Improvements of Yonghong PLC in Kiln Batching and Weighing Systems

Abstract: This article mainly introduces the modification scheme of Yonghong PLC in the feeding system.
Keywords: Yonghong, kiln, weighing programmable control

1. Introduction
In many PLC control systems, weighing and control are usually separated because it's rare for PLCs to offer built-in weighing unit expansion, forcing users to separate the two. If necessary, data can be acquired via communication for automatic control. However, this is generally inconvenient, requiring wiring for weighing and communication, as well as data acquisition. Furthermore, weighing accuracy is limited by the instrument and environment, and the cost is relatively high. This paper mainly uses the FBs-1LC weighing module and FBs-7SG2 display module provided by Yonghong PLC to modify the weighing system in a kiln batching process.

2. Introduction to Yonghong PLC Products
2.1 Yung-Hong FBs-1LC Weighing Module
The FBs-1LC is a member of the FATEK FBs series of PLC analog input modules. It can be used for weak signals generated by load cells. This module represents the measured signal as a 16-bit signed number. The hardware provides a standard 5V excitation voltage and can drive loads up to 250Ω. It supports signal ranges of 10, 25, 50, and 100mV.
To filter out ambient noise accompanying the signal, this module also provides a sampling signal averaging function (2, 4, or 8 times averaging) for more accurate measurement value acquisition. It also offers sampling periods of 5, 10, 20, and 25 Hz. The module occupies 8 DO output points, mainly used to select relevant parameters, as shown in the table below:

Different parameters are selected based on the system architecture to achieve the most ideal measurement results. The external wiring method of the module is shown below:

Figure 2.1 Wiring diagram of FBs-1LC weighing module

The conversion result is represented by a 16-bit number with a plus or minus sign. To obtain the actual engineering unit value, the LCNV (FCN33) or MLC (FCN34) instruction must be added to the program for conversion. Because the signal from the weighing unit is very weak, zero-point adjustment is usually required in applications to overcome the zero-point drift phenomenon of the circuit.
The weighing module primarily replaces the original weighing instrument (HT9800) module in the system. This instrument works directly with the display panel, transmitting data via communication to display the weighing weight. For the weight display, we use the FBs-7SG display module to replace the original display panel.

2.2 FBS-7GS1/2 Display Module
In addition to providing direct drive I/O for LED displays, Yung-Hong PLCs also offer the FBs-7SG module, a dedicated LED display module unit. Users simply input the corresponding values ​​into the automatically allocated output registers to display the desired content (the module is available in both decoded and non-decoded versions). It easily displays English (16-segment LEDs) or numbers (7-segment LEDs) without requiring extensive programming.

Figure 2.2 FBs-7SG2 System Architecture Diagram

Based on the existing network communication of Yonghong PLC, only two network devices need to be added: a wireless router and a wireless access point (supporting client mode) to convert the original wired communication to a wireless interface. The system configuration will be described below.

2.3 System Hardware Modification
2.3.1 Composition of the original weighing system
The original system solution involved the customer using two systems: a separate weighing unit where the material proportions were manually measured before a PLC control system was activated to feed and mix the materials. All proportions were stored in the weighing controller, and feeding was controlled wirelessly until the displayed value approached the set value, at which point the feeding was reduced until the value matched. This method was neither highly accurate nor easy to operate, failing to achieve truly automated and precise weighing and counterweighting.

Figure 2.3 Schematic diagram of the original weighing system

Table 2.1 Yonghong PLC Ethernet Network Specifications

The original control system used an OMRON PLC. To eliminate the need for a separate weighing controller and integrate weighing and control, the control PLC will be replaced with a Yung-Hong FBs-PLC. The system transformation will be shown in the following diagram:

Figure 2.4 Schematic diagram of the modified weighing control system

Through system upgrades, all ingredient weight data can be stored on a large PLC. PLC calculations enable automatic weighing control, resulting in a more precise and stable system. Costs will be significantly reduced, and operator tasks will be simplified.

3. Introduction to Yonghong Weighing Program
3.1 Weighing Program Processing
Because of the different sensor sensitivities, it is necessary to adjust the range of the FBs-1LC module to meet the requirements of the current sensor.

Figure 3.1 Flowchart of weighing module range design program

The measurement range is selected by changing the value of R0 (0~3). Note that Y8~Y11 vary depending on the location of the module expansion; the system will automatically assign them. To select the sampling frequency and average value, follow the same procedure as for range selection, which will not be described separately.

The values ​​from the weighing unit are digital quantities. To display the engineering values ​​intuitively, a linear conversion operation is required.

Figure 3.2 Flowchart of linear transformation design program for weighing module

Because sensors inevitably experience zero-point drift, and tare weight processing is required based on the mechanical structure, the following program uses a delay to automatically tune the linear transformation parameters, thereby achieving automatic tuning of the weighing unit.

Figure 3.3 Schematic diagram of the self-tuning design program for the weighing module parameters

After obtaining the weight value R20 of the project quantity, the user can implement various controls according to the actual program.

3.2 Weighing Value Display Control
To facilitate direct display of the weighing value, the system utilizes the FBs-7SG1 unit, configured in non-decoding mode. The program transformation is straightforward: simply perform the corresponding BCD code conversion and then send the result to the OR display register.

Figure 3.4 Design diagram of the decimal point control program for the display module

According to the OR register allocated by the system, R3904 is the control decimal point register. Sending 2 to R3904 indicates that the second hour marker is illuminated. The system then displays the decimal part in tenths.

Figure 3.5 Numerical display program design diagram of the display module

This network converts the weighing value into CBD code and sends it to the display register R3905. The LED will then display the obtained weight value.

4. Conclusion
Yung-Hong PLCs offer comprehensive expansion interfaces, enabling users to more easily obtain system solutions, achieve better control and improve system reliability, while significantly reducing hardware costs and enhancing system operability.

References:
[1] Yung-Hong Programmable Logic Controller User Manual I and User Manual II. Yung-Hong Electric Co., Ltd., Taiwan
[2] Yung-Hung PLC Programming Software User Manual. Yung-Hung Electric Co., Ltd., Taiwan
[3] Hengtian Weighing Display Controller Manual. Hangzhou Hengtian Electronics Co., Ltd.
[5] KL-S Series Junction Box Instruction Manual. Ningbo Keli Electric Manufacturing Co., Ltd.

About the author:
Sun Hengxiao, graduated from the Department of Automation, Hefei University of Technology, mainly engaged in technical support and industry application work in the automation industry. Contact: 13924603139