Gas meter current control circuit based on M-Bus communication

Abstract

The utility model discloses a gas meter current control circuit based on M-Bus communication, which is characterized by comprising a transmitting end circuit and a receiving end circuit, the transmitting end circuit is connected with a single chip microcomputer, the receiving end circuit is connected with the transmitting end circuit through an M-Bus communication bus, the transmitting end circuit is used for converting a transmitting signal of the single chip microcomputer into a current signal, and the receiving end circuit is connected with the receiving end circuit through the M-Bus communication bus. And the receiving end circuit is used for detecting the current signal change and decoding the current signal change into a digital signal. Compared with the prior art, the gas meter current control circuit based on the M-Bus communication has the advantages that the gas meter current control circuit based on the M-Bus communication is carried out in a two-wire system communication mode, corresponding level signals are converted and modulated through current signals, the stability of signal transmission is improved, and the anti-interference capacity is improved.

Description

Technical Field

[0001] The utility model relates to a gas meter signal circuit, in particular to a gas meter current control circuit based on M-Bus communication. Background Art

[0002] Gas meter communication control is a key link in the intelligent gas meter system. Currently, the four-wire communication method based on RS-485 is widely used in the market. This communication method has been used in the field of industrial automation and instrument control for many years and has high reliability and anti-interference ability.

[0003] The existing RS-485 four-wire communication system uses two wires, VCC and GND, to power the device, and uses two wires, TX and RX, to send and receive data respectively. This communication method uses the Modbus protocol for data transmission, which can achieve multi-point communication and long-distance data transmission. In actual applications, the four wires are connected to the corresponding interfaces of the microcontroller to form a complete communication loop.

[0004] However, the existing four-wire RS-485 communication method has obvious limitations in gas meter applications. First, gas meters are usually installed in special locations in residential buildings, such as kitchen corners, pipe wells and other small spaces, and the wiring space is very limited. The layout of four communication lines not only increases the difficulty of installation, but also easily causes communication failures due to line aging or external force damage. Secondly, more lines mean more wiring terminals and connection points, which not only increases the installation cost, but also increases the workload of later maintenance.

[0005] Especially when renovating old residential areas or installing smart gas meters in existing buildings, the original pipeline layout often cannot meet the wiring requirements of four-wire communication. Adding new lines is not only difficult to construct, but may also affect the appearance and safety of the building. In addition, the material cost and construction cost of four wires are relatively high, which will significantly increase the total project investment when applied on a large scale.

[0006] Therefore, the M-BUS two-wire communication method only requires two wires, VCC and GND, to complete the power supply and data transmission functions at the same time, which not only greatly simplifies the wiring project, but also reduces the installation and maintenance costs. However, to realize this communication method, it is necessary to solve the problems of signal modulation and interference suppression when the power supply and data transmission share two wires. Utility Model Content

[0007] The purpose of the utility model is to provide a gas meter current control circuit based on M-Bus communication. This circuit uses a two-wire communication method to convert and modulate the corresponding level signal through the current signal, thereby improving the stability of the transmission signal and improving the anti-interference ability.

[0008] The above technical objectives of the utility model are achieved through the following technical solutions:

[0009] A gas meter current control circuit based on M-Bus communication, characterized in that it includes a transmitting end circuit and a receiving end circuit, wherein the transmitting end circuit is connected to a single-chip microcomputer, and the receiving end circuit is connected to the transmitting end circuit through an M-Bus communication bus, the transmitting end circuit is used to convert a transmission signal of the single-chip microcomputer into a current signal, and the receiving end circuit is used to detect a change in the current signal and decode it into a digital signal; wherein:

[0010] The transmitting end circuit includes: the input end TXD1 is connected to the single-chip microcomputer for receiving the serial port transmission signal; the transistor Q5 is connected in series with the input end for controlling the current on and off according to the high and low levels of the input signal; the transistor Q1 is connected in parallel with the transistor Q5 for controlling the switch of the main current signal according to the collector voltage of the transistor Q5; the power supply V+ provides the main current signal for the transistor Q1, and the main current forms a current signal through the voltage divider resistor R4 and is transmitted to the receiving end circuit;

[0011] The receiving end circuit includes: the power supply VCC-40V is connected to the communication bus MBUS+ through the current limiting resistor R5 and the filter inductor L1; the comparison resistor R40 and the comparison resistor R41 are connected to the voltage comparator U5, which is used to detect the change of the current signal and convert it into a voltage signal; the AND gate logic chip U4 is connected to the voltage comparator output, which is used for logic processing and outputting digital signals to the receiving end of the microcontroller.

[0012] The utility model is further configured as follows: the transistor Q5 in the transmitting end circuit is an NPN transistor, the base of which is connected to the input end TXD1 through a current limiting resistor R21, and is turned on when the input signal is at a high level, and is turned off when the input signal is at a low level.

[0013] The utility model is further configured as follows: the transistor Q1 in the transmitting end circuit is an NPN transistor, the base of which is controlled by the collector voltage of the transistor Q5. When the transistor Q5 is turned off, the transistor Q1 is turned on to form a main current signal.

[0014] The utility model is further configured as follows: the filter inductor L1 in the receiving end circuit is used to suppress high-frequency interference signals, and the filter inductor L1 is connected to a fuse F1 for disconnecting the circuit to protect components when the current exceeds 145mA.

[0015] The utility model is further configured as follows: the voltage comparator U5 in the receiving end circuit is a LM393 comparator, whose inverting end is connected to a comparison resistor R40, and whose non-inverting end is connected to a comparison resistor R41, so as to realize level detection of the input signal.

[0016] The utility model is further configured as follows: the AND gate logic chip U4 in the receiving end circuit is used to perform logic processing on the output signal of the voltage comparator, and is connected with a pull-up resistor R35 to output a digital signal to the receiving end of the single-chip microcomputer.

[0017] In summary, the utility model has the following beneficial effects:

[0018] The two-wire current control circuit based on M-Bus communication designed in this application optimizes the communication method of the gas meter by integrating the power supply function and the data transmission function on two communication lines. Compared with the traditional RS-485 four-wire communication method, this application has certain advantages in wiring, cost, power consumption and reliability. By reducing the number of communication cables, the circuit simplifies the wiring project, which is especially suitable for gas meter installation scenarios with limited space, significantly reducing the installation complexity and construction costs. In addition, the circuit design abandons the reliance on dedicated gas communication chips and adopts simple and efficient discrete components, further reducing hardware and maintenance costs.

[0019] This circuit achieves signal transmission by controlling the change of current. Compared with the voltage signal method, the current signal has stronger anti-interference ability and can ensure the stability and reliability of communication in complex environments. At the same time, it adopts a low-power design and consumes almost no current in the non-communication state, which significantly improves the overall energy efficiency. The receiving end detects the signal through the current change and uses the voltage comparator and logic processing unit to achieve efficient signal decoding. The entire communication process does not require complex signal processing algorithms, making the decoding circuit more flexible and easy to implement.

[0020] In addition, M-Bus communication supports long-distance signal transmission. The circuit design can meet the application requirements of remote meter reading and adapt to the expansion of various smart metering devices such as gas meters, water meters, and electricity meters. The combination of data transmission and power supply functions further improves the integration of the equipment, reduces the design requirements of additional interfaces, and enhances the overall reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the circuit diagram of the sending end;

[0022] Figure 2 This is the circuit diagram of the receiving end. DETAILED DESCRIPTION

[0023] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "page", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0024] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0025] In the description of the present utility model, "multiple" means two or more than two, unless otherwise clearly specified and specifically defined. In the present utility model, unless otherwise clearly specified and defined, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to the specific circumstances.

[0026] The utility model is further described in detail below in conjunction with the accompanying drawings.

[0027] A gas meter current control circuit based on M-Bus communication comprises a sending end circuit and a receiving end circuit.

[0028] like Figure 1 As shown, the transmitting end circuit includes an input terminal TXD1. The input terminal TXD1 is connected to the port of the single-chip microcomputer and is used to provide a serial port transmission signal, and the signal can be a high level or a low level.

[0029] The input terminal TXD1 is connected in series with a resistor R21. The resistor R21 is connected to a transistor Q5. The resistor R21 is used to limit the current input from TXD1 to the transistor Q5, thereby protecting the transistor Q5. The transistor Q5 is a first-stage switch for controlling the current, and is controlled by a signal from the input terminal TXD1. When a high level is input to TXD1, Q5 is turned on, and when a low level is input to TXD1, Q5 is turned off.

[0030] One end of transistor Q5 is grounded, and the other end is connected to resistor R5. Resistor R5 is connected to a 3.3V power supply VCC. Resistor R5 is used to limit the collector current passing through Q5, thereby protecting transistor Q5. Transistor Q5 is connected in parallel with transistor Q1. Transistor Q1 serves as a second-stage switch and is controlled by the collector voltage of Q5.

[0031] One end of the collector of transistor Q1 is connected to resistor R4, and the other end is grounded. Resistor R4 is connected to power supply V+. V+ is 40V. Resistor R4 is used to divide voltage and current to protect transistor Q1. On the other hand, it is used to form a load current signal when Q1 is turned on and transmitted to the receiving end circuit.

[0032] When TXD1 is at a high level, R21 transmits the signal to the base of transistor Q5 (NPN type), Q5 is turned on, and the current flows from the power supply VCC through the current limiting resistor R9 (1kΩ) into the collector of Q5, and then connects to the ground through the emitter. At this time, the collector voltage of Q5 is close to 0V, and the base voltage of Q1 (NPN type) is also close to 0V, so Q1 is cut off, no current flows through R4 (300Ω), and only R9 and Q5 consume a small static current in the overall circuit.

[0033] When TXD1 is low, R21 transmits the low-level signal to the base of Q5, Q5 is cut off, no current flows between R9 and Q5, and the collector voltage of Q5 is pulled up to the voltage of VCC3.3. At this time, the base of Q1 is pulled to a high level through the collector of Q5, Q1 is turned on, and the current flows from +V through R4 into the collector of Q1, and then through the emitter of Q1 to ground. At this time, the current consumed by R4 is 133mA.

[0034] The above transmitting end circuit completes the switching control of the R4 current by controlling the high and low level signals of TXD1.

[0035] like Figure 2 As shown, the receiving end circuit includes a power supply VCC-40V. The power supply is connected to a current limiting resistor R5. The resistor R5 is connected to a filter inductor L1 and a fuse F1. The fuse F1 is connected to an interface CON1. ​​Among them, the interface CON1 is used to connect to an external communication bus, that is, the current signal of the transmitting end circuit is input through the interface CON1. ​​The fuse F1 is limited to 145mA to prevent the current overload from burning the components. The filter inductor L1 is used to eliminate high-frequency noise and ensure the stability of the current communication signal. The current limiting resistor R5 is used to limit the current of the communication bus MBUS+, thereby protecting the subsequent circuits.

[0036] The receiving end circuit also includes a comparison resistor R40 and a comparison resistor R41 connected in parallel with the above-mentioned current limiting resistor R5. R40 and R41 are connected in parallel with a voltage comparator U5. The voltage comparator U5 has a plurality of pins, wherein pin 1 is an output terminal, pin 2 is connected to the comparison resistor R40, and pin 3 is connected to the comparison resistor R41. Among them, pin 2 is an inverting terminal, and pin 3 is a non-inverting terminal. Pin 2 is connected in parallel with a capacitor C17. Capacitor C17 is used to maintain the voltage level of the inverting terminal when the current signal changes instantaneously.

[0037] Pin 1 of the voltage comparator U5 is connected to an AND gate logic chip U4. U4 is used to perform logic processing on the output signal of the voltage comparator U5 and output the final digital signal to the single chip microcomputer.

[0038] The above receiving circuit realizes signal reception by detecting the current change in the M-Bus communication circuit. The VCC-40V voltage at the input end enters the communication bus MBUS+ through the current limiting resistor R5, and after passing through the filter inductor L1 and the fuse F1, enters the sending circuit or remains in standby state.

[0039] When the transmitting end is at a low level, R4 consumes 133mA of current, and the main current flows from VCC-40V through R5 and L1 into R4 at the transmitting end, forming an obvious current change. At this time, the voltage flowing through R40 and R41 decreases, and after voltage division, the signal voltage at the in-phase end (1IN+) decreases, causing the voltage comparator U5 to output a low level. The output of the voltage comparator U5 enters the AND gate logic chip U4, and finally outputs a low level to MBUS_RX through the pull-up resistor R35.

[0040] When the transmitting end is at a high level, R4 consumes no current, the main current is basically zero, and the voltage divider circuit increases the voltage at the in-phase end of LM393, outputs a high level, and finally MBUS_RX outputs a high level to the MCU RX pin. The entire circuit converts the current signal change into a digital signal output through current limiting, filtering and logic processing.

[0041] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but such modifications are protected by patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A gas meter current control circuit based on M-Bus communication, characterized in that: It includes a transmitting circuit and a receiving circuit, wherein the transmitting circuit is connected to a single-chip microcomputer, and the receiving circuit is connected to the transmitting circuit via an M-Bus communication bus. The transmitting circuit is used to convert the transmission signal of the single-chip microcomputer into a current signal, and the receiving circuit is used to detect the change of the current signal and decode it into a digital signal; wherein: The sending end circuit includes: The input terminal TXD1 is connected to the microcontroller to receive the signal sent by the serial port; Transistor Q5 is connected in series with the input terminal to control the current on and off according to the high and low levels of the input signal; The transistor Q1 is connected in parallel with the transistor Q5, and is used to control the switch of the main current signal according to the collector voltage of the transistor Q5; The power supply V+ provides the main current signal to the transistor Q1, and the main current forms a current signal through the voltage divider resistor R4 and is transmitted to the receiving end circuit; The receiving circuit includes: The power supply VCC-40V is connected to the communication bus MBUS+ through the current limiting resistor R5 and the filter inductor L1; The comparison resistor R40 and the comparison resistor R41 are connected to the voltage comparator U5 to detect the change of the current signal and convert it into a voltage signal; The AND gate logic chip U4 is connected to the voltage comparator output for logic processing and outputting digital signals to the receiving end of the microcontroller.

2. The gas meter current control circuit based on M-Bus communication according to claim 1, characterized in that: The transistor Q5 in the transmitting end circuit is an NPN transistor, the base of which is connected to the input end TXD1 through a current limiting resistor R21, and is turned on when the input signal is at a high level, and is turned off when the input signal is at a low level.

3. The gas meter current control circuit based on M-Bus communication according to claim 1, characterized in that: The transistor Q1 in the transmitting end circuit is an NPN transistor, and its base is controlled by the collector voltage of the transistor Q5. When the transistor Q5 is turned off, the transistor Q1 is turned on to form a main current signal.

4. The gas meter current control circuit based on M-Bus communication according to claim 1, characterized in that: The filter inductor L1 in the receiving end circuit is used to suppress high-frequency interference signals. The filter inductor L1 is connected to a fuse F1 for disconnecting the circuit to protect components when the current exceeds 145 mA.

5. The gas meter current control circuit based on M-Bus communication according to claim 1, characterized in that: The voltage comparator U5 in the receiving end circuit is a LM393 comparator, whose inverting end is connected to a comparison resistor R40 and whose non-inverting end is connected to a comparison resistor R41, so as to realize level detection of the input signal.

6. The gas meter current control circuit based on M-Bus communication according to claim 1, characterized in that: The AND gate logic chip U4 in the receiving end circuit is used to perform logic processing on the output signal of the voltage comparator, and is connected to the pull-up resistor R35 to output the digital signal to the receiving end of the single-chip microcomputer.

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