling: The pre-cooled culture material is further cooled. If the outdoor environment temperature meets the cooling demand, the outdoor natural cold source is preferred, and the insufficient part uses the refrigeration unit to meet the process requirements. The culture material temperature is required to be 20±2°C.

Inoculation: The temperature of the inoculation room is required to be 20±2℃.

Mycelium culture: The environment temperature of the culture room should be controlled at 20-23℃±1℃, and the humidity should be 60%±5%.

Fruiting: The temperature should be 18-20℃±1℃, and the low temperature should be 10℃±1℃.

3.1 Control plan

Siemens S7-200 SMART series PLC is small, fast, standardized, with network communication capabilities, stronger functions, and high reliability. The controller body is equipped with a standard Ethernet interface, which integrates powerful Ethernet communication functions. Through the Ethernet interface, it can also communicate with other CPU modules, touch screens, and computers for easy networking. The controller integrates a Micro SD card slot, and the general Micro SD card on the market can be used to update the program and upgrade the PLC firmware, which greatly facilitates the service support of the engineer to the end user, and eliminates the need to return to the factory for the PLC firmware upgrade Inconvenience of service. The CPU supports the standard TCP/IP protocol and can be connected to the Ethernet to achieve centralized control.

The main control objectives of this system are temperature, humidity, and carbon dioxide concentration. The control area is divided according to functions. A set of control system based on S7-200 SMART SR40 CPU is selected for pre-cooling room, cooling room and inoculation room, and one set is based on S7-200 The control system of SMART SR60 CPU is used in three cultivation rooms, and a control system based on S7-200 SMART SR60 CPU is used in five fruiting rooms. Due to the large number of analog quantity acquisition parts, special analog quantity acquisition modules are used. The man-machine interface uses the Kunlun Tongtai 7-inch touch screen. The centralized monitoring software of the upper computer selects the three-dimensional force control configuration software, and uses the standard Ethernet interface of the CPU body to realize communication.

3.2 I/O list

According to the equipment to be controlled on site and the control points to be monitored, the I/O quantity list of each system is as follows:

Among them, 1# system is pre-cooling room, cooling room and inoculation room, 2# system is three culture rooms, and 3# system is five fruiting rooms.

3.3 Host computer centralized monitoring program

This project uses three-dimensional force control configuration software, which integrates the Ethernet driver of the S7-200 SMART series PLC, as shown in the figure below:

The I/O device configuration can be completed according to the device configuration wizard, as shown in the figure below:

The CPU IP address of each system is selected in the same network segment: 172.16.1.* (can be modified in HMI).

4.1 Control flow chart

The control program mainly controls the required parameters in each room. The main control flow is shown in the following figure:

4.2 Analog input processing

The detection signals of humidity and carbon dioxide are 4-20mA, corresponding to humidity 0-100% and carbon dioxide 0-10000ppm, which can be easily created through the configuration, programming and operating software STEP 7-Micro/WIN SMART of the S7-200 SMART controller Add user library files, encapsulate the program blocks with common functions into user library programs, which is convenient to call and improve programming efficiency. The analog processing program is as follows:

4.3 IP address modification

If there are multiple devices that need to be networked, you need to modify the IP address of the CPU of all devices. You can set the CPU by obtaining the IP address (GIP_ADDR instruction) and setting the IP address (SIP_ADDR instruction), which is used in this project With this function, as shown in the figure below:

4.4 Communication with man-machine interface

The local operation panel of this system uses Kunlun Tongtai 7-inch touch screen. The S7-200 SMART controller communicates with the touch screen through the serial port. The communication settings are as follows:

Controller side:

HMI side:

4.5 Host computer configuration

The system can realize local control and centralized control of the upper computer. The centralized control of the upper computer can realize the functions of data collection and processing, equipment status monitoring, equipment remote control, and system parameter setting. Some real-time monitoring screens are as follows:

The successful application of Siemens S7-200 SMART series PLC in this project ensures the efficient, stable and safe operation of air-conditioning equipment, and all controlled indicators meet the user's technological requirements. The standard integrated Ethernet interface of the Siemens S7-200 SMART series PLC brings convenient networking and stable and high-speed communication; the controller's integrated Micro SD card slot brings great convenience to the upgrade and update of user applications , Improve the work efficiency of engineering designers.