Wireless Communication Solution Based on PLC Control and Touch Screen

Introduction to PLC-touch screen

Touch-type industrial graphic display (referred to as touch screen) is a new type of programmable control terminal and a new generation of high-tech human-machine interface (called HMI or MMI abroad). It is an intelligent operation display that replaces traditional control panels and keyboards. It can be used for parameter setting, data display, depicting the automatic control process in the form of curve, animation, etc., and can simplify the control program of PLC. It has the characteristics of small size, simple connection, dustproof, shockproof, waterproof, anti-electromagnetic and so on.

PLC is a kind of programmable controller, which has the characteristics of high operation speed, rich instructions, powerful functions, high reliability, convenient use, flexible programming, and strong anti-interference ability. In recent years, with the continuous advancement of science and technology, various industries have higher and higher requirements for the automation of their production equipment and systems. The use of modern automation control technology has the advantages of reducing labor intensity, optimizing production technology, improving labor productivity and reducing production costs. plays a very important role.

Application fields of PLC-touch screen

• Automatic control of traditional industrial equipment and machinery;
• Small and medium-sized process control systems;
• Remote maintenance service system;
• Energy-saving monitoring and control system;

Specific solutions based on PLC control and touch screen

3.1 Urban (factory) sewage treatment automation control system solution

1 System overview

The lower control station of the sewage treatment engineering automation system adopts the latest intelligent controller with the functions of upper computer, PLC and field bus as the main control device, and is also equipped with relays, contactors, intelligent thermal relays, power transmitters, etc. The device completes the protection and control of process equipment, process data acquisition and control functions, etc. In addition, the system also includes online water quality analysis instruments, transmitters, regulating valves, solenoid valves, various pumps and fans, etc.

2 Main control functions of the system

* Automatic oil discharge control: After the sewage enters the grease trap, the controller automatically opens the steam valve to heat the sewage according to the water temperature, so that the water temperature reaches the set temperature, and starts the oil floating machine to work. Absorb the oil slick on the water surface to achieve the purpose of oil discharge;

* Control of the submersible pump of the sump: After the sewage enters the sump, the submersible pump is started and stopped according to the water level, and the sewage is sent to the first-level air flotation pool;

* Coagulation dosing pump control: control the start and stop of the coagulation dosing pump according to the start and stop of the submersible pump;

* Alkali addition and pH value control: automatically adjust the amount of alkali addition according to the detected pH value, so that the pH value after neutralization is controlled at 6~9;

* Return pump control: Control the start and stop of the return pump according to the start and stop of the submersible pump;

* Fan control: Automatically control the start and stop of the fan according to the oxygen content measurement in the oxidation pool;

* Automatic timed sludge discharge control for the first and second sedimentation tanks;

* Filter timing backwash control.

3 System Features

* Based on Windows NT/2000/XP platform, adopt object-oriented technology and method for system design and software implementation;

* Strong openness, following international standards such as ODBC, COM/DCOM, Active X, IEC-1131-3;

* Able to integrate WINCC, IFIX, FIX32, RSVIEW, INTOUCH, Block King and other blocking software according to user needs;

* The system interface is intuitive and has a complete browsing function;

* The system has complete functions, advanced technology, simple operation and less maintenance;

* Rich and convenient expansion capabilities, which can be easily extended based on existing systems;

* The system provides rich forms of reports to provide basis for statistics and decision-making.

4 System indicators

* Data refresh 1s;

* Event sequence resolution "2ms;

* Control command response time ≤ 1s;

* Adjustment screen response time <1s.

Main hardware configuration of the system

The system hardware consists of programmable controller (including digital input/output module and analog input module), WPLC-C wireless transparent transmission terminal, host computer, frequency converter, sensor and some electrical components.

(1) PLC: S7-400 series from SIEMENS (equipped with digital expansion input/output modules and analog input modules)

(2) Inverter: VLT series of DAFOSS company is used; according to the data sent by PLC (PH value, aeration oxygen content, water tank liquid level, flow meter and other analog signals, water pump operation, electric valve opening, fault alarm, etc. are digital signal) value to adjust the operation of the equipment, and feed back its internal operating parameters to the PLC and the host computer.

(3) Host computer: It can be used as an engineer station to program PLC and configuration software, and an operator station can monitor the operation of the system. The upper computer is Yanhong YH-MB945VEA.