Isolated RS485 circuit capable of automatically controlling transceiving mode

Abstract

The utility model discloses an isolation type RS485 automatic transmit-receive mode control circuit, comprising an RS485 automatic transmit-receive mode circuit comprising an NPN type triode, the base electrode of which is connected with the transmitting pin of the serial port of a single-chip microcomputer; a collector electrode is connected to 485-DIR of the 485 isolation transceiver and is connected to a 5V power supply through a 10K resistor; the emitter is connected with GND; the power supply isolation circuit adopts an isolation power supply module to isolate a power supply used by the single chip microcomputer and a power supply at the bus end of the 485 isolation transceiver; a 485 level conversion and bus protection circuit; provided is a serial port data transmit-receive indicating lamp circuit. The circuit at least has the following beneficial effects that the protection level of the circuit is improved, the risk of damaging an expensive control circuit is reduced, the stability of communication on an RS485 bus can be improved, automatic switching of RS485 transceiving control is realized, hardware wiring is facilitated, and software logic is reduced; and the product cost is reduced by using a small number of electronic components.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of communication circuits, in particular to an isolated RS485 automatic control circuit for receiving and transmitting modes. BACKGROUND

[0002] At present, many industrial controls use RS485 buses for communication between devices, and the I / O of device cables is prone to be affected by electric transient noise from various signal sources. If the transient noise has sufficient amplitude and duration, the transceiver or adjacent sensitive circuit may be damaged.

[0003] Therefore, in order to more stably and safely perform RS485 communication, it is particularly important to isolate the serial port of a single-chip microcomputer from an RS485 bus, and a separate control pin is needed to switch the receiving or transmitting mode of RS485, which requires an additional control pin in hardware and the logic of a software program needs to switch the receiving or transmitting mode. CONTENT OF THE UTILITY MODEL

[0004] Therefore, the application provides an isolated RS485 automatic control circuit for receiving and transmitting modes to solve the problems in the prior art.

[0005] In order to achieve the above purpose, the application provides the following technical scheme:

[0006] An isolated RS485 automatic control circuit for receiving and transmitting modes comprises:

[0007] The RS485 automatic receiving and transmitting mode circuit comprises an NPN triode, the base electrode of which is connected to the transmitting pin of the serial port of a single-chip microcomputer, the collector electrode of which is connected to 485-DIR of the 485 isolated transceiver and connected to a 5V power supply through a 10K resistor, and the emitter electrode of which is connected to GND.

[0008] The power supply isolation circuit uses an isolated power supply module to isolate the power supply used by the single-chip microcomputer and the power supply of the bus end of the 485 isolated transceiver.

[0009] The 485 level conversion and bus protection circuit uses resistors, fuses, unidirectional and bidirectional TVS diodes to build a protection circuit for the RS485 bus.

[0010] The serial port data receiving and transmitting indicator light circuit is connected in parallel with the LED light of the transmitting pin and the receiving pin of the serial port.

[0011] Optionally, the RS485 automatic receiving and transmitting mode circuit specifically comprises: the collector electrode of the NPN triode with the type of S8050 is connected to the 485-DIR network, and one end of the 10K surface-mounted resistor is connected.

[0012] The emitter of the NPN triode is connected to the GND network, and the base of the NPN triode is connected to one end of the 4.7K chip resistor;

[0013] One end of the 10K chip resistor is connected to the 5V network;

[0014] One end of the 4.7K chip resistor is connected to the USART1-TX network.

[0015] Optionally, the power isolation circuit specifically comprises: the positive electrode of the first chip electrolytic capacitor with the bit number C45, and one end of the first chip capacitor are commonly connected to the 5V network through the 1-pin connection bit of the isolation power module with the model IB0505LS-1WR3;

[0016] The negative electrode of the first chip electrolytic capacitor and one end of the first chip capacitor are commonly connected to the GND network through the 2-pin connection of the isolation power module;

[0017] The negative electrode of the second chip electrolytic capacitor and one end of the second chip capacitor are commonly connected to the GND-1 network through the 4-pin connection of the isolation power module;

[0018] The positive electrode of the second chip electrolytic capacitor and one end of the second chip capacitor are commonly connected to the 5V-1 network through the 6-pin connection of the isolation power module.

[0019] Optionally, the 485 level conversion and bus protection circuit specifically comprises: the 1-pin of the 485 isolation transceiver with the model ISO3082DWR is connected to the 5V network, the 2-pin, 7-pin, 8-pin are connected to the GND network, the 3-pin is connected to the USART1-RX network, the 4-pin, 5-pin are connected to the 485-DIR network, the 6-pin is connected to the GND network, the 9-pin, 10-pin, 15-pin are connected to the GND-1 network, and the 16-pin is connected to the 5V-1 network;

[0020] The 12-pin is connected to one end of the first 10R chip resistor, and the 13-pin is connected to one end of the second 10R chip resistor.

[0021] Optionally, one end of the first 10R chip resistor is connected to one end of the first 1.5K chip resistor, the 120R chip resistor, the cathode of the first unidirectional TVS diode with the model SMF5.0A, one end of the bidirectional TVS diode with the model SMF5.0CA, and one end of the first chip fuse with the bit number U14;

[0022] One end of the second 10R chip resistor is connected to the 120R chip resistor, the second 1.5K chip resistor of R20, one end of the bidirectional TVS diode, the cathode of the second unidirectional TVS diode with the model SMF5.0A, and one end of the first chip fuse; one end of the first 1.5K chip resistor is connected to the 5V-1 network;

[0023] One end of the second 1.5K chip resistor is connected to the GND-1 network; the anodes of the first unidirectional TVS diode and the second unidirectional TVS diode are connected to the GND-1 network; one end of the first chip fuse is connected to the 485-A network; and one end of the second chip fuse is connected to the 485-B network.

[0024] Optionally, the serial port data transceiver indicator circuit specifically includes: the anode of the first surface-mount LED is connected to the anode of the second surface-mount LED, and they are both connected to a 3.3V network; the cathode is connected to one end of the first 1K surface-mount resistor.

[0025] The cathode of the second surface-mount LED is connected to one end of the second 1K surface-mount resistor; one end of the first 1K surface-mount resistor is connected to the USART1-RX network; and one end of the second 1K surface-mount resistor is connected to the USART1-TX network.

[0026] Compared with the prior art, this application has at least the following beneficial effects:

[0027] It improves the protection level of the circuit and reduces the risk of damage to expensive control circuits. It can also improve the stability of communication on the RS485 bus, realize the automatic switching of RS485 transmit and receive control, facilitate hardware wiring and reduce software logic; and reduce product costs by using fewer electronic components. Attached Figure Description

[0028] To more intuitively illustrate the prior art and this application, exemplary drawings are provided below. It should be understood that the specific shapes and structures shown in the drawings should not generally be regarded as limiting conditions for implementing this application; for example, based on the technical concept disclosed in this application and the exemplary drawings, those skilled in the art are able to easily make conventional adjustments or further optimizations to the addition / reduction / classification, specific shapes, positional relationships, connection methods, size ratios, etc. of certain units (components).

[0029] Figure 1 The overall architecture diagram of an isolated RS485 automatic control transceiver mode circuit provided in this application;

[0030] Figure 2 The circuit diagram of RS485 automatic transmit / receive mode for an isolated RS485 automatic control transceiver mode provided in this application;

[0031] Figure 3 A power isolation circuit diagram for an isolated RS485 automatic control transceiver mode circuit provided in this application;

[0032] Figure 4 A circuit diagram of 485 level conversion and bus protection for an isolated RS485 automatic control transceiver mode circuit provided in this application;

[0033] Figure 5 This application provides a circuit diagram of a serial port data transceiver indicator light for an isolated RS485 automatic control transceiver mode circuit. Detailed Implementation

[0034] The present application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] This utility model provides an isolated RS485 automatic control transceiver mode circuit, such as... Figure 1 As shown, it includes:

[0036] RS485 Automatic Transmit / Receive Mode Circuit: This circuit uses one NPN transistor. The base is connected to the transmit pin of the microcontroller's serial port; the collector is connected to the direction control pin (485-DIR) of the 485 isolated transceiver and pulled up to 5V through a 10K resistor; the emitter is connected to GND. When there is no data, the transmit pin of the microcontroller's serial port is high, which makes the collector and emitter of the transistor conduct, and the direction control pin of the 485 isolated transceiver is low, in receive mode. When there is data, the transmit pin of the microcontroller's serial port is low, which makes the collector and emitter of the transistor not conduct, and the direction control pin of the 485 isolated transceiver is high, in transmit mode. This achieves automatic switching without the need for extra pins to control the switching between transmit and receive modes.

[0037] like Figure 2 As shown, the collector of the S8050 NPN transistor with reference number Q1 is connected to the 485-DIR network and one end of the 10K surface mount resistor with reference number R21. The emitter is connected to the GND network, and the base is connected to one end of the 4.7K surface mount resistor with reference number R23. One end of the surface mount resistor with reference number R21 is connected to the 5V network, and one end of the 4.7K surface mount resistor with reference number R23 is connected to the USART1-TX network.

[0038] Power isolation circuit: This part uses an isolation power module to isolate the power supply used by the microcontroller from the power supply at the bus end of the RS485 isolation transceiver, thereby reducing the impact of high levels on the RS485 bus on the microcontroller circuit.

[0039] like Figure 3As shown, pin 1 of the isolated power supply module with tag number U20 and model number IB0505LS-1WR3 is connected to the positive terminal of the first surface-mount electrolytic capacitor C45 and one end of the first surface-mount capacitor C46, ​​which are connected to the 5V network. Pin 2 is connected to the negative terminal of the first surface-mount electrolytic capacitor C45 and one end of the first surface-mount capacitor C46, ​​which are connected to the GND network. Pin 4 is connected to the negative terminal of the second surface-mount electrolytic capacitor C47 and one end of the second surface-mount capacitor C48, which are connected to the GND-1 network. Pin 6 is connected to the positive terminal of the second surface-mount electrolytic capacitor C47 and one end of the second surface-mount capacitor C48, which are connected to the 5V-1 network.

[0040] 485 Level Conversion and Bus Protection Circuit: This section uses resistors, fuses, and unidirectional and bidirectional TVS diodes to build a protection circuit for the RS485 bus, ensuring the integrity of signals on the bus and protecting the 485 isolation transceiver from electrical breakdown damage. The data receive pin of the 485 isolation transceiver is connected to GND, which, together with the automatic transceiver circuit, enables automatic switching between transmit and receive modes for 485 communication.

[0041] like Figure 4As shown, for the ISO3082DWR 485 isolated transceiver (tag U13), pin 1 is connected to the 5V network, pins 2, 7, and 8 are connected to the GND network, pin 3 is connected to the USART1-RX network, pins 4 and 5 are connected to the 485-DIR network, pin 6 is connected to the GND network, pins 11 and 14 are left unconnected, pins 9, 10, and 15 are connected to the GND-1 network, pin 16 is connected to the 5V-1 network, and pin 12 is connected to the tag R17. One end of a 10R surface mount resistor is connected to pin 13 of the second 10R surface mount resistor (R19). One end of the first 10R surface mount resistor (R17) is connected to the first 1.5K surface mount resistor (R16), one end of the 120R surface mount resistor (R18), the cathode of the SMF5.0A unidirectional TVS diode (U16), one end of the SMF5.0CA bidirectional TVS diode (D5), and the first surface mount resistor (U14). One end of the chip fuse; one end of the second 10R chip resistor in tag R19 is connected to the 120R chip resistor in tag R18, one end of the second 1.5K chip resistor in tag R20, one end of the bidirectional TVS diode (model SMF5.0CA) in tag D5, one end of the second unidirectional TVS diode (model SMF5.0A) in tag U17, and one end of the second chip fuse in tag U15; one end of the first 1.5K chip resistor in tag R16 is connected to the 5V-1 network; one end of the second 1.5K chip resistor in tag R20 is connected to the GND-1 network; the anodes of the first unidirectional TVS diode (model SMF5.0A) in tag U16 and the anodes of the second unidirectional TVS diode (model SMF5.0A) in tag U17 are connected to the GND-1 network; one end of the first chip fuse in tag U14 is connected to the 485-A network; one end of the second chip fuse in tag U15 is connected to the 485-B network.

[0042] Serial port data transceiver indicator circuit: To provide a clear indication when the serial port is receiving and sending data, LEDs are connected in parallel to the transmit and receive pins of the serial port.

[0043] like Figure 5 As shown, the anode of the first surface mount LED (LED3) is connected to the anode of the second surface mount LED (LED4), and both are connected to a 3.3V network. The cathode is connected to one end of the first 1K surface mount resistor (R25). The cathode of the second surface mount LED (LED4) is connected to one end of the second 1K surface mount resistor (R26). One end of the first 1K surface mount resistor (R25) is connected to the USART1-RX network. One end of the second 1K surface mount resistor (R26) is connected to the USART1-TX network.

[0044] Note: The “485-A” network and the “485-B” network are A and B on the RS485 bus.

[0045] The technical features of the above embodiments can be combined in any way (as long as there is no contradiction in the combination of these technical features). For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; these embodiments not explicitly written should also be considered to be within the scope of this specification.

Claims

1. A circuit for isolated RS485 automatic control transceiver mode, characterized in that, include: The RS485 automatic transmit / receive mode circuit includes an NPN transistor, with its base connected to the transmit pin of the microcontroller's serial port; its collector connected to the 485-DIR of the 485 isolation transceiver and connected to a 5V power supply through a 10K resistor; and its emitter connected to GND. The power isolation circuit uses an isolation power module to isolate the power supply used by the microcontroller from the power supply at the bus end of the 485 isolation transceiver. The RS485 level conversion and bus protection circuit uses resistors, fuses, and unidirectional and bidirectional TVS diodes to build a protection circuit for the RS485 bus. The serial port data transceiver indicator circuit has LEDs connected in parallel to the transmit and receive pins of the serial port.

2. The circuit for an isolated RS485 automatic control transceiver mode according to claim 1, characterized in that, The RS485 automatic transmit / receive mode circuit specifically includes: the collector of an S8050 NPN transistor is connected to the 485-DIR network and one end of a 10K chip resistor; The emitter of an NPN transistor is connected to the GND network, and the base of an NPN transistor is connected to one end of a 4.7K chip resistor. One end of the 10K chip resistor is connected to a 5V network; One end of the 4.7K chip resistor is connected to the USART1-TX network.

3. The circuit for an isolated RS485 automatic control transceiver mode according to claim 1, characterized in that, The power isolation circuit specifically includes: pin 1 of the isolation power module with model number IB0505LS-1WR3 is connected to the positive terminal of the first surface-mount electrolytic capacitor with reference number C45, and one end of the first surface-mount capacitor, which are connected to the 5V network. Pin 2 of the isolation power module is connected to the negative terminal of the first surface-mount electrolytic capacitor and one end of the first surface-mount capacitor, and together they are connected to the GND network; The four pins of the isolated power supply module are connected to the negative terminal of the second surface-mount electrolytic capacitor and one end of the second surface-mount capacitor, which are then connected to the GND-1 network. Pin 6 of the isolated power supply module is connected to the positive terminal of the second surface-mount electrolytic capacitor and one end of the second surface-mount capacitor, which are then connected to the 5V-1 network.

4. The circuit for an isolated RS485 automatic control transceiver mode according to claim 1, characterized in that, The 485 level conversion and bus protection circuit specifically includes: pin 1 of the ISO3082DWR 485 isolated transceiver is connected to the 5V network, pins 2, 7, and 8 are connected to the GND network, pin 3 is connected to the USART1-RX network, pins 4 and 5 are connected to the 485-DIR network, pin 6 is connected to the GND network, pins 9, 10, and 15 are connected to the GND-1 network, and pin 16 is connected to the 5V-1 network; Pin 12 is connected to one end of the first 10R surface mount resistor, and pin 13 is connected to one end of the second 10R surface mount resistor.

5. The circuit for an isolated RS485 automatic control transceiver mode according to claim 1, characterized in that, One end of the first 10R chip resistor is connected to one end of the first 1.5K chip resistor, one end of the 120R chip resistor, the cathode of the first unidirectional TVS diode of model SMF5.0A, one end of the bidirectional TVS diode of model SMF5.0CA, and one end of the first chip fuse of reference number U14. One end of the second 10R chip resistor is connected to one end of the 120R chip resistor, one end of the second 1.5K chip resistor R20, one end of the bidirectional TVS diode, the cathode of the second unidirectional TVS diode (model SMF5.0A), and one end of the first chip fuse; one end of the first 1.5K chip resistor is connected to the 5V-1 network. One end of the second 1.5K chip resistor is connected to the GND-1 network; the anodes of the first unidirectional TVS diode and the second unidirectional TVS diode are connected to the GND-1 network; one end of the first chip fuse is connected to the 485-A network; and one end of the second chip fuse is connected to the 485-B network.

6. The circuit for an isolated RS485 automatic control transceiver mode according to claim 1, characterized in that, The serial port data transceiver indicator circuit specifically includes: the anode of the first surface-mount LED is connected to the anode of the second surface-mount LED, and they are both connected to a 3.3V network; the cathode is connected to one end of the first 1K surface-mount resistor. The cathode of the second surface-mount LED is connected to one end of the second 1K surface-mount resistor; one end of the first 1K surface-mount resistor is connected to the USART1-RX network; and one end of the second 1K surface-mount resistor is connected to the USART1-TX network.

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