Abstract : This paper introduces a novel automatic batching device that solves the problem of batching instruments not being able to perform multiple functions in one unit. Based on a microcontroller design, this batching device, through the tight integration of software and hardware, is adaptable to different types of sensors and applicable to various industries. Furthermore, it features preset ingredient settings, automatic tare, ingredient display, recipe storage, and power failure protection, achieving both high precision and versatility. Keywords : single-chip microcomputer; automatic dosage apparatus; signal acquisition; sensor Abstract : This paper introduces the development of an automatic dosage apparatus, which, based on a single-chip microcomputer, can solve the problem of dosage. Through the combination of software and hardware, the automatic dosage apparatus can dispose of all kinds of signals from different types of sensors and fields. It has functions such as initialization, automatic labeling, dosage display, dosage storage, power failure protection, and so on. Keywords : single-chip microcomputer; automatic dosage apparatus; signal acquisition; sensor 1. Overview Currently, for a specific industry, the types and ranges of sensors used in dispensing instruments are basically fixed, and the number of types of ingredients dispensed is also basically fixed. Therefore, current dispensing instruments have limited applications. Different dispensing instruments need to be designed for different industries, making mass production difficult. This results in low resource utilization and excessively high product production costs. Therefore, developing a new type of dispensing instrument that can adapt to various types of sensors, has intelligent tare, precise dispensing, and allows operators to select the number of ingredient types has broad application value. This design focuses on a microcontroller-based, universal automatic batching device adaptable to various types of sensors and applicable to different industries. 2. System Design Scheme Currently, sensor technology is quite mature, and the output voltage signals of sensors are relatively standardized. However, different sensors still output voltage signals differently. To address this, the amplification factor required for different voltage signals varies during initial input signal processing. Using an amplifier with adjustable amplification factor in the design can easily solve this problem. The control circuit design can be based on the industry with the most ingredient types. For example, in the feed industry, the number of ingredient types is generally 8; in the construction industry, it's generally 2-3; and in other industries, such as metallurgy and chemicals, it's generally less than 8. Therefore, the hardware design is based on 8 ingredient types. In other words, the batching device can batch up to 8 types of ingredients. The specific application will be determined based on the actual situation, and the software implementation will be used for the final design. The structure of the automatic batching device is shown in Figure 1: The electrical signal sent by the sensor is conditioned by the corresponding conditioning circuit to become an analog voltage signal of 0~10V suitable for A/D conversion. After the voltage signal is converted by A/D, the digital signal is output by the output terminal of the A/D converter to the microcontroller. The microcontroller processes the digital signal to form various control signals to control the entire batching process. The circuit also includes a data storage, keyboard, display circuit, communication and printing interface circuit. Before using the batching device, different formulas can be input into the controller via the keyboard. These data will be stored in the data storage. When using it, just call up the corresponding formula via the keyboard and press the confirmation key. The batching device will automatically complete the batching. The batching progress can be monitored at any time via the digital tube. In addition, the operator can also determine the number of batching types and the amount of each material. This can be achieved by inputting the corresponding data via the keyboard according to the operation procedure. The input formula can be directly stored in the controller. When using it next time, just select the formula to call it directly. The operation is quite simple [4]. 3. Hardware Circuit Design 3.1 Signal Acquisition Circuit Design The weighing scale is an important component of the automatic batching system. Using a high-precision, stable force sensor is crucial for the weighing scale; strain gauges are typically used as the sensing element. The signal transmitted by the sensor is input via a 4051 analog switch. In the amplifier circuit design, a single-ended input differential measurement amplifier circuit is selected. To design a universal automatic batching instrument, sensor variations must be considered when processing the input signal, and the amplification factor must also vary depending on the application. Therefore, R can be replaced with an adjustable resistor with a tunable amplification factor. A multiplexer is used to select different resistors, thereby changing the amplification factor and achieving a certain degree of versatility. In the amplifier circuit diagram (Figure 2), AD7501 forms the tunable resistor R. When the multiplexer's selection signal is different, the resistance value of R is different, and the amplifier's amplification factor changes. However, in practical applications, due to various reasons, the amplification factor requirements of the input signal are very complex. Therefore, the resistance value of R must be both variable and adjustable. To meet the usage requirements, a potentiometer is connected in series inside R. Before the controller leaves the factory, the staff adjusts the potentiometer by experiment to ensure that the amplifier amplification factor accurately meets the amplification requirements. 3.2 A/D conversion circuit design and reset circuit The hardware interface circuit between AD574A and 8051 microcontroller is shown in Figure 3. AD574A has an on-chip clock, so no external clock signal is required. The circuit adopts a unipolar input mode and can convert 0~10V and 0~20V analog signals. When AD574A is configured with 89C51, since AD574A outputs 12-bit digital data, the microcontroller needs to read the conversion result in two steps: first the high 8 bits, then the low 4 bits. The reading of the high 8 bits or the low 4 bits is controlled by A0=0 or A0=1 respectively [1]. The microcontroller can read the data converted by the AD574A using interrupt, polling, and delay methods. In this design, the microcontroller uses the delay method, employing delay statements in the program to provide sufficient time for the AD574A to complete the A/D conversion. The reset circuit is crucial for ensuring the reliable operation of the microcontroller system. Here, we use the dedicated watchdog integrated chip X25045, which internally comprises an oscillator, counter, and differentiating circuit. The timing interval can range from 200 milliseconds to 2 seconds. The chip also contains 512 bytes of E2PROM to store system parameters; the timing interval must be set according to the program's execution cycle. 3.3 Keyboard and Display Circuit Design In this design, the keyboard and display circuit uses the ZLG7289A chip. The ZLG7289A is an intelligent display driver chip designed by Guangzhou Zhouligong Microcontroller Development Co., Ltd. It features an SPI serial interface and can simultaneously drive an 8-digit common-cathode seven-segment display (or 64 independent LEDs). This chip can also connect to a keyboard matrix with up to 64 keys, allowing a single chip to handle all functions of LED display and keyboard interface. With the corresponding keyboard display subroutine, it can realize the normal operation of an 8-digit red LED display and 15 buttons, including numeric and function keys, on a batching instrument. 4. Software System Design The development of microcontroller application system software often requires certain programming techniques. ⑴ Modular Design Method: The modular programming method decomposes a complete and long program into several smaller, relatively independent program modules. Each program module is designed, programmed, and debugged separately, and finally, the debugged program modules are connected into a larger program. ⑵ Top-Down Programming Method: Start designing from the main program, using symbols to represent the output terminal programs and subroutines. After the main program is written, the output terminal programs and subroutines are written, finally completing the design of the entire system software. Debugging is also carried out in this order. (3) Bottom-up programming method: First, understand the programming methods of each chip used in the system, and write the subroutine modules for setting and using each chip. Then write the main program, which often completes the functions of the entire system by calling the subroutines of each chip module. The automatic batching system adopts modular programming technology in software design. According to the functions of the system, it is divided into several relatively independent modules, including serial communication module, display module, A/D conversion module, data processing module, and batching control module. The main program mainly completes data acquisition, batching control, and numerical display functions. After powering on, the subroutine is initialized first, including setting the interrupt entry, RAM area self-test, and setting each flag bit. Then the instrument model is displayed, followed by the main measurement program, and relay control is performed simultaneously. At this time, pressing the function key can enter the key-operated rotary rotor program. The key function can be selected according to the key value, such as setting control value and parameter calibration. The main program flow is shown in Figure 6. 5. Anti-interference measures Generally speaking, interference is mainly caused by external electromagnetic fields, unreasonable grounding wires, and AC ripple of rectifier power supply. That is, when the input signal voltage Vi=0 at the input terminal of the amplifier circuit, AC interference voltage may appear at the output terminal[3]. For stray electromagnetic field interference, reasonable layout and shielding suppression measures can be adopted. Connecting the common terminal of each stage directly to the negative common ground of the DC power supply can overcome the interference caused by incorrect grounding point arrangement. For interference caused by DC power supply voltage fluctuation, a regulated power supply can be used, and a sufficiently large electrolytic capacitor or tantalum capacitor filter circuit can be added to the input and output terminals of the regulated power supply. For operational amplifiers, in order to prevent DC power supply interference, a tantalum capacitor can be added between the power supply pin and ground to prevent low-frequency interference, and a monolithic capacitor can be added to prevent high-frequency interference. For high-frequency interference caused by sudden changes in AC grid load. The following measures can be taken to suppress interference: (1) Add a shielding layer between the primary and secondary sides of the power transformer in the regulated power supply, and ensure that the shielding layer is well grounded; (2) Add a filter circuit at the AC input of the regulated power supply to filter out high-frequency interference; (3) Use "floating ground," that is, separate the AC ground wire and the DC ground wire, and only connect the AC ground wire to the earth. Before data processing, the sampled data is generally filtered to eliminate or reduce noise interference in the measured signal. This design uses average value filtering, employing a purely software method to eliminate noise interference, and the filtering parameters can be flexibly modified. 5. Conclusion The development of the new automatic batching instrument makes it suitable for different types of sensors and applicable to different industries, solving the problem that current batching instruments cannot be used for multiple purposes. This general-purpose batching instrument has a simple structure, flexible functions, is easy to maintain, and has good anti-interference capabilities, which helps improve the reliability and cost-effectiveness of the system, and has significant application and promotion value. References [1] Song Dinghua. Microcontroller Principles and Interface Experiments [M]. Beijing: Tsinghua University Press, 2002.11. [2] Luan Guidong. Sensors and Their Applications [M]. Xi'an: Xi'an University of Electronic Science and Technology Press, 2002.1. [3] Lu Wenke. Electronic Detection Technology [M]. Beijing: National Defense Industry Press, 2002. [4] He Rui, Jia Lei. Research and Application of Automatic Batching System Based on PLC Control [J]. Microcomputer Information, 2007, (23) 86-87. About the Author: Zhou Xiaohui (1980-), female (Han nationality), assistant lecturer of the School of Electrical and Information Engineering, Shaanxi University of Science and Technology, master's degree, mainly engaged in the research of electrical drive. Contact information: Mobile phone: 13689292009 Email: School of Electrical and Information Engineering, Shaanxi University of Science and Technology, Weiyang University Park, Xi'an, Shaanxi Province, 710021, China E-mail: [email protected]