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Author of the application of PLC in water purification equipment: Chen Guangtao's industrial development * * It has played an indelible role in the development of the economy, especially in China today. The development of industry has driven the rapid development of related industries and has become one of the important pillars of the national economy. However, after the rapid development of industry, * * We all understand that the development of industry also means the destruction of the natural environment, especially the serious pollution of water sources. Therefore, the protection of water sources, sewage treatment, and water purification are very important. As people's quality of life continues to improve, especially hospitals, chemical laboratories and other units have put forward higher requirements for water quality. Therefore, according to the needs of the current situation, there is also a corresponding demand for better water purification equipment. This has promoted the rapid growth of purification equipment companies, and also requires the control part to be more stable and reliable! For example, some water purification equipment manufacturers are currently increasing investment in capital and technology, using PLC to replace the previous single-chip microcomputer control system. Device control background: System composition: Power module + PCB control board based on 8051 microcontroller and extended A/D and I/O chips ； system analysis: The system uses a single-chip microcomputer to implement an automatic control system. Because the overall design of the circuit is not very reasonable, protection measures such as spikes are not good, and circuit faults can easily occur. This also increases services and implicitly increases product costs, affecting the company's market development. Therefore, users are eager to replace the original system with a more reliable system to reduce service volume and overall costs. Principle description: The chemical reaction takes place in a special reaction box. The PLC controls two heating signals and collects the PT100 temperature signal in time to keep the reaction box at the set temperature. The PLC then sends out pulses to control the metering pump to control the amount of ClO2 added, so that the appropriate concentration of ClO2 reacts with water to achieve the purpose of disinfection. control requirements: 1. Temperature control: The system reaction needs to be carried out at a specified temperature, so the temperature of the water in the reaction box needs to be kept constant. The specific method is to set a temperature D414, set the hysteresis D410, and set the over-temperature D535. When the collected temperature D310 is less than D414, the heating starts. When the temperature reaches D414+D410, the heating stops. When the temperature drops to D414, it is heated again, so that the temperature hovers within the set hysteresis to achieve the purpose of constant temperature. If the temperature exceeds the over-temperature setting D535, heating will be stopped and an alarm will be issued. 2. ClO2 dosage control: System control requires strict control of the concentration of ClO2 added to the reactor to fully disinfect the water without causing secondary pollution, so the control accuracy of chlorine is extremely high. The specific method is to calculate the dosage of ClO2 based on the flow rate of the water to be disinfected and the unit dosage. Then, the sensor feeds back the residual chlorine in the water to the controller (PLC), compares the residual chlorine with the set value (target value), and determines the correction speed and amplitude of the unit dosage based on the difference between the two. Calculate the new unit dosage, thereby controlling the dosage within a reasonable range. Water flow rate After the residual chlorine is lower than the set value (i.e. target value), increase the unit dosage, and the increase is controlled by the difference. The detected flow signal is involved in the calculation after a delay. The delay length can be set from 0 to 150 minutes. After calculation, the frequency of the control pump (that is, the amount of ClO2 added) is obtained. The frequency calculation formula of the output control metering pump is obtained.: 3. Alarm control: Pressure water underpressure, negative pressure system overpressure, lack of raw materials----alarm, stop metering pump water shortage, overtemperature, high temperature-----alarm, stop heating device selection: 1.Controller: Use Delta DVP14SS11T2+DVP04PT-S+DVP06XA-S. The host DVP14SS11T2 is responsible for the two heating signals of the reaction box. ； And control the frequency of the metering pump to control the amount of ClO2 added to the reaction box. DVP04PT-S collects 2 temperature signals from the reaction box ； 2.Display part: Using Delta DOPA-A57GSTD and TP04 terminal display. Different displays are used according to the different choices of end users. 3.MILTON ROY LMI electromagnetic drive diaphragm metering pump: (Model P766-y/Flow rate 0.08~7.6L/H/Pressure 3.5bar) Supply ClO2 to the reactor. The metering pump is controlled by PLC pulses. Every time PLC sends a pulse, the metering pump operates once and outputs one stroke of ClO2, up to 100 times/minute. ； The stroke of the metering pump can be manually adjusted, that is, the amount of liquid that the metering pump can output per action can be set in the range of 0~100%. 4. Sodium chlorate and hydrochloric acid are supplied using solenoid valve switches. 5. The temperature of the reaction box is collected using standard Pt100, which is directly collected and converted using Delta DVP04PT-S, which is very convenient. 6. ClO2 concentration collection uses the CDE 2-mA-2ppm special ClO2 sensor of German Promint Fluid Control (China) Co., Ltd., which can directly output 4~20mA to the DVP06XA-S module for collection. market analysis: As people's daily lives improve, they pay special attention to the water used in the production of products. If the water source is unclean, how can we produce reassuring products or even food? Without good water, how can chemical experiments be analyzed accurately? Without good clean water, how can a hospital provide adequate protection for patients? In many industries, better water is needed to ensure the smooth progress of the next step, so purification equipment will increase day by day. Judging from some domestic purification manufacturers, they are currently increasing capital investment, and the sales situation is generally good, and manufacturers are also very busy. Therefore, the water treatment industry is a promising industry supported by automation manufacturers. summary: The rise of water purification equipment manufacturers is undoubtedly a good opportunity for Delta PLC. According to the several manufacturers we have contacted so far, technicians do not yet have a deep understanding of the functions of automated electrical implementation. They need to communicate and cultivate, and they also need to have the patience to promote our PLC. In this kind of small equipment, Delta PLC has the inherent advantages of small size and strong functions, and can easily realize the required functions. Therefore, water purification equipment is an industry with great potential for equipment matching. Delta's PLC technology should be applied to more water purification equipment to improve the automation control level of water purification equipment and improve control accuracy.