Analog quantity acquisition circuit

Abstract

The utility model discloses an analog quantity acquisition circuit, which comprises a master control circuit, a program downloading circuit, an analog quantity acquisition circuit, an RS485 communication circuit, a digital quantity input circuit and a power supply circuit, wherein the program downloading circuit is used for realizing one-key downloading and running of a program, the analog quantity acquisition circuit is used for monitoring change of physical quantity, standardizing input voltage and completing analog-digital conversion, and the RS485 communication circuit is used for realizing long-distance and multi-node transmission and receiving of data. The digital quantity input circuit is used for converting the level of an external digital quantity signal into a signal level in the PLC, and the power supply circuit is used for providing a working power supply for the whole circuit. According to the analog quantity acquisition circuit, external switching signals can be converted into digital signals which can be accepted by the interior of the PLC through the analog quantity acquisition and digital quantity input interface circuit, and the processing efficiency of electric signals is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to signal collection conversion technical field, concretely is analog quantity collection circuit. BACKGROUND

[0002] In the circuit of sampling analog quantity, in order to obtain more accurate collection precision and guarantee the consistency of batch products, the traditional method is to input a calibration power supply with higher voltage precision as reference voltage, MCU forms a calibration voltage or current coefficient value by sampling the voltage at this time, and then calculates the accurate sampling value by measuring value and voltage or current coefficient value, thereby overcoming the problem of inconsistent circuit parameters in sampling circuit, and guaranteeing the precision and consistency of analog circuit sampling. But the existing analog quantity collection circuit has low collection efficiency, less analog quantity collection quantity, and the collected electric signal cannot be directly converted into digital signal. UTILITY MODEL CONTENTS

[0003] The utility model discloses a kind of analog quantity collection circuits, and analog quantity collection, digital quantity input interface circuit can directly convert external switch signal into digital signal, to solve the problem proposed in the above background technology.

[0004] To achieve the above object, the utility model provides the following technical scheme: an analog quantity collection circuit, including main control circuit, program download circuit, analog quantity collection circuit, RS485 communication circuit, digital quantity input circuit and power supply circuit;The output of program download circuit, analog quantity collection circuit and digital quantity input circuit is respectively electrically connected with the input of main control circuit, and RS485 communication circuit is connected with main control circuit and establishes bidirectional communication;Program download circuit is used to realize one-key download and running of program, analog quantity collection circuit is used to monitor the change of physical quantity, isolation, standard input voltage and complete analog-digital conversion, RS485 communication circuit is used to realize the transmission and reception of long-distance, multiple nodes of data, digital quantity input circuit is used to convert the level of external digital quantity signal into the signal level of PLC internal, and power supply circuit is used to power supply entire circuit.

[0005] Further, the main control circuit includes a main control chip U12, the model of the main control chip U12 is STM32F103VET6, the main control chip U12 has the functions of a reset circuit, a crystal oscillator circuit, a switch switching circuit, a power failure detection circuit, and an indicator lamp, the crystal oscillator circuit includes a crystal oscillator Y1, a second capacitor C43, a third capacitor C40, a crystal oscillator Y2, a fourth capacitor C57, and a fifth capacitor C46, the first end of the crystal oscillator Y1 is connected to the second capacitor C43, the second end of the crystal oscillator Y1 is connected to the third capacitor C40, the first end of the crystal oscillator Y2 is connected to the fourth capacitor C57, and the second end of the crystal oscillator Y2 is connected to the fifth capacitor C46; the power failure detection circuit is an LED circuit, the LED circuit is used for indicating the running state LED_RUN, the error state LED_ERR, and the power indicator lamp; the switch switching circuit includes a six-pin switch chip U1, the pin 1 of the U1 is connected to the ground, the pin 2 of the U1 is connected to the input port of the “SWITCH” through a 10K resistor R59, the pin 3 of the U1 is connected to the 3V3 power supply, and the pins 4, 5, and 6 of the U1 are not connected.

[0006] Further, the switch switching circuit is used for switching to the backup power supply when the main power supply is powered off, the VBAT pin in the backup power supply circuit is a battery power input, the middle part has a 3V battery BT1 with the model of CR1220, the positive electrode of the battery is connected to the VBAT, the negative electrode is connected to the ground, there is a diode D5 with the model of SK34 between the positive electrode of the battery and the VBAT, the positive electrode of the diode D5 faces the VBAT, the negative electrode faces the battery, there is another diode D6 with the model of SK34 between the negative electrode of the battery and the ground, the positive electrode of the diode D6 faces the battery, and the negative electrode faces the ground; a 100nF capacitor C50 is connected between the positive electrode of the battery and the ground, and is used for filtering.

[0007] Further, the main control circuit further includes a power management circuit, the power management circuit is provided with a transistor U53 with the model of EL354C, the base of the transistor U53 is connected to a resistor R56, the collector is connected to the 3.3V power supply, the emitter is connected to a 10K resistor R57, the other end of the resistor R57 is connected to the 24V power supply, the emitter of the transistor U53 is further connected to a diode, the positive electrode of the diode is connected to the 24V power supply, the negative electrode is connected to a 1K resistor R58, the other end of the resistor R58 is connected to the ground, the capacitor C56 is connected in parallel across the resistor R56, and the capacitor C56 and the resistor R56 are used for filtering and stabilizing the “POWER_DOWN” signal.

[0008] Further, the program download circuit includes a Type-C interface circuit and a CH340C chip U3, the Type-C interface circuit is used for connecting external devices, and the CH340C chip U3 is used for converting a USB signal into a serial port signal, so that the device can download a program through a serial port; the Type-C interface circuit is provided with a chip U6, which has the functions of processing a power supply VBUS, data transmission D- and D+, and configuring channels CC1 and CC2; the CH340C chip U3 has the functions of processing a power supply VCC, data receiving and sending RXD and TXD, and control signals CTS# and DSR#.

[0009] Further, the analog signal acquisition circuit is used for converting an analog signal into a digital signal, and includes an analog input channel ADC, a digital analog conversion DAC, and an operational amplifier LM224; the analog input channel ADC is provided with two analog input channels, which are marked as ADC1 and ADC2 respectively, each channel is composed of a plurality of resistors and capacitors, and is used for acquiring external analog signals; after the input signals of each channel pass through a resistor and capacitor network, the input signals are connected to an analog input pin of a microcontroller, and the acquired analog signals are digitized through the analog input pin of the microcontroller; the digital analog conversion DAC is provided with a DAC1 module, which is used for converting a digital signal into an analog signal; after the output signal of the DAC1 module passes through a resistor and capacitor network, the output signal is connected to an analog output pin of the microcontroller; the operational amplifier LM224 is used for signal amplification and conditioning, and the converted analog signal is used for controlling external devices or performing other analog signal processing.

[0010] Further, each module in the RS485 communication circuit has a 5V power supply input, which is marked as 5V, and a ground GND, and the power supply is connected to other elements through a resistor R10 and a resistor R14; each module in the RS485 communication circuit has an RS485 transceiver SP485, which is used for implementing an RS485 communication protocol; the pins of the transceiver include “RO”, “RE”, “DE”, “DI”, “VCC”, and “GND”; the “RO” and “DI” pins are connected to a serial port communication, and are used for receiving and sending data; the “RE” and “DE” pins are connected to a power supply and a ground through resistors, and are used for controlling the working mode of the transceiver; each module in the RS485 communication circuit further includes a plurality of protection diodes SMBJ6.5CA, and resistors R11, R13, R12, and R14 used for current limiting and voltage dividing.

[0011] Further, the digital quantity input circuit includes:

[0012] The input port is COM common terminal and IN input terminal; the output port is GND ground terminal and VCC power terminal; the signal output terminal is connected to the input signal terminal of the internal circuit; the input port COM and NI of each module are connected through a TVS diode and a resistor for protecting the circuit from transient voltage; the input signal is subjected to signal isolation through optical couplings ELM611 and EL354N; the input side of the optical couplings is connected to COM and NI, and the output side is connected to VCC and GND of the internal circuit; and the output signal of the optical couplings is connected to the signal output terminal of the internal circuit through a resistor.

[0013] Further, the power supply circuit is connected to the circuit through an input 24V voltage, a 2A 30V fuse F1, a transient voltage suppression diode TVS0 SMBJ40CA for protecting the circuit from transient voltage, a diode M7 for circuit protection and rectification, a 1K 100MHz 3A common mode filter L5 for energy storage and filtering, multiple large-capacity 470uF / 50V electrolytic capacitors C502, C503, C504 and C506 for filtering, a 1uF ceramic capacitor C501 for further filtering, a 68uH inductor L1 and a 220uF / 35V electrolytic capacitor C6 for final filtering and energy storage, and a pin 1-VIN of a power conversion chip U4 connected to the input power supply and outputting a converted 5V voltage through a pin 2-VOUT, the converted 5V voltage being converted into a 3.3V voltage through a chip U2 voltage regulator, and capacitors C9, C10 and C11 for filtering to ensure the stability of the output voltage.

[0014] Compared with the prior art, the utility model has the advantages that:

[0015] The analog quantity acquisition circuit is used for one-key downloading and running of programs through the set program downloading circuit, the analog quantity acquisition circuit is used for monitoring the change of physical quantity, isolating and standardizing input voltage and completing analog-digital conversion, the RS485 communication circuit is used for realizing long-distance and multi-node transmission and reception of data, and the digital quantity input circuit is used for converting the level of external digital quantity signals into the signal level of PLC, so that the external switch signal is converted into a digital signal through the analog quantity acquisition and digital quantity input interface circuit, and the processing efficiency of the analog quantity acquisition circuit on electric signals is improved. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is the circuit module frame diagram of the utility model;

[0017] Figure 2 is the main control circuit connection diagram of the utility model;

[0018] Figure 3is the power-off detection circuit connection diagram of the utility model;

[0019] Figure 4 is the switch switching circuit connection diagram of the utility model;

[0020] Figure 5 is the standby power supply circuit connection diagram of the utility model;

[0021] Figure 6 is the power management circuit connection diagram of the utility model;

[0022] Figure 7 is the program download circuit connection diagram of the utility model;

[0023] Figure 8 is the analog quantity acquisition circuit connection diagram of the utility model;

[0024] Figure 9 is the RS485 communication circuit connection diagram of the utility model;

[0025] Figure 10 is the digital quantity input circuit connection diagram of the utility model;

[0026] Figure 11 is the power circuit connection diagram of the utility model. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the utility model.

[0028] As Figure 1 shown: the utility model provides an analog quantity acquisition circuit in this embodiment, including main control circuit, program download circuit, analog quantity acquisition circuit, RS485 communication circuit, digital quantity input circuit and power circuit;Among them, the output of program download circuit, analog quantity acquisition circuit and digital quantity input circuit is respectively connected with the input of main control circuit, RS485 communication circuit and main control circuit establish bidirectional communication connection;Specifically, program download circuit is used for realizing one key download and running of program, analog quantity acquisition circuit is used for monitoring the change of physical quantity, isolating, standardizing input voltage and completing analog-digital conversion, RS485 communication circuit is used for realizing long distance, multi-node transmission and receiving of data, digital quantity input circuit is used for converting the level of external digital signal into the signal level of PLC, and power circuit is used for power supply of the whole circuit.

[0029] The specific circuit principle in the above embodiment is as follows:

[0030] As shown in Figure 2 : the master control circuit includes a master control chip U12, the model of the master control chip U12 is STM32F103VET6, the master control chip U12 has the functions of a reset circuit, a crystal oscillator circuit, a switch switching circuit, a power failure detection circuit, and an indicator lamp, the crystal oscillator circuit includes a crystal oscillator Y1, a second capacitor C43, a third capacitor C40, a crystal oscillator Y2, a fourth capacitor C57, and a fifth capacitor C46, the first end of the crystal oscillator Y1 is connected to the second capacitor C43, the second end of the crystal oscillator Y1 is connected to the third capacitor C40, the first end of the crystal oscillator Y2 is connected to the fourth capacitor C57, and the second end of the crystal oscillator Y2 is connected to the fifth capacitor C46.

[0031] Specifically, please refer to Figure 3 , the power failure detection circuit is an LED circuit, the LED circuit is used for indicating the running state (LED_RUN) and error state (LED_ERR) of the device and a power indicator lamp, and functions to detect whether the main power supply is powered off. The connection of the ground and the power supply ensures the stable operation of the circuit, when the main power supply is powered off, the VDD voltage decreases, and the circuit composed of a diode and a resistor triggers a power failure detection signal.

[0032] Please refer to Figure 4 , the switch switching circuit includes a six-pin switch chip U1, the pin 1 of U1 is connected to the ground, the pin 2 of U1 is connected to the input port of “SWITCH” through a 10K resistor R59, the pin 3 of U1 is connected to the 3V3 power supply, and the pins 4, 5, and 6 of U1 are not connected. This switch switching circuit is used to switch to the backup power supply when the main power supply is powered off.

[0033] As shown in Figure 5 : the VBAT pin in the backup power supply circuit represents the battery power input, which is used to provide backup power when the main power supply is powered off. There is a 3V battery (BT1) in the middle part, the model of which is CR1220, the positive electrode of the battery is connected to “VBAT”, and the negative electrode is connected to the ground. There is a diode (D5) between the positive electrode of the battery and “VBAT”, the model of which is SK34, the positive electrode of the diode (D5) faces “VBAT”, and the negative electrode faces the battery. There is another diode (D6) between the negative electrode of the battery and the ground, the model of which is also SK34, the positive electrode of the diode (D6) faces the battery, and the negative electrode faces the ground. A 100nF capacitor (C50) is connected between the positive electrode of the battery and the ground for filtering. The main function is to provide a stable 3.3V power supply for other electronic devices, and the diode prevents reverse connection of the power supply, and the capacitor is used for filtering to reduce noise in the power supply.

[0034] In the above embodiment, the master control circuit further includes a power management circuit, as shown in Figure 6As shown: The transistor (U53) in the power management circuit is an EL354C. The base of the transistor is connected to resistor R56, the collector is connected to a 3.3V power supply, and the emitter is connected to a 10K resistor (R57). The other end of resistor R57 is connected to a 24V power supply. The emitter of the transistor is also connected to a diode. The anode of the diode is connected to the 24V power supply, and the cathode is connected to a 1K resistor (R58). The other end of resistor R58 is connected to ground. Capacitor C56 and resistor R56 may be used for filtering and stabilizing the "POWER_DOWN" signal. The circuit is used for power management. In applications that require controlling the on and off of the 24V power supply, when the "POWER_DOWN" signal is high, transistor U53 conducts, allowing the 24V power supply to flow to ground through resistors R57 and R58, thereby turning on the 24V power supply.

[0035] like Figure 7 As shown, the program download circuit in this embodiment is the device's program download interface. The Type-C interface is used to connect to external devices, and the CH340C chip converts USB signals into serial signals so that the device can download programs via the serial port. The U6 chip is a Type-C interface chip that handles power (VBUS), data transmission (D- and D+), and configuration channels (CC1 and CC2). The U3 is a USB-to-serial chip, model CH340C, that handles power (VCC), data reception and transmission (RXD and TXD), and control signals (CTS#, DSR#, etc.).

[0036] like Figure 8 As shown, the analog signal acquisition circuit in this embodiment is mainly used to convert analog signals into digital signals for processing by a microcontroller or other digital devices. It includes an analog input channel (ADC), a digital-to-analog converter (DAC), and an operational amplifier (LM224), as detailed below:

[0037] Analog Input Channel (ADC): There are two analog input channels in the diagram, labeled ADC1 and ADC2 respectively. Each channel consists of multiple resistors and capacitors and is used to acquire external analog signals. The input signal of each channel is connected to the analog input pin of the microcontroller after passing through the resistor and capacitor network. The acquired analog signal is digitized through the analog input pin of the microcontroller.

[0038] Digital-to-Analog Converter (DAC): The diagram shows a DAC1 module, which converts digital signals into analog signals. The output signal of the DAC1 module is connected to the analog output pin of the microcontroller after passing through a network of resistors and capacitors. The LM224 operational amplifier is used for signal amplification and conditioning. The converted analog signal can be used to control external devices or perform other analog signal processing.

[0039] Referring to Figure 9 The RS485 communication circuit in the embodiment includes:

[0040] Power supply and ground: Each module has a 5V power input labeled "5V" and a ground (GND), the power supply is connected to other components through a 10K resistor (R10, R14).

[0041] RS485 transceiver: Each module has an RS485 transceiver (SP485) for implementing the RS485 communication protocol, the transceiver pins include "RO", "RE", "DE", "DI", "VCC", "GND", "RO" and "DI" pins are connected to serial communication for receiving and sending data, "RE" and "DE" pins are connected to power supply and ground through resistors for controlling the working mode of the transceiver. Ensure stable transmission of signals and safety of the circuit.

[0042] Protection diodes and resistors: Each module contains multiple protection diodes (SMBJ6.5CA) to prevent static electricity and overvoltage, resistors (R11, R13, R12, R14) for current limiting and voltage division.

[0043] As Figure 10 shown, the digital input circuit in the embodiment ensures that the external digital input signal can be safely and stably transmitted to the internal circuit through protection components and optocoupler isolation, which includes:

[0044] Input port: COM common end, IN input end. Output port: GND ground end, VCC power supply end, connected to the power supply of the internal circuit. Signal output end: connected to the input signal end of the internal circuit. The input port (COM and NI) of each module is connected through a TVS diode (such as SMBJ6.5CA) and a resistor (such as R601, R602) for protecting the circuit from transient voltage.

[0045] The input signal is signal isolated by an optocoupler (ELM611, EL354N). The input side of the optocoupler is connected to COM and NI, and the output side is connected to the VCC and GND of the internal circuit. The output signal of the optocoupler is connected to the signal output end of the internal circuit through a resistor (such as R603, R604) to prevent excessive current from damaging components.

[0046] Referring to Figure 11 The main function of the power supply circuit in the embodiment is to stabilize and filter the input voltage, and then output a stable voltage. The combination of multiple capacitors and inductors ensures the purity and stability of the output voltage. Specifically as follows:

[0047] The power input is connected to the circuit through an input 24V voltage, through a 2A 30V fuse (F1), a transient voltage suppression diode (TVS0 SMBJ40CA) for protecting the circuit from transient voltage, a diode M7 for circuit protection, rectification. A 1K 100MHz 3A common mode filter (L5) for energy storage and filtering. Multiple large capacity 470uF / 50V electrolytic capacitors (C502, C503, C504, C506) for filtering, ensuring the stability of the input voltage, a 1uF ceramic capacitor (C501) for further filtering. A 68uH inductor (L1) and a 220uF / 35V electrolytic capacitor (C6) for final filtering and energy storage. The U4 power conversion chip (XL1509-5V) pin 1 (VIN) is connected to the input power, and the converted 5V voltage is output through pin 2 (VOUT). The converted 5V voltage is converted to 3.3V voltage through AMS1117-3V3 (U2) voltage regulator. Capacitors (C9, C10, C11) are used for filtering to ensure the stability of the output voltage.

[0048] It should be noted that the relational terms herein such as first and second and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any such actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus.

[0049] Although the embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An analog quantity acquisition circuit, characterized by: The application relates to a one-key program downloading and running device for PLC, which comprises a main control circuit, a program downloading circuit, an analog quantity acquisition circuit, an RS485 communication circuit, a digital quantity input circuit and a power supply circuit; the output ends of the program downloading circuit, the analog quantity acquisition circuit and the digital quantity input circuit are electrically connected with the input end of the main control circuit; the main control circuit is in bidirectional communication connection with the RS485 communication circuit; the program downloading circuit is used for realizing one-key program downloading and running; the analog quantity acquisition circuit is used for monitoring the change of physical quantity, isolating and standardizing input voltage and completing analog-digital conversion; the RS485 communication circuit is used for realizing long-distance and multi-node transmission and reception of data; the digital quantity input circuit is used for converting the level of external digital quantity signals into the signal level of PLC; and the power supply circuit is used for providing working power supply for the whole circuit.

2. The analog acquisition circuit of claim 1, wherein: The main control circuit comprises a main control chip U12, the model of the main control chip U12 is STM32F103VET6, and the main control chip U12 has the functions of a reset circuit, a crystal oscillator circuit, a switch switching circuit, a power-off detection circuit and an indicator lamp; the crystal oscillator circuit comprises a crystal oscillator Y1, a second capacitor C43, a third capacitor C40, a crystal oscillator Y2, a fourth capacitor C57 and a fifth capacitor C46; the first end of the crystal oscillator Y1 is connected with the second capacitor C43; the second end of the crystal oscillator Y1 is connected with the third capacitor C40; the first end of the crystal oscillator Y2 is connected with the fourth capacitor C57; and the second end of the crystal oscillator Y2 is connected with the fifth capacitor C46; the power-off detection circuit is an LED circuit, which is used for indicating the running state LED_RUN, the error state LED_ERR and the power supply indicator lamp of the equipment; the switch switching circuit comprises a six-pin switch chip U1; the pin 1 of the U1 is connected with the ground; the pin 2 of the U1 is connected with the input port of "SWITCH" through a 10K resistor R59; the pin 3 of the U1 is connected with a 3V3 power supply; and the pins 4, 5 and 6 of the U1 are not connected.

3. The analog acquisition circuit of claim 2, wherein: The switch switching circuit is used for switching to a backup power supply when the main power supply is powered off; the VBAT pin in the backup power supply circuit is connected with a battery power supply; a 3V battery BT1 with the model of CR1220 is arranged in the middle part; the positive pole of the battery is connected with the VBAT; the negative pole of the battery is connected with the ground; a diode D5 with the model of SK34 is arranged between the positive pole of the battery and the VBAT; the positive pole of the diode D5 faces the VBAT; the negative pole of the diode D5 faces the battery; another diode D6 with the model of SK34 is arranged between the negative pole of the battery and the ground; the positive pole of the diode D6 faces the battery; the negative pole of the diode D6 faces the ground; and a 100nF capacitor C50 is arranged between the positive pole of the battery and the ground and used for filtering.

4. The analog acquisition circuit of claim 3, wherein: The main control circuit further comprises a power management circuit, the power management circuit is provided with a transistor U53, the model is EL354C, the base of the transistor U53 is connected to a resistor R56, the collector is connected to a 3.3V power supply, and the emitter is connected to a 10K resistor R57, the other end of the resistor R57 is connected to a 24V power supply, the emitter of the transistor U53 is also connected to a diode, the positive electrode of the diode is connected to a 24V power supply, the negative electrode is connected to a 1K resistor R58, the other end of the resistor R58 is connected to the ground, and the two ends of the resistor R56 are connected in parallel with a capacitor C56, and the capacitor C56 and the resistor R56 are used for filtering and stabilizing the "POWER_DOWN" signal.

5. The analog acquisition circuit of claim 1, wherein: The program download circuit comprises a Type-C interface circuit and a CH340C chip U3, the Type-C interface circuit is used for connecting external equipment, and the CH340C chip U3 is used for converting a USB signal into a serial signal, so that the device can download the program through the serial port; the Type-C interface circuit is provided with a chip U6, which has the functions of processing a power supply VBUS, data transmission D- and D+, and configuring channels CC1 and CC2; the CH340C chip U3 has the functions of processing a power supply VCC, data receiving and sending RXD and TXD, and control signals CTS# and DSR#.

6. The analog acquisition circuit of claim 1, wherein: The analog signal acquisition circuit is used for converting an analog signal into a digital signal, and comprises an analog input channel ADC, a digital analog conversion DAC and an operational amplifier LM224; the analog input channel ADC is provided with two analog input channels, which are marked as ADC1 and ADC2 respectively, each channel is composed of a plurality of resistors and capacitors, and is used for acquiring external analog signals; the input signals of each channel are connected to the analog input pin of the microcontroller after passing through the resistor and capacitor network, and the acquired analog signals are digitized through the analog input pin of the microcontroller; the digital analog conversion DAC is provided with a DAC1 module, which is used for converting a digital signal into an analog signal, and the output signal of the DAC1 module is connected to the analog output pin of the microcontroller after passing through the resistor and capacitor network; and the operational amplifier LM224 is used for signal amplification and conditioning, and the converted analog signal is used for controlling external equipment or performing other analog signal processing.

7. The analog acquisition circuit of claim 1, wherein: Each module in the RS485 communication circuit has a 5V power input marked as 5V and a ground GND, and the power supply is connected to other elements through a 10K resistor R10 and a resistor R14; Each module in the RS485 communication circuit has an RS485 transceiver SP485 for implementing the RS485 communication protocol, and the pins of the transceiver include "RO", "RE", "DE", "DI", "VCC", "GND", the "RO" and "DI" pins are connected to serial communication for receiving and sending data, and the "RE" and "DE" pins are connected to the power supply and ground through resistors for controlling the working mode of the transceiver; Each module in the RS485 communication circuit also includes a plurality of protection diodes SMBJ6.5CA, and resistors R11, R13, R12, and R14 for current limiting and voltage dividing.

8. The analog acquisition circuit of claim 1, wherein: The digital input circuit comprises: The input port: COM common end and IN input end; The output port: GND ground end and VCC power supply end; The signal output end: connected to the input signal end of the internal circuit; The input port COM and NI of each module are connected through a TVS diode and a resistor for protecting the circuit from transient voltage; The input signal is signal isolated through optocoupler ELM611, EL354N; The input side of the optocoupler is connected to COM and NI, and the output side is connected to VCC and GND of the internal circuit, and the output signal of the optocoupler is connected to the signal output end of the internal circuit through a resistor.

9. The analog acquisition circuit of claim 1, wherein: The power supply circuit connects to the circuit through a 2A 30V fuse F1 by inputting a 24V voltage, a transient voltage suppression diode TVS0 SMBJ40CA is used to protect the circuit from transient voltage, a diode M7 is used for circuit protection and rectification, a 1K 100MHz 3A common mode filter L5 is used for energy storage and filtering, a plurality of large-capacity 470μF / 50V electrolytic capacitors C502, C503, C504, and C506 are used for filtering, a 1μF ceramic capacitor C501 is used for further filtering, a 68μH inductor L1 and a 220μF / 35V electrolytic capacitor C6 are used for final filtering and energy storage; The pin 1-VIN of the power conversion chip U4 is connected to the input power supply, and the converted 5V voltage is output through the pin 2-VOUT, the converted 5V voltage is converted to 3.3V voltage through the chip U2 voltage regulator, and the capacitors C9, C10, and C11 are used for filtering to ensure the stability of the output voltage.

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