Application of Programmable Controller in Mixed Liquid Processing Control

0 Introduction
In the production and processing of some mixed liquid materials, in addition to the control of the normal production process, the material temperature needs to be detected and controlled, making the control requirements of the production process more stringent; if the control is improper, a large amount of waste will be generated, causing serious economic losses. The use of relay-contactor control system has the disadvantages of using a large number of intermediate relays, slow control action, poor accuracy, and poor stability. The high failure rate and complex operation are prone to waste, resulting in increased processing costs and serious impact on the economic benefits of the enterprise; if the FX2N-48MR programmable controller is used for control, the expected control effect can be achieved.

1 A certain processing control process
The following describes a certain processing control process, and the process flow chart is shown in Figure 1.

If the control switch is set to the automatic state, press the start button SB3 to open the cooking feed valve, and add the raw materials required for production into the cooker (feeding); when the liquid level sensor detects that the liquid level entering the cooker reaches the specified position, its switch signal X25 (SL) is input into the programmable controller to control the closing of the feed valve, and at the same time start the stirring motor to stir the raw materials, and open the hot air valve Y4 to pass hot air to heat the raw materials (cooking), and the temperature sensor X24 (STl) detects the temperature of the raw materials. When the temperature of the raw materials reaches 90°C, the heating is stopped; at this time, the cooling water valve Y5 is opened to speed up the circulation speed of the cooling water to achieve rapid cooling (cooling). When the temperature of the raw materials cools to 60°C, the action signal of the temperature sensor switch X26 (ST2) is input into the programmable controller to control the cooling to stop (complete the cooking process). Then open the feeding homogenization valve to allow the raw materials in the cooking pot to enter the homogenizer for stirring. Set the homogenization time to 10 min. After the time is reached, open the aging process valve Y3, and the raw materials enter the aging device, and the temperature is cooled again in the aging device (aging). In the aging device, the temperature of the raw material is detected by the temperature sensor. When the raw material temperature cools to 40℃, the switch X27 (ST3) action signal is input into the programmable controller to control the cooling stop. At this time, the processing is completed and the finished product is output for filling.
When the manual/automatic switch K is placed in the manual position, each control process can be started and stopped independently.

2 Prepare the input/output signal address table
According to the control process and requirements, prepare the input/output signal address table. The input signal address table is shown in Table 1, and the output signal address table is shown in Table 2.

3 Control wiring schematic design
According to the input/output signal address table and the control principle of the programmable controller, the control wiring schematic of the programmable controller is designed, as shown in Figure 2.

4 Ladder diagram design
According to the control wiring schematic diagram, process control flow and programming rules of FX2N-48MR programmable controller, the ladder diagram program is designed, as shown in Figure 3.

Program description:
(1) The output switch signals of Y1~Y6 respectively control the output of the drive circuit Q1~Q6, which are used to drive the corresponding valve electric actuator. When the output is high level "1", the corresponding valve is controlled to open, and when the output is low level "0", the corresponding valve is controlled to close.
(2) The detection and control of whether the valve is opened and closed are completed by the internal circuit of the electric actuator.
(3) The photocoupler TLP521-4 is used to isolate the PLC from the valve electric actuator circuit to avoid mutual interference between the valve electric actuator and the PLC in the circuit.
(4) The emergency stop button SBl9 (X23) adopts a red mushroom-shaped self-locking button, and it is also the main stop button.

5 Conclusion
FX2N-48MR programmable controller has small size, light weight, stable and reliable performance, low price, high control stability, and convenient programming. It is especially used in valve control systems, saving a large number of intermediate relays, improving the response speed of the entire control system, and the system has good real-time performance. After the production process is controlled by the programmable controller, the production process works stably, is easy to operate, and works reliably after operation, which improves the automation technology of processed products. It not only reduces the generation of waste and costs, but also improves production efficiency. It can be said that "one-time investment brings lifelong benefits."