Ultrasonic detection liquid flow rate circuit

Abstract

The invention discloses an ultrasonic detection liquid flow rate circuit, which relates to the field of cleaning, and comprises a communication port used for constructing communication between a control circuit and an upper computer; the control circuit is used for controlling the transmitting circuit to transmit the ultrasonic signals, receiving the ultrasonic signals fed back by the receiving circuit, obtaining the time difference between transmitting and receiving of the ultrasonic waves and judging the flow water speed; the transmitting circuit is used for receiving the control of the control circuit and transmitting an ultrasonic signal during working; the receiving circuit is used for receiving ultrasonic signals during working and feeding back the ultrasonic signals to the control circuit; the beneficial effects of the invention are that the liquid flow rate can be effectively and reliably detected by monitoring the time interval of transmitting and receiving ultrasonic waves, a peripheral circuit is simple, the portability is strong, the number of ports occupying a main chip is small, the sensor can be easily matched with a main circuit, the power consumption is low, and when the sensor does not need to work, the sensor can be conveniently operated. The upper computer can close the emission function by closing the enabling port.

Description

Technical Field

[0001] This invention relates to the field of cleaning, specifically to an ultrasonic circuit for detecting liquid flow rate. Background Technology

[0002] Currently, some cleaning appliances on the market (such as air purifiers, electric mops, and robot vacuum cleaners) require control of water output based on different application scenarios.

[0003] Currently, the mainstream flow control scheme mainly controls the water output by controlling the duty cycle of water valves or pumps. However, due to the lack of a system for accurately detecting flow velocity, the flow control scheme is inaccurate and needs improvement. Summary of the Invention

[0004] The purpose of this invention is to provide an ultrasonic circuit for detecting liquid flow rate, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An ultrasonic circuit for detecting liquid flow rate includes:

[0007] Communication port, used to establish communication between the control circuit and the host computer;

[0008] The control circuit is used to control the transmitting circuit to emit ultrasonic signals, receive ultrasonic signals fed back by the receiving circuit, obtain the time difference between ultrasonic emission and reception, and determine the flow rate and water velocity.

[0009] The transmitting circuit is used to receive control from the control circuit and emits ultrasonic signals during operation.

[0010] The receiving circuit is used to receive ultrasonic signals during operation and feed them back to the control circuit.

[0011] The communication port is connected to the first and second terminals of the control circuit; the third, fourth, and fifth terminals of the control circuit are connected to the transmitting circuit; and the receiving circuit is connected to the sixth and seventh terminals of the control circuit.

[0012] The diameter of the pipe through which the liquid flows is D. The transmitting and receiving circuits are embedded in the pipe wall, and the transmitting and receiving surfaces of the transmitting and receiving circuits are completely aligned. The distance between the transmitting and receiving surfaces of the transmitting and receiving circuits is L, and the speed of the liquid flow is Vm.

[0013] The angle between the vertical connecting line of the transmitting circuit and the receiving circuit and the tube body is Since the velocity gain of the ultrasonic waves generated by the liquid flow is Vm·cosφ, where φ does not change, the larger the liquid flow velocity Vm, the faster the receiving circuit receives the ultrasonic signal. Therefore, the liquid flow velocity can be calculated based on the time difference between sending and receiving the ultrasonic waves.

[0014] As a further embodiment of the present invention: the communication port includes interface J1, the first end of interface J1 is grounded, the second end and the third end of interface J1 are connected to the first end and the second end of the control circuit, the third end of interface J1 is connected to a 5V voltage, and interface J1 is externally connected to a host computer.

[0015] As a further embodiment of the present invention: the control circuit includes a chip STC11, pin 1 of chip STC11 (the first end of the control circuit) is connected to the communication port and one end of resistor R3, pin 2 of chip STC11 (the second end of the control circuit) is connected to the communication port and one end of resistor R2, the other end of resistor R2 is connected to the other end of resistor R3 and 5V voltage, pins 12, 13 and 14 of chip STC11 (the third, fourth and fifth ends of the control circuit) are connected to the transmitting circuit, and pins 9 and 10 of chip STC11 (the sixth and seventh ends of the control circuit) are connected to the receiving circuit.

[0016] As a further embodiment of the present invention: the transmitting circuit includes a chip MAX232, an ultrasonic transmitter, and a transistor Q1. Pins 10 and 11 of the chip MAX232 are connected to the fourth and fifth terminals of the control circuit, pins 7 and 14 of the chip MAX232 are respectively connected to the two ends of the ultrasonic transmitter, pin 16 of the chip MAX232 is connected to the emitter of the transistor Q1, the base of the transistor Q1 is connected to the third terminal of the control circuit, and the collector of the transistor Q1 is connected to a 5V voltage.

[0017] As a further embodiment of the present invention: the receiving circuit includes:

[0018] The frequency selection and signal amplification module is used to amplify the received ultrasonic signal in two stages and output it to the signal conversion module;

[0019] The signal conversion module is used to convert the two-stage amplified ultrasonic signal into a digital signal and output it to the feedback output module.

[0020] The feedback output module is used to feed back voltage signals to the control circuit based on digital signals.

[0021] The output of the frequency selection and signal amplification module is connected to the input of the signal conversion module, the output of the signal conversion module is connected to the input of the feedback output module, and the output of the feedback output module is connected to the fifth and sixth terminals of the control circuit.

[0022] As a further embodiment of the present invention: the frequency selection and signal amplification module includes a chip TL074, an ultrasonic receiver, one end of the ultrasonic receiver being grounded, the other end of the ultrasonic receiver being connected to one end of a resistor R17, the other end of resistor R17 being connected to one end of a capacitor C15, the other end of capacitor C15 being connected to one end of a resistor R18, pin 13 of the chip TL074, pin 12 of the chip TL074 being connected to a voltage signal VT, and pin 14 of the chip TL074 being connected to the other end of resistor R18 and one end of resistor R19. One end of resistor R19 is connected to one end of resistor R15, one end of capacitor C10, and one end of capacitor C12. The other end of resistor R15 is connected to pin 10 of chip TL074. The other end of capacitor C10 is connected to one end of resistor R14 and pin 9 of chip TL074. The other end of capacitor C12 is connected to the other end of resistor R14, pin 8 of chip TL074, and one end of resistor R13. The other end of resistor R13 is connected to one end of capacitor C9. The other end of capacitor C9 is connected to the input terminal of the signal conversion module.

[0023] As a further embodiment of the present invention: the signal conversion module includes a chip TL074. Pin 2 of the chip TL074 is connected to one end of resistor R8. The other end of resistor R8 is connected to one end of resistor R6, one end of resistor R11, one end of resistor RC7, one end of capacitor C7, and one end of resistor R16. The other end of resistor R6 is connected to the sixth terminal of the control circuit. The other end of resistor R11 is connected to a 5V voltage. The other end of resistor RC7, capacitor C7, and resistor R16 are grounded. Pin 3 of the chip TL074 is connected to one end of resistor R10 and one end of resistor R9. The other end of resistor R10 is connected to one end of resistor R12 and pin 6 of the chip TL074. Pin 5 of the chip TL074 is connected to voltage VT. The other end of resistor R12 is connected to pin 7 of the chip TL074 and the output terminal of the frequency selection and signal amplification module. The other end of resistor R9 is connected to the seventh terminal of the control circuit. Pin 1 of the chip TL074 is connected to the input terminal of the feedback output module.

[0024] As a further embodiment of the present invention: the feedback output module includes a transistor Q2, the collector of transistor Q2 is connected to one end of resistor R7 and the seventh terminal of the control circuit, the other end of resistor R7 is connected to a 5V voltage, the emitter of transistor Q2 is grounded, the base of transistor Q2 is connected to one end of resistor RB and one end of resistor RA, the other end of resistor RB is grounded, and the other end of resistor RA is connected to the output terminal of the signal conversion module.

[0025] Compared with the prior art, the beneficial effects of the present invention are: the present invention can effectively and reliably detect liquid flow rate by monitoring the time interval between ultrasonic transmission and reception, the peripheral circuit is simple, highly portable, occupies few ports of the main chip, can be easily adapted to the main circuit, has low power consumption, and when the sensor is not needed, the host computer can turn off the transmission function by turning off the enable port. Attached Figure Description

[0026] Figure 1 This is a circuit diagram of an ultrasonic circuit for detecting liquid flow rate.

[0027] Figure 2 This is a schematic diagram illustrating the principle of ultrasonic detection of liquid flow rate. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0029] Please see Figure 1 An ultrasonic circuit for detecting liquid flow rate, comprising:

[0030] Communication port, used to establish communication between the control circuit and the host computer;

[0031] The control circuit is used to control the transmitting circuit to emit ultrasonic signals, receive ultrasonic signals fed back by the receiving circuit, obtain the time difference between ultrasonic emission and reception, and determine the flow rate and water velocity.

[0032] The transmitting circuit is used to receive control from the control circuit and emits ultrasonic signals during operation.

[0033] The receiving circuit is used to receive ultrasonic signals during operation and feed them back to the control circuit.

[0034] The communication port is connected to the first and second terminals of the control circuit; the third, fourth, and fifth terminals of the control circuit are connected to the transmitting circuit; and the receiving circuit is connected to the sixth and seventh terminals of the control circuit.

[0035] Please see Figure 2 The diameter of the pipe through which the liquid flows is D. The transmitting circuit (A in the figure) and the receiving circuit (B in the figure) are embedded in the pipe wall (specifically, the ultrasonic transmitter and ultrasonic receiver are embedded in the pipe wall), and the transmitting and receiving surfaces of the transmitting circuit and the receiving circuit (specifically, the ultrasonic transmitter and ultrasonic receiver) are completely facing each other. The distance between the transmitting and receiving surfaces of the transmitting circuit and the receiving circuit is L, and the speed of the liquid flow is Vm.

[0036] The angle between the vertical connecting line of the transmitting circuit and the receiving circuit and the tube body is Since the velocity gain of the ultrasonic waves generated by the liquid flow is Vm·cosφ, where φ does not change, the larger the liquid flow velocity Vm, the faster the receiving circuit receives the ultrasonic signal. Therefore, the liquid flow velocity can be calculated based on the time difference between sending and receiving the ultrasonic waves.

[0037] In this embodiment: Please refer to Figure 1 The communication port includes interface J1. The first end of interface J1 is grounded. The second and third ends of interface J1 are connected to the first and second ends of the control circuit, respectively. The third end of interface J1 is connected to a 5V voltage. Interface J1 is connected to an external host computer.

[0038] Interface J1 facilitates communication between the host computer and the control circuit. It can also be used as a power source for the circuit by introducing a 5V power supply.

[0039] In this embodiment: Please refer to Figure 1 The control circuit includes the STC11 chip. Pin 1 of the STC11 chip (the first end of the control circuit) is connected to the communication port and one end of resistor R3. Pin 2 of the STC11 chip (the second end of the control circuit) is connected to the communication port and one end of resistor R2. The other end of resistor R2 is connected to the other end of resistor R3 and a 5V voltage. Pins 12, 13, and 14 of the STC11 chip (the third, fourth, and fifth ends of the control circuit) are connected to the transmitting circuit. Pins 9 and 10 of the STC11 chip (the sixth and seventh ends of the control circuit) are connected to the receiving circuit.

[0040] The STC11 chip is an MCU, responsible for sending a 40kHz PWM to the transmitting circuit and parsing the 40kHz signal returned by the receiving circuit; the STC11 chip is externally connected to a crystal oscillator circuit consisting of capacitor C1, capacitor C6, and crystal oscillator Y1; resistors R2 and R3 are pull-up resistors for IIC communication (serial communication).

[0041] In this embodiment: Please refer to Figure 1 The transmitting circuit includes a MAX232 chip, an ultrasonic transmitter, and a transistor Q1. Pins 10 and 11 of the MAX232 chip are connected to the fourth and fifth terminals of the control circuit, pins 7 and 14 of the MAX232 chip are connected to the two ends of the ultrasonic transmitter, pin 16 of the MAX232 chip is connected to the emitter of the transistor Q1, the base of the transistor Q1 is connected to the third terminal of the control circuit, and the collector of the transistor Q1 is connected to a 5V voltage.

[0042] The MAX232 charge pump chip converts the 5V peak-to-peak PWM voltage pulse into a 20V peak-to-peak PWM voltage pulse and outputs it to the ultrasonic transmitter for transmission.

[0043] The MAX232 chip is a charge pump chip that can convert the +5V and 0V levels to +10V and -10V, thereby driving the ultrasonic transmitter more effectively. Capacitors C3 and C4 are flying capacitors, and capacitors C8 and C11 are energy storage capacitors, with the final output being ±10V. Transistor Q1 and resistor R5 form the charge pump enable drive circuit, which can turn off the MAX232 chip to save power when the ultrasonic transmitter is not working.

[0044] In this embodiment: Please refer to Figure 1 The receiving circuit includes:

[0045] The frequency selection and signal amplification module is used to amplify the received ultrasonic signal in two stages and output it to the signal conversion module;

[0046] The signal conversion module is used to convert the two-stage amplified ultrasonic signal into a digital signal and output it to the feedback output module.

[0047] The feedback output module is used to feed back voltage signals to the control circuit based on digital signals.

[0048] The output of the frequency selection and signal amplification module is connected to the input of the signal conversion module, the output of the signal conversion module is connected to the input of the feedback output module, and the output of the feedback output module is connected to the fifth and sixth terminals of the control circuit.

[0049] In this embodiment: Please refer to Figure 1 The frequency selection and signal amplification module includes a TL074 chip and an ultrasonic receiver. One end of the ultrasonic receiver is grounded, and the other end is connected to one end of resistor R17. The other end of resistor R17 is connected to one end of capacitor C15. The other end of capacitor C15 is connected to one end of resistor R18 and pin 13 of the TL074 chip. Pin 12 of the TL074 chip is connected to the voltage signal VT. Pin 14 of the TL074 chip is connected to the other end of resistor R18 and one end of resistor R19. The other end of resistor R19 is connected to one end of resistor R15, one end of capacitor C10, and one end of capacitor C12. The other end of resistor R15 is connected to pin 10 of the TL074 chip. The other end of capacitor C10 is connected to one end of resistor R14 and pin 9 of the TL074 chip. The other end of capacitor C12 is connected to the other end of resistor R14, pin 8 of the TL074 chip, and one end of resistor R13. The other end of resistor R13 is connected to one end of capacitor C9. The other end of capacitor C9 is connected to the input terminal of the signal conversion module.

[0050] In this embodiment: Please refer to Figure 1The signal conversion module includes a TL074 chip. Pin 2 of the TL074 chip is connected to one end of resistor R8. The other end of resistor R8 is connected to one end of resistor R6, one end of resistor R11, one end of resistor RC7, one end of capacitor C7, and one end of resistor R16. The other end of resistor R6 is connected to the sixth terminal of the control circuit. The other end of resistor R11 is connected to a 5V voltage. The other end of resistor RC7, capacitor C7, and resistor R16 are grounded. Pin 3 of the TL074 chip is connected to one end of resistor R10 and one end of resistor R9. The other end of resistor R10 is connected to one end of resistor R12 and pin 6 of the TL074 chip. Pin 5 of the TL074 chip is connected to voltage VT. The other end of resistor R12 is connected to pin 7 of the TL074 chip and the output terminal of the signal amplification module. The other end of resistor R9 is connected to the seventh terminal of the control circuit. Pin 1 of the TL074 chip is connected to the input terminal of the feedback output module.

[0051] In this embodiment: Please refer to Figure 1 The feedback output module includes transistor Q2. The collector of transistor Q2 is connected to one end of resistor R7 and the seventh terminal of the control circuit. The other end of resistor R7 is connected to a 5V voltage. The emitter of transistor Q2 is grounded. The base of transistor Q2 is connected to one end of resistor RB and one end of resistor RA. The other end of resistor RB is grounded. The other end of resistor RA is connected to the output terminal of the signal conversion module.

[0052] The TL074 chip contains four independent operational amplifiers, which select, amplify, and compare the received signal from the ultrasonic receiver before transmitting the PWM signal to the MCU.

[0053] Among them, resistors R17, R18, R19 and capacitor C15 are configured to provide a first-stage signal amplification factor of 4.7; resistors R13, R14, R15 and capacitors C9, C10, C12 are configured to provide a frequency selection circuit with a center frequency of 40kHz; resistors R10 and R15 are configured to provide a second-stage signal amplification factor of 37.5; resistors R8, R11, and R16 are configured to provide a comparator with a reference voltage of 2.5V; resistor R9 connects the positive input port (pin 3 of chip TL074) and the output port (pin 7 of chip TL074) of the comparator to form a Schmitt trigger; resistors Ra, Rb, R7 and transistor Q2 form the circuit for the amplifier to drive the MCU port; capacitors C7 and C16 are filter capacitors.

[0054] The ultrasonic receiver captures a 40kHz ultrasonic signal (modulated by the liquid flow rate) after propagation through the liquid. The signal is amplified 4.7 times by the first operational amplifier (R17 / R18 / R19 / C15) of the TL074 chip. A bandpass filter, composed of resistors R13, R14, R15 and capacitors C9, C10, and C12, with a center frequency set to 40kHz, filters out non-target frequency noise. The frequency-selected signal is further amplified 37.5 times by the second operational amplifier (R10 / R15). A third operational amplifier, acting as a comparator (reference voltage 2.5V, R8 / R11 / R16), converts the analog signal into a digital pulse. A hysteresis loop, formed by resistor R9, eliminates signal jitter and ensures waveform stability. Finally, a driver circuit composed of resistors Ra, Rb, R7, and transistor Q2 transmits the processed PWM signal to the STC11 chip for calculating the time difference and deriving the flow rate.

[0055] The working principle of this invention is as follows: the communication port is used to establish communication between the control circuit and the host computer; the control circuit is used to control the transmitting circuit to transmit ultrasonic signals, receive ultrasonic signals fed back by the receiving circuit, obtain the time difference between ultrasonic transmission and reception, and determine the flow rate and water speed; the transmitting circuit is used to receive the control of the control circuit and transmit ultrasonic signals during operation; the receiving circuit is used to receive ultrasonic signals during operation and feed them back to the control circuit.

[0056] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and not restrictive.

[0057] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An ultrasonic circuit for detecting liquid flow rate, characterized in that, The ultrasonic circuit for detecting liquid flow rate includes: Communication port, used to establish communication between the control circuit and the host computer; The control circuit is used to control the transmitting circuit to emit ultrasonic signals, receive ultrasonic signals fed back by the receiving circuit, obtain the time difference between ultrasonic emission and reception, and determine the flow rate and water velocity. The transmitting circuit is used to receive control from the control circuit and emits ultrasonic signals during operation. The receiving circuit is used to receive ultrasonic signals during operation and feed them back to the control circuit. The communication port is connected to the first and second terminals of the control circuit; the third, fourth, and fifth terminals of the control circuit are connected to the transmitting circuit; and the receiving circuit is connected to the sixth and seventh terminals of the control circuit. The diameter of the pipe through which the liquid flows is D. The transmitting and receiving circuits are embedded in the pipe wall, and the transmitting and receiving surfaces of the transmitting and receiving circuits are completely aligned. The distance between the transmitting and receiving surfaces of the transmitting and receiving circuits is L, and the speed of the liquid flow is Vm. The angle between the vertical connecting line of the transmitting circuit and the receiving circuit and the tube body is Since the velocity gain of the ultrasonic waves generated by the liquid flow is Vm·cosφ, where φ does not change, the larger the liquid flow velocity Vm, the faster the receiving circuit receives the ultrasonic signal. Therefore, the liquid flow velocity can be calculated based on the time difference between sending and receiving the ultrasonic waves.

2. The ultrasonic liquid flow rate detection circuit according to claim 1, characterized in that, The communication port includes interface J1. The first end of interface J1 is grounded. The second and third ends of interface J1 are connected to the first and second ends of the control circuit, respectively. The third end of interface J1 is connected to a 5V voltage. Interface J1 is connected to an external host computer.

3. The ultrasonic liquid flow rate detection circuit according to claim 1, characterized in that, The control circuit includes a chip STC11. Pin 1 of the chip STC11 is connected to the communication port and one end of resistor R3. Pin 2 of the chip STC11 is connected to the communication port and one end of resistor R2. The other end of resistor R2 is connected to the other end of resistor R3 and a 5V voltage. Pins 12, 13, and 14 of the chip STC11 are connected to the transmitting circuit. Pins 9 and 10 of the chip STC11 are connected to the receiving circuit.

4. The ultrasonic liquid flow rate detection circuit according to claim 1, characterized in that, The transmitting circuit includes a MAX232 chip, an ultrasonic transmitter, and a transistor Q1. Pins 10 and 11 of the MAX232 chip are connected to the fourth and fifth pins of the control circuit, pins 7 and 14 of the MAX232 chip are connected to the two ends of the ultrasonic transmitter, pin 16 of the MAX232 chip is connected to the emitter of the transistor Q1, the base of the transistor Q1 is connected to the third terminal of the control circuit, and the collector of the transistor Q1 is connected to a 5V voltage.

5. The ultrasonic liquid flow rate detection circuit according to any one of claims 1 to 4, characterized in that, The receiving circuit includes: The frequency selection and signal amplification module is used to amplify the received ultrasonic signal in two stages and output it to the signal conversion module; The signal conversion module is used to convert the two-stage amplified ultrasonic signal into a digital signal and output it to the feedback output module. The feedback output module is used to feed back voltage signals to the control circuit based on digital signals. The output of the frequency selection and signal amplification module is connected to the input of the signal conversion module, the output of the signal conversion module is connected to the input of the feedback output module, and the output of the feedback output module is connected to the fifth and sixth terminals of the control circuit.

6. The ultrasonic liquid flow rate detection circuit according to claim 5, characterized in that, The frequency selection and signal amplification module includes a TL074 chip and an ultrasonic receiver. One end of the ultrasonic receiver is grounded, and the other end is connected to one end of resistor R17. The other end of resistor R17 is connected to one end of capacitor C15. The other end of capacitor C15 is connected to one end of resistor R18 and pin 13 of the TL074 chip. Pin 12 of the TL074 chip is connected to the voltage signal VT. Pin 14 of the TL074 chip is connected to the other end of resistor R18 and one end of resistor R19. The other end of resistor R19 is connected to one end of resistor R15, one end of capacitor C10, and one end of capacitor C12. The other end of resistor R15 is connected to pin 10 of the TL074 chip. The other end of capacitor C10 is connected to one end of resistor R14 and pin 9 of the TL074 chip. The other end of capacitor C12 is connected to the other end of resistor R14, pin 8 of the TL074 chip, and one end of resistor R13. The other end of resistor R13 is connected to one end of capacitor C9. The other end of capacitor C9 is connected to the input terminal of the signal conversion module.

7. The ultrasonic liquid flow rate detection circuit according to claim 5, characterized in that, The signal conversion module includes a TL074 chip. Pin 2 of the TL074 chip is connected to one end of resistor R8. The other end of resistor R8 is connected to one end of resistor R6, one end of resistor R11, one end of resistor RC7, one end of capacitor C7, and one end of resistor R16. The other end of resistor R6 is connected to the sixth terminal of the control circuit. The other end of resistor R11 is connected to a 5V voltage. The other end of resistor RC7, capacitor C7, and resistor R16 are grounded. Pin 3 of the TL074 chip is connected to one end of resistor R10 and one end of resistor R9. The other end of resistor R10 is connected to one end of resistor R12 and pin 6 of the TL074 chip. Pin 5 of the TL074 chip is connected to voltage VT. The other end of resistor R12 is connected to pin 7 of the TL074 chip and the output terminal of the frequency selection and signal amplification module. The other end of resistor R9 is connected to the seventh terminal of the control circuit. Pin 1 of the TL074 chip is connected to the input terminal of the feedback output module.

8. The ultrasonic liquid flow rate detection circuit according to claim 5, characterized in that, The feedback output module includes transistor Q2. The collector of transistor Q2 is connected to one end of resistor R7 and the seventh terminal of the control circuit. The other end of resistor R7 is connected to a 5V voltage. The emitter of transistor Q2 is grounded. The base of transistor Q2 is connected to one end of resistor RB and one end of resistor RA. The other end of resistor RB is grounded. The other end of resistor RA is connected to the output terminal of the signal conversion module.

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