According to the data of AT89C51 and HX711, the hardware configuration circuit principle of the weighing instrument is displayed.

The digital display weighing instrument designed in the article is a weighing control display device based on a resistor strain force sensor and a single-chip microcomputer design. The detection range is 0-10kg, the measurement accuracy is ±2g, and the LCD display displays information Accurate measurement data information, in addition, several accurate measurement data information can be sent to the electronic computer for display information according to serial communication. The system software has the characteristics of high precision, stable characteristics, and simple actual operation. The frame diagram of the weighing instrument design scheme is shown in Figure 1 below: 1. Hardware configuration circuit principle 1.1. Weight sensor resistor strain force type weight sensor is composed of resistance strain gauges, polyurethane elastomers and inspection power supply circuits. . The polyurethane elastomer causes elastic deformation under external force, and the resistance strain gage attached to its surface also causes deformation. After the resistance strain gage is deformed, its resistance value will change (expand or decrease), and then be relatively accurately measured The power circuit transforms this resistor into an electronic signal (working voltage or current), and then completes the whole process of converting the external force into an electronic signal. Check the power supply circuit as shown in Figure 2, and change the resistor of the resistance strain gauge into a working voltage output. Because the Wheatstone bridge has many advantages, such as the ability to suppress the hazards of temperature transitions, the ability to suppress the influence of lateral forces, and the ability to more easily deal with the compensation problem of the weight sensor, the Wheatstone bridge has gained widespread popularity among the weight sensors. use. The weight sensor generally has a total of four I/O wires, and the output resistance is generally 350Ω, 480Ω, 700Ω, and 1000Ω. The input terminal will generally carry out some temperature and sensitivity compensation. The input terminal resistor will be 20-100Ω higher than the output terminal. Therefore, I/O terminals can be distinguished by measuring the resistance with a digital multimeter. 1.2. The output data signal strength of the operational amplifier strain force type weight sensor is not large (mV or even μV order of magnitude), and there is often a lot of noise. For such data signals, the first step in the power supply circuit is generally to select an instrumentation amplifier to first increase the small data signal. The instrumentation amplifier power circuit has a stronger common-mode rejection capability than a simple differential signal operational amplifier. The most important purpose of increasing is not the gain value, but only to improve the frequency stability of the power supply circuit. In this design, the instrumentation amplifier uses the structure of OP07 three operational amplifiers. As shown in Figure 3. When R1u003dR2, R3u003dR4, Rfu003dR5, the gain value of the power supply circuit is: Gu003d(1+2R1/RG1)(Rf/R3). It can be seen from the formula calculation that the adjustment of the gain value of the power supply circuit can be completed by changing the resistance value of RG1. 1.3. A/D conversion power supply circuit The A/D converter selects the electronic scale dedicated integrated icHX711, which is a 24-bit A/D converter integrated ic designed for high-precision electronic scales. Compared with other integrated ICs of the same type, this integrated IC integrates peripheral circuits necessary for other integrated ICs of the same type, such as an adjustable regulated power supply, an on-chip digital clock oscillator, and so on. Enter the switch to select safe channel A or safe channel B at will, and the internal low-noise programmable controller amplifier between the two is connected. The programmable controller gain value of safety channel A is 128 or 64, and the corresponding full credit differential signal input data signal amplitude value is ±20mV or ±40mV respectively. The safety channel B is a fixed gain value of 32, and the matched full-scale differential signal key-in working voltage is ±80mV. The safety channel B is used to check the main parameters of the system software including rechargeable batteries. In this design, the output of the instrumentation amplifier is led to the input terminal of the safety channel A simulation analog differential signal. The weighing instrument 1.4, MCU design and communication interface MCU design selects AT89C51 integrated ic, and communication interface with function keys, LCD display and electronic computer As shown in Figure 5. The HX711 serial communication line leads to the P1.0 and P1.1 ports of the microcontroller design. After the design and solution of the single-chip microcomputer, the weighing data information is sent to the LCD display. In addition, the precise measurement data information is sent to the electronic computer to display the information according to the serial port communication.