An industrial control board based on STM32F103 single-chip microcomputer

Abstract

The utility model discloses an industrial control board based on STM32F103 singlechip, it includes main control chip, RS 485 level conversion circuit, digital I / O circuit and LED pilot lamp, and RS 485 circuit realizes efficient level conversion through three stage anti -interference framework magnetic pearl filtering, photo -coupler isolation, TVS protection, and digital I / O circuit adopts photo -coupler and isolation amplifier to enhance signal stability, and is equipped with LED pilot lamp feedback state, and the application effectively reduces the code rate less than 10 ‑7 , reduces signal dithering, and the temperature drift attenuation is only 2.1%, is suitable for industrial automation and intelligent manufacturing system, has simple structure, low in cost, stable performance and the advantages such as.

Description

Technical Field

[0001] This utility model relates to the field of industrial control technology, and in particular to an industrial control board based on an STM32F103 microcontroller. Background Technology

[0002] With the rapid development of Industry 4.0 and intelligent manufacturing technologies, the performance requirements of core control units in modern industrial control systems have significantly increased. According to relevant market research reports, the global industrial automation controller market reached $48 billion in 2023, and its compound annual growth rate remains high. However, existing industrial control boards still have many shortcomings in terms of anti-interference capabilities and signal stability in complex electromagnetic environments. For example, in high-interference scenarios such as frequency converters and servo systems, traditional RS-485 hardware circuits (such as the MAX3485 chip) often have a bit error rate exceeding 10% when facing 4kV EFT burst interference. -4 Furthermore, the communication interruption time exceeds 20ms, severely impacting the system's reliability and real-time performance. In addition, the design of digital I / O circuits also faces challenges. Traditional discrete input filtering circuits typically employ RC hardware filtering combined with low-speed optocouplers (such as the PC817). Within the operating temperature range of -40℃ to 85℃, the current transfer ratio attenuates by more than 30%, resulting in signal jitter times of 5 to 8ms, further reducing the system's stability and accuracy.

[0003] These limitations in existing technologies not only restrict the performance improvement of industrial control systems but also increase the difficulty of system maintenance and troubleshooting. Especially in high-noise environments, issues such as ground loop interference, electrostatic discharge, and surge current pose serious threats to circuit safety and signal integrity. Therefore, there is an urgent need for an industrial control board design that can effectively solve the above problems to meet the demands of modern industrial control systems for high performance, high reliability, and high stability. This invention is based on this background and aims to improve the anti-interference capability, signal stability, and environmental adaptability of industrial control boards through innovative design, thereby providing a more reliable solution for the fields of industrial automation and intelligent manufacturing. Utility Model Content

[0004] The purpose of this invention is to provide an industrial control board based on the STM32F103 microcontroller to overcome the shortcomings of the existing technology.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] An industrial control board based on an STM32F103 microcontroller includes the following components: a main control chip, an RS-485 level conversion circuit, a digital I / O circuit, and LED indicators. The main control chip is an STM32F103 microcontroller, which acts as the core controller responsible for logic control and data processing. The RS-485 level conversion circuit achieves efficient conversion between TTL and RS-485 levels and provides anti-interference and protection functions. The digital I / O circuit achieves electrical isolation of input signals through optocouplers and enhances signal stability through isolation amplifiers. The LED indicators are connected to the power supply through current-limiting resistors to provide visual feedback on the circuit's operating status.

[0007] Furthermore, the RS-485 level conversion circuit includes a level converter, a signal conditioning module, and a protection module. The level converter uses an SP3485EN chip to convert the TTL level signal output by the STM32F103 microcontroller into an RS-485 level signal. The DI terminal is connected to the USART_TX pin of the STM32F103 via a ferrite bead FB1 (nominal impedance 600Ω 100MHz) to suppress high-frequency noise; the measured noise attenuation reaches 42dB. The RE / DE terminals are electrically isolated via an EL3H7 optocoupler to break the ground loop and prevent interference signals from flowing back to the main control chip. A TVS diode SMBJ6.0CA (response time ≤1ns) is connected in parallel to the differential line to discharge surge current, with a maximum discharge capacity of 20A.

[0008] Specifically, the signal conditioning module consists of resistors R14, R19, R20, R21, capacitors C12 and C13, and a common-mode choke L1 (with an inductance of 10mH), forming a second-order filter with a cutoff frequency of 500kHz, improving the common-mode rejection ratio (CMRR) to 65dB. The protection module includes TVS diodes D12 and D13 (model SMBJ6.0CA, clamping voltage 6.0V±5%), connected in parallel on the differential line with a spacing of ≤2mm to prevent reverse voltage damage.

[0009] Furthermore, the digital I / O circuit includes an optocoupler, an isolation amplifier, and LED indicators. The optocoupler is an EL3H7 model, featuring an electrical isolation strength of 3750Vrms and an ultra-low current transfer ratio (CTR) temperature drift of 0.018% / ℃. A 1kΩ resistor R314 is connected in series at the input, and an ESD diode D34 (model PESD5V0S1BA) is connected in parallel, forming a π-type protection network capable of withstanding ±20kV electrostatic discharge as specified in IEC 61000-4-2. A temperature-compensated bias resistor R315 (4.7kΩ) ensures that signal gain fluctuation is <3% within an ambient temperature range of -40℃ to 85℃.

[0010] Specifically, the isolation amplifier, composed of resistors R314, R315, R317 and transistor Q17 (model NCE6005AS), is used to amplify the isolation signal output from the optocoupler. The LED indicator is connected to the power supply via current-limiting resistors R313 and R318, achieving millisecond-level status feedback in conjunction with the 3μs high-speed response of the EL3H7.

[0011] Furthermore, the present invention also includes a method for manufacturing an industrial control board, the specific steps of which are as follows: S1 Soldering an STM32F103 microcontroller onto a circuit board, and providing it with clock signals and reset functions through a crystal oscillator circuit and a reset circuit; S2 Connecting the level converter, signal conditioning module, and protection module in the RS-485 level conversion circuit to the corresponding pins of the STM32F103 microcontroller; S3 Installing the optocoupler, isolation amplifier, and LED indicator in the digital I / O circuit, and completing the electrical connection; S4 Performing circuit testing to ensure that the functions and performance of the industrial control board meet the design requirements.

[0012] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0013] First, the RS-485 level conversion circuit significantly reduces the bit error rate (BER) through a three-level anti-interference architecture (ferrite bead filtering, optocoupler isolation, and TVS protection), achieving a BER <10 under 4kV EFT burst interference conditions. -7 Secondly, the digital I / O circuit achieves electrical isolation through optocouplers, effectively reducing signal jitter and achieving a signal delay of only 0.38ms. Furthermore, within a temperature range of -40℃ to 85℃, signal gain fluctuation is <3%, and temperature drift attenuation is only 2.1%. Finally, this invention employs low-cost components (such as the STM32F103 microcontroller and SP3485EN level converter), resulting in a simple overall design that is easy to manufacture and suitable for various industrial automation and intelligent manufacturing systems.

[0014] In summary, through innovative design and optimization, this invention provides a high-performance, low-cost industrial control board that can effectively solve the problems of electromagnetic interference and signal jitter in the prior art, and significantly improve the reliability and stability of industrial control systems. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall circuit structure of the present invention;

[0016] Figure 2 This is a circuit diagram of RS-485 level conversion in an embodiment of the present invention;

[0017] Figure 3 This is a digital I / O circuit diagram in an embodiment of the present invention.

[0018] Attached image annotations:

[0019] U5, Level Shifter (SP3485EN);

[0020] FB1, ferrite bead (600Ω 100MHz);

[0021] R14, R19, R20, R21, resistors;

[0022] C12, C13, capacitors;

[0023] L1, Common mode choke (10mH);

[0024] D12, D13, TVS diode (SMBJ6.0CA).

[0025] U6, STM32F103 microcontroller;

[0026] X1, Crystal oscillator (8MHz);

[0027] C80, C81, capacitors;

[0028] R5, resistor;

[0029] C14, capacitor;

[0030] LED1, LED2, LED3, LED indicator lights;

[0031] R3, R4, R334, current-limiting resistors;

[0032] U84, U85, Optical Coupler (EL3H7);

[0033] R314, resistor;

[0034] D34, ESD diode (PESD5V0S1BA).

[0035] R315, temperature-compensated bias resistor (4.7kΩ);

[0036] R317, resistor;

[0037] Q17, Transistor (NCE6005AS);

[0038] LED63, LED64, LED indicator lights;

[0039] R313, R318, current-limiting resistors. Detailed Implementation

[0040] To make the above-mentioned objects, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.

[0041] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. When the number of elements is referred to as "multiple," it can be any number of two or more. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0043] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings:

[0044] An industrial control board based on the STM32F103 microcontroller integrates RS-485 level conversion circuitry and digital I / O circuitry to achieve efficient signal processing and electrical isolation, thereby significantly improving anti-interference capability and signal stability. The specific embodiments of the invention are described in detail below with reference to the accompanying drawings.

[0045] like Figure 1 As shown, the overall circuit structure of this invention includes an STM32F103 microcontroller U6, an RS-485 level conversion circuit, a digital I / O circuit, and peripheral auxiliary circuits. The STM32F103 microcontroller U6 serves as the main control chip, employing an ARM Cortex-M3 core, possessing high-performance computing capabilities and abundant peripheral interface resources. Pins PA3, PA4, and PA5 of U6 are connected to the RS-485 level conversion circuit for data transmission and reception; pins PB13, PB14, and PB15 are connected to the digital I / O circuit for isolating and amplifying external signals and providing status indication. Furthermore, U6 provides a stable clock signal through an external crystal oscillator X1 (8MHz) and its matching capacitors C80 and C81, and ensures reliable system startup through a reset circuit (including resistor R5 and capacitor C14).

[0046] The specific structure of the RS-485 level conversion circuit is as follows: Figure 2As shown, the circuit consists of a level converter U5 (model SP3485EN), ​​a signal conditioning module, and a protection module. The level converter U5 converts the TTL level signal output from the STM32F103 into an RS-485 level signal to meet the long-distance communication requirements in industrial environments. The DI terminal is connected to the PA3 pin via a ferrite bead FB1 (nominal impedance 600Ω 100MHz) to suppress high-frequency noise; the measured noise attenuation reaches 42dB. The RE / DE terminals are electrically isolated via an optocoupler EL3H7 to break the ground loop and prevent interference signals from flowing back to the main control chip. Differential lines A and B are connected in parallel with TVS diodes D12 and D13 (model SMBJ6.0CA), with a spacing ≤2mm, to discharge surge current, with a maximum discharge capacity of 20A. The signal conditioning module consists of resistors R14, R19, R20, R21, capacitors C12 and C13, and a common-mode choke U1 (inductance value 100μH). R20 (10kΩ) and R14 (4.7kΩ) form a DC bias network for the signal line: R20 pulls the input signal (PA3) to GND, and R14 pulls it to +5V, jointly stabilizing the signal level and enhancing anti-interference capability. R19 (1kΩ) and R21 (1kΩ) form an RS-485 bus termination bias circuit: ensuring that the bus maintains a logic "1" state (A>B 200mV) when idle. C12 (10pF) and C13 (10pF) constitute a high-frequency filter network: suppressing RF interference >100MHz and preventing signal edge ringing. Common-mode choke U1 (100μH) provides common-mode noise suppression: blocking high-frequency common-mode interference (>10MHz) from propagating into the circuit, while allowing differential-mode signals to pass through without loss. This forms a second-order filter with a cutoff frequency of 500kHz and a common-mode rejection ratio (CMRR) of 65dB, effectively improving signal integrity. The above design significantly reduces the bit error rate in high-interference scenarios, achieving a bit error rate of <10 under 4kVEFT burst interference conditions. -7 The signal delay is only 0.38ms.

[0047] The specific structure of digital I / O circuits is as follows: Figure 3As shown, the system includes optocouplers U84 and U85 (model EL3H7), an isolation amplifier, and LED indicators. Optocouplers U84 and U85 provide 3750Vrms of electrical isolation and an ultra-low current transfer ratio (CTR) temperature drift of 0.018% / ℃ for electrical isolation of the input signal. A 1kΩ resistor R314 is connected in series at the input, and an ESD diode D34 (model PESD5V0S1BA) is connected in parallel, forming a π-type protection network capable of withstanding ±20kV electrostatic discharge as specified in IEC 61000-4-2. The isolation amplifier consists of resistors R314, R315, and R317, and transistor Q17 (model NCE6005AS). R315 (4.7kΩ) is a temperature-compensated bias resistor, ensuring signal gain fluctuation <3% within an ambient temperature range of -40℃ to 85℃. LED indicator lights LED63 and LED64 are connected to the power supply through current-limiting resistors R313 and R318. Combined with the 3μs high-speed response characteristic of EL3H7, millisecond-level status feedback is achieved, ensuring that the system's operating status is intuitively visible.

[0048] The working principle of this invention is as follows: When data needs to be sent, the STM32F103 microcontroller U6 outputs a TTL level signal to the RS-485 level conversion circuit through the PA3 pin. After being filtered by the ferrite bead FB1, the signal enters the level converter U5, which converts it into an RS-485 differential signal and sends it to the industrial site through differential lines A and B. Simultaneously, TVS diodes D12 and D13 discharge surge current on the differential lines, protecting the circuit from reverse voltage damage. When data is received, the RS-485 differential signal is converted back to a TTL level signal through U5, and after optocoupler isolation at the RE / DE terminals, it returns to the STM32F103 for processing. The digital I / O circuit uses optocouplers U84 and U85 to electrically isolate external input signals. The isolated signal is then amplified by an isolation amplifier before returning to the STM32F103, ensuring signal stability and reliability. LED indicators provide real-time feedback on the circuit's operating status, facilitating monitoring and maintenance.

[0049] This invention also provides a method for manufacturing an industrial control board, with the following specific steps: S1 Soldering an STM32F103 microcontroller onto a circuit board, and installing a crystal oscillator circuit and a reset circuit to provide clock signals and reset functions; S2 Connecting the level converter U5, signal conditioning module, and protection module in the RS-485 level conversion circuit to the corresponding pins of the STM32F103; S3 Installing optocouplers U84 and U85, isolation amplifiers, and LED indicators in the digital I / O circuit, and completing the electrical connections; S4 Performing circuit testing to ensure that the functions and performance of the industrial control board meet the design requirements.

[0050] The industrial control board of this invention is suitable for industrial automation and intelligent manufacturing systems, and performs particularly well in high-interference scenarios such as frequency converters and servo drives. Through a three-level anti-interference architecture (ferrite bead filtering, optocoupler isolation, and TVS protection) and optimized signal conditioning design, the system's anti-interference capability and signal stability are significantly improved. Furthermore, by employing low-cost components (such as the STM32F103 microcontroller and SP3485EN level converter) and a modular design, the overall structure is simple and easy to manufacture, meeting the high-performance, low-power, and high-reliability requirements of modern industrial control systems for core control units. Third-party testing (report number EMC2023-TEST008) shows that the bit error rate of this invention is <10% under 4kV EFT burst interference conditions. -7 With a signal delay of 0.38ms and a temperature drift attenuation of only 2.1%, it fully demonstrates its technical advantages and practicality.

[0051] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. For those skilled in the art, several modifications and improvements can be made without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. An industrial control board based on an STM32F103 microcontroller, characterized in that: The system includes a main control chip, an RS-485 level conversion circuit, a digital I / O circuit, and LED indicators. The main control chip is an STM32F103 microcontroller. The RS-485 level conversion circuit is used to convert between TTL and RS-485 levels. The digital I / O circuit achieves electrical isolation of the input signal through an optocoupler and enhances signal stability through an isolation amplifier. The LED indicators are connected to the power supply through a current-limiting resistor.

2. The industrial control board as described in claim 1, characterized in that: The RS-485 level conversion circuit includes a level converter, a signal conditioning module, and a protection module. The level converter uses an SP3485EN chip. The DI terminal is connected to the USART_TX pin of the STM32F103 through a ferrite bead FB1. The RE / DE terminals are electrically isolated through an EL3H7 optocoupler. The differential lines are connected in parallel with TVS diodes SMBJ6.0CA.

3. The industrial control board as described in claim 2, characterized in that: The signal conditioning module consists of resistors R14, R19, R20, R21, capacitors C12 and C13, and a common-mode choke L1, forming a second-order filter with a cutoff frequency of 500kHz.

4. The industrial control board as described in claim 2, characterized in that: The protection module includes TVS diodes D12 and D13, which are connected in parallel on the differential line with a spacing of ≤2mm.

5. The industrial control board as described in claim 1, characterized in that: The digital I / O circuit includes an optocoupler, an isolation amplifier, and an LED indicator. The optocoupler is an EL3H7 model, with a 1kΩ resistor R314 connected in series at the input and an ESD diode D34 connected in parallel.

6. The industrial control board as described in claim 5, characterized in that: The isolation amplifier consists of resistors R314, R315, R317 and transistor Q17, where R315 is a temperature-compensated bias resistor.

7. The industrial control board as described in claim 1, characterized in that: It also includes a crystal oscillator circuit and a reset circuit. The crystal oscillator circuit includes a crystal oscillator X1 and its matching capacitors C80 and C81. The reset circuit includes a resistor R5 and a capacitor C14.

8. The industrial control board as described in claim 1, characterized in that: The LED indicator is connected to the power supply through current-limiting resistors R313 and R318, and status feedback is achieved by combining the high-speed response characteristics of EL3H7.

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