CAN parallel operation head and tail terminal resistor automatic closing system

Abstract

The utility model provides a CAN parallel operation head and tail terminal resistor automatic closing system which comprises a plurality of parallel operation machines and parallel operation lines, the parallel operation machines are sequentially connected through the parallel operation lines, and each parallel operation machine is provided with a terminal resistor, a switching circuit and a logic circuit. The switching circuit is connected to the terminal resistor and is used for controlling the on-off of the parallel machine and the terminal resistor; and the logic circuit is connected to the parallel machine and the switching circuit, and is used for judging whether the parallel machine is a head-tail machine or not and controlling the switching circuit to connect or disconnect the terminal resistor. According to the utility model, the logic circuit is arranged to judge whether the parallel machine is the head-tail machine, and the switching circuit is controlled to connect or disconnect the terminal resistor and the parallel machine, so that the closing of the terminal resistor of the head-tail machine and the opening of the terminal resistor of the intermediate machine are realized, the operation of manually increasing the terminal resistor is avoided, and the working efficiency is improved. And the risk of manual misoperation is reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to CAN parallel machine technology field, more specifically refers to a CAN parallel machine head terminal resistance automatic closing system. BACKGROUND

[0002] CAN parallel machine refers to multiple machines through CAN (full name: Controller Area Network, CAN bus) bus parallel communication. According to the technical requirements of multiple machine CAN parallel communication, the first and last two machines need to increase a 120 ohm resistance as terminal resistance to improve the rising and falling rate of CAN waveform.

[0003] At present, the common first and last machine terminal resistance conduction mode has the following three kinds: one is that each machine is provided with a terminal resistance dial switch, and when N machines are CAN parallel communication, the first and last two dial switches are closed, and the middle one is disconnected;Two is that each machine does not have a terminal resistance, and a terminal resistance is added to the parallel port of the first and last two machines;Three is that each machine is provided with a resistance with a large resistance value, which is suitable for a fixed number of parallel machines, and if the number of machines changes, the resistance value also needs to be adjusted artificially. The above modes need manual operation, and there is a risk of misoperation, which affects the CAN communication quality and reliability. UTILITY MODEL CONTENTS

[0004] The utility model aims at overcoming the defects of prior art, and provides a CAN parallel machine head terminal resistance automatic closing system to solve the technical problem that the traditional first and last machine terminal resistance conduction needs manual operation and has high risk of misoperation.

[0005] The utility model embodiment provides a CAN parallel machine head terminal resistance automatic closing system, including a plurality of parallel machine and parallel machine line, a plurality of parallel machine are connected in proper order through a plurality of parallel machine line, wherein: the parallel machine is equipped with terminal resistance, switch circuit and logic circuit;The switch circuit is connected to the terminal resistance, and is used for controlling the on-off of the parallel machine and the terminal resistance;The logic circuit is connected to the parallel machine and the switch circuit, and is used for judging whether the parallel machine is the first and last machine, and controls the switch circuit and inserts or cuts off the terminal resistance.

[0006] Among them, the parallel machine is equipped with parallel machine input network port and parallel machine output network port, and the parallel machine output network port of the parallel machine is connected with the parallel machine input network port of the next parallel machine through the parallel machine line, and the logic circuit is connected to the parallel machine input network port and the parallel machine output network port, and is used for detecting whether the parallel machine input network port and the parallel machine output network port are connected with the parallel machine line, to judge whether the parallel machine is the intermediate machine or the first and last machine.

[0007] The parallel machine output network interface and the parallel machine input network interface are respectively provided with a first signal interface and a second signal interface, the first signal interface is sequentially connected with a first pull-up resistor and a first power supply, the second signal interface is sequentially connected with a second pull-up resistor and a second power supply, and the first signal interface and the second signal interface are respectively connected to the logic circuit.

[0008] The logic circuit comprises an AND gate chip, the first signal interface and the second signal interface are respectively connected to a first input end and a second input end of the AND gate chip, and the input end of the AND gate chip is connected to the switch circuit.

[0009] The switch circuit comprises a first switch tube, a second switch tube, a third switch tube, a third pull-up resistor and a third power supply, a first pole of the first switch tube is connected to an output end of the AND gate chip, the third pull-up resistor and the third power supply are sequentially connected to a second pole of the first switch tube, and a third pole of the first switch tube is grounded, first poles of the second switch tube and the third switch tube are connected to the second pole of the first switch tube, a second pole of the second switch tube is connected to the terminal resistor, the parallel machine input network interface and the parallel machine output network interface are connected to one end of the terminal resistor away from the second switch tube, and the parallel machine input network interface and the parallel machine output network interface are connected to a second pole of the third switch tube.

[0010] The third power supply is greater than an amplitude of a voltage signal of the parallel machine line.

[0011] The switch circuit further comprises a first isolation resistor, a first end of the first isolation resistor is connected to the second pole of the first switch tube, and the other end is connected to a third pole of the second switch tube and a third pole of the third switch tube.

[0012] The switch circuit comprises a relay, a fourth pull-up resistor and a fourth power supply, the relay is provided with a coil and a switching switch, one end of the coil is connected to an output end of the AND gate chip, the fourth pull-up resistor and the fourth power supply are sequentially connected to the other end of the coil, a moving contact of the switching switch is connected to the terminal resistor, the parallel machine input network interface and the parallel machine output network interface are connected to one end of the terminal resistor away from the moving contact, a first fixed contact of the switching switch is connected to the parallel machine input network interface and the parallel machine output network interface, and a second fixed contact of the switching switch is disconnected.

[0013] The switch circuit comprises a photocoupler, a fifth pull-up resistor and a fifth power supply; the photocoupler comprises a light emitting diode and a phototransistor, the fifth pull-up resistor and the fifth power supply are sequentially connected to the positive electrode of the light emitting diode, and the negative electrode of the light emitting diode is connected to the output end of the AND gate chip; the first electrode of the phototransistor is connected to the parallel machine input network port and the parallel machine output network port, the second electrode of the phototransistor is used for receiving the light signal of the light emitting diode, the third electrode of the phototransistor is connected to the terminal resistor, and the parallel machine input network port and the parallel machine output network port are connected to one end of the terminal resistor away from the third electrode of the phototransistor.

[0014] The terminal resistor is installed in the interior of the parallel machine.

[0015] The CAN parallel machine first-end and last-end terminal resistor automatic closing system has the advantages that the logical circuit is arranged to judge whether the parallel machine is the first-end machine or the last-end machine, and the switch circuit is controlled to connect or disconnect the terminal resistor and the parallel machine, so that the terminal resistor of the first-end machine and the last-end machine is closed and the terminal resistor of the intermediate machine is disconnected, manual operation of adding the terminal resistor is avoided, human error risk is reduced, the installation method is simple and convenient, and the installation of the CAN parallel machine first-end and last-end terminal resistor automatic closing system can be completed by connecting the parallel machine lines between the parallel machines.

[0016] The above description is only a summary of the technical scheme of the utility model, in order to more clearly understand the technical means of the utility model, can be implemented according to the content of the specification, and in order to let the above and other purposes, characteristics and advantages of the utility model can be more obvious and easy to understand, the following preferred embodiments are described in detail as follows. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A block schematic diagram of a CAN parallel machine first-end and last-end terminal resistor automatic closing system is provided in the utility model;

[0018] Figure 2 A connection schematic diagram of a parallel machine and a logical circuit of a CAN parallel machine first-end and last-end terminal resistor automatic closing system is provided in the utility model;

[0019] Figure 3 A circuit structure schematic diagram of a switch circuit of the second embodiment of the utility model is provided;

[0020] Figure 4 A circuit structure schematic diagram of a switch circuit of the third embodiment of the utility model is provided;

[0021] Figure 5 A circuit structure schematic diagram of a switch circuit of the fourth embodiment of the utility model is provided.

[0022] REFERENCE SIGNS:

[0023] 1, parallel machine; 2, parallel line; 3, switch circuit; 4, logic circuit. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the utility model more clearly, the following will be further described in combination with the drawings and specific embodiments. The technical scheme in the embodiments of the utility model will be clearly and completely described below in combination with the drawings of the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the utility model.

[0025] It should be understood that the terms "comprising" and "including" as used in the specification and the appended claims indicate the presence of the recited features, integers, steps, operations, elements, and / or components but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0026] It should also be understood that the terms used in the specification of the utility model herein are only for the purpose of describing specific embodiments and are not intended to limit the utility model. As used in the specification and the appended claims of the utility model, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0027] It should be further understood that the term "and / or" as used in the specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0028] Embodiment one

[0029] Referring to Figures 1-2 As shown in the drawings, the embodiment discloses a CAN parallel machine head terminal resistance automatic closing system, which comprises a plurality of parallel machines 1 and parallel lines 2, the plurality of parallel machines 1 are connected in sequence through the plurality of parallel lines 2; the parallel machine 1 is provided with a terminal resistance, a switch circuit 3 and a logic circuit 4; the switch circuit 3 is connected to the terminal resistance and is used for controlling the on-off of the parallel machine 1 and the terminal resistance; the logic circuit 4 is connected to the parallel machine 1 and the switch circuit 3 and is used for judging whether the parallel machine 1 is the first or last machine and controlling the switch circuit 3 to access or cut off the terminal resistance.

[0030] In implementation, the user first connects several parallel machines 1 through the parallel lines 2 in sequence; the start CAN parallel machine head terminal resistance automatic closing system is started, when the logic circuit 4 detects that the corresponding parallel machine 1 is the machine located at the head or tail, that is, when the parallel machine 1 is the head and tail machine, the logic circuit 4 drives the switch circuit 3 to connect the terminal resistance with the parallel machine 1, so as to connect the terminal resistance to the head and tail machine, when the logic circuit 4 detects that the corresponding parallel machine 1 is the machine located between the head and tail, that is, when the parallel machine 1 is the intermediate machine, the logic circuit 4 drives the switch circuit 3 to maintain the state that the terminal resistance is disconnected with the parallel machine 1, so as to cut off the connection between the terminal resistance and the parallel machine 1.

[0031] The CAN parallel machine head terminal resistance automatic closing system of the embodiment judges whether the parallel machine 1 is the head and tail machine through the logic circuit 4, and controls the switch circuit 3 to connect or disconnect the terminal resistance with the parallel machine 1, thereby realizing the terminal resistance closing of the head and tail machine and the terminal resistance disconnection of the intermediate machine, eliminating the manual operation of increasing the terminal resistance, reducing the risk of human error operation, and simplifying the installation method, which only needs to connect the parallel lines 2 between the parallel machines 1 to complete the installation of the CAN parallel machine head terminal resistance automatic closing system.

[0032] Specifically, the parallel machine 1 is provided with a parallel machine input network port J2 and a parallel machine output network port J1, the parallel machine output network port J1 of the parallel machine 1 is connected with the parallel machine input network port J2 of the next parallel machine 1 through the parallel line 2, the logic circuit 4 is connected with the parallel machine input network port J2 and the parallel machine output network port J1, and is used for detecting whether the parallel machine input network port J2 and the parallel machine output network port J1 are both connected with the parallel line 2, so as to judge whether the parallel machine 1 is the intermediate machine or the head and tail machine. Only one of the parallel machine input network port J2 and the parallel machine output network port J1 of the head and tail machine is connected with the parallel line 2, the parallel machine input network port J2 and the parallel machine output network port J1 of the intermediate machine are both connected with the connected parallel machine 1 through the parallel line 2, and the logic circuit 4 can simply and conveniently judge whether the parallel machine 1 is the intermediate machine or the head and tail machine by detecting the connection of the parallel machine input network port J2 and the parallel machine output network port J1 of the corresponding parallel machine 1 with the parallel line 2.

[0033] Specifically, the parallel output network port J1 and the parallel input network port J2 are respectively provided with a first signal interface and a second signal interface. The first signal interface is sequentially connected to a first pull-up resistor R1 and a first power supply, and the second signal interface is sequentially connected to a second pull-up resistor R2 and a second power supply. The first signal interface and the second signal interface are respectively connected to logic circuit 4. The first pull-up resistor R1 and the first power supply are used to enhance the driving capability of the output signal of the first signal interface, and the second pull-up resistor R2 and the second power supply are used to enhance the driving capability of the output signal of the second signal interface, so that the first signal interface or the second signal interface presents a high level when connected to the system. When multiple parallel machines 1 are connected in sequence, the first signal interface and the second signal interface of the intermediate machine are connected to the connected circuit and present a high level under the action of the first pull-up resistor R1, the first power supply, the second pull-up resistor R2, and the second power supply. If the first signal interface of the first and last machines is connected to the connected circuit through the parallel line 2, the first signal interface presents a high level, and the corresponding second signal interface is not connected to the connected circuit through the parallel line 2, so the second signal interface presents a non-high level.

[0034] In this embodiment, both the first and second power supplies are 5V. For example... Figure 2 As shown, pin 8 of the parallel output network port J1, i.e., the first signal interface, is pulled up to 5V via pin 7, and pin 7 of the parallel input port, i.e., the first signal interface, is pulled up to 5V via pin 8. The signals from pin 8 of the parallel output network port J1 and pin 7 of the parallel input port are then transmitted to logic circuit 4 for logical judgment. During the logical judgment process of logic circuit 4, a high-level signal with a certain driving capability can be transmitted to logic circuit 4 more reliably, reducing interference and attenuation during signal transmission, thereby ensuring the accuracy of the logical judgment.

[0035] Specifically, logic circuit 4 includes an AND gate chip U1; a first signal interface and a second signal interface are respectively connected to the first and second input terminals of the AND gate chip U1, and the input terminal of the AND gate chip U1 is connected to the switching circuit 3. When both the first and second signal interfaces are high, i.e., when the current parallel machine 1 is an intermediate machine, the output terminal of the AND gate chip U1 outputs a high-level signal to drive the switching circuit 3 to disconnect the terminating resistor from the current parallel machine 1; when either the first or second signal interface is high, i.e., when the current parallel machine 1 is the first or last machine, the output terminal of the AND gate chip U1 outputs a low-level signal to drive the switching circuit 3 to connect the terminating resistor to the current parallel machine 1. This reduces the computation speed, simplifies the control method, and helps improve the efficiency of automatic connection between the first and last machines and the terminating resistor.

[0036] In the embodiment, the parallel line 2 is a CAN bus, and the terminal resistance is 120Ω. The standard characteristic impedance of the CAN bus is about 120Ω. By setting the terminal resistance to 120Ω, the terminal resistance can be matched with the characteristic impedance of the bus, signal reflection can be effectively reduced, accurate signal transmission can be ensured, and the differential signal level on the bus can be stabilized. It can be understood that in other embodiments, the type of the parallel line 2 and the resistance value of the terminal resistance can be adjusted according to actual needs.

[0037] Specifically, the parallel input network port J2 and the parallel output network port J1 are each provided with a first communication interface and a second communication interface, the first communication interface and the second communication interface are connected to the CANH communication line and the CANL communication line of the CAN bus respectively, and the terminal resistance and the switch circuit 3 are connected between the first communication interface and the second communication interface. As shown in FIG. X, the 4-pin of the parallel input network port J2 and the parallel output network port J1 is connected to the terminal resistance, and the 5-pin of the parallel input network port J2 and the parallel output network port J1 is connected to the switch circuit 3. The switch circuit 3 is closed to connect the terminal resistance to the parallel machine 1, and the switch circuit 3 is disconnected to disconnect the terminal resistance from the parallel machine 1.

[0038] Specifically, the terminal resistance is installed inside the parallel machine 1. The existing terminal resistance is externally connected to the parallel machine 1, and waterproof setting needs to be performed at the connection position. The terminal resistance is not suitable for the parallel machine 1 with high waterproof requirements. By setting the terminal resistance inside the parallel machine 1, the high-cost waterproof connection material and structure are not needed, and the cost of the CAN parallel machine head-terminal resistance automatic closing system is greatly saved.

[0039] Embodiment Two

[0040] Referring to FIG. X, Figures 1-3 As shown in FIG. X, the embodiment discloses a CAN parallel machine head-terminal resistance automatic closing system, which is based on the CAN parallel machine head-terminal resistance automatic closing system of embodiment one.

[0041] Specifically, the switch circuit 3 of the CAN parallel machine head terminal resistance automatic closing system of the embodiment comprises: a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, a third pull-up resistor R5 and a third power supply; the first pole of the first switch tube Q1 is connected to the output end of the AND gate chip U1, the third pull-up resistor R5 and the third power supply are connected to the second pole of the first switch tube Q1 in sequence, and the third pole of the first switch tube Q1 is grounded; the first poles of the second switch tube Q2 and the third switch tube Q3 are connected to the second pole of the first switch tube Q1, the second pole of the second switch tube Q2 is connected to the terminal resistance R6, and the parallel input network port J2 and the parallel output network port J1 are connected to one end of the terminal resistance R6 away from the second switch tube Q2, and the parallel input network port J2 and the parallel output network port J1 are connected to the second pole of the third switch tube Q3. The third pull-up resistor R5 and the third power supply are connected to the second pole of the first switch tube Q1 in sequence, which ensures that the first switch tube Q1 can stably receive the signal output by the AND gate chip U1, and also prevents signal interference and attenuation to a certain extent, thereby ensuring that the switch circuit 3 can accurately respond to the control signal of the logic circuit 4. The connection mode of the first switch tube Q1, the second switch tube Q2 and the third switch tube Q3 enables the first switch tube Q1 to control the states of the second switch tube Q2 and the third switch tube Q3 at the same time, so as to control the conduction and cut-off of the second switch tube Q2 and the third switch tube Q3 to realize the connection and disconnection of the terminal resistance R6 and the parallel machine 1. When the second switch tube Q2 and the third switch tube Q3 are both conductive, the terminal resistance R6 is connected to the parallel machine 1; when the second switch tube Q2 and the third switch tube Q3 are both cut off, the terminal resistance R6 is disconnected from the parallel machine 1.

[0042] It can be understood that the first switch tube Q1, the second switch tube Q2 and the third switch tube Q3 are IGBT or MOSFET. IGBT and MOSFET have high switching speed, low on-resistance and good current driving capability, which helps to improve the inverter efficiency and reliability. If the first switch tube Q1, the second switch tube Q2 and the third switch tube Q3 are MOSFET, the first pole is the gate, the second pole is the drain, and the third pole is the source; if the first switch tube Q1, the second switch tube Q2 and the third switch tube Q3 are IGBT, the first pole is the gate, the second pole is the collector, and the third pole is the emitter.

[0043] Specifically, the first communication interface and the second communication interface are connected to the terminal resistance R6 and the second pole of the third switch tube Q3, respectively. As shown in Figures 2-3 the 4-pin of the parallel input network port J2 and the parallel output network port J1 is connected to the terminal resistance R6, and the 5-pin of the parallel input network port J2 and the parallel output network port J1 is connected to the second pole of the third switch.

[0044] Specifically, the third power supply is greater than the voltage signal amplitude of the parallel line 2. In this embodiment, the third power supply is 12V. The output end of the logic circuit 4 outputs a DRV-OUT signal and transmits it to the switching circuit 3. When the DRV-OUT signal is at a high level, the first switch tube Q1 is turned on, the second switch tube Q2 and the third switch tube Q3 are turned off, and then the terminal resistor R6 is turned off. When the DRV-OUT signal is at a low level, the first switch tube Q1 is turned off, the driving voltage of the second switch tube Q2 and the third switch tube Q3 is 12V, which is greater than the voltage signal amplitude of the parallel line 2. The voltage signal amplitude of the parallel line 2 is the voltage difference between the bus high-level signal CANH and the bus low-level signal CANL. Generally, the voltage of the bus high-level signal CANH is about 3.5V, the voltage of the bus low-level signal CANL is about 1.5V, and the voltage signal amplitude of the parallel line 2 is about 2V. Therefore, the second switch tube Q2 and the third switch tube Q3 are turned on, and the terminal resistor R6 is closed, thereby realizing the automatic closing control of the terminal resistor R6 on the first and last machines.

[0045] Specifically, the switching circuit 3 further comprises a first isolation resistor R7. The first end of the first isolation resistor R7 is connected to the second pole of the first switch tube Q1, and the other end is connected to the third pole of the second switch tube Q2 and the third pole of the third switch tube Q3. The first isolation resistor R7 plays an isolation role, avoiding the interference of the second switch tube Q2 and the third switch tube Q3 to the signal of the second pole of the first switch tube Q1. In addition, the first isolation resistor R7 can also limit the current flowing from the second pole of the first switch tube Q1 to the third poles of the second switch tube Q2 and the third switch tube Q3, thereby protecting the second switch tube Q2 and the third switch tube Q3 from being damaged by excessive current.

[0046] Embodiment three

[0047] Referring to Figure 1 , 2 , 4, the embodiment discloses a CAN parallel machine first and last terminal resistor automatic closing system based on the CAN parallel machine first and last terminal resistor automatic closing system of embodiment one.

[0048] Specifically, the switch circuit 3 of the CAN parallel machine head terminal resistance automatic closing system of the embodiment comprises a relay RLY1, a fourth pull-up resistor R8 and a fourth power supply; the relay RLY1 is provided with a coil and a switching switch, one end of the coil is connected to an output end of an AND gate chip U1, the fourth pull-up resistor R8 and the fourth power supply are connected to the other end of the coil in sequence; a moving contact of the switching switch is connected to a terminal resistor R6, a parallel input network port J2 and a parallel output network port J1 are connected to one end of the terminal resistor R6 away from the moving contact, a first fixed contact of the switching switch is connected to the parallel input network port J2 and the parallel output network port J1, and a second fixed contact of the switching switch is disconnected. More specifically, one end of the terminal resistor R6 away from the moving contact is connected to a first communication interface, and the first fixed contact is connected to a second communication interface. As shown in Figure 4 , a 1st pin and a 2nd pin of the relay RLY1 are connected to the fourth pull-up resistor R8 and the output end of the AND gate chip U1 respectively, and the coil is connected between the 1st pin and the 2nd pin of the relay RLY1; a 3rd pin and a 4th pin of the relay RLY1 are connected to the terminal resistor R6 and the second communication interface respectively, the fixed contact is connected to the 3rd pin of the relay RLY1, the first moving contact is connected to the 4th pin of the relay RLY1, the 5th pin of the relay RLY1 is disconnected, and the second moving contact is connected to the 5th pin of the relay RLY1. An output end of the logic circuit 4 outputs a DRV-OUT signal and transmits it to the switch circuit 3; when the DRV-OUT signal is at a high level, the relay RLY1 does not act; when the DRV-OUT signal is at a low level, the moving contact and the first fixed contact of the relay RLY1 are attracted, so that the terminal resistor R6 is connected in parallel between the first communication interface and the second communication interface, and the terminal resistor R6 is automatically connected to the head and tail machines.

[0049] Embodiment Four

[0050] Referring to Figure 1 , 2 , 5, the embodiment discloses a CAN parallel machine head terminal resistance automatic closing system based on the CAN parallel machine head terminal resistance automatic closing system of embodiment one.

[0051] Specifically, the switch circuit 3 of the CAN parallel machine head terminal resistance automatic closing system of the embodiment comprises: a photocoupler U2, a fifth pull-up resistor R9 and a fifth power supply; the photocoupler U2 comprises a light-emitting diode and a photo transistor, the fifth pull-up resistor R9 and the fifth power supply are sequentially connected to the positive electrode of the light-emitting diode, and the negative electrode of the light-emitting diode is connected to the output end of the AND gate chip U1; the first electrode of the photo transistor is connected to the parallel machine input network port J2 and the parallel machine output network port J1, the second electrode of the photo transistor is used for receiving the light signal of the light-emitting diode, the third electrode of the photo transistor is connected to the terminal resistor R6, and the parallel machine input network port J2 and the parallel machine output network port J1 are connected to one end of the terminal resistor R6 away from the third electrode of the photo transistor. Figure 5 As shown in the figure, the 1 pin of the photocoupler U2 is connected to the fifth pull-up resistor R9, the 2 pin of the photocoupler U2 is connected to the output end of the AND gate chip U1, the 3 pin of the photocoupler U2 is connected to the second communication interface, and the 4 pin of the photocoupler U2 is connected to the terminal resistor R6; the light-emitting diode is connected between the 1 pin and the 2 pin of the photocoupler U2, and the photo transistor is connected between the 3 pin and the 4 pin of the photocoupler U2. It can be understood that, in the embodiment, the first electrode, the second electrode and the third electrode of the photo transistor are respectively the emitter, the base and the collector. The output end of the logic circuit 4 outputs a DRV-OUT signal and transmits it to the switch circuit 3; when the DRV-OUT signal is at a high level, the DRV-OUT signal is connected to the negative electrode of the light-emitting diode, at this time, the voltage difference between the two ends of the light-emitting diode is not enough to make it conduct light, so that the photo transistor cannot receive light and is in a cut-off state, that is, the photocoupler U2 is not conductive; when the DRV-OUT signal is at a low level, the negative electrode of the light-emitting diode receives a low-level signal, at this time, the fifth power supply provides a high level to the positive electrode of the light-emitting diode through the fifth pull-up resistor R9, and a sufficient forward voltage difference is formed between the two ends of the light-emitting diode, so that the light-emitting diode is conductive and emits light, so that the light emitted by the light-emitting diode irradiates the second electrode of the photo transistor, the photoelectric effect of the photo transistor occurs, the first electrode and the third electrode of the photo transistor present a low resistance state, that is, the first electrode and the third electrode of the photo transistor are conductive, so that the terminal resistor R6 is connected in parallel between the first communication interface and the second communication interface, and the terminal resistor R6 is automatically connected to the head and tail machines.

[0052] The CAN parallel machine head terminal resistance automatic closing system of the utility model, through setting logic circuit judges whether parallel machine is head and tail machine, and thereby controls switch circuit to connect or disconnect terminal resistance and parallel machine, and further realizes terminal resistance closing of head and tail machine and terminal resistance disconnecting of intermediate machine, eliminates manual operation of increasing terminal resistance, reduces artificial misoperation risk, and simple and convenient installation mode, only needs user to connect parallel machine between parallel machine, and can complete installation of CAN parallel machine head terminal resistance automatic closing system.

[0053] The above is only to further illustrate the technical content of the utility model by way of examples, so that the reader can more easily understand, but does not represent the embodiment of the utility model is limited to this, any technical extension or re-creation made according to the utility model, are protected by the utility model. The protection scope of the utility model is subject to the claims.

Claims

1. A CAN parallel machine head-end terminal resistance automatic closing system, comprising a plurality of parallel machines and parallel lines, a plurality of said parallel machines are connected in sequence through a plurality of said parallel lines, characterized in that: The parallel machine is provided with a terminal resistor, a switch circuit and a logic circuit; the switch circuit is connected to the terminal resistor and is used for controlling the on-off of the parallel machine and the terminal resistor; The logic circuit is connected to the parallel machine and the switch circuit and is used for judging whether the parallel machine is a head-tail machine and controlling the switch circuit to connect or cut off the terminal resistor.

2. The CAN stub terminator auto-closing system of claim 1, wherein, The parallel machine is provided with a parallel machine input network port and a parallel machine output network port, the parallel machine output network port is connected to the parallel machine input network port of the next parallel machine through a parallel line, the logic circuit is connected to the parallel machine input network port and the parallel machine output network port and is used for detecting whether the parallel machine input network port and the parallel machine output network port are both connected to the parallel line so as to judge whether the parallel machine is a middle machine or a head-tail machine.

3. The CAN stub terminator auto-closing system of claim 2, wherein, The parallel machine output network port and the parallel machine input network port are respectively provided with a first signal interface and a second signal interface, the first signal interface is connected with a first pull-up resistor and a first power supply in sequence, the second signal interface is connected with a second pull-up resistor and a second power supply in sequence, and the first signal interface and the second signal interface are respectively connected to the logic circuit.

4. The CAN stub terminator auto-closing system of claim 3, wherein, The logic circuit comprises an AND gate chip; the first signal interface and the second signal interface are respectively connected to a first input end and a second input end of the AND gate chip, and the input end of the AND gate chip is connected to the switch circuit.

5. The CAN stub terminator auto-closing system of claim 4, wherein, The switch circuit comprises a first switch tube, a second switch tube, a third switch tube, a third pull-up resistor and a third power supply; a first pole of the first switch tube is connected to an output end of the AND gate chip, the third pull-up resistor and the third power supply are connected to a second pole of the first switch tube in sequence, and a third pole of the first switch tube is grounded; first poles of the second switch tube and the third switch tube are connected to the second pole of the first switch tube, a second pole of the second switch tube is connected to the terminal resistor, the parallel machine input network port and the parallel machine output network port are connected to one end of the terminal resistor away from the second switch tube, and the parallel machine input network port and the parallel machine output network port are connected to a second pole of the third switch tube.

6. The CAN stub terminator auto-closing system of claim 5, wherein, The third power supply is greater than an amplitude of a voltage signal of the parallel line.

7. The CAN stub terminator auto-close system of claim 6, wherein, The switch circuit further comprises a first isolation resistor; a first end of the first isolation resistor is connected to the second pole of the first switch tube, and the other end is connected to a third pole of the second switch tube and a third pole of the third switch tube.

8. The CAN stub terminator auto-closing system of claim 4, wherein, The switch circuit comprises a relay, a fourth pull-up resistor and a fourth power supply; the relay is provided with a coil and a switching switch, one end of the coil is connected to an output end of the AND gate chip, the fourth pull-up resistor and the fourth power supply are connected to the other end of the coil in sequence; a moving contact of the switching switch is connected to the terminal resistor, the parallel machine input network port and the parallel machine output network port are connected to one end of the terminal resistor away from the moving contact, a first fixed contact of the switching switch is connected to the parallel machine input network port and the parallel machine output network port, and a second fixed contact of the switching switch is open.

9. The CAN stub terminator auto-closing system of claim 4, wherein, The switch circuit comprises a photocoupler, a fifth pull-up resistor and a fifth power supply; the photocoupler comprises a light-emitting diode and a phototransistor, the fifth pull-up resistor and the fifth power supply are connected to the positive pole of the light-emitting diode in sequence, and the negative pole of the light-emitting diode is connected to the output end of the AND gate chip; the first pole of the phototransistor is connected to the parallel machine input network port and the parallel machine output network port, the second pole of the phototransistor is used for receiving the light signal of the light-emitting diode, the third pole of the phototransistor is connected to the terminal resistor, and the parallel machine input network port and the parallel machine output network port are connected to one end of the terminal resistor away from the third pole of the phototransistor.

10. The CAN stub terminator auto-closing system according to any one of claims 1-9, wherein, The terminal resistor is installed in the interior of the parallel machine.

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