A pre-I / O signal conditioning circuit for an industrial optical bus control system

Abstract

The application discloses a pre-I / O signal conditioning circuit for an industrial optical bus control system, which comprises a channel module, an A / D converter, an MCU, a D / A converter and a power supply; the channel module comprises a control output circuit, a voltage-to-current circuit, a current-to-voltage circuit and two wiring terminals, the two wiring terminals are C terminal and D terminal respectively, the C terminal and the D terminal are connected with the current-to-voltage circuit, the MCU is connected with the control output circuit, the control output circuit is connected with the power supply, the control output circuit and the voltage-to-current circuit are connected with the current-to-voltage circuit, the D / A converter is connected with the voltage-to-current circuit, and the current-to-voltage circuit is connected with the A / D converter. The problems of many wiring terminals and complex wiring are solved, and wiring is facilitated.

Description

Technical Field

[0001] This application relates to the field of industrial automation control, and in particular to a front-end I / O signal conditioning circuit for an industrial optical bus control system. Background Technology

[0002] Industrial optical bus control systems are primarily designed for the application needs of ultra-large projects in the process industry and can be applied to DCS and SCADA scenarios.

[0003] Distributed control systems (DCS) are a new generation of instrument control systems based on microprocessors. They employ the design principles of decentralized control functions, centralized display and operation, and consideration of both decentralized autonomy and comprehensive coordination.

[0004] DCS systems are widely used in industrial automation control. As the field control devices in industrial automation control become increasingly complex, the types of modules required for DCS systems are also increasing. Modules in a DCS system are generally defined according to the type of external input signals, and can typically be categorized as 8-channel analog input modules, 16-channel analog input modules, 8-channel analog output modules, 16-channel analog output modules, 16-channel digital input modules, 32-channel digital input modules, 16-channel digital output modules, and 32-channel digital output modules.

[0005] In actual application scenarios, a set of equipment often only has a dozen or so instruments, and these instruments have digital input (DI), digital output (DO), analog input (AI), and analog output (AO) signals that need to be connected to the DCS.

[0006] See attached document Figure 1 Existing analog input (AI) modules include an MCU, power supply, ADC, and channel components. When wiring a four-wire analog device, terminals B and D need to be connected. The output current of the four-wire analog device first passes through terminal B, then through the sampling resistor, and finally flows back to its internal components from terminal D. When wiring a two-wire analog device, terminals A and B need to be connected. The power supply for the two-wire analog device is provided by the module, so the current flows out from terminal A, then through the external device, then through terminal B, then through the sampling resistor, and finally flows back to the module.

[0007] Reference Figure 2 Existing analog output (AO) modules include an MCU, power supply, DAC, and channel components. When wiring the device, it is necessary to connect to terminals B and D. The analog current signal flows out from terminal B, then through the external device, then through terminal D, and finally flows back into the module.

[0008] Reference Figure 3 Existing digital input (DI) modules include an MCU, power supply, and channel components. External devices are mainly categorized into wet contact and dry contact types. For wet contact devices, wiring requires connecting to terminals C and D. The device has an internal power supply; the output current first passes through terminal C, then through the module's internal detection circuit, and finally returns to the module from terminal D. For dry contact devices, wiring requires connecting to terminals A and C. The module needs to provide an excitation current to the external device. This excitation current flows out from terminal A, through the external device, then through terminal C, then through the detection circuit, and finally returns to the module.

[0009] Reference Figure 4 Existing digital output (DO) modules include an MCU, a power supply, and a channel section. When wiring devices, both the C and D terminals need to be connected. When an external device requires power or excitation current from the module, the current first flows through the control output circuit, then through the C terminal, then through the external device, then through the D terminal, and finally back into the module.

[0010] In this situation, 4 to 6 modules are often needed to meet the actual functional requirements, but most modules only use 2 to 4 channels, resulting in a serious waste of hardware resources. Furthermore, due to the different functions of the modules, there are many external input signal terminals, and the terminal definitions for each input signal are different, leading to a complex wiring method, which needs improvement. Summary of the Invention

[0011] To address the shortcomings of existing technologies, this application provides a front-end I / O signal conditioning circuit for industrial optical bus control systems, aiming to solve the aforementioned problems.

[0012] A front-end I / O signal conditioning circuit for an industrial optical bus control system includes:

[0013] Channel module, used to connect external devices;

[0014] An A / D converter is used to acquire the voltage of the channel module;

[0015] The MCU is used to read the data converted by the A / D converter and write data to the D / A converter.

[0016] A D / A converter is used to convert data written to the MCU into analog voltage;

[0017] Power supply, used to power the A / D converter, D / A converter and MCU;

[0018] Each channel module includes a control output circuit, a voltage-to-current circuit, a current-to-voltage circuit, and two terminals, namely terminal C and terminal D. Both terminal C and terminal D are connected to the current-to-voltage circuit. The MCU is connected to the control output circuit, which is connected to the power supply. Both the control output circuit and the voltage-to-current circuit are connected to the current-to-voltage circuit. The D / A converter is connected to the voltage-to-current circuit, and the current-to-voltage circuit is connected to the A / D converter.

[0019] Optionally, the channel module further includes a protection circuit, and the C-terminal and D-terminal are connected to the protection circuit.

[0020] Optionally, the channel module further includes a switch S1 and two connecting contacts, including contact one and contact two. Contact one is connected to the MCU, and contact two is connected to the power supply. The switch S1 is located between the protection circuit and the current-to-voltage circuit.

[0021] Optionally, the channel module has 16 channels.

[0022] Optionally, the channel module has 32 channels.

[0023] This application also provides a wiring method for a front-end I / O signal conditioning circuit in an industrial optical bus control system, as detailed below:

[0024] When the external device is a four-wire analog input device, close the switch S1 inside the channel module on contact one. The channel module enables the current to voltage conversion circuit, and closes the voltage to current conversion circuit and the control output circuit. The current of the four-wire device flows from terminal C into the whole module, then through the current to voltage conversion circuit, and finally back to the external device through terminal D.

[0025] When the external device is an analog output device, the switch S1 inside the channel needs to be closed on contact one. The channel module enables the voltage to current conversion circuit, closes the current to voltage conversion circuit and the control output circuit. The analog output device is powered by the module's power supply. Therefore, the current flows through the voltage to current conversion circuit, then through terminal C, then through the external device, and finally through terminal D back into the overall module.

[0026] When the external device is a digital wet contact device, the switch S1 inside the channel module needs to be closed on contact one. The channel enables the current to voltage conversion circuit, and disables the voltage to current conversion circuit and the control output circuit. The output signal of the external device is provided by the power supply inside the device. The current is input into the module through the C terminal, then through the current to voltage conversion circuit, and finally flows back to the external device through the D terminal.

[0027] When the external device is a digital dry contact device, the switch S1 inside the channel module needs to be closed on contact one. The channel module enables the current-to-voltage circuit and the voltage-to-current circuit, and closes the control output circuit. The output signal of the external device requires the module to provide an excitation current. The excitation current is provided by the voltage-to-current circuit. The current is output from the C terminal to the external device through the voltage-to-current circuit, and finally flows back to the overall module through the D terminal.

[0028] When the external device is a digital output device, the switch S1 inside the channel module needs to be closed on contact one. The channel module enables the control output circuit and closes the current-to-voltage circuit and the voltage-to-current circuit. The digital output device is powered by the module's power supply. Therefore, the current flows through the control output circuit, then through terminal C, then through the external device, and finally back to the entire module through terminal D.

[0029] When the external device is a two-wire analog input device, the switch S1 inside the channel module is closed at contact two, the channel enables the current to voltage conversion circuit, and closes the voltage to current conversion circuit and the control output circuit. The two-wire device is powered by the module's power supply, so the current flows out from terminal D, then through the external device, and then back to the entire module through terminal C.

[0030] In summary, this application includes at least one of the following beneficial technical effects:

[0031] 1. It solves the problem of complex module types, improves the versatility of modules, reduces the overall hardware cost, thereby saving production costs, reducing management costs, and lowering maintenance costs.

[0032] 2. To solve the problems of multiple terminals and complex wiring, the four terminals A, B, C, and D are reduced to two terminals C and D, making wiring easier and saving time and effort. Attached Figure Description

[0033] Figure 1 This is a structural block diagram of the connection between analog input devices and modules in the existing technology.

[0034] Figure 2 This is a structural block diagram of the connection between analog output devices and modules in the existing technology.

[0035] Figure 3 This is a structural block diagram of the connection between digital input devices and modules in the existing technology.

[0036] Figure 4 This is a structural block diagram of the connection between digital output devices and modules in the existing technology.

[0037] Figure 5 This is a structural block diagram of an embodiment of this application.

[0038] Figure 6 This is a structural block diagram of the wiring method of the four-wire analog input device in the embodiments of this application.

[0039] Figure 7 This is a structural block diagram of the wiring method for analog output devices in the embodiments of this application.

[0040] Figure 8 This is a structural block diagram of the wiring method of the digital wet contact input device in the embodiments of this application.

[0041] Figure 9 This is a structural block diagram of the wiring method of the digital dry contact input device in the embodiments of this application.

[0042] Figure 10 This is a structural block diagram of the wiring method of the digital output device in the embodiments of this application.

[0043] Figure 11 This is a structural block diagram of the wiring method for a two-wire analog input device in an embodiment of this application.

[0044] Figure 12 This is a circuit diagram of the protection circuit in an embodiment of this application.

[0045] Figure 13 This is a circuit diagram of the control output circuit in an embodiment of this application.

[0046] Figure 14 This is a circuit diagram of the voltage-to-current conversion circuit in the embodiments of this application.

[0047] Figure 15 This is a circuit diagram of the current-to-voltage conversion circuit in the embodiments of this application.

[0048] Figure 16 This is a circuit diagram of switch S1 in an embodiment of this application. Detailed Implementation

[0049] To facilitate understanding of this application, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the application. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0050] This application discloses a front-end I / O signal conditioning circuit for an industrial optical bus control system. (Refer to...) Figure 5The system includes channel modules, an A / D converter, an MCU, a D / A converter, and a power supply. The channel modules connect to external devices; the A / D converter acquires the voltage from the channel modules; the MCU reads the converted data from the A / D converter and writes data to the D / A converter; the D / A converter converts the data written by the MCU into analog voltage; and the power supply powers the A / D converter, D / A converter, and MCU. Each channel module includes a control output circuit, a voltage-to-current conversion circuit, a protection circuit, a current-to-voltage conversion circuit, and two terminals, designated C and D. Both C and D are connected to the current-to-voltage conversion circuit. The MCU is connected to the control output circuit, which is connected to the power supply. Both the control output circuit and the voltage-to-current conversion circuit are connected to the current-to-voltage conversion circuit. The D / A converter is connected to the voltage-to-current conversion circuit, and the current-to-voltage conversion circuit is connected to the A / D converter. The protection circuit is connected to both C and D terminals. Preferably, the number of channel modules can be set to 16 or 32, depending on actual needs.

[0051] Reference Figure 5 The channel module also includes a switch S1 and two connection contacts, namely contact one and contact two. Contact one is connected to the MCU, and contact two is connected to the power supply. Switch S1 is positioned between the protection circuit and the current-to-voltage circuit. Users can adjust switch S1 according to the type of external device connected, so that switch S1 contacts one of the connection contacts, thereby enabling the channel module to adapt to different external devices.

[0052] This application also provides a wiring method for a front-end I / O signal conditioning circuit in an industrial optical bus control system, as detailed below:

[0053] Reference Figure 5 and Figure 6 When the external device is a four-wire analog input device, the switch S1 inside the channel module is closed on contact one. The channel module enables the current to voltage circuit, closes the voltage to current circuit and the control output circuit. The current of the four-wire device flows from terminal C into the whole module, then through the current to voltage circuit, and finally flows back to the external device through terminal D.

[0054] Reference Figure 5 and Figure 7 When the external device is an analog output device, the switch S1 inside the channel needs to be closed on contact one. The channel module enables the voltage to current conversion circuit, closes the current to voltage conversion circuit and the control output circuit. The analog output device is powered by the module's power supply. Therefore, the current flows through the voltage to current conversion circuit, then through terminal C, then through the external device, and finally through terminal D back into the overall module.

[0055] Reference Figure 5 and Figure 8 When the external device is a digital wet contact device, the switch S1 inside the channel module needs to be closed on contact one. The channel enables the current to voltage circuit, and disables the voltage to current circuit and the control output circuit. The output signal of the external device is provided by the power supply inside the device. The current is input into the module through the C terminal, then through the current to voltage circuit, and finally flows back to the external device through the D terminal.

[0056] Reference Figure 5 and Figure 9 When the external device is a digital dry contact device, the switch S1 inside the channel module needs to be closed on contact one. The channel module enables the current to voltage circuit and the voltage to current circuit, and closes the control output circuit. The output signal of the external device needs the module to provide an excitation current. The excitation current is provided by the voltage to current circuit. The current is output from the C terminal to the external device through the voltage to current circuit, and finally flows back to the whole module through the D terminal.

[0057] Reference Figure 5 and Figure 10 When the external device is a digital output device, the switch S1 inside the channel module needs to be closed on contact one. The channel module enables the control output circuit and closes the current-to-voltage circuit and voltage-to-current circuit. The digital output device is powered by the module's power supply. Therefore, the current flows through the control output circuit, then through terminal C, then through the external device, and finally back to the overall module through terminal D.

[0058] Reference Figure 5 and Figure 11 When the external device is a two-wire analog input device, the switch S1 inside the channel module is closed on contact two, the channel enables the current to voltage conversion circuit, and closes the voltage to current conversion circuit and the control output circuit. The two-wire device is powered by the module's power supply, so the current flows out from the D terminal, then through the external device, and then back to the overall module through the C terminal.

[0059] Reference Figure 12 The protection circuit includes diode DZ1 and capacitor C1. One end of diode DZ1 is connected to terminal C and the other end is connected to terminal D. One end of capacitor C1 is connected to terminal C and the other end is connected to terminal D. The protection circuit is used to protect other internal circuits from damage. Diode DZ1 can provide protection when the external input voltage is too high.

[0060] Reference Figure 13The control output circuit includes resistors R1, R3, and R5, a field-effect transistor Q2, and a transistor Q3. One end of resistor R1 is connected to the power supply, and the other end is connected to resistor R3. The drain of the field-effect transistor Q2 is connected to the collector (C) terminal, the source is connected to the power supply, and the gate is connected to resistor R3. One end of resistor R5 is connected to the CH DO port of the MCU, and the other end is connected to the base of the transistor Q3. The emitter of the transistor Q3 is grounded. The control output circuit is a digital output used to control external digital output devices, mainly for controlling the power supply and de-energization of external devices. When the CH DO port is high, the power supply in the module is output at the collector (C); when the CH DO port is low, the voltage output at the collector (C) is 0.

[0061] Reference Figure 14 The voltage-to-current conversion circuit includes chip U2, resistor R2, operational amplifiers U1A and U1B, resistors RJ1, RJ2, RJ3, and R4, transistors Q1 and Q4. One end of resistor R2 is connected to pin 5 of chip U2, and the other end is connected to the positive input terminal of operational amplifier U1A. The negative input terminal of operational amplifier U1A is connected to the emitter of transistor Q4, and its output terminal is connected to the base of transistor Q4. The collector of transistor Q4 is connected to the first end of resistor RJ2, and the second end of resistor RJ2 is connected to the power supply. One end of resistor RJ3 is grounded, and the other end is connected to the emitter of transistor Q4. The positive input terminal of operational amplifier U1B is connected to the collector of transistor Q4, its negative input terminal is connected to the first end of resistor RJ1, and its output terminal is connected to the first end of resistor R4. The second end of resistor R4 is connected to the base of transistor Q1. The collector of transistor Q1 is connected to terminal C, and the emitter is connected to the first terminal of resistor RJ1. The second terminal of resistor RJ1 is connected to the power supply.

[0062] Reference Figure 15 The current-to-voltage circuit includes chip U4, field-effect transistor Q6, resistors R7, R8, and R9. One end of resistor R7 is connected to the C terminal and the other end is connected to pin 4 of chip U4. One end of resistor R8 is connected to the C terminal and the other end is connected to the drain of field-effect transistor Q6. Resistor R9 is connected to the CH AI port of the MCU and the other end is connected to the gate of field-effect transistor Q6. Pin 5 of chip U4 is connected to the source of field-effect transistor Q6.

[0063] Reference Figure 16The circuit for switch S1 includes resistors R10, R11, R12, and R13, a field-effect transistor (FET) Q7, a transistor Q8, and an FET Q9. One end of resistor R12 is connected to the CH / VCC port of the MCU, and the other end is connected to the base of transistor Q8. The collector of transistor Q8 is connected to the first end of resistor R11, and the emitter of transistor Q8 is grounded. The second end of resistor R11 is connected to the gate of FET Q7. One end of resistor R10 is connected to the power supply, and the other end is connected to the second end of resistor R11. The drain of FET Q7 is connected to the D terminal, and the source is connected to the power supply. The drain of FET Q9 is connected to the D terminal, and the source is grounded. One end of resistor R13 is connected to the CH / GND port of the MCU, and the other end is connected to the gate of FET Q9.

[0064] The current-to-voltage circuit is mainly used to acquire 4-20mA analog signals.

[0065] When acquiring a 4-20mA four-wire signal, the CH AI port must first be set to high level to ensure Q6 is fully conducting. Simultaneously, the CH GND port in switch S1 circuit must be set to high level, and the CH VCC port to low level. This connects the D port to the circuit's GND, allowing current from the external device to flow into resistor R8. U4 then acquires the input current value by measuring the voltage across resistor R8.

[0066] When acquiring a two-wire 4-20mA signal, the CH AI port must first be set to high level to ensure Q6 is fully conducting. Simultaneously, the CH GND port in switch S1 circuit must be set to low level, and the CH VCC port to high level. This allows the D terminal to output the voltage of the module's power supply. This voltage powers external devices, which then output analog signal current. The final current output from the device flows into resistor R8. U4 obtains the input current value by acquiring the voltage across resistor R8.

[0067] When the input signal is a digital wet contact, the CH AI port needs to be set to low level first to disconnect Q6; at the same time, the CH GND port and CH VCC port in the switch S1 circuit need to be set to high level. The purpose is to connect the D terminal to the circuit's GND. Then U4 can directly detect the voltage changes at the C and D terminals. When the voltage input at the C and D terminals is greater than a certain value, the input DI signal is considered to be in a closed state. When the voltage input at the C and D terminals is less than a certain value, the input DI signal is considered to be in an open state.

[0068] When the input signal is a digital dry contact, the CH AI port needs to be set to low level first to disconnect Q6; at the same time, the CH GND port and CH VCC port in the switch S1 circuit need to be set to high level, so that the D terminal is connected to the circuit's GND; then, a small current is output using a voltage-to-current circuit. When the C and D terminals are connected to a dry contact, if the dry contact is closed, the voltage detected by U4 will be relatively small, so the input DI signal can be considered to be in a closed state; if the dry contact is open, the voltage detected by U4 will be relatively large, so the input DI signal can be considered to be in an open state.

[0069] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A pre-amplifier I / O signal conditioning circuit for an industrial optical bus control system, characterized in that: include: Channel module, used to connect external devices; An A / D converter is used to acquire the voltage of the channel module; The MCU is used to read the data converted by the A / D converter and write data to the D / A converter. A D / A converter is used to convert data written to the MCU into analog voltage; Power supply, used to power the A / D converter, D / A converter and MCU; Each channel module includes a control output circuit, a voltage-to-current circuit, a current-to-voltage circuit, and two terminals, designated as C and D. Both C and D terminals are connected to the current-to-voltage circuit. The MCU is connected to the control output circuit, which is connected to a power supply. Both the control output circuit and the voltage-to-current circuit are connected to the current-to-voltage circuit. The D / A converter is connected to the voltage-to-current circuit, and the current-to-voltage circuit is connected to the A / D converter. Each channel module also includes a protection circuit, with C and D terminals connected to it. The channel module further includes a switch S1 and two connecting contacts, contact one and contact two. Contact one is connected to the MCU, and contact two is connected to the P power supply. The switch S1 is positioned between the protection circuit and the power supply. Between the current-to-voltage circuits, when the external device is a digital dry contact device, the switch S1 inside the channel module needs to be closed on contact one. The channel module activates the current-to-voltage circuit and the voltage-to-current circuit, and closes the control output circuit. The output signal of the external device requires the module to provide an excitation current, which is provided by the voltage-to-current circuit. The current is output from terminal C to the external device through the voltage-to-current circuit, and finally flows back to the overall module through terminal D. When the external device is a two-wire analog input device, the switch S1 inside the channel module is closed on contact two. The channel activates the current-to-voltage circuit, and closes the voltage-to-current circuit and the control output circuit. The two-wire device is powered by the module's Power supply, so the current flows out from terminal D, then through the external device, and then flows back to the overall module through terminal C.

2. The pre-amplifier I / O signal conditioning circuit for an industrial optical bus control system according to claim 1, characterized in that: The channel module has 16 channels.

3. The pre-amplifier I / O signal conditioning circuit for an industrial optical bus control system according to claim 1, characterized in that: The channel module has 32 channels.

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