Intelligent Bluetooth electronic scale

Abstract

The invention discloses an intelligent Bluetooth electronic scale, which is characterized in that the electronic scale comprises a weighing sensor, an amplifier, an A / D converter, a control chip, a display, a keyboard and a Bluetooth module, the weighing sensor detects the mass of an object, converts a pressure signal into a weak current signal and transmits the weak current signal to the amplifier, the amplifier amplifies the weak current signal and transmits the amplified weak current signal to the control chip; the control chip is connected with the keyboard, the keyboard is connected with the control chip, then the control chip converts the data into digital signals through the A / D converter, the control chip can analyze and process the digital signals, the analyzed and processed data are displayed through the displayer, and a user can conduct commodity type selection, peeling and data sending operation through the keyboard. The control chip can transmit processed data to a mobile phone APP through the Bluetooth module, and the mobile phone APP processes, displays and stores the data after receiving the data so that the data can be looked up by a user in the later period. The device is convenient to carry, visual in reading, convenient to operate and capable of interacting with a mobile phone APP.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic scales, and in particular to an intelligent Bluetooth electronic scale. Background Art

[0002] In today's society, scales are an important measuring tool that is widely used in people's daily lives and various commercial activities. Scales play an indispensable role in many places such as vegetable markets, supermarkets, homes, and express delivery points.

[0003] Traditional lever scales, which operate based on the principle of mechanical balance, have a certain historical background, but they have many disadvantages. Their structure is relatively bulky and not easy to carry and move, which is quite inconvenient for users to frequently change the sales location; in terms of accuracy, they are limited by mechanical structure and manual reading, which is difficult to meet the modern requirements for high-precision measurement and prone to reading errors; when reading, they need to rely on weights and scale markings, which is complicated and not intuitive, and requires certain professional knowledge of users. The operation steps are cumbersome and costly in terms of manpower and time. With the development of science and technology, electronic scales came into being. Thanks to the application of electronic technology, sensor technology and new materials, electronic scales are far superior to traditional lever scales in terms of ease of operation, intuitive reading and portability, greatly expanding the application scenarios and can be widely adapted to the needs of different industries. From the technical principle point of view, the built-in high-precision sensor can keenly capture weight changes and convert them into electrical signals for precise processing; the structural materials are selected from lightweight and sturdy alloys, plastics, etc., to ensure durability while reducing weight.

[0004] However, existing traditional electronic scales still have key defects. In commercial transaction scenarios, such as when used by vegetable market vendors and small supermarket owners, although they can quickly calculate the fees based on the type of goods, weighing results and preset unit prices to assist in transaction settlement, they lack data storage and historical bill backtracking functions. Merchants are often helpless when they want to conduct in-depth analysis of sales trends of different time periods and different goods in order to accurately judge market demand and make scientific decisions on purchasing plans. This not only hinders the refined operation of merchants, but also easily causes supply and demand imbalances, inventory backlogs or out-of-stock problems due to lack of information in the upstream and downstream collaboration of the supply chain, affecting the overall economic benefits.

[0005] The disclosure of the above background technology content is only used to assist in understanding the concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of the present application. Summary of the invention

[0006] The purpose of the present invention is to provide an intelligent Bluetooth electronic scale to solve the technical problem of the lack of data storage and historical bills in the traditional electronic scales in the above-mentioned prior art.

[0007] To this end, the present invention proposes an intelligent Bluetooth electronic scale.

[0008] Preferably, the present invention may also have the following technical features:

[0009] Preferably, it includes a weighing sensor, an amplifier, an A / D converter, a control chip, a display, a keyboard and a Bluetooth module. The weighing sensor detects the mass of the object, converts the pressure signal into a weak current signal, and then transmits it to the amplifier. The amplifier amplifies the weak current signal and then converts it into a digital signal through the A / D converter. The control chip can analyze and process the digital signal. The data after analysis and processing are displayed through the display. The user can use the keyboard to select the product type, peel and send data. The control chip can transmit the processed data to the mobile phone APP via the Bluetooth module. After receiving the data, the mobile phone APP processes, displays and saves it for later user reference.

[0010] Preferably, it also includes a sensor signal acquisition circuit, a signal amplification circuit and an A / D conversion circuit. The sensor signal acquisition circuit uses a weighing sensor to collect the weight of the object to be weighed, converts the weight signal that cannot be recognized by the single-chip microcomputer into a weak electric signal, and transmits it to the single-chip microcomputer for processing after amplification by the signal amplification circuit and conversion by the A / D conversion circuit.

[0011] Preferably, it also includes an overweight alarm circuit, which will sound an alarm when the weighed value exceeds a set value.

[0012] Preferably, the overweight alarm circuit includes a power buzzer and a drive circuit thereof.

[0013] Preferably, the control chip is a STC89C52RC single-chip microcomputer chip.

[0014] Preferably, the weighing sensor is a strain resistance weighing sensor.

[0015] Preferably, the weighing sensor is a parallel beam weighing sensor with a measuring range of 20 kg.

[0016] Preferably, the A / D converter is an HX711 chip.

[0017] Preferably, the Bluetooth module is a BT08B Bluetooth module, which is equivalent to a transfer station for data transmission. Through the Bluetooth module, the mobile phone and the electronic scale can achieve short-distance wireless data transmission and communication.

[0018] Preferably, the display is one of a digital tube, an LCD1602, an LCD12864 liquid crystal display screen and an OLED liquid crystal screen.

[0019] The beneficial effects of the present invention compared with the prior art include:

[0020] 1. Impact on society: The Bluetooth electronic scale involved in the present invention has a measuring range of 20kg. In life, there are relatively few electronic scales with this measuring range and Bluetooth function, OLED screen display, and can be used with mobile phone APP. The Bluetooth electronic scale of the present invention is small in size, easy to carry, intuitive in reading, easy to operate, and can interact with mobile phone APP. The weight and profit of the goods can be saved and viewed on the mobile phone, which provides great convenience for merchants in subsequent decision-making and can provide a reference data for later purchases.

[0021] 2. Impact on the economy: Most of the components of the smart Bluetooth electronic scale of the present invention are very common electronic components, which are low in cost and very convenient to purchase, and can be used for large-scale production.

[0022] 3. Impact on the environment: The present invention uses industrial plate making, and there is no need to purchase materials such as copper sheets and corrosive liquids that are difficult to subsequently process, thereby avoiding the waste of corrosive liquids due to the production process and the impact of improper subsequent processing of the corrosive liquids on the environment. The finished product can be powered by rechargeable batteries, which can avoid the pollution of the environment caused by the use of disposable batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a hardware system block diagram of a specific implementation mode of the present invention.

[0024] Figure 2 Schematic diagram of a Wheatstone bridge according to a specific embodiment of the present invention.

[0025] Figure 3 It is a force diagram of the bridge arm of a specific implementation mode of the present invention.

[0026] Figure 4 It is a resistance value variation diagram of a specific implementation mode of the present invention.

[0027] Figure 5 It is a schematic diagram of the working process of the sensor according to a specific embodiment of the present invention.

[0028] Figure 6 It is a pin diagram of STC89C52RC according to a specific embodiment of the present invention.

[0029] Figure 7 It is a schematic diagram of a minimum system circuit of a single chip microcomputer according to a specific implementation mode of the present invention.

[0030] Figure 8 It is an internal block diagram of HX711 according to a specific implementation mode of the present invention.

[0031] Fig. 9 It is a SOP-16L package diagram and pin diagram of the HX711 chip according to a specific embodiment of the present invention.

[0032] Fig.10 It is a schematic diagram of the HX711 module according to a specific embodiment of the present invention.

[0033] Fig.11 It is a schematic diagram of the connection between HX711 and a single-chip microcomputer according to a specific implementation mode of the present invention.

[0034] Fig.12 It is a schematic diagram of the internal principle of a 0.96-inch OLED according to a specific embodiment of the present invention.

[0035] Fig.13 It is a schematic diagram of the connection between an OLED display screen and a single-chip microcomputer according to a specific implementation manner of the present invention.

[0036] Fig.14 It is a schematic diagram of a power supply circuit according to a specific embodiment of the present invention.

[0037] Fig.15 It is a principle diagram of an alarm circuit according to a specific embodiment of the present invention.

[0038] Fig.16 It is a schematic diagram of the connection between a Bluetooth module and a single-chip microcomputer according to a specific implementation mode of the present invention.

[0039] Fig.17 It is a schematic diagram of a matrix keyboard according to a specific embodiment of the present invention.

[0040] Fig.18 It is a main program flow chart of a specific implementation mode of the present invention.

[0041] Fig.19 It is a flowchart of the HX711 reading A / D value program according to a specific implementation mode of the present invention.

[0042] Fig. 20 This is the key scanning process of the specific implementation mode of the present invention.

[0043] Fig.21 It is the APP interface of the specific implementation mode of the present invention.

[0044] Fig. 22 It is a Bluetooth connection flow chart of a specific implementation mode of the present invention.

[0045] Fig.23 This is the process of receiving data by a mobile phone APP in a specific implementation manner of the present invention.

[0046] Fig.24 It is a schematic diagram of an initial power supply circuit of a specific implementation mode of the present invention.

[0047] Fig.25It is a power supply principle diagram of a specific implementation mode of the present invention.

[0048] Fig.26 It is a schematic diagram of a red warning light lighting up according to a specific embodiment of the present invention.

[0049] Fig. 27 It is a schematic diagram of the test results of the OLED screen according to a specific embodiment of the present invention.

[0050] Fig.28 It is a mobile phone APP test diagram of a specific implementation mode of the present invention. DETAILED DESCRIPTION

[0051] The present invention will be further described in detail below in conjunction with specific implementations and with reference to the accompanying drawings. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope of the present invention and its application.

[0052] Non-limiting and non-exclusive embodiments will be described with reference to the following figures, wherein like reference numerals refer to like parts unless otherwise specifically stated.

[0053] The present invention proposes an intelligent Bluetooth electronic scale, which includes a weighing sensor, an amplifier, an A / D converter, a control chip, a display, a keyboard and a Bluetooth module. The basic working principle is to use a weighing sensor to detect the mass of an object, convert a pressure signal into a weak current signal, and then transmit it to the amplifier. The amplification circuit appropriately amplifies the weak current signal, and then converts it into a digital signal through the A / D converter. The control chip can analyze and process these digital signals, and the data after analysis and processing are displayed through the display. In addition, the intelligent Bluetooth electronic scale has a keyboard, and the user can use the keyboard to select the type of goods, peel and send data. The intelligent Bluetooth electronic scale has a Bluetooth module, and the control chip can transmit the processed data to a mobile phone APP via the Bluetooth module. After the mobile phone APP receives the data, it processes, displays and saves it, which is very convenient to use. When the weighing value exceeds the set value, the alarm circuit will alarm. The electronic scale involved in the present invention is very small in size and easy to carry. It can be used in daily goods trading and settlement scenarios such as supermarkets and vegetable markets.

[0054] 1. Basic introduction of electronic scales

[0055] 1.1 Hardware system composition

[0056] The hardware system of the smart Bluetooth electronic scale can be divided into the following parts: sensor signal acquisition circuit, signal amplification circuit, A / D conversion circuit, power supply, key input, Bluetooth communication, MCU minimum system, display, overweight alarm circuit; the overall design scheme block diagram of the smart Bluetooth electronic scale is as follows: Figure 1 shown.

[0057] The signal acquisition circuit of the smart Bluetooth electronic scale uses a weighing sensor to collect the weight of the object to be weighed, and converts the weight signal that the microcontroller cannot recognize into a weak current signal. After being amplified by the signal amplifier circuit and converted by the A / D conversion circuit, it is transmitted to the microcontroller for processing. The power supply circuit supplies power to the microcontroller minimum system. The microcontroller minimum system will control and coordinate the realization of the functions of the entire hardware system and is the brain of the hardware circuit. The overweight alarm circuit alarms according to the set value. The display circuit can display the content to be displayed according to the needs. The microcontroller can send data to the mobile phone APP through the Bluetooth communication circuit.

[0058] 1.3 Selection of hardware solutions

[0059] 1.3.1 Selection of control chip

[0060] Solution 1: Use STC89C52RC microcontroller chip. It has many advantages. It is a relatively low power chip in microcontrollers. It has 40 pins, including 32 I / O ports. It also has timers, counters, interrupts and other resources.

[0061] Solution 2: Use the STM32F103RCT6 MCU chip. It is an STM32 chip using the ARM Cortex-M3 framework, supports a maximum frequency of 72MHz, and has 48K RAM. It has 5 serial ports, 2 basic timers, 3 12-bit ACDs and other resources.

[0062] Scheme comparison: The present invention requires a single-chip microcomputer to perform various processing on the measured data. The single-chip microcomputers in the two schemes are sufficient for this task. In the context of the global chip shortage, the cost of the chip must be considered when selecting a chip. After checking the online information, the price of the STM32F103RCT6 single-chip microcomputer chip is much more expensive than that of the STC89C52RC single-chip microcomputer chip. The STC89C52RC chip is also easier to operate, and its internal resources are sufficient. Therefore, this invention adopts the STC89C52RC single-chip microcomputer chip of Scheme 1 to design the single-chip microcomputer circuit and realize various functions.

[0063] 1.3.2 Weighing sensor selection

[0064] The weighing sensor is a very important component of the smart Bluetooth electronic scale. Its main function is to convert the measured mass into an electrical signal and transmit it to facilitate subsequent detection and processing.

[0065] There are many types of weighing sensors, which can be divided into different types according to different principles: vibration weighing sensors, capacitance weighing sensors, deformation magnetic pole weighing sensors, hydraulic weighing sensors, photoelectric electronic weighing sensors, strain resistor weighing sensors and gyro weighing sensors. Strain resistor weighing sensors and hydraulic weighing sensors are the most widely used in practical applications.

[0066] Among them, strain gauge type weighing sensors have many excellent features, such as its sensor structure is relatively simple compared with other types of sensors, and its production cost is relatively low. The strain gauge or strain film can sense the stress of the measured object and convert it into resistance, which is then converted into voltage or current by the bridge. Generally speaking, the strain gauge will be subjected to two forces. When subjected to tension, the resistance value of the strain gauge increases. Conversely, when subjected to pressure, the resistance value will decrease.

[0067] The internal circuit of the sensor usually adopts a Wheatstone bridge, such as Figure 2 shown.

[0068] When R 1 =R 2 =R 3 =R 4 =R, it belongs to an equal-arm bridge. Then the output voltage U 0 for;

[0069]

[0070] When ΔR< <R i When the high-order terms are ignored, the linear output voltage U 0 ＇ for;

[0071]

[0072] The sensor used is generally a full-bridge circuit, with strain gauges attached to each bridge arm. When the bridge arm is subjected to a downward force, Figure 3 shown.

[0073] According to R = ρL / S, the resistance R 1 and R 3 When the resistance wire is pulled, its length L will increase and its cross-sectional area S will decrease. 1 and R 3 The resistance value will become larger, the resistor R 2 and R 4 When the resistance wire is subjected to pressure, its length L will decrease and its cross-sectional area S will increase. 1 and R 3 The resistance of the strain gauge on the bridge arm will change as follows: Figure 4 shown.

[0074] R 1 and R 3 When the resistance value increases due to the pulling force, ΔR 1 =ΔR 3 =ΔR, and R 2 and R 4 The resistance value decreases under pressure, ΔR 2 =ΔR 4 =-ΔR, ΔR 1、 ΔR 2、 ΔR 3、 ΔR 4 Substitute the value of into the formula:

[0075]

[0076] The output voltage U 03 for;

[0077]

[0078] This embodiment uses a parallel beam weighing sensor with a range of 20kg, which is a resistance strain type pressure sensor. Its working process is as follows: Figure 5 shown.

[0079] 1.3.3 A / D Converter Selection

[0080] In order to enable the microcontroller to detect the voltage signal transmitted back by the resistive strain pressure sensor, it is very important to choose a suitable A / D sensor.

[0081] Solution 1: Use ADC0809 chip. ADC0809 is an 8-bit CMOS successive approximation A / D converter. It has eight input channels to choose from. It is a relatively simple A / D converter and is also relatively easy to understand.

[0082] Solution 2: Use the HX711 chip. It has two input channels, an integrated amplifier, and gains of 32, 64, and 128. You can choose different amplification factors according to different needs. It has an integrated voltage regulator power supply. In addition, the chip also has an on-chip clock oscillator.

[0083] Comparison of solutions: The ADC0809 chip has low accuracy and weak anti-interference ability. It requires more complex hardware circuits to make it work, making the design more complex and inefficient. After using ADC0809, it is necessary to build additional amplification circuits, making the hardware design more complex. Because its output is parallel output, using a single-chip microcomputer to control and receive data will use more IO ports. The HX711 chip has higher accuracy and has a 24-bit A / D conversion. It is a chip developed for the use of weighing sensors. This embodiment uses a resistive strain gauge pressure sensor. Using HX711 to collect its output voltage signal is a very good choice. The chip cost of the HX711 module is similar to that of ADC0809, so the better HX711 is selected as the A / D converter.

[0084] 1.3.4 Display Selection

[0085] The display is one of the channels to obtain information from the smart Bluetooth electronic scale, so it is very necessary to choose a good and appropriate display circuit.

[0086] Solution 1: Use digital tube as display circuit. It is composed of LED in a specific arrangement. Its display method is very simple. You only need to program the places that need to be lit according to the needs. However, it can display very little content and is generally only used to display numbers. It is cheap and easy to operate, and it is also relatively common in the market.

[0087] Solution 2: Use LCD1602. LCD1602 is a screen that relies on backlight for display. It has two lines of display content, each line can display 16 characters, can display English and numbers, but cannot display Chinese. The screen backlight brightness can be adjusted by adjusting the voltage on the fixed pin, and the brightness can be adjusted according to needs.

[0088] Solution 3: Use LCD12864 LCD display. LCD12864 is the same type of display as LCD1602. It can display more content than LCD1602. It has many built-in Chinese character libraries. The screen backlight brightness can be adjusted by adjusting the voltage on the fixed pin.

[0089] Solution 4: Use OLED LCD screen. Thanks to its advanced display technology, OLED screen does not require backlight, has relatively low power consumption, can be made very thin, and displays rich colors. It is now widely used in mobile phones, computers, TVs and other products.

[0090] Comparison of schemes: The hardware part of the digital tube display of scheme 1 is relatively simple to make, the display interface is intuitive and neat, and the software programming is relatively simple, but it can only display numbers, and the display content is single. If more numbers need to be displayed, more IO ports need to be added, and more decoders need to be added to the hardware circuit, which makes the construction of the hardware circuit relatively complicated and cost-effective. The LCD1602 of scheme 2 can display numbers and English, but the displayed content is still less, and Chinese cannot be displayed. Compared with other display schemes in this product, it is not the best choice. The LCD12864 of scheme 3 is relatively expensive, and many external pins are required. If you only want to use a few pins to drive it, you need to build more peripheral circuits, which will increase the hardware cost. The OLED screen of scheme 4 is more common in daily life. The size of the display content can be selected according to needs, and color content can be displayed. The price is relatively low, and the displayed content is also a lot. After comprehensive consideration, this embodiment selects OLED liquid crystal display screen as the display screen of the smart Bluetooth electronic scale.

[0091] 1.3.5 Communication module selection

[0092] The Bluetooth module of the smart Bluetooth electronic scale is used when the microcontroller needs to send data to the mobile phone. The microcontroller only needs to use the serial port to transmit data. That is to say, when the mobile phone APP is connected to the Bluetooth module of the microcontroller, it can receive the information sent by the microcontroller through the serial port. The Bluetooth module is equivalent to a transit station for data transmission. With this medium, the mobile phone can realize short-distance wireless data transmission and communication with the electronic scale.

[0093] The communication interface module selected by the present invention is the JDY-24M Bluetooth serial port module. The Bluetooth interface module of JDY-24M adopts the Bluetooth standard V5.0. The system supports UART and supports the Bluetooth serial port of SPP. It is compatible with the HC-06 Bluetooth module. The JDY-24M Bluetooth serial port module is selected as the data transmission module of the present invention.

[0094] 1.3.6 Selection of key circuit

[0095] In order for users to be able to select products and perform other operations by pressing keys, a keyboard circuit is essential. There are two keyboard selection options as follows;

[0096] Solution 1: Use independent buttons, each button can work independently and use a single-chip microcomputer IO port independently. Because the I / O port of the control chip microcomputer can output to the outside and detect the voltage level of the I / O input, its advantage is that each button works independently and will not affect the status of other I / O ports during the work process. Its software program writing is also relatively simple, and the configuration of the hardware circuit is also relatively flexible. However, if more buttons are needed, more I / O ports will be occupied, thereby consuming more IO port resources.

[0097] Solution 2: Use matrix keys, that is, arrange the keys in a matrix manner and connect each column of each row with a line.

[0098] The present invention needs to use 16 keys. In the above scheme 1, each key uses an IO port of a single-chip microcomputer for identification and control, which will use 16 IO ports of the single-chip microcomputer, while the matrix keyboard of scheme 2 only uses 8 IO ports of the single-chip microcomputer. In actual use, the software programming of the matrix keyboard is slightly more complicated than that of the independent keyboard, but it occupies less resources of the single-chip microcomputer, so using the matrix keyboard as the keyboard circuit of the smart Bluetooth electronic scale is the preferred solution.

[0099] 2 System Hardware Design

[0100] The hardware system is the foundation of the entire smart Bluetooth electronic scale. Whether the hardware design is reasonable, the selection of each component and the design of the parameters are correct will directly affect the stability and performance of the product. If the hardware circuit design is not good enough, no matter how good the software programming algorithm is, it will be useless.

[0101] 2.1 MCU Minimum System

[0102] The single-chip microcomputer chip used in the present invention is the STC89C52RC single-chip microcomputer chip of Hongjing, which is a relatively simple and classic control chip. It uses a very classic MCS-51 core, and has been optimized and improved on this basis, so that it can have more functions and more resources than the traditional 51 single-chip microcomputer, making it more powerful. Now it can provide them with reliable, flexible and efficient solutions as a control chip for embedded control application systems. It is fully compatible with the system instructions of the traditional 51 single-chip microcomputer. The pin diagram of STC89C52RC is as follows Figure 6 shown.

[0103] The core circuit of the smart Bluetooth electronic scale is the minimum working system of the single-chip microcomputer built using STC89C52RC. The minimum system of the single-chip microcomputer is composed of the single-chip microcomputer STC89C52CR chip, reset circuit, and crystal oscillator circuit. The system schematic diagram is as follows Figure 7 shown.

[0104] The crystal oscillator circuit includes two 30pF capacitors and a quartz crystal oscillator, which is equivalent to the heart of the single-chip microcomputer and continuously provides clock pulses to the single-chip microcomputer. Because the present invention needs to use Bluetooth data transmission, in order to make data transmission more stable and reliable, and to make the baud rate generated by the single-chip microcomputer more accurate, this embodiment will select a 11.0952MHz crystal oscillator for the design of the crystal oscillator circuit.

[0105] The reset circuit is designed with a capacitor button and a pull-down resistor. The STC89C52RC microcontroller is reset at a high level. The condition for the microcontroller to enter the reset state is that when the internal oscillator is operating normally, the reset input terminal RST remains at a high level for at least two machine cycles (24 oscillation cycles). The CPU samples the reset signal, starts the reset sequence, and completes the reset operation.

[0106] 2.2A / D conversion circuit design

[0107] Generally, the voltage value of the voltage signal that can be output by the weighing sensor is a relatively small analog voltage signal. In order to collect the signal transmitted back by the sensor, and process and convert it, the present invention uses the HX711 chip as the conversion chip. The HX711 is a serial data output bus type analog-to-digital (AD) converter. The HX711 is a chip designed for electronic precision scales. It has an amplification part and a 24-bit A / D conversion part integrated inside. It has many excellent characteristics, a high degree of integration, and a very sensitive response speed to the signal. It also has a signal amplification function. The internal block diagram of the HX711 is as follows: Figure 8 As shown. HX711 has 16 pins, each with a corresponding function, such as Fig. 9 The figure shows the SOP-16L package of HX711.

[0108] The control signals of the HX711 chip can be driven by pins, and no additional program writing control is required. It is very convenient to use. Different signal amplification factors can be selected according to different needs. It has 128, 64, 32 and other amplification factors to choose from. In addition, its internal power supply can also power the weighing sensor, and there is no need to build additional power supplies on the circuit board. The schematic diagram of the HX711 module is as follows: Fig.10 shown.

[0109] For ease of use, the present invention uses the HX711 module, which has four pins, namely VCC, GND, and the 11th pin PD_SCK and the 12th pin DOUT of the HX711. In terms of hardware, the HX711 module needs to be powered when it is used, and two IO ports of the single-chip microcomputer are connected to the 11th pin PD_SCK and the 12th pin DOUT of the HX711, and the driving can be used in software programming. The present invention uses the P2^2 of the STC89C52RC single-chip microcomputer to connect to the 11th pin PD_SCK of the HX711, and uses the P2^3 of the STC89C52RC single-chip microcomputer to connect to the 12th pin DOUT of the HX711. The connection principle diagram is as follows: Fig.11 shown.

[0110] 2.3 Display Circuit Design

[0111] The display of weight, price and other data is a very necessary function of the smart Bluetooth electronic scale. It is a way to obtain data from the single-chip microcomputer. It can display the weighing data processed by the single-chip microcomputer, and the data can be easily and intuitively seen. This embodiment uses SSD1306 to drive a 0.96-inch four-row pin OLED screen. The chip contains 128 segments and 64 common terminals. It is specially developed for driving a common cathode OLED screen. SSD1306 integrates a contrast controller, display RAM and crystal oscillator, thereby reducing a lot of peripheral circuits and reducing the power consumption of driving the OLED screen. It has a large number of levels of brightness control, and a total of 256 levels can be controlled. The data transmission protocol of SSD1306 can support three protocols, namely: 6800 / 8000 serial port, IIC interface and SPI interface, which are sufficient for most devices. This embodiment uses a 4-pin 0.96-inch OLED display screen. The microcontroller can use the IIC protocol to communicate with SSD1306 to drive the OLED screen to display the content. The content to be displayed can be driven by the programming of the microcontroller to display the content and data. The internal schematic diagram of the 0.96-inch OLED screen is shown as follows: Fig.12 shown.

[0112] The 0.96-inch OLED liquid crystal display screen used in this embodiment has four pins, two of which are connected to the external power supply to enable the internal normal operation, and the remaining two pins are the SCL clock line and the SDL data line. It is only necessary to use the two IO ports of the microcontroller to connect them respectively, and the OLED screen can be driven to display in the subsequent software programming. The connection principle diagram of OLED and the microcontroller is shown in FIG. Fig.13 shown.

[0113] 2.4 Power supply circuit design

[0114] In order to reliably and stably power the single-chip microcomputer and various hardware circuits, the power supply circuit uses a 3.7V polymer lithium battery in series to step down the voltage to 5V to power the STC89C52RC single-chip microcomputer and various modules. The LM7805 integrated voltage regulator is used as the core of the step-down circuit. Because the LM7805 requires very few peripheral devices to form a voltage regulator circuit, the hardware cost can be reduced. The LM7805 has various protection circuits integrated inside to make it stable. It is very reliable and simple to use in actual applications, and its cost is relatively low. Because of the convenient design and ease of use of the LM7805, it is often seen in the process of electronic production.

[0115] The power supply circuit uses 5VDC voltage stable output, and the overall LM7805 rectifier is used. 0.1uF capacitors C4 and C7 are set at the input and output ends of LM7805 respectively to filter the voltage, while R2 resistor is a load resistor. LED1 is used as the indicator light of the power supply, and LED1 will light up when the circuit starts to supply power. When the output value of the power supply is large, the LM7805 chip should be equipped with a heat dissipation component.

[0116] LM7805 is very common in the process of circuit design. It can stably output DC 5V voltage and has a wide range of uses. It also has an integrated protection circuit, so you can design and build your own peripheral circuit to output the value you need.

[0117] The power supply circuit diagram is as follows Fig.14As shown, each device has its own role. Among them, C4 is a 0.1uF capacitor, which can rectify and filter the input voltage value. After it is rectified and filtered, the voltage will get a value with very small ripple, which makes the voltage quality of the LM7805 input end higher. The C4 rectifier filter capacitor is usually related to the needs of the circuit. Generally speaking, the larger the load value of the circuit, the larger the value of the C4 rectifier filter capacitor should be selected accordingly. C5 is a 220uF capacitor, which is the capacitor required for the LM7805 chip to work. Especially when the rectifier filter capacitor is not tightly connected to the LM7805, it is an indispensable part. Its role is to make the work of the amplifier inside the LM7805 stable. The value of the C5 capacitor is based on the value required by the manufacturer who designed this chip. They stipulate that the value of the capacitor should be greater than or equal to 0.33uF, and its design in the hardware circuit tries to make it tightly connected with the pin 1 (input end) and pin 2 (common end to ground) of the LM7805 chip. C6 is a 220uF capacitor, which is also required for the LM7805 chip to work. Its function is to stabilize the operation of the amplifier inside the LM7805. In addition, it can also improve the over-response of the voltage during the adjustment process. Its value is also based on the value required by the manufacturer who designed this chip. They stipulate that the value of the capacitor should be greater than or equal to 0.1uF, and its design in the hardware circuit tries to make it tightly connected with pin 3 (output end) and pin 2 (common end to ground) of the LM7805 chip. C7 capacitor is designed for decoupling of the load circuit. It can form a short-distance local loop with the load. Its value is related to the different working modes of the load circuit. R2 is a circuit that provides loads here. R2 is to avoid damage to the circuit due to excessive voltage regulation current. SW5 is a self-locking six-pin switch. It is between the input power supply and LM7805. This switch can be used to control the power supply of the entire circuit.

[0118] 2.5 Alarm circuit design

[0119] Because the weighing range of the weighing sensor is limited, in order to avoid irreparable damage to the weighing sensor during weighing, an overweight alarm circuit is designed. When the weight sent back by the weighing sensor is greater than the set value, the alarm circuit starts to work and reminds the user of overweight. The core part includes: power buzzer and its drive circuit, LED, the circuit schematic diagram is as follows Fig.15 shown.

[0120] The buzzer of the overweight alarm circuit uses a 5V active buzzer. Because the current output by the IO port of the single-chip microcomputer is relatively weak, the active buzzer cannot work. Therefore, the buzzer cannot be directly connected to the IO port pin of the single-chip microcomputer. At this time, a 5V power supply is required to drive the buzzer to work. The switching circuit composed of transistors can be used to control the buzzer. The transistor of the switching circuit here uses the PNP type SS8550. The pin P2.4 of the single-chip microcomputer is used to control the transistor switch. When the P2.4 pin of the single-chip microcomputer outputs a low level, the transistor is turned on, the buzzer can work normally, and can make a sound to remind the user of overweight. At the same time, the P2.4 port of the single-chip microcomputer is in a low level state, the LED2 light-emitting diode is also turned on, the light-emitting diode lights up, and the user can also see the overweight alarm indicator light.

[0121] 2.6 Communication interface circuit design

[0122] The communication method used by the smart bluetooth electronic scale is to use bluetooth communication. The bluetooth module used in this embodiment is a BT08B bluetooth module, which has a wide voltage range. It can be powered by a voltage of 3.3V or a voltage of 5V. It is easy to use and can be seen in many scenes where single-chip microcomputers use bluetooth. It can be used as a host or a slave. It is a high-performance bluetooth serial port module. It is simple to use and can be directly used with the serial port of the single-chip microcomputer without any other programming. After the user uses the mobile phone bluetooth to pair with the bluetooth module, bluetooth is the medium between the mobile phone and the smart bluetooth electronic scale. The mobile phone and the single-chip microcomputer can use it to transmit data without learning and mastering its internal communication principle, which is very convenient to use. When the single-chip microcomputer needs to send data to the mobile phone, it can be sent directly through the serial port, and the mobile phone can receive the data by connecting to bluetooth.

[0123] In the actual connection, the connection of the Bluetooth module is also very simple. You only need to cross-connect the RXD and RXD of the microcontroller and the Bluetooth module respectively. The actual connection is as follows Fig.16 Communication is possible as shown.

[0124] 2.7 Design of key circuit

[0125] The key circuit is an essential hardware in the smart Bluetooth electronic scale. The user interacts with the smart Bluetooth electronic scale through the keyboard. The keyboard can be used to select the required product type, peel the product, and press the button to send data to the mobile phone APP.

[0126] The keyboard circuit of this embodiment has a total of 16 keys. A 4X4 matrix keyboard circuit is selected, with 4 keys in each row. There are 4 rows in total. The same end of the keys in each row is connected to lead out four wires, and the remaining unconnected end of the keys in each column is also connected to lead out four wires. 8 IO ports are used to control and detect the 16 keyboards.

[0127] The present invention connects the eight wires derived from the 4X4 matrix keyboard to the eight IO ports of P1 of the single-chip microcomputer. The specific design principle diagram is shown in FIG. Fig.17 The functions of each button are shown in Table 2-1.

[0128] Table 2-1 Key Function Table

[0129] Product 1 Product 2 Product 3 Product 4 Product 5 Product 6 Product 7 Product 8 Item 9 Item 10 Product 11 Product 12 Product 13 Product 14 Peeling send

[0130] 3. System software design

[0131] 3.1 Design of the main program

[0132] In the application written by the software program, the timer 0 of the STC89C52RC microcontroller and the serial port will be used to send data. First, the timer 0 and the serial port will be initialized. Before using the OLED screen, the OLED screen must also be initialized. To transmit data using the serial port Bluetooth, the special function register must be set to initialize the serial port. The serial port is initialized and set to work in mode 1. It is set to 8-bit UART with variable baud rate. Use timer 1 to set the baud rate of the serial port to 9600. Timer 0 is initialized to timer working mode 1, 16-bit timing mode, and a timer interrupt is entered every 20ms for key detection. When timer 0, the microcontroller serial port and the OLED screen are initialized, the peeling function is called to start peeling the electronic scale. After completing these preparations, the microcontroller program will enter the While (1) loop and keep detecting and working. The main program design flow chart is as follows Fig.18 shown.

[0133] 3.2 Subroutine Design

[0134] 3.2.1 Read A / D value program

[0135] The function is to make the HX711 chip perform analog-to-digital conversion on the collected signal. When the data output pin DOUT of the HX711 chip pin 12 is in a high level state, it means that the HX711 chip is not ready yet and cannot output data. At this time, the PD_SCK of the HX711 pin 13 inputs a low level to wait for the HX711A / D converter to start working. When the data output pin DOUT of the HX711 chip pin 12 changes from a high level to a low level, it means that the A / D converter starts working. At this time, 25 clock pulses should be input to the PD_SCK of the HX711 pin 13, of which the first 24 pulses are used to take out the data value output by the HX711 data pin 12DOUT. The function of the 25th clock pulse is to set the input channel for the next A / D conversion to the A channel and the gain of the amplifier to 128 times. HX711 selects the channel and gain of the next measurement data according to the number of PD_SCK pulses. The specific process is as follows Fig.19 shown.

[0136] 3.2.2 Key detection subroutine

[0137] The key circuit used in the present invention uses a 4*4 matrix keyboard circuit, and its software programming is more complicated than that of an independent keyboard. The method used for this programming is a row and column scanning method. Its specific principle is that the single chip microcomputer first outputs a high level to the lead-out line of each column of the matrix keyboard, and outputs a low level to the lead-out line of each row. When a key is pressed, because the IO of the single chip microcomputer has a line and function, when the low level output by the single chip microcomputer in each column is connected and short-circuited with the high level output by the single chip microcomputer in each row through the key, the IO port that originally outputs the high level will be pulled low. At this time, the single chip microcomputer detects through programming which column the IO port level connected to is pulled low, so it can be known which column the key is pressed, and it is pulled down for the next judgment. Since it is only known which column of the matrix keyboard is pressed, but it is not known which key in this column is pressed, the key can be detected through row scanning. The principle is the same as that of column scanning. After row scanning and column scanning, it can be known which row and column the key is pressed. The single chip microcomputer knows which key is pressed, and can perform subsequent processing according to demand. Since the processing speed of the microcontroller is very fast, it is necessary to perform software debounce before using it for key detection. If it is not debounced, when it is pressed once, the microcontroller may detect more than one time. At this time, the result recognized by the microcontroller does not match the result of the operation, so the key must be debounced. The specific design is as follows: Fig. 20 shown.

[0138] 3.2.3 Timer interrupt subroutine

[0139] Because the STC89C52RC chip is used to drive the display of the OLED screen, the OLED display function is used in the main function, and the OLED display sub-function will take up more running time. If the key detection function is placed in the main function, it may happen that when the key is pressed, the program has not yet run to the key detection function, which will cause the microcontroller to fail to recognize the pressed key. Therefore, a timer interrupt is used to detect whether the key is pressed. The timer interrupt is entered every 20ms, and the value returned by the key detection function is stored for subsequent function and data analysis.

[0140] 3.2.4 Data processing subroutine

[0141] Because the smart Bluetooth electronic scale needs to send data to the mobile phone APP through the Bluetooth serial port, but the SUBF register can only send one byte of data at a time, so the weight and price obtained need to be processed separately and then saved into an array variable. The method of data processing here is to split each bit of weight and price and save them separately. For example, if the weight value transmitted back by weighing is 12345 (in g), this value can be split into five digits 1, 2, 3, 4, and 5 and stored in the numerical variable: When the button 16 is pressed to send data, the SBUF register will take the data out of the array variable and send it, and the mobile phone APP will process and convert the data after receiving the data.

[0142] 3.2.5 Key Function Processing Subroutine

[0143] When the value of the button is retrieved, each button has its own function. Different operations should be performed according to the function. The operation should be judged according to the value retrieved by the button. When the value of the button is 1-14, the product number and price corresponding to each button are assigned to the variable for display and processing; when the value retrieved by the button is 15, the peeling subroutine will be called, and the smart Bluetooth electronic scale will start peeling; when the pressed value is 16, the data will be sent to the mobile phone APP for processing through the Bluetooth serial port. The corresponding matrix keyboard buttons are shown in Table 3-1.

[0144] Table 3-1 Matrix keyboard key function table

[0145] Product 1 Product 2 Product 3 Product 4 Product 5 Product 6 Product 7 Product 8 Item 9 Item 10 Product 11 Product 12 Product 13 Product 14 Peeling send

[0146] 3.3 Design and development of mobile APP

[0147] First, we designed the mobile phone APP interface. The interface of the APP design is relatively simple. Because the mobile phone needs to receive the data sent by the electronic scale, the display interface has Bluetooth connection and Bluetooth disconnection buttons. In addition, there are also product names, costs, prices, weights, profits, and historical data can be viewed to clarify the data. The specific design is as follows: Fig.21 shown.

[0148] After setting up the APP interface, the next step is to enter the logic design. Because Bluetooth is used to receive the data sent by the electronic scale, the Bluetooth client is used. Only when the Bluetooth is connected can the mobile phone APP receive the mobile phone data. The logic of the Bluetooth connection is that when the Bluetooth connection button is pressed, the elements of the Bluetooth connection are set to the address and name of the Bluetooth client. The user selects the Bluetooth connection according to the address and name of the Bluetooth client. After the selection is completed, if the connection is successful, a text of successful Bluetooth connection will pop up. If the connection fails, a dialog box will pop up to prompt that the Bluetooth connection failed. Please check whether the Bluetooth device is turned on and try to connect again. The connection process is as follows Fig. 22 shown.

[0149] When the Bluetooth connection is successful, the timer will be turned on to detect the data sent by the microcontroller. When the Bluetooth client receives the data, it will analyze, process, save and display the data transmitted by the electronic scale. The working process is as follows: Fig.23 shown.

[0150] In order to save the data sent by the MCU and keep it saved after exiting the APP, the micro-database component in APPInventor is used. Every time a set of data is received from the MCU, it is saved in the micro-database. When exiting the APP and re-entering it, the previously saved data is retrieved from the micro-database, so that the data can be saved locally.

[0151] 4 System debugging and testing

[0152] In order to find out as many design errors as possible in the hardware and software of the smart Bluetooth electronic scale, to ensure the normal function and reliability of the product while further improving its own design and development capabilities for software and hardware; necessary debugging will be carried out on the product to discover the defects and problems in the design of the smart Bluetooth electronic scale, solve and improve the problems, so that the product can function normally.

[0153] 4.1 Circuit Debugging

[0154] The debugging of the smart Bluetooth electronic scale is first to debug the hardware circuit board. The hardware is made by industrial board making, which is much more reliable than manual board making and production. Before soldering the components to the PCB board, it is necessary to confirm whether the drawn schematic diagram and PCB are consistent with the received PCB board. If they are consistent, the next step of soldering can be carried out. In the process of circuit soldering, you need to be extra careful and place the corresponding components in the specified position. After soldering the components to the PCB board, you need to check the components and circuits on the PCB board again. Generally, a multimeter is used to check the continuity of the circuit and components. The focus is on whether there is a cold solder joint or a component pin leak during the soldering of the PCB circuit board. In the process of hardware circuit board soldering, this process needs to be carried out very carefully to avoid burning the components due to circuit soldering errors.

[0155] Before powering on the circuit board, it is necessary to repeatedly confirm that there is no problem with the connection of the circuit components. After confirming that there is no problem with the circuit, the power supply can be connected to the input end of the power supply circuit, and the voltage at the output end of the power supply can be checked with a multimeter to see if it is correct. If it is correct, the devices of other modules can be connected. After powering on the circuit, it is necessary to check whether the working status of the chip and other devices is normal, whether there is heating and other phenomena, and the working status of the indicator light. When the components or circuits send abnormal working status, the power supply should be removed immediately, and it is necessary to check the schematic diagram, PCB and circuit board of the smart Bluetooth electronic scale again to see if there are any problems, rethink which part may have problems or omissions, and analyze, improve and solve the problems.

[0156] 4.1.1 Debugging of power supply circuit

[0157] Test the entire circuit. In order to make it easier to debug the circuit later, you can solder the components of the power supply part to the circuit board. First use a multimeter to test the circuit of the power supply part. When the output of the power supply is the expected normal value, continue to solder other parts to the circuit board. If the power supply output is abnormal, analyze the cause and make improvements.

[0158] The original hardware circuit design is that the power supply circuit uses a series CR2032 button battery as the power supply. After the batteries are connected in series, the entire system is powered by the LM7805 step-down circuit. When the power supply is connected to the circuit, the voltage is measured using a multimeter. After measurement, it is found that when the button battery is used in series, the power supply output voltage cannot reach 5V, and the button battery's own voltage is also dropping sharply. Cut off the power supply to analyze the problem. The initial power supply circuit design is as follows Fig.24 shown.

[0159] Cause analysis: After debugging and analysis, it was found that when using RC2032 button batteries for step-down power supply, the RC2032 button batteries have limited capacity and output current, so the LM7805 cannot be used for normal step-down. Solution: Replace the CR2032 button batteries with several 3.7V polymer lithium batteries with larger battery capacity in series, and then step down the voltage through the LM7805 to power the entire system. After redesigning the power supply circuit, the schematic diagram is as follows Fig.25 shown.

[0160] 4.1.2 Testing of the Minimum System

[0161] After the power circuit is debugged, connect the power supply to the single-chip microcomputer minimum system. Test the single-chip microcomputer minimum system, use a multimeter to check whether the power output end of the single-chip microcomputer power supply circuit is within the working range of the single-chip microcomputer. If it is 5V and in normal working condition, connect the single-chip microcomputer minimum system to the computer using a USB to TTL downloader, and use a dedicated burning application to burn the test program into the single-chip microcomputer chip. When the test program can be burned into the single-chip microcomputer chip normally, it means that the core circuit single-chip microcomputer minimum system can work normally. If the test program cannot be burned into the single-chip microcomputer chip normally, it is necessary to check whether there are problems with the circuit design and whether there are errors in the wiring of the downloader. If there are no problems with the above, it is necessary to check the components of the crystal oscillator circuit for damage to the crystal oscillator, and consider replacing new components or chips before the next step of testing.

[0162] 4.2 Joint testing of software and hardware

[0163] In order to test the peripheral circuit of the single-chip microcomputer, software and hardware joint debugging is used. First, the connection part of the peripheral circuit is checked to see if there is any problem with the wiring of the circuit, whether there is any short circuit or short circuit that should not exist, etc. After the circuit is checked, start writing a software test program to test the peripheral circuit, check whether the hardware circuit can work normally, and whether the displayed results are consistent with the program writing. If not, analyze and judge whether it is a problem with the circuit design or the program writing, and find out the problem and solve it.

[0164] 4.2.1 Test of overload alarm circuit

[0165] The overweight alarm circuit is composed of a light-emitting diode and an active buzzer. First, the connection on the circuit board is checked with a multimeter to see if there is any cold soldering or leaking soldering. After checking that there is no problem with the circuit connection, start writing a software program to test the circuit. By outputting the IO voltage of the microcontroller connected to the circuit as low, you can know whether the circuit can work normally. The circuit is connected to P2^4 of the microcontroller. When the P2^4 pin of the microcontroller outputs a low level, the buzzer can sound and the red LED alarm light will light up. Fig.26 shown.

[0166] 4.2.2 OLED display test

[0167] The debugging of OLED LCD screen is as follows:

[0168] Check the connection of the circuit. Carefully check whether the connection between the pins of the OLED LCD screen and the IO pins of the microcontroller is correct. At this time, you need to be extra careful not to connect the polarity of the power supply incorrectly, otherwise the OLED LCD screen may be burned.

[0169] Next, we need to write a simple program to test the OLED LCD screen. First, we need to initialize the OLED screen, read the OLED driver data sheet, use the initialization program according to the content of the data sheet, generate and save the content to be tested through the module software, and write it into the program to start testing the OLED so that it can display.

[0170] This test is to divide the OLED LCD screen into 4 lines, each line displays "Screen testing:" through the programming to make it display, the test results are as follows Fig. 27 As shown, the test results show that the OLED LCD screen can display normally and the circuit of this part is normal.

[0171] 4.3 Product Testing

[0172] After the above tests, the entire product can be tested next. Now combine the software and hardware to debug the system and measure the data, connect the various modules of the circuit, burn the written software program into the STC89C52RC microcontroller, connect the power supply of the smart Bluetooth electronic scale, and press the switch to start testing the product.

[0173] When the working indicator light of the smart Bluetooth electronic scale lights up, open the mobile phone APP, find the Bluetooth connection, connect the mobile phone APP with the smart Bluetooth electronic scale, and when the product button 13 is pressed on the matrix keyboard of the smart Bluetooth electronic scale, the OLED displays the corresponding product number, price, weight and total price on the screen. When a 500g weight is placed on the tray of the weighing sensor, the OLED displays the obtained information.

[0174] When the smart Bluetooth electronic scale presses the send data button on the matrix keyboard, the data sent by the smart Bluetooth electronic scale can be received on the mobile phone APP and the profit can be calculated based on the cost and saved in the database. The mobile phone APP displays the following information: Fig.28 shown.

[0175] When you press the Tare button on the matrix keyboard and wait for a while, the weight value displayed on the OLED screen will be cleared to 0. Put an object on the tray of the weighing sensor, and the electronic scale will start weighing and obtaining data again.

[0176] The following are the measurement data using weights using a smart Bluetooth electronic scale as shown in Table 5-1:

[0177] Table 4-1 Accuracy comparison test

[0178] Weight value 30g 100g 300g 500g 1000g 1500g Measurements 30g 100g 300g 500g 1001g 1501g

[0179] 4.4 Error analysis

[0180] In the process of testing the smart Bluetooth electronic scale to measure objects, it was found that there was a certain error between the value of the weighed object and the actual value of the object. The cause of the error is related to many factors.

[0181] One of the reasons for the error of the smart Bluetooth electronic scale is that the software program is not accurate enough in data processing. When the values ​​sent back by the resistance strain pressure sensor were processed at the beginning, it was found that the error between the measured value and the actual value was very large at the beginning of debugging. After step-by-step debugging and measurement, the error value can be adjusted to a smaller value. In addition, when the microcontroller retrieves data from HX711, if it is interrupted, it will also cause the data obtained by the electronic scale to have large fluctuations and errors. Therefore, when the microcontroller obtains data from HX711, turn off the interrupt first, and turn on the interrupt after obtaining the data. The data transmission will not be affected and no error will be generated when the data is obtained.

[0182] Due to environmental reasons and the manufacturing process of the resistance strain type pressure sensor itself, the weight of the object collected by the sensor and the output voltage are in a nonlinear relationship. This error is inevitable. When the nonlinear error of the weighing sensor is large, it is necessary to calibrate the output value of the sensor and use different algorithms for calibration in different measurement ranges, so that the error can be reduced.

[0183] Those skilled in the art will appreciate that numerous variations to the above description are possible, and that the examples and figures are intended only to describe one or more specific implementations.

[0184] Although what is considered as exemplary embodiments of the present invention has been described and described, it will be understood by those skilled in the art that various changes and substitutions may be made thereto without departing from the spirit of the present invention. In addition, many modifications may be made to adapt specific situations to the teachings of the present invention without departing from the central concept of the present invention described herein. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but the present invention may also include all embodiments and their equivalents that fall within the scope of the present invention.

Claims

1. A smart Bluetooth electronic scale, characterized by: It includes a weighing sensor, an amplifier, an A / D converter, a control chip, a display, a keyboard and a Bluetooth module. The weighing sensor detects the mass of the object, converts the pressure signal into a weak current signal, and then transmits it to the amplifier. The amplifier amplifies the weak current signal and then converts it into a digital signal through the A / D converter. The control chip can analyze and process the digital signal. The data after analysis and processing is displayed through the display. The user can use the keyboard to select the product type, peel and send data. The control chip can transmit the processed data to the mobile phone APP via the Bluetooth module. After receiving the data, the mobile phone APP processes, displays and saves it for later user reference.

2. The smart Bluetooth electronic scale according to claim 1, characterized in that: It also includes a sensor signal acquisition circuit, a signal amplification circuit and an A / D conversion circuit. The sensor signal acquisition circuit uses a weighing sensor to collect the weight of the object to be weighed, and converts the weight signal that cannot be recognized by the single-chip microcomputer into a weak electric signal, which is amplified by the signal amplification circuit and converted by the A / D conversion circuit and then transmitted to the single-chip microcomputer for processing.

3. The smart Bluetooth electronic scale according to claim 1, characterized in that: It also includes an overweight alarm circuit, which will sound an alarm when the weighing value exceeds the set value.

4. The smart Bluetooth electronic scale according to claim 3, characterized in that: The overweight alarm circuit comprises a power buzzer and a driving circuit thereof.

5. The smart Bluetooth electronic scale according to claim 1, characterized in that: The control chip is a STC89C52RC single-chip microcomputer chip.

6. The smart Bluetooth electronic scale according to claim 1, characterized in that: The weighing sensor is a strain resistance weighing sensor.

7. The smart Bluetooth electronic scale according to claim 6, characterized in that: The weighing sensor is a parallel beam weighing sensor with a measuring range of 20 kg.

8. The smart Bluetooth electronic scale according to claim 1, characterized in that: The A / D converter is a HX711 chip.

9. The smart Bluetooth electronic scale according to claim 1, characterized in that: The Bluetooth module is a BT08B Bluetooth module, which is equivalent to a transfer station for data transmission. Through the Bluetooth module, the mobile phone and the electronic scale can realize short-distance wireless data transmission and communication.

10. The smart Bluetooth electronic scale according to claim 1, characterized in that: The display is one of a digital tube, an LCD1602, an LCD12864 liquid crystal display screen and an OLED liquid crystal screen.

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