# Fifth Lichuang Electronic Design Competition #Digital dual-channel mv signal amplifier

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[Please fill it out during the registration stage] 1. Introduce yourself to the team. Two good friends collaborated in their spare time. They are both engineers, love embedded, and are fans of Jialichuang. 2. Briefly introduce the project, a dual-channel mV signal acquisition. The amplifier supports -10-10V signal output, supports 4-20mA output, supports 422 protocol, has non-linear correction function, and supports multiple filtering modes. [Please fill in during the competition stage] 1. Describe the project details. Conventional mv signal collectors and operational amplifiers are built with analog circuits, and their debugging zero points and full scales use sliding rheostat. This method of debugging is very important for industrial on-site maintenance. Very cumbersome and complicated. And it is not conducive to resource collection and information integration. To address this problem, this solution designs a digital mV signal amplifier based on GD32F103C8T6. The amplifier capable of dual-channel mV signal acquisition supports -10-10V signal output, supports 4-20mA output, supports 422 protocol, has non-linear correction function, and supports multiple filtering modes. (1) With the increase of time and changes in temperature, the sensor will produce temperature drift and time drift. If manual repair is performed at this time, it will affect the efficiency, and the amplification circuit on some products is not easy to disassemble or is placed improperly, which will cause Increased labor and risk. (2) The amplifier circuit body that also uses a sliding rheostat has poor seismic resistance and is easily affected by vibrations in the position of the sliding rheostat. (3) The product itself has poor versatility. Because the amplification factor of the hardware analog circuit is fixed, the circuit has poor versatility and poor interchangeability. (4) It does not have long-distance communication function, and it is slow to detect faults when problems occur. (5) Single filtering method: only resistance-capacitance filtering. In order to solve the above problems, a digital signal amplifier needs to be designed. Its characteristics are: (1) It has software parameter adjustment function and can adjust software parameters according to the input mV signal range of different sensors. (2) With non-linear correction function (3) Able to have a variety of filtering modes (4) With long-distance communication function 2. Describe the challenges faced by the project and the problems solved 2.1 Power supply problem For the Sensor body, the bridge signal is usually used for power supply. , the analog circuit uses 12V or 9V power supply. We also entered such a blind spot in the early stage, but the TM7705 did not collect the mV signal, or collected the wrong mV signal. According to the relevant datasheet, it was found that 5V is used to power the Sensor body. After careful analysis, if 12V or 9V power supply is used, the bridge voltage should be half of it. In this way, even the differential voltage signal, bridge signal, and ground signal are half of the power supply of the main body. Therefore, it is higher than the input signal requirements of TM7705, so the bridge voltage power supply must not be higher than 5V. Based on this, the voltage in this article uses 5V power supply, and in order to avoid the power supply ripple generated by the switching power supply. All are powered by linear power supplies to ensure power supply stability. 2.2 Problems that occur when TM7705 collects signals. When TM7705 collects dual-channel signals, signal confusion occurs. In response to this, I carefully read the datasheet and conducted experiments. I found that the problem can be solved by reading it twice during the reading process.

< br> 3. Describe the key points involved in the hardware and software parts of the project 3.1 0-5V to 4-20mA This amplifier circuit needs to support both current and voltage modes, so the following circuit is designed. In the figure, OUT_A is the voltage input terminal. We set it to Vin. Node b is the current output terminal. R38 is the analog load. According to the concept of "virtual short", Vb = 2 V3-Vin (1) is obtained from the next feedback branch. The feedback branch obtains Va = 2*V2. According to the "virtual short", we know that V2 = V3, so Va = 2 V3(2) List the node current equation of point b: IL = Vb/RL= [Va-Vb]/R36+[ V3-Vb]/R34 Substituting (1) and (2) into: Obtain: IL = Vin/R36+(Vin-V3)/R34 Because R34>>R36, the final load current expression: IL = Vin/R36 3.2 Nonlinear correction designs a method through serial communication, collects mV signals at zero point and full scale time, and designs correction parameters. A linear function or a quadratic function can be used for correction. The host computer software is developed using C#. 3.3 Acquisition signal filtering Various methods are used to filter the acquisition signal (1) Median filtering method (2) Arithmetic average filtering method (3) Recursive average filtering method (also known as synovial membrane filtering method) (4) First-order lag filter method

4. The project materials list shows a mV signal generator and a voltmeter. The core components are shown in the table below, and more details can be found in the attachments.

5. Upload project pictures 5.1. Print the competition logo picture on the PCB. If not, it will be regarded as giving up the competition and adopt GD32 development. The model GD32F103C8T6 uses Jialichuang/Lichuang Mall SMT for proofing and welding.  5.2. Other pictures of the project < span lang="EN-US ">< /span> 6. Demonstrate your project and record it as a video for upload< span lang="EN-US">< /span> 6.1. The official website of the video upload competition has been uploaded 6.2. The video title and link of Station B are fifth. The 5th Lichuang Electronic Design Competition: Dual-channel Digital MV Signal Amplifier - Introduction https://www.bilibili.com/video/BV1vh411Z7NN The 5th Lichuang Electronic Design Competition: Dual-channel Digital MV Signal Amplifier - Project Introduction https:// www.bilibili.com/video/BV1mZ4y1T7Ws The work of the 5th Lichuang Electronic Design Competition - Dual-channel mv signal digital amplifier (key) https://www.bilibili.com/video/BV1Wt4y1D7BP The 5th Lichuang Electronic Design Competition ：Dual-channel digital mv signal amplifier-summary https://www.bilibili.com/video/BV1fh411R7Fr < br> < br>