A multi-functional communication detection circuit for power operation and maintenance site

Abstract

The utility model discloses a kind of electric power operation and maintenance field multifunctional communication detection circuit, it includes signal input module, signal conditioning module, multi-mode switching module, signal processing module, signal output module and main control unit connected in turn.The multi-mode switching module is connected with main control unit, signal processing module is also connected with signal output module.Signal input module is realized noise suppression by magnetic ring inductance and filter capacitor, signal conditioning module utilizes operational amplifier to carry out signal amplification and filtering, multi-mode switching module is realized signal switching by reference voltage generation unit and switch tube, signal output module uses photoelectric isolator to improve anti-interference capability.The utility model can efficiently detect carrier communication, 485 communication, infrared communication and wireless public network communication and various communication modes, solve the problem of independent equipment in prior art, complex operation and low efficiency, improve compatibility and stability under complex electromagnetic environment simultaneously.

Description

Technical Field

[0001] This utility model belongs to the field of power communication and detection technology, specifically, it relates to a multi-functional communication and detection circuit for power operation and maintenance sites. Background Technology

[0002] Power line carrier communication (PLC) technology has matured, involving loading high-frequency signals carrying information onto power lines and acquiring the transmitted signals through dedicated modulation / demodulation modules. A typical application of PLC technology is in smart remote meter reading systems, where accurate detection of the zero-crossing point of the AC current on the power line is crucial for reliable communication. This method eliminates the need for additional communication cables.

[0003] In power system maintenance sites, multiple communication methods coexist, including carrier communication, RS-485 communication, infrared communication, and wireless public network communication. However, in practical applications, the detection and testing of different communication methods usually rely on independent equipment or modules, resulting in complex operations and low efficiency. For example, traditional RS-485 communication testing requires signal reading through a dedicated interface, while infrared communication is limited by distance and angle requirements. Furthermore, the detection of wireless public network signal strength is often difficult to guarantee accuracy due to environmental interference, and traditional methods lack integrated support for multiple communication methods.

[0004] Current technologies include some devices that attempt to integrate Bluetooth app connectivity, but these primarily focus on optimizing a single communication method and fail to fully cover the detection needs of multiple communication modes. Furthermore, existing technologies still have shortcomings in terms of compatibility and stability, especially in complex electromagnetic environments, which may affect the reliability of detection results. Utility Model Content

[0005] The purpose of this utility model is to provide a multi-functional communication detection circuit for power operation and maintenance sites, which mainly solves the problems of independent detection equipment with multiple communication methods, complex operation and low efficiency in the existing technology, while overcoming the defects of insufficient compatibility and stability of traditional methods in complex electromagnetic environments.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is as follows:

[0007] A multi-functional communication detection circuit for power operation and maintenance sites includes a signal input module, a signal conditioning module, a multi-mode switching module, a signal processing module, a signal output module, and a main control unit connected in sequence. The multi-mode switching module is connected to the main control unit, and the signal processing module is also connected to the signal output module. The multi-mode switching module includes a reference voltage generation unit connected to the signal processing module, a resistor R1 connected to the output terminal of the reference voltage generation unit, an adjustable potentiometer VR1 and a resistor R2 connected in series with the other end of resistor R1, a switching transistor Q9 whose base is connected to the other end of resistor R2, and resistors R3 and R4 connected to the collector of switching transistor Q9. The other end of resistor R3 is connected to the main control unit, the other end of resistor R4 is grounded, the adjustment terminal of the adjustable potentiometer VR1 is connected to the signal processing module, and the emitter of switching transistor Q9 is connected to the output terminal of the reference voltage generation unit.

[0008] Furthermore, in this utility model, the reference voltage generation unit includes a current-limiting resistor R0 with one end connected to VDD, a reference chip U1 with its cathode connected to the other end of the current-limiting resistor R0, voltage-dividing resistors R18 and R19 connected to the reference terminal of the reference chip U1, a filter capacitor C7 with one end connected to the VDD end of the current-limiting resistor R0 and grounded, and a filter capacitor C8 with one end connected to the common terminal of the current-limiting resistor R0 and the filter capacitor C7 and the other end connected to the cathode of the reference chip U1; wherein, the other end of the voltage-dividing resistor R18 is connected to the cathode of the reference chip U1, the other end of the voltage-dividing resistor R19 is grounded, the anode of the reference chip U1 is grounded, and the cathode of the reference chip U1 is connected to the emitter of the switching transistor Q9.

[0009] Furthermore, in this utility model, the signal input module includes a magnetic ring inductor L1, a filter capacitor C1, and a magnetic ring inductor L2 connected in series, a filter capacitor C2 connected to one end of the magnetic ring inductor L1 and grounded, and a filter capacitor C3 connected to the common terminal of the magnetic ring inductor L1 and the filter capacitor C2; wherein, one end of the filter capacitor C3 connected to the magnetic ring inductor L2 is connected to the signal conditioning module, and the other end of the magnetic ring inductor L2 is grounded.

[0010] Furthermore, in this utility model, the signal conditioning module includes an operational amplifier U3 whose non-inverting input terminal is connected to one end of the filter capacitor C3 and the magnetic ring inductor L2, a resistor R5 connected to the inverting input terminal of the operational amplifier U3, and a filter capacitor C4 connected between the inverting input terminal of the operational amplifier U3 and ground.

[0011] Furthermore, in this utility model, the multi-mode switching module also includes a current-limiting switch Q10 whose collector is connected to one end of resistor R5, a control switch Q11 whose collector and base are respectively connected to the base and emitter of the current-limiting switch Q10, resistors R6 and R7 connected to the base of the current-limiting switch Q10, a control transistor Q12 whose collector is connected to the other end of resistor R6 and whose emitter is grounded, and resistors R8 and R9 connected in parallel with one end connected to the emitter of the control switch Q11 and the other end connected to the output of operational amplifier U3; wherein, the other end of resistor R7 is grounded.

[0012] Furthermore, in this invention, the signal processing module includes a resistor R10 connected to the base of the control transistor Q12, a resistor R11 connected to the other end of the resistor R10, and a resistor R12 with one end connected to the other end of the resistor R11 and the other end grounded; wherein, the common terminal of the resistors R10 and R11 is connected to the adjustment terminal of the adjustable potentiometer VR1, and the common terminal of the resistors R11 and R12 is connected to the signal output module.

[0013] Furthermore, in this utility model, the signal output module includes a resistor R13 with one end connected to the common terminal of resistors R11 and R12, a resistor R14 with one end connected to the common terminal of resistors R10 and R11, a resistor R15 with one end connected to the other end of resistors R13 and R14, a resistor R16 connected to the ground terminal of resistor R12, a diode D1 with its positive terminal connected to the other end of resistor R15 and its negative terminal connected to the other end of resistor R16, a diode D2 with its negative terminal connected to the other end of resistor R15 and its positive terminal connected to the other end of resistor R16, a filter capacitor C5 connected in parallel across diode D2, an operational amplifier U2 with its positive input terminal connected to the negative terminal of diode D2 and its negative input terminal connected to the positive terminal of diode D2, and a Zener diode Z1 with its negative terminal connected to the output terminal of operational amplifier U2 and its positive terminal grounded; wherein, the output terminal of operational amplifier U2 is also connected to the anode of reference chip U1.

[0014] Furthermore, in this utility model, the signal output module also includes a resistor R17, a filter capacitor C6, and an opto-isolator. One end of the resistor R17 is connected to the output terminal of the operational amplifier U2, and the other end of the resistor R17 is connected to the positive input terminal of the filter capacitor C6 and the opto-isolator. The other end of the filter capacitor C6 is grounded and connected to the negative input terminal of the opto-isolator. The emitter of the output terminal of the opto-isolator is grounded, and the collector of the output terminal of the opto-isolator is connected to the receiving port of the main control unit.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) This utility model achieves integrated detection of multiple communication methods such as carrier communication, 485 communication, infrared communication, and wireless public network communication by sequentially connecting a signal input module, a signal conditioning module, a multi-mode switching module, a signal processing module, and a signal output module, combined with the control of the multi-mode switching module by the main control unit. Compared with the problems of existing technologies that rely on independent equipment, are complex to operate, and are inefficient, this solution does not require frequent replacement or debugging of equipment. It can complete the rapid detection of multiple types of signals by automatically switching the detection mode through the main control unit, which significantly simplifies the operation process and improves the detection efficiency of power operation and maintenance sites.

[0017] (2) This utility model employs multiple anti-interference technologies in key modules: the signal input module suppresses noise through a magnetic ring inductor and a filter capacitor; the signal conditioning module uses an operational amplifier for filtering and amplification; the signal output module uses an opto-isolator for electrical isolation; and the reference voltage generation unit stabilizes the reference level through filter capacitors C7 and C8. These designs work together to effectively reduce the impact of electromagnetic interference on the detection signal, solve the defects of poor compatibility and unstable detection results of traditional equipment in strong electromagnetic environments, and ensure the reliability of signal transmission and processing.

[0018] (3) The multi-mode switching module of this utility model provides a stable reference level through a reference voltage generation unit, and realizes dynamic switching of signal paths by combining adjustable potentiometer VR1 and switching transistor Q9, and precisely controls the switching logic through the main control unit. This module supports flexible adjustment of signal amplitude and path selection for different communication methods. For example, it can adapt to the signal difference between carrier communication and 485 communication by adjusting the adjustable potentiometer VR1, and switch the detection path of infrared and wireless public network communication by controlling transistor Q12. This design solves the problem of fixed function of single device in the prior art and difficulty in adapting to diversified communication detection needs, realizes accurate adaptation to different communication protocols and signal types, and improves the versatility and scenario adaptability of the circuit. Attached Figure Description

[0019] Figure 1 This is the circuit schematic diagram of this utility model. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiments of the present invention include, but are not limited to, the following embodiments.

[0021] like Figure 1As shown, this utility model discloses a multi-functional communication detection circuit for power operation and maintenance sites, comprising a signal input module, a signal conditioning module, a multi-mode switching module, a signal processing module, a signal output module, and a main control unit. These modules work together to achieve unified detection and efficient processing of various communication methods, including carrier communication, RS-485 communication, infrared communication, and wireless public network communication.

[0022] In this embodiment, the signal input module consists of a magnetic ring inductor L1, a filter capacitor C1, a magnetic ring inductor L2, a filter capacitor C2, and a filter capacitor C3. After the external signal enters the circuit through the magnetic ring inductor L1, it passes sequentially through the filter capacitor C1 and the magnetic ring inductor L2 for high-frequency interference suppression and noise filtering. The magnetic ring inductors L1 and L2 are used to suppress high-frequency interference signals, and their design parameters are configured according to the characteristics of the electromagnetic environment in the actual application to ensure good suppression of interference in specific frequency bands. The filter capacitor C1 works with the magnetic ring inductor L1 to achieve preliminary filtering of high-frequency components, while the filter capacitors C2 and C3 further reduce the noise components in the signal. One end of the filter capacitor C3 is connected to the signal conditioning module, and the other end is connected to the magnetic ring inductor L2. The other end of the magnetic ring inductor L2 is grounded to form a complete signal loop. The signal processed by the signal input module is then transmitted to the signal conditioning module for further amplification and filtering.

[0023] In this embodiment, the core of the signal conditioning module is operational amplifier U3. Its non-inverting input is connected to the end of the filter capacitor C3 connected to the magnetic ring inductor L2, and its inverting input is connected to ground through resistor R5. The negative feedback loop of operational amplifier U3 consists of resistor R5 and filter capacitor C4. This loop achieves precise amplification and high-frequency noise suppression by controlling the signal gain and limiting the bandwidth. The resistance value of resistor R5 ranges from 1 kΩ to 10 kΩ, and the specific value is adjusted according to actual needs to meet the signal processing requirements of different communication methods. The capacitance of filter capacitor C4 is set to 10 nF to 100 nF. When used in conjunction with resistor R5, it can effectively filter out high-frequency noise and preserve the integrity of the target signal. The output of the signal conditioning module is connected to the multi-mode switching module, providing a stable foundation for subsequent signal processing.

[0024] The multi-mode switching module consists of a reference voltage generation unit, resistor R1, adjustable potentiometer VR1, resistor R2, switching transistor Q9, resistors R3 and R4, and auxiliary circuitry. The reference voltage generation unit includes a current-limiting resistor R0, a reference chip U1, voltage divider resistors R18 and R19, and filter capacitors C7 and C8. One end of the current-limiting resistor R0 is connected to the power supply VDD, and the other end is connected to the cathode of the reference chip U1. The anode of the reference chip U1 is grounded, and the reference terminal is connected to ground through voltage divider resistors R18 and R19, thus forming a stable reference voltage output. The magnitude of the reference voltage is determined by the ratio of voltage divider resistors R18 and R19, typically set to 2.5V for reference level matching in subsequent circuits. Filter capacitors C7 and C8 are connected to the current-limiting resistor R0 and the reference chip U1, respectively, to filter out power supply noise and improve the stability of the reference voltage. The output of the reference voltage generation unit is connected to one end of the adjustable potentiometer VR1 via resistor R1. The other end of the adjustable potentiometer VR1 is connected to the base of the switching transistor Q9 via resistor R2. The emitter of the switching transistor Q9 is connected to the output of the reference voltage generation unit, and its collector is connected to the main control unit via resistor R3, and grounded via resistor R4. Resistors R3 and R4 together form a voltage divider network, providing a stable signal reference for the main control unit. The adjustment terminal of the adjustable potentiometer VR1 is connected to the signal processing module, and the signal amplitude is dynamically controlled by adjusting the resistance value of the adjustable potentiometer VR1.

[0025] The multi-mode switching module also includes a current-limiting switch Q10, a control switch Q11, a control transistor Q12, and resistors R6, R7, R8, and R9. The collector of the current-limiting switch Q10 is connected to one end of resistor R5, its base is connected to the collector of the control switch Q11 via resistor R6, and its emitter is connected to the base of the control switch Q11. The emitter of the control switch Q11 is connected to the output of operational amplifier U3 via resistors R8 and R9 in parallel, and its base is grounded via resistor R7. The collector of the control transistor Q12 is connected to the other end of resistor R6, its emitter is grounded, and its base is connected to the signal processing module. The current-limiting switch Q10 and the control switch Q11 work together with resistors R6 and R7 to achieve current limiting and switching control functions, while the control transistor Q12 selectively conducts the signal path by adjusting its base current. This design allows the multi-mode switching module to flexibly switch signal paths under different communication modes, ensuring system compatibility in complex electromagnetic environments.

[0026] The signal processing module consists of resistors R10, R11, and R12. One end of resistor R10 is connected to the base of the control transistor Q12, and the other end is connected to ground through resistor R11. The other end of resistor R11 is grounded through resistor R12. The common terminal of resistors R10 and R11 is connected to the adjustment terminal of the adjustable potentiometer VR1, and the common terminal of resistors R11 and R12 is connected to the signal output module. The combination of resistors R10, R11, and R12 adjusts and matches the signal amplitude, ensuring that the output signal meets the requirements of subsequent modules. The resistance value of resistor R10 is set to 1 kΩ to 10 kΩ, and the resistance values ​​of resistors R11 and R12 are each set to 100 Ω to 1 kΩ. The specific values ​​are adjusted according to the actual application scenario.

[0027] The signal output module consists of resistors R13, R14, R15, and R16, diodes D1 and D2, filter capacitor C5, operational amplifier U2, Zener diode Z1, resistor R17, filter capacitor C6, and an opto-isolator. One end of resistor R13 is connected to the common terminal of resistors R11 and R12, and the other end is connected to the anode of diode D1 through resistor R15. One end of resistor R14 is connected to the common terminal of resistors R10 and R11, and the other end is also connected to the anode of diode D1 through resistor R15. The anode of diode D2 is connected to one end of resistor R16, and the cathode is connected to the other end of resistor R15. Filter capacitor C5 is connected in parallel across diode D2 to filter out high-frequency noise. The non-inverting input of operational amplifier U2 is connected to the cathode of diode D2, and the non-inverting input is connected to the anode of diode D2. The output is grounded through Zener diode Z1. The negative terminal of Zener diode Z1 is connected to the output terminal of operational amplifier U2, while its positive terminal is grounded, used to clamp the output signal within a safe range. The output terminal of operational amplifier U2 is also connected to the positive input terminal of filter capacitor C6 and opto-isolator via resistor R17. The other end of filter capacitor C6 is grounded and connected to the negative input terminal of the opto-isolator. The emitter of the opto-isolator's output terminal is grounded, and its collector is connected to the main control unit's receiving port. The signal output module achieves stable signal output through the bidirectional rectification of diodes D1 and D2 combined with the driving capability of operational amplifier U2. The use of the opto-isolator further enhances the system's anti-interference capability.

[0028] The main control unit receives signals from the signal output module and performs subsequent processing and analysis. Internally, the main control unit integrates a microprocessor and memory, enabling it to decode, analyze, and store received signals, while also supporting the parsing and display of multiple communication protocols. In this embodiment, the main control unit can be an STM32F103C8T6. This chip, with its combination of "multiple serial ports + rich I / O + industrial-grade reliability + low cost," perfectly meets the core requirements of power operation and maintenance communication detection circuits, such as "protocol parsing, multi-mode control, signal storage, and anti-interference," making it the optimal choice for the current scenario. The main control unit achieves electrical isolation through an opto-isolator to prevent external interference from affecting the system. In actual operation, the main control unit determines the current communication mode based on the characteristics of the received signal and adjusts the circuit's operating state through a multi-mode switching module to adapt to different communication needs. For example, when detecting a 485 communication signal, the main control unit changes the signal amplitude by adjusting the resistance of the adjustable potentiometer VR1, while simultaneously controlling transistor Q12 to select the corresponding signal path, ensuring accurate signal transmission and processing. When detecting infrared communication signals, the main control unit uses a stable reference level provided by the reference voltage generation unit to accurately measure the signal strength. For wireless public network communication signals, the main control unit utilizes the high-gain characteristics of the signal conditioning module to amplify weak signals, while simultaneously improving signal quality through the filtering and voltage regulation functions of the signal output module.

[0029] In specific application scenarios, such as in intelligent remote meter reading systems, this circuit can simultaneously detect carrier communication signals and RS-485 communication signals on power lines, generating corresponding data reports through the main control unit's analysis function. During the debugging of infrared communication equipment, this circuit achieves precise measurement of signal strength by adjusting the adjustable potentiometer VR1 and the control transistor Q12, helping technicians quickly locate problems. For wireless public network signal detection tasks, the circuit ensures the reliability of detection results through the high-gain characteristics of the signal conditioning module and the anti-interference design of the signal output module. In actual operation, users only need to connect the signal to be tested to the signal input module; the main control unit can automatically identify the signal type and complete the detection and analysis, greatly simplifying the operation process.

[0030] In summary, this invention achieves unified detection of multiple communication methods through integrated design. The use of technologies such as a reference voltage generation unit and opto-isolators enhances the system's stability and anti-interference capabilities. The rational design and parameter configuration of each module ensure the accuracy of signal transmission and processing, meeting the requirements for high-precision detection. This invention features a compact circuit structure and reliable performance, making it suitable for various communication detection scenarios in power operation and maintenance sites, demonstrating significant technological advancements and application value.

[0031] The above embodiments are merely one of the preferred embodiments of this utility model and should not be used to limit the scope of protection of this utility model. Any modifications or refinements made to the main design concept and spirit of this utility model that are not of substantial significance, but solve the same technical problem as this utility model, should be included within the scope of protection of this utility model.

Claims

1. A multi-functional communication detection circuit for power operation and maintenance sites, characterized in that, The system includes a signal input module, a signal conditioning module, a multi-mode switching module, a signal processing module, a signal output module, and a main control unit connected in sequence. The multi-mode switching module is connected to the main control unit, and the signal processing module is also connected to the signal output module. The multi-mode switching module includes a reference voltage generation unit connected to the signal processing module, a resistor R1 connected to the output terminal of the reference voltage generation unit, an adjustable potentiometer VR1 and a resistor R2 connected in series with the other end of resistor R1, a switching transistor Q9 whose base is connected to the other end of resistor R2, and resistors R3 and R4 connected to the collector of switching transistor Q9. The other end of resistor R3 is connected to the main control unit, the other end of resistor R4 is grounded, the adjustment terminal of the adjustable potentiometer VR1 is connected to the signal processing module, and the emitter of switching transistor Q9 is connected to the output terminal of the reference voltage generation unit.

2. The multi-functional communication detection circuit for power operation and maintenance sites according to claim 1, characterized in that, The reference voltage generation unit includes a current-limiting resistor R0 connected to VDD at one end, a reference chip U1 whose cathode is connected to the other end of the current-limiting resistor R0, voltage-dividing resistors R18 and R19 connected to the reference terminal of the reference chip U1, a filter capacitor C7 whose one end is connected to the VDD end of the current-limiting resistor R0 and grounded, and a filter capacitor C8 whose one end is connected to the common terminal of the current-limiting resistor R0 and the filter capacitor C7 and whose other end is connected to the cathode of the reference chip U1; wherein, the other end of the voltage-dividing resistor R18 is connected to the cathode of the reference chip U1, the other end of the voltage-dividing resistor R19 is grounded, the anode of the reference chip U1 is grounded, and the cathode of the reference chip U1 is connected to the emitter of the switching transistor Q9.

3. The multi-functional communication detection circuit for power operation and maintenance sites according to claim 2, characterized in that, The signal input module includes a magnetic ring inductor L1, a filter capacitor C1, and a magnetic ring inductor L2 connected in series, a filter capacitor C2 connected to one end of the magnetic ring inductor L1 and grounded, and a filter capacitor C3 connected to the common terminal of the magnetic ring inductor L1 and the filter capacitor C2; wherein, the end of the filter capacitor C3 connected to the magnetic ring inductor L2 is connected to the signal conditioning module, and the other end of the magnetic ring inductor L2 is grounded.

4. The multi-functional communication detection circuit for power operation and maintenance sites according to claim 3, characterized in that, The signal conditioning module includes an operational amplifier U3 whose non-inverting input is connected to one end of the filter capacitor C3 and the magnetic ring inductor L2, a resistor R5 connected to the inverting input of the operational amplifier U3, and a filter capacitor C4 connected between the inverting input of the operational amplifier U3 and ground.

5. A multi-functional communication detection circuit for power operation and maintenance sites according to claim 4, characterized in that, The multi-mode switching module also includes a current-limiting switch Q10 whose collector is connected to one end of resistor R5, a control switch Q11 whose collector and base are connected to the base and emitter of the current-limiting switch Q10, respectively, resistors R6 and R7 connected to the base of the current-limiting switch Q10, a control transistor Q12 whose collector is connected to the other end of resistor R6 and whose emitter is grounded, and resistors R8 and R9 connected in parallel, with one end connected to the emitter of the control switch Q11 and the other end connected to the output of operational amplifier U3; wherein, the other end of resistor R7 is grounded.

6. A multi-functional communication detection circuit for power operation and maintenance sites according to claim 5, characterized in that, The signal processing module includes a resistor R10 connected to the base of the control transistor Q12, a resistor R11 connected to the other end of the resistor R10, and a resistor R12 with one end connected to the other end of the resistor R11 and the other end grounded; wherein, the common terminal of the resistors R10 and R11 is connected to the adjustment terminal of the adjustable potentiometer VR1, and the common terminal of the resistors R11 and R12 is connected to the signal output module.

7. A multi-functional communication detection circuit for power operation and maintenance sites according to claim 6, characterized in that, The signal output module includes a resistor R13 with one end connected to the common terminal of resistors R11 and R12, a resistor R14 with one end connected to the common terminal of resistors R10 and R11, a resistor R15 with one end connected to the other end of resistors R13 and R14, a resistor R16 connected to the ground terminal of resistor R12, a diode D1 with its positive terminal connected to the other end of resistor R15 and its negative terminal connected to the other end of resistor R16, a diode D2 with its negative terminal connected to the other end of resistor R15 and its positive terminal connected to the other end of resistor R16, a filter capacitor C5 connected in parallel across diode D2, an operational amplifier U2 with its positive input terminal connected to the negative terminal of diode D2 and its negative input terminal connected to the positive terminal of diode D2, and a Zener diode Z1 with its negative terminal connected to the output terminal of operational amplifier U2 and its positive terminal grounded; wherein, the output terminal of operational amplifier U2 is also connected to the anode of reference chip U1.

8. A multi-functional communication detection circuit for power operation and maintenance sites according to claim 7, characterized in that, The signal output module also includes a resistor R17, a filter capacitor C6, and an opto-isolator. One end of the resistor R17 is connected to the output terminal of the operational amplifier U2, and the other end of the resistor R17 is connected to the positive input terminal of the filter capacitor C6 and the opto-isolator. The other end of the filter capacitor C6 is grounded and connected to the negative input terminal of the opto-isolator. The emitter of the output terminal of the opto-isolator is grounded, and the collector of the output terminal of the opto-isolator is connected to the receiving port of the main control unit.

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