Photoelectric acquisition circuit based on RS485 communication interface

Abstract

The utility model provides a photoelectric acquisition circuit based on an RS485 communication interface. The photoelectric acquisition circuit comprises a power supply module, a signal acquisition module, an analog-to-digital conversion module, a microcontroller module and an RS485 communication module. Photoelectric signals are collected through the signal collection module and converted into micro voltage signals, the analog-to-digital conversion module converts analog voltage signals into digital voltage signals, the microcontroller obtains engineering values after processing and analysis, and the RS485 communication module transmits the engineering values to a terminal. Micro-current signals collected by a photoelectric detector are processed, the resolution ratio of a collection circuit is high, the lower detection limit reaches the nA level, and the circuit gain and the collection precision of a detection end are improved by selecting a high-precision chip and optimizing the circuit design.

Description

[Technical Field]

[0001] This utility model relates to the field of electronic information technology, and in particular to a four-channel photoelectric acquisition circuit based on an RS485 communication interface. [Background Technology]

[0002] With the rapid development of artificial intelligence technology, people have increasingly higher requirements for environmental information detection. For example, intelligent driving systems need to detect the environmental information around the vehicle so that the vehicle can automatically take avoidance measures; intelligent aquaculture systems need to detect dissolved oxygen information in the water so that the aquaculture water can be automatically oxygenated. Photodetectors, due to their high detection accuracy, fast fiber optic transmission speed, long transmission distance, and low loss, require careful selection based on specific application environments and needs, including transmission distance, signal quality, and cost, to ensure optimal performance. However, the light signals detected by photodetectors are weak, resulting in very small photocurrents, sometimes reaching the nA level. Simultaneously, environmental detection requires the simultaneous acquisition of multiple signals; for example, intelligent driving systems need to simultaneously acquire signals from the left, right, front, and rear blind spots. Therefore, how to process weak photocurrent signals, select high-precision chips, optimize photoelectric acquisition circuit design, and simultaneously improve the gain and acquisition accuracy of the detection end circuit have become key technical problems that need to be solved. [Utility Model Content]

[0003] This invention provides a photoelectric acquisition circuit based on an RS485 communication interface, which solves the problem in the prior art that it is impossible to improve the resolution of weak photocurrent signal processing circuits, while improving the gain and acquisition accuracy of the detection end circuit.

[0004] This utility model provides a photoelectric acquisition circuit based on an RS485 communication interface, comprising: a power supply module, a signal acquisition module, an analog-to-digital converter module, a microcontroller module, and an RS485 communication module. The power supply module provides power to the signal acquisition module, the analog-to-digital converter module, the microcontroller module, and the RS485 communication module. The signal acquisition module converts the optical signal acquired by the photodiode into an electrical signal, converts the current signal into a voltage signal, and performs operational amplification on the converted voltage signal. The photodiode may include one or more photodiodes. The analog-to-digital converter module converts the operationally amplified analog voltage signal into a digital voltage signal. The microcontroller module processes and analyzes the digital voltage signal, converts the digital voltage signal into an engineering value, and provides a PWM wave for the light source. The RS485 communication module transmits the processed and analyzed engineering value to a terminal.

[0005] Optionally, the power module includes a power regulation and buck circuit that regulates and bucks the power supplied by the lithium battery or solar panel to 5V and 3.3V.

[0006] Optionally, it also includes a light source driving module, wherein the microcontroller module generates a PWM wave to control the LED power in the light source driving module, and the microcontroller module adjusts the duty cycle of the PWM wave to control the LED switching time.

[0007] Optionally, the signal acquisition module includes an AD8304 chip and a photodiode, which includes an 8-channel single-ended photodiode or a 4-channel differential photodiode.

[0008] Optionally, the analog-to-digital conversion module includes an ADS1256 chip, which includes an 8-channel single-ended acquisition port or a 4-channel differential acquisition port.

[0009] Optionally, the microcontroller module includes a GD32F303RCT6 chip, the microcontroller module is connected to the analog-to-digital converter module via an SPI interface, and the microcontroller module is connected to the RS485 communication module via a USART interface.

[0010] Optionally, the RS485 communication module includes a MAX3485 chip or an SP3485EN chip, and the RS485 communication module supports the Modbus protocol.

[0011] Optionally, it also includes a storage module and a temperature acquisition module. The storage module includes an M24C64 chip, and the temperature acquisition module transmits the acquired temperature information to the microcontroller module via an I2C interface.

[0012] Optionally, it also includes an execution module, wherein the microcontroller module controls the execution module based on the processed and analyzed engineering values ​​and preset thresholds.

[0013] Optionally, it may also include a filtering module, which includes a low-pass filter.

[0014] As can be seen from the above technical solution, this utility model provides a photoelectric acquisition circuit based on an RS485 communication interface, including: a power supply module, a signal acquisition module, an analog-to-digital converter module, a microcontroller module, and an RS485 communication module. The signal acquisition module acquires photoelectric signals and converts them into micro-voltage signals. The analog-to-digital converter module converts the analog voltage signals into digital voltage signals. The microcontroller processes and analyzes the signals to obtain engineering values, and the RS485 communication module transmits these engineering values ​​to the terminal. The circuit processes the micro-current signals acquired by the photodetector, achieving high resolution and a detection lower limit at the nA level. By selecting high-precision chips and optimizing the circuit design, the gain and acquisition accuracy of the detection end circuit are improved. [Attached Image Description]

[0015] Figure 1 A structural block diagram of a photoelectric acquisition circuit based on an RS485 communication interface is provided for one embodiment of this utility model;

[0016] Figure 2 A circuit diagram of a power supply module provided in one embodiment of this utility model;

[0017] Figure 3 A circuit diagram of a light source driving module provided in one embodiment of this utility model;

[0018] Figure 4 A circuit diagram of a signal acquisition module provided in one embodiment of this utility model;

[0019] Figure 5 A circuit diagram of an analog-to-digital converter module provided in one embodiment of the present invention;

[0020] Figure 6 A circuit diagram of a microcontroller module provided in one embodiment of this utility model;

[0021] Figure 7 A circuit diagram of an RS485 communication module provided in one embodiment of this utility model;

[0022] Figure 8 A circuit diagram of a storage module provided in one embodiment of the present utility model;

[0023] Figure 9 This is a structural block diagram of a photoelectric acquisition circuit based on an RS485 communication interface, provided for another embodiment of the present invention.

Detailed Implementation Methods

[0024] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0025] Figure 1 This diagram illustrates a structural block diagram of a photoelectric acquisition circuit based on an RS485 communication interface according to an embodiment of the present invention. Figure 1 As shown, the photoelectric acquisition circuit based on the RS485 communication interface in this embodiment includes: a power supply module 11, a signal acquisition module 12, an analog-to-digital conversion module 13, a microcontroller module 14, and an RS485 communication module 15.

[0026] In a specific embodiment, the power supply module 11 provides power to the signal acquisition module, analog-to-digital converter module, microcontroller module, and RS485 communication module; the signal acquisition module 12 converts the optical signal acquired by the photodiode into an electrical signal, the current signal into a voltage signal, and performs operational amplification on the converted voltage signal; the photodiode includes one or more; the analog-to-digital converter module 13 converts the operationally amplified analog voltage signal into a digital voltage signal; the microcontroller module 14 processes and analyzes the digital voltage signal, converts the digital voltage signal into an engineering value, and provides a PWM wave for the light source; the RS485 communication module 15 transmits the processed and analyzed engineering value to the terminal.

[0027] Figure 2 A circuit diagram of a power supply module provided in an embodiment of the present invention is shown, as follows: Figure 2 As shown, the power module includes a power regulation and buck circuit. The power module has a lithium battery or solar panel power supply port, supporting 5-36V input. The power input terminal uses the FDS4435BZ chip, a P-channel MOSFET chip with a maximum withstand voltage of -30V and a maximum current of -7A. It features low on-resistance and high performance, primarily used in power management, load switching, and synchronous rectification applications. It is specifically designed to minimize on-resistance and maintain low gate charge, minimizing undesirable voltage spikes in synchronous rectification and exhibiting excellent switching performance.

[0028] The DC-DC converter uses the SCT2450STER chip, which has an input voltage range of 3.8V-36V and can support transient overshoot voltages up to 38V, reducing the requirements for input surge protection design. It is a high-power density fully integrated synchronous buck DC-DC converter with an output current of up to 5A. The SCT2450STER chip can regulate and step down the power supplied by lithium batteries or solar panels to 5V to provide 5V power to the analog-to-digital converter module.

[0029] The 5V to 3.3V voltage regulator circuit uses the AMS1117 chip, which provides 1A output current and can operate with a voltage drop as low as 1V. The AMS1117 chip can regulate and step down the 5V voltage to 3.3V, providing 3.3V power to the microcontroller module, RS485 communication module, analog-to-digital converter module and storage module, and providing a 1A current source to the power drive module.

[0030] Figure 3 A circuit diagram of a light source driving module according to an embodiment of the present invention is shown, as follows: Figure 3As shown, the light source driver module includes an OPA350 high-speed single-supply rail-to-rail operational amplifier and an IRF540NSTRLPBF Zener transistor. The OPA350 is a high-performance operational amplifier widely used in electronic devices, featuring excellent performance including low input bias current, low distortion, high bandwidth, and low noise. It can provide a large output current and is suitable for applications driving low load resistance. The IRF540NSTRLPBF is an N-channel MOSFET that can be used as a power switching device in power management circuits such as switching power supplies, voltage regulators, and inverters to achieve high-efficiency energy conversion. LED_V is the pulse width modulation (PWM) wave output port generated by the microcontroller in the microcontroller module. The LED power is controlled by adjusting the amplitude of the PWM wave. A photodetector can be optimally selected based on the LED power; the photodetector's detection limit can reach the nA level. Selecting the optimal photodetector improves the gain and acquisition accuracy of the photodetector circuit. The LED switching time is controlled by adjusting the PWM wave duty cycle; the LED is on when the PWM wave is in the positive half-cycle and off when the PWM wave is at 0. Adjusting the PWM wave duty cycle according to acquisition requirements saves energy and extends chip lifespan.

[0031] Figure 4 A circuit diagram of a signal acquisition module according to an embodiment of the present invention is shown, as follows: Figure 4 As shown, the signal acquisition module includes an AD8304 chip and a photodiode. A photodiode is a photodetector that converts light into an electrical signal. It has unidirectional conductivity and is a semiconductor device that converts light signals into electrical signals. It uses the intensity of light to change the current in a circuit. Therefore, the intensity of light can be detected by measuring the output current of the photodiode, thereby detecting the measured value. For example, after the light emitted by an LED undergoes an oxygen quenching reaction, the photodiode receives the fluorescence after the quenching reaction. The oxygen content can be obtained by detecting the output current of the photodiode. One or more photodiodes are included, and the number is determined according to the object being measured. It can include up to 8-channel single-ended photodiodes or 4-channel differential photodiodes. Multi-channel acquisition improves the efficiency and applicability of the acquisition circuit.

[0032] The AD8304 chip includes a photodiode interface, with the photodiode output connected to the AD8304 chip. The AD8304 chip includes a logarithmic converter and a linear operational amplifier. Since the photodiode outputs a weak current signal, the logarithmic amplifier performs a logarithmic conversion from current to voltage. This weak current signal is amplified and converted to improve circuit gain. To accommodate different analog-to-digital conversion input voltage requirements, the operational amplifier acts as a buffer stage to adjust the voltage value. The AD8304's VOUT pin connects to any one of the ADS1256's pins AIN0-AIN7. The nA-level weak current signal output from the photodiode is converted into a voltage signal by the AD8304 chip and input to the analog-to-digital converter module.

[0033] Figure 5 A circuit diagram of an analog-to-digital conversion module according to an embodiment of the present invention is shown, as follows: Figure 5 As shown, the analog-to-digital converter (ADC) module includes a REF3125 chip, an OPA350 chip, and an ADS1256 chip. The REF3125 serves as a voltage reference source, providing a precise reference voltage for the operational amplifier and playing a crucial role in achieving high-precision conversion for the subsequent ADC. The OPA350 chip further amplifies the analog signal for the operational amplifier. The ADS1256 chip is a 24-bit Sigma-Delta ADC with low noise and high resolution performance. It includes 8 single-ended acquisition ports or 4 differential acquisition ports AIN0-AIN7, allowing simultaneous input of 8 channels of analog voltage signals for ADC conversion. The high-precision ADS1256 chip provides higher resolution, more accurately converting analog signals into digital signals and improving the resolution of the processing circuit.

[0034] Figure 6 A circuit diagram of a microcontroller module provided in an embodiment of the present invention is shown, as follows: Figure 6As shown, the microcontroller module includes the GD32F303RCT6 chip. The GD32F303RCT6 is a 32-bit general-purpose microcontroller based on the ARM Cortex-M4 core, combining a high-precision analog unit and rich peripheral interfaces. The GD32F303RCT6 processes and analyzes the digital voltage signal after analog-to-digital conversion, converting it into corresponding actual engineering values, such as dissolved oxygen, temperature, and humidity. The GD32F303RCT6 can achieve precise output PWM waves through a timer. Using the timer and its corresponding PWM function, PWM waveforms can be generated and modulated to control LED power and switching. Pins PA5, PA6, PA7, PA8, and PA9 of the GD32F303RCT6 chip are connected to pins SCLK, DIN, DOUT, CS, and DRDY of the ADS1256, respectively. The analog-to-digital converter module and the microcontroller module communicate based on the SPI protocol. Pin PA10 of the GD32F303RCT6 chip is connected to pin DI of the MAX3485 chip, and pin PA11 of the GD32F303RCT6 chip is connected to pin RO of the MAX3485 chip. The microcontroller module and the RS485 communication module communicate based on the USART protocol.

[0035] Figure 7 The circuit diagram of an RS485 communication module according to an embodiment of the present invention is shown below. Figure 7 As shown, the RS485 communication module includes a MAX3485 chip or an SP3485EN chip. The MAX3485E or SP3485EN includes a driver and a receiver, supports the Modbus protocol, and is a half-duplex communication chip. Modbus is a serial communication protocol commonly used for connection between industrial electronic devices. RS485 includes two signal lines and two power lines. Based on the Modbus protocol, the RS485 communication module transmits processed and analyzed engineering values ​​from the microcontroller to the terminal, such as transmitting analyzed temperature and humidity values ​​to a computer.

[0036] Figure 8 A circuit diagram of a storage module provided in an embodiment of the present invention is shown, as follows: Figure 8 As shown, the storage module includes an M24C64 chip, which includes a 64Kbit serial I2C bus electrically erasable programmable memory (EEPROM) used as a peripheral memory for storing data in the microcontroller module. Pin PB6 of the GD32F303RCT6 chip is connected to pin SCL of the M24C64 chip, and pin PB7 of the GD32F303RCT6 chip is connected to pin SDA of the M24C64 chip. The microcontroller module and the storage module communicate based on the I2C protocol.

[0037] In a specific embodiment, the photoelectric acquisition circuit further includes a temperature acquisition module, an execution module, and a filtering module. The temperature acquisition module includes a temperature sensor that collects ambient temperature information and transmits it to the microcontroller module via the I2C protocol. The photoelectric acquisition circuit acquires temperature information while simultaneously collecting environmental information and can correct the environmental information based on the temperature data. The microcontroller module controls the execution module to turn the execution device on or off based on the processed and analyzed actual engineering value and a preset threshold. For example, during fiber optic dissolved oxygen acquisition, after processing and analysis by the microcontroller module, if the actual engineering value is 3 mg / L and the preset threshold is 5 mg / L, then the execution module is controlled to turn on the oxygenator to increase oxygen levels until the dissolved oxygen reaches the preset threshold of 5 mg / L. The photoelectric acquisition circuit is easily affected by harmonic signal interference after I / V conversion. A filtering module can be added after the signal acquisition circuit. The filtering circuit includes a low-pass filter to filter out high-frequency interference signals.

[0038] Figure 9 A structural block diagram of a photoelectric acquisition circuit based on an RS485 communication interface, according to another embodiment of the present invention, is shown below. Figure 9 As shown, the power supply provides power to the LED output, the microcontroller unit (MCU), and the RS485 interface. The MCU controls the LED power. After the LED outputs light, the photodiode (PD) receives the light signal. The PD signal conversion circuit converts the light signal into an electrical signal. The electrical signal is then converted into a digital signal by the AD chip. The digital signal is input to the MCU for analysis and processing based on the SPI protocol. The processed signal is then transmitted to the RS485 chip based on the USART protocol. The RS485 chip transmits the signal to the terminal through the RS485 interface. The weak current signal collected by the PD is processed by the PD signal conversion circuit, the AD chip, and the MCU, and then transmitted to the terminal through the RS485 interface. The weak current signal is converted into an engineering value. Based on high-precision chip and circuit design, noise signals are filtered out, the collected signal is retained, and the circuit resolution and anti-interference ability are improved.

[0039] It should be noted that the above embodiments are illustrative of the present invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0040] Those skilled in the art will understand that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it; although the utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope defined by the claims of this utility model.

Claims

1. A photoelectric acquisition circuit based on an RS485 communication interface, characterized in that, include: The system includes a power supply module, a signal acquisition module, an analog-to-digital converter module, a microcontroller module, and an RS485 communication module. The power module is used to provide power to the signal acquisition module, the analog-to-digital conversion module, the microcontroller module and the RS485 communication module; The signal acquisition module is used to convert the optical signal acquired by the photodiode into an electrical signal, the current signal into a voltage signal, and to perform computational amplification on the converted voltage signal. The photodiode includes one or more. The analog-to-digital converter module is used to convert the operationally amplified analog voltage signal into a digital voltage signal; The microcontroller module is used to process and analyze digital voltage signals, convert digital voltage signals into engineering values, and provide PWM waves for the light source; The RS485 communication module is used to transmit the processed and analyzed engineering values ​​to the terminal.

2. The photoelectric acquisition circuit according to claim 1, characterized in that, Also includes: The power module includes a power voltage regulator and step-down circuit, which regulates and steps down the power supplied by the lithium battery or solar panel to 5V and 3.3V.

3. The photoelectric acquisition circuit according to claim 1, characterized in that, It also includes a light source driving module, wherein the microcontroller module generates a PWM wave to control the LED power in the light source driving module, and the microcontroller module adjusts the duty cycle of the PWM wave to control the LED switching time.

4. The photoelectric acquisition circuit according to claim 1, characterized in that, Also includes: The signal acquisition module includes an AD8304 chip and a photodiode, which includes an 8-channel single-ended photodiode or a 4-channel differential photodiode.

5. The photoelectric acquisition circuit according to claim 4, characterized in that, Also includes: The analog-to-digital conversion module includes an ADS1256 chip, which includes an 8-channel single-ended acquisition port or a 4-channel differential acquisition port.

6. The photoelectric acquisition circuit according to claim 1, characterized in that, Also includes: The microcontroller module includes a GD32F303RCT6 chip. The microcontroller module is connected to the analog-to-digital converter module via an SPI interface and to the RS485 communication module via a USART interface.

7. The photoelectric acquisition circuit according to claim 1, characterized in that, Also includes: The RS485 communication module includes a MAX3485 chip or an SP3485EN chip, and the RS485 communication module supports the Modbus protocol.

8. The photoelectric acquisition circuit according to claim 1, characterized in that, It also includes a storage module and a temperature acquisition module. The storage module includes an M24C64 chip, and the temperature acquisition module transmits the acquired temperature information to the microcontroller module via an I2C interface.

9. The photoelectric acquisition circuit according to claim 1, characterized in that, It also includes an execution module, which is controlled by the microcontroller module based on the processed and analyzed engineering values ​​and preset thresholds.

10. The photoelectric acquisition circuit according to claim 1, characterized in that, It also includes a filtering module, which includes a low-pass filter.

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