Scales are the most common and most popular metering equipment. The traditional mechanical scale is bulky, cumbersome, and subject to external extrusion and collision deformation. In the long-term use, due to metal corrosion, mechanical wear will bring irreversible damage to the mechanical department, which directly leads to the accuracy of the mechanical scale. Electronic scales have many advantages over mechanical scales, such as low cost, fast response, stability, and high intelligence.
This article mainly introduces the design of voice electronic scale based on MSP430 and HX711. First of all, let us first understand the detailed introduction of the voice electronic scale.
How voice electronic scales work
The weighing instrument converts the gravity into a voltage or current analog signal through a weight sensor mounted on the machine. After being amplified and filtered, the A/D processor converts the digital signal into a digital signal, and the digital signal is calculated by a central processing unit (CPU). Processing, and the peripheral functions and various interface circuits are also connected to the CPU application, and finally displayed by the display screen in digital form, and voice broadcast is performed by TTS technology.
Voice electronic scale features
The voice electronic scale is controlled by a microcomputer, which can automatically and quickly measure the height and weight of a person without any manual operation. The measurement results can be displayed and voiced, and the body shape can be judged according to the measurement result. It is an ideal choice for hospitals, medical examination stations and various fitness places.
1, fashionable, beautiful and generous, large screen LED display;
2. Chinese/English, Chinese/Russian or Chinese/Vietnamese bilingual selection;
3, thermal printer, printing speed, clear and beautiful font;
4, energy-saving design, low consumption electrode;
5. The internal counter records the number of measurements, and remains valid after power failure, which is convenient for operation and management;
6, calendar clock, power outage is still accurate time;
How to use the voice electronic scale
1. In order to ensure accuracy, it is best to test whether the power is sufficient before use.
2, should be placed on the surface of the water stable and solid, can not pad paper and other items under the scale, the use of tilting or shaking the table will affect the reading of the electronic scale, so the level of placement is the impact of accuracy An important factor.
3. After opening, wait until the value is 0 before you can go up and weigh.
Note on voice electronic scales
1. Avoid using or storing in direct sunlight, high temperature, humidity, dust concentration or vibration.
Second, do not use the fan directly under the blow, do not vigorously impact, be careful when weighing.
Third, it must be used within the specified voltage range, otherwise it will cause damage.
Fourth, do not call overloaded goods, so as not to damage the sensor.
5. Zero must be set before weighing to ensure accurate and reliable weighing.
6. When not in use for a long time, the power plug should be unplugged.
7. Read the instructions thoroughly before use to fully understand the functions of the scale.
8. Keep the weighing pan clean and do not rinse with water.
Second, based on MSP430, HX711 voice electronic scale design1, the overall composition of the system
Firstly, the weight signal of the substance is measured by a measuring circuit composed of a resistance strain type pressure sensor, and is transmitted to the HX7I 1 signal converter as an analog signal. The module amplifies the analog signal, converts it into a digital signal and transmits it to the JMSP430 MCU. The data is transmitted to the display circuit after being processed by the single chip microcomputer, and finally the data 2 is displayed by the display circuit. The system structure block diagram is shown in Figure 1.
2, module introduction
2.1, the main control chip
MSP430 MCU 3 is a 16-bit MCU with a fine-grained instruction set (RISC) structure. It has a rich addressing mode, a simple 27 core instructions and a large number of analog instructions. A large number of registers and on-chip data memory are available. Participate in a variety of operations; there are also efficient table lookup processing instructions; while having high performance and low power consumption. This series of microcontrollers is widely used in control systems.
2.2, YZC-1B load cell
The YZC-IB load cell is embedded with two strain gauges on the upper surface. At the same time, there are two identical strain gauges on the lower surface. The upper and lower joints form a full-arm bridge. When the strain gauge is not subjected to external force, the output voltage is zero. When acting, the resistance of the strain gauge on the upper surface becomes larger, the resistance of the strain gauge on the lower surface becomes smaller, and the bridge is unbalanced. Since the resistance of the same resistance wire is the same, the output voltage and the resistance change are linear. The relationship is then converted into a voltage signal by a corresponding measuring circuit. This process completes the process of converting the external force into an electrical signal, thus measuring the weight.
2.3, HX711 analog-to-digital conversion chip
The HX711 is a 24-bit E-O type A/D converter chip HX711. In the actual use of electronic scales, this high-resolution slow A / D conversion chip is used because people do not have high requirements for weight measurement speed. The connection circuit between the chip and the main control chip is very simple. Only two lines of DATA and SCLK are connected to the main control chip, and two control signals are driven by the pins, and there is no need to program the internal registers of the chip.
2.4, WTV020-SD voice module
The WTV020-SD module is a high-capacity storage type voice module that can re-write voice content, and can be plugged into an SD card memory with a maximum capacity of IGB. Can load WAV format speech and format speech. The WTV020-SD module is based on the AD4WTV020SD-20S voice chip, with MP3 control mode, button-to-one control mode, power-on loop playback control mode and two-wire serial port control mode.
2.5, LM4229 LCD module
The driver for the LM4229 is the T6963C, an LCD controller for LCD control driver integrated circuits (LSIs) and data display memories. It has an 8-bit parallel data bus and control lines for read and write operations with the MPU interface, which can be directly connected to the TMPZ-80. The T6963C has a 128-word character generation ROM that can be used to control up to 64KB of external memory RAM.
3, the conclusion
The electronic scale measuring system of this design includes weight measurement, LCD display, button control, voice broadcast, real-time clock, unit price storage, automatic pricing, price accumulation, peeling, overweight alarm and other functions. With the rapid development of society, people's needs are increasingly famous, and diversified electronic scales will have extremely broad market prospects.
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â—Use with a load that exceeds the rated torque
â—Frequent starting
â—Momentary reversals of turning direction
â—Impact loads
â—Long-term continuous operation
â—Forced turning using the output shaft
â—Use in which the permitted overhang load or the permitted thrust load is exceeded
â—A pulse drive ,e.g.,a short break,counter electromotive force,PWM control
â—Use of a voltage that is nonstandard as regards the rated voltage
â—Use outside the prescribed temperature or relative-humidity range,or in a special environment.
â—Please consult with us about these or any other conditions of use that may apply,so that we can be sure that you select the most appropriate model.
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