Underground high-temperature RS485 communication circuit
By using a combination circuit of comparator U1 and protection resistor in the high-temperature environment of the well, the problem of high cost of RS485 communication in the high-temperature environment of the well is solved, and stable and low-cost communication function is achieved.
Patent Information
- Application Number
- CN202423233982.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2025-12-09
- Estimated Expiration
- 2034-12-26
AI Technical Summary
Existing RS485 chips are difficult to meet the needs of downhole operations in high-temperature environments, and are also expensive, resulting in high circuit costs.
A comparator U1 with a shutdown mode is used, which, through the 485_A and 485_B signal lines and the 485_RX, 485_TXN and 485_TXP signal lines, realizes the signal reception and transmission of the RS485 communication protocol, replacing the traditional RS485 chip. Combined with protection resistors and decoupling capacitors, the circuit can be stably operated in an environment of 200℃.
It enables the normal operation of RS485 communication function in high-temperature environments, reduces costs, improves the reliability and stability of the circuit, and avoids the need to purchase expensive chips.
Smart Images
Figure CN223650999U_ABST
Abstract
Description
Technical Field
[0001] This utility model belongs to the field of communication circuit technology, and in particular relates to a high-temperature RS485 communication circuit for underground mining. Background Technology
[0002] When instruments are operating downhole, the communication protocol between instruments is mostly RS485. RS485 bus transmission protocol is a serial bus communication protocol standard that adopts a balanced transmission and differential reception structure design. This communication protocol has strong anti-interference ability, fast transmission rate and long transmission distance, so it is widely used in the petroleum industry.
[0003] Due to the high temperatures encountered in downhole operations, conventional instruments need to withstand long-term operation at 175°C, while ultra-high temperature instruments need to withstand long-term operation at 200°C. While commercially available RS485 chips are inexpensive, they typically have built-in thermal shutdown functions with shutdown temperatures generally below 170°C, failing to meet these requirements. RS485 chips that can operate at 175-200°C are expensive, resulting in higher circuit costs. Therefore, commercially available RS485 chips generally do not meet these requirements.
[0004] To address this issue, we propose a high-temperature RS485 communication circuit for underground applications. Utility Model Content
[0005] The purpose of this invention is to solve the problem that the RS485 chips required for high-temperature use are expensive and the circuit cost is high in the existing technology, and to propose a high-temperature RS485 communication circuit for underground use.
[0006] To achieve the above objectives, the present invention adopts the following technical solution:
[0007] A downhole high-temperature RS485 communication circuit includes a comparator U1 with a shutdown mode. The output pin 1 of the comparator U1 is connected to a 485_RX signal line for transmitting a single-ended received signal. The negative input terminal 3 of the comparator U1 is connected in parallel with an RS485_A signal line and a 485_TXN signal line. The positive input terminal 4 of the comparator U1 is connected in parallel with an RS485_B signal line and a 485_TXP signal line. The power supply pin 6 of the comparator U1 is connected to a power supply.
[0008] The comparator U1 enable pin 5 is connected to the 485_EN signal line. When the comparator U1 enable pin 5 is low, the output is normal and used to receive signals. When the enable pin 5 is high, the output is in a high-impedance state and is used to turn off the output.
[0009] Preferably, a decoupling capacitor C1 with a capacitance of 0.1μF is connected between the power supply pin 6 of the comparator U1 and the +5V power supply, and the other end of the decoupling capacitor C1 is grounded.
[0010] Preferably, a protective second resistor R2 with a resistance value of 20Ω is provided between the positive input terminal 4 of the comparator U1 and the RS485_A signal line.
[0011] Preferably, a protective resistor R3 with a resistance of 20Ω is provided between the negative input terminal 3 of the comparator U1 and the RS485_B signal line.
[0012] Preferably, a first resistor R1 with a resistance of 10KΩ is connected in parallel between the output pin 1 of the comparator U1 and the 485_RX signal line, and the other end of the first resistor R1 is connected to a +5V power supply.
[0013] Preferably, a second resistor R2 with a resistance of 10KΩ is connected in parallel between the comparator U1 enable pin 5 and the 485_EN signal line, and the other end of the second resistor R2 is grounded.
[0014] In summary, the technical effects and advantages of this utility model are as follows: This downhole high-temperature RS485 communication circuit, through a comparator and RS485_A and RS485_B signal lines, achieves signal reception of 485_RX, and disables the reception function by pulling 485_EN high. It also achieves signal transmission through 485_TXN and 485_TXP signal lines. This circuit achieves RS485 communication protocol transmission without using an RS485 chip. It is compact and meets the requirements for long-term use at 200℃. Compared to existing devices, it avoids the need for expensive RS485 chips that meet the requirements of 175-200℃, thus reducing operating costs and improving reliability. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the structure of this utility model. Detailed Implementation
[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.
[0017] Reference Figure 1A downhole high-temperature RS485 communication circuit includes a comparator U1 with a shutdown mode. The output pin 1 of the comparator U1 is connected to a 485_RX signal line for transmitting a single-ended received signal to the receiving end. The negative input terminal 3 of the comparator U1 is connected in parallel with an RS485_A signal line and a 485_TXN signal line. The positive input terminal 4 of the comparator U1 is connected in parallel with an RS485_B signal line and a 485_TXP signal line. The power supply pin 6 of the comparator U1 is connected to a power supply.
[0018] The enable pin 5 of comparator U1 is connected to 485_EN. When the enable pin 5 of comparator U1 is low, the output is normal and used to receive signals. When the enable pin 5 is high, the output is in a high-impedance state and is used to turn off the output.
[0019] The RS485 communication circuit provided by this utility model supports the RS485 half-duplex communication protocol, that is, it supports bidirectional transmission, but only one direction of transmission can exist at a time. The two signal lines are denoted as A and B respectively; the voltage of signal line A is called VA and the voltage of signal line B is called VB. +2V < |VA - VB| < +6V represents "1"; -6V < |VA - VB| < -2V represents "0". The above RS485 communication protocol is prior art and will not be described in detail.
[0020] By default, 485_EN = 0, and the circuit remains in receive mode.
[0021] In receive mode, signals A and B are transmitted to the positive and negative input terminals of the comparator via a twisted pair cable. When VA > VB, 485_RX = 1; when VA < VB, 485_RX = 0, thus achieving signal reception.
[0022] In transmit mode, 485_EN is pulled high 1µs in advance, at which time the receive function is turned off; 1µs later, 485_TXP and 485_TXN are used to output the transmit signal.
[0023] When 485_TXP = 1 and 485_TXN = 0, VA > VB, and the transmitted signal is at a high level, i.e., 485_TX = 1; when 485_TXP = 0 and 485_TXN = 1, VA < VB, and the transmitted signal is at a low level, i.e., 485_TX = 0, thus realizing signal transmission.
[0024] In summary, this downhole high-temperature RS485 communication circuit can replace conventional RS485 chips to achieve RS485 communication functionality. Moreover, the solution has a simple structure, small size, and low cost. It has been tested at 200℃ for more than 200 hours and still maintains normal function, demonstrating good stability.
[0025] A 0.1μF decoupling capacitor C1 is connected between the power supply pin 6 of comparator U1 and the +5V power supply. The other end of the decoupling capacitor C1 is grounded to filter out high-frequency noise on the power supply and ensure stable power supply to U1.
[0026] To prevent damage to the communication pins of comparator U1 from sudden high voltage or current surges from the RS485 bus, a second protective resistor R2 with a resistance of 20Ω is provided between the positive input terminal 4 of comparator U1 and the RS485_A signal line; a protective resistor R3 with a resistance of 20Ω is provided between the negative input terminal 3 of comparator U1 and the RS485_B signal line.
[0027] A first resistor R1 with a resistance of 10KΩ is connected in parallel between the output pin 1 of comparator U1 and the 485_RX signal line. The other end of the first resistor R1 is connected to a +5V power supply, which serves as a pull-up resistor to ensure that the output signal remains at a stable high level when there is no effective differential input.
[0028] A second resistor R2 with a resistance of 10KΩ is connected in parallel between the enable pin 5 of comparator U1 and the 485_EN signal line, and the other end of the second resistor R2 is grounded. This serves as a pull-down resistor to ensure that 485_EN is low in the default state and comparator U1 remains in the receiving state.
[0029] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.
Claims
1. A high-temperature RS485 communication circuit for underground drilling, characterized in that, The comparator includes a comparator with a shutdown mode. The output pin of the comparator is connected to a 485_RX signal line for transmitting a single-ended received signal. The negative input of the comparator is connected in parallel with an RS485_A signal line and a 485_TXN signal line. The positive input of the comparator is connected in parallel with an RS485_B signal line and a 485_TXP signal line. The power supply pin of the comparator is connected to a power supply. The comparator enable pin is connected to the 485_EN signal line. When the comparator enable pin is low, the output is normal and used to receive signals. When the enable pin is high, the comparator output is in a high-impedance state and is used to turn off the output.
2. The downhole high-temperature RS485 communication circuit according to claim 1, characterized in that, A 0.1μF decoupling capacitor is connected between the comparator power supply pin and the +5V power supply, and the other end of the decoupling capacitor is grounded.
3. The downhole high-temperature RS485 communication circuit according to claim 1, characterized in that, A second protective resistor with a resistance of 20Ω is provided between the positive input terminal of the comparator and the RS485_A signal line.
4. The downhole high-temperature RS485 communication circuit according to claim 3, characterized in that, A protective resistor with a resistance of 20Ω is provided between the negative input terminal of the comparator and the RS485_B signal line.
5. The downhole high-temperature RS485 communication circuit according to claim 1, characterized in that, A first resistor with a resistance of 10KΩ is connected in parallel between the comparator output pin and the 485_RX signal line, and the other end of the first resistor is connected to a +5V power supply.
6. The downhole high-temperature RS485 communication circuit according to claim 1, characterized in that, A second resistor with a resistance of 10KΩ is connected in parallel between the comparator enable pin and the 485_EN signal line, and the other end of the second resistor is grounded.