Hardware circuit simultaneously compatible with NPN interface and PNP interface of PLC
By designing hardware circuits compatible with PLC NPN and PNP interfaces, using interface protection units, semiconductor execution units and isolation units, the compatibility problems caused by different IO connection methods in the prior art are solved, and the cost reduction and relay life extension are achieved.
Patent Information
- Application Number
- CN202421403636.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-19
- Publication Date
- 2025-05-09
- Estimated Expiration
- 2034-06-19
AI Technical Summary
There are two different connection methods for the IO interface design of existing PLCs, NPN and PNP, which makes the same circuit design unable to be compatible with different IO connection methods. It is necessary to use intermediate relays to achieve compatibility, which increases the cost and relay life.
A hardware circuit is designed, including an interface protection unit, a semiconductor execution unit and an isolation unit, to achieve compatibility with different level standards through passive passive devices and semiconductor devices, and signal isolation isolates using optocoupler or magnetic isolation devices.
It realizes compatibility with the NPN and PNP interfaces of PLC, reduces the material and storage costs of sensor manufacturers, avoids the trouble of relays, and realizes unlimited switching times through semiconductor devices, solving the problem of relay life.
Smart Images
Figure CN222850875U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of PLC circuits, in particular to a hardware circuit which is compatible with both NPN and PNP interfaces of PLCs. Background Art
[0002] As the degree of industrial automation increases, more and more simple and repetitive industrial operations are completed by industrial robots, thus realizing industrial automation, reducing labor costs and improving production efficiency. In the automated assembly line, PLC (programmable logic controller) plays a very important role as one of the core components of automation.
[0003] Among them, IO (signal input and output) is a very important link, including the acquisition of analog signals (pressure, temperature, speed, etc.), the acquisition of digital signals (switching quantity), and the output of digital signals. These inputs and outputs constitute the core of the normal operation of each module in the industrial field.
[0004] However, due to the different designs of PLCs and sensors, there are currently two different ways to connect digital IO, namely NPN type ( Figure 3 ) and PNP type ( Figure 4 ), which is the so-called common source and ground connection method.
[0005] These two connection methods have their own advantages. Generally speaking, for the IO of PLC, the on-site power supply is generally DC 24V (except for special cases, some old standards use DC110V, which is rare now). PNP connection is generally used by foreign companies in Europe and the United States. The advantage is that it is easy to judge the fault when a fault occurs, because 24V is more obvious than 0V, and the electrical environment of the factory is relatively poor, various electromagnetic fields interact with each other, and 24V is much more anti-interference than 0V. NPN connection; generally Japanese and some domestic manufacturers are willing to use this connection method, because the power delivered to the site is 0V. When the cable is damaged on site, the 0V cable touches the ground wire and will not cause the upper-level switching power supply to trip or be damaged. Therefore, it is more adaptable and can better protect the system.
[0006] Due to the difference in the wiring types of the two, two circuit design requirements are also proposed for the sensor end, and the same circuit design cannot cope with different IO connection methods. The general solution now is to use an intermediate relay to achieve compatibility with different standards ( Figure 5 , Figure 6 ), although it can meet the conversion requirements, it also increases the cost of additional materials and wiring. At the same time, for scenarios with frequent on-off switching, the life of the relay is also an unavoidable problem. Utility Model Content
[0007] In view of the above problems, the utility model provides a hardware circuit which is compatible with both the NPN and PNP interfaces of a PLC, so as to solve the problems of product cost and reduced relay life caused by the existing compatible design.
[0008] To achieve the above object, the technical solution adopted by the utility model is: a hardware circuit compatible with both the NPN and PNP interfaces of a PLC, comprising an interface protection unit, a semiconductor execution unit and an isolation unit;
[0009] The interface protection unit is composed of passive components, including a gas discharge tube for surge protection, a varistor, an ESD clamp device for static electricity protection, and a PTC device for short circuit protection; the interface protection unit is used to protect against short circuits caused by abnormal voltage misconnection or human operation;
[0010] The semiconductor execution unit includes an action execution unit and a polarity reversal unit; the semiconductor execution unit is used to achieve polarity reversal of the input signal and perform on-off operations according to the command signal of the sensor end;
[0011] The isolation unit is an optical coupler or a magnetic isolation device, which is used to achieve isolation of strong and weak electrical signals;
[0012] The interface protection unit is connected to a semiconductor execution unit, and the semiconductor execution unit is connected to a sensor control IO through an isolation unit.
[0013] Compared with the prior art, the beneficial effects of the utility model are:
[0014] Through the hardware implementation of the interface circuit compatible with PLCs of different electrical level standards, the sensor manufacturer does not need to care about the wiring mode of the on-site PLC (NPN and PNP compatible) or the electrical level standard (12V, 24V, 48V can all be used), which can effectively reduce the material and storage costs for sensor manufacturers. The on-site system also saves the trouble of relays. At the same time, because semiconductor devices are used, the number of switches is theoretically unlimited, which solves the problem of relay life.
[0015] As a further improvement of the above scheme, the device circuit connection relationship of the interface protection unit is: the output signal common end is connected to a varistor through a time-delay fuse, then connected in series with a PTC self-recovery fuse, and finally connected in parallel with a TVS tube to form a two-pole protection.
[0016] The technical effect of the above improvement is: the common end of the output signal is firstly short-circuited through a slow-blow fuse. When the equipment load short-circuit fails, this device burns randomly to keep other bus devices unaffected. Then, a varistor is connected immediately after the signal output end and the fuse to prevent surge damage to the equipment and keep the voltage between the output signal and the common end within the voltage range allowed by the device. Then, a PTC self-recovery fuse is connected in series, and then a TVS tube is connected in parallel to form a two-pole protection. The PTC can limit the output current. When the external load is abnormal, the output can be automatically cut off to protect the equipment from damage. The TVS conduction speed is faster than the varistor. The two work together to protect the actuator from damage.
[0017] As a further improvement of the above solution, the action execution unit is a passive relay used for switching.
[0018] As a further improvement of the above scheme, the circuit connection relationship of the polarity reversal unit is as follows: the external input DC signal or AC signal is converted into a DC or pulse DC signal with a determined polarity through a bridge rectifier array, the rectified positive electrode is connected to the drain of the power PMOS tube, and the rectified negative electrode is connected to the source of the power PMOS tube. Finally, the gate and source voltages of the PMOS tube are controlled by the isolated power supply to achieve on and off.
[0019] The polarity reversal unit converts the level or alternating current of different connection methods into the direct current or pulse voltage required by the action execution unit.
[0020] As a further improvement of the above solution, the isolation unit is an optical coupler or a magnetic isolation device.
[0021] The technical effect of the above improvement is that the control end can easily achieve voltage isolation of several thousand volts through magnetic coupling or optical coupling, effectively protecting the safety of people and equipment. BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Figure 1 This is a control signal flow chart of the circuit of the utility model.
[0023] Figure 2 This is a circuit schematic diagram of the utility model.
[0024] Figure 3 It is a schematic diagram of NPN type connection in the prior art.
[0025] Figure 4 It is a schematic diagram of the PNP type connection method in the prior art.
[0026] Figure 5 Schematic diagram of different sensors connected by NPN connection in PLC in the prior art.
[0027] Figure 6Schematic diagram of different sensors connected by PNP connection in PLC in the prior art. DETAILED DESCRIPTION
[0028] In order to enable those skilled in the art to better understand the technical solution, the utility model is described in detail below in conjunction with embodiments. The description in this section is only exemplary and explanatory and should not have any limiting effect on the protection scope of the utility model.
[0029] Embodiment 1:
[0030] like Figure 1-2 As shown, the specific solution of this embodiment is: a hardware circuit compatible with both the NPN and PNP interfaces of a PLC, including an interface protection unit, a semiconductor execution unit and an isolation unit;
[0031] The interface protection unit is composed of passive components, including a gas discharge tube for surge protection, a varistor, an ESD clamp device for static electricity protection, and a PTC device for short circuit protection; the interface protection unit is used to protect against short circuits caused by abnormal voltage misconnection or human operation;
[0032] The semiconductor execution unit includes an action execution unit and a polarity reversal unit; the semiconductor execution unit is used to achieve polarity reversal of the input signal and perform on-off operations according to the command signal of the sensor end;
[0033] The isolation unit is an optical coupler or a magnetic isolation device, which is used to achieve isolation of strong and weak electrical signals;
[0034] The interface protection unit is connected to a semiconductor execution unit, and the semiconductor execution unit is connected to a sensor control IO through an isolation unit.
[0035] Embodiment 2:
[0036] like Figure 1-2 As shown, as a preferred embodiment of the above embodiment, a hardware circuit compatible with both the NPN and PNP interfaces of a PLC includes an interface protection unit, a semiconductor execution unit and an isolation unit;
[0037] The interface protection unit is composed of passive components, including a gas discharge tube for surge protection, a varistor, an ESD clamp device for static electricity protection, and a PTC device for short circuit protection; the interface protection unit is used to protect against short circuits caused by abnormal voltage misconnection or human operation;
[0038] The semiconductor execution unit includes an action execution unit and a polarity reversal unit; the semiconductor execution unit is used to achieve polarity reversal of the input signal and perform on-off operations according to the command signal of the sensor end;
[0039] The isolation unit is an optical coupler or a magnetic isolation device, which is used to achieve isolation of strong and weak electrical signals;
[0040] The interface protection unit is connected to the semiconductor execution unit, and the semiconductor execution unit is connected to the sensor control IO through the isolation unit; the device circuit connection relationship of the interface protection unit is: the output signal common end is connected to the varistor through the time-delay fuse, and then the PTC self-recovery fuse is connected in series, and finally the TVS tube is connected in parallel to form a two-pole protection; through the signal transmission and processing of each module, the weak low-voltage signal emitted by the sensor is converted into an isolated active node signal that meets different working conditions on site, realizing the abstraction of the hardware layer for users, without having to worry about the internal processing details.
[0041] Embodiment 3:
[0042] like Figure 1-2 As shown, as a preferred embodiment of the above embodiment, a hardware circuit compatible with both the NPN and PNP interfaces of a PLC includes an interface protection unit, a semiconductor execution unit and an isolation unit;
[0043] The interface protection unit is composed of passive components, including a gas discharge tube for surge protection, a varistor, an ESD clamp device for static electricity protection, and a PTC device for short circuit protection; the interface protection unit is used to protect against short circuits caused by abnormal voltage misconnection or human operation;
[0044] The semiconductor execution unit includes an action execution unit and a polarity reversal unit; the semiconductor execution unit is used to achieve polarity reversal of the input signal and perform on-off operations according to the command signal of the sensor end;
[0045] The isolation unit is an optical coupler or a magnetic isolation device, which is used to achieve isolation of strong and weak electrical signals;
[0046] The interface protection unit is connected to the semiconductor execution unit, and the semiconductor execution unit is connected to the sensor control IO through the isolation unit; the action execution unit is a passive relay used for switching.
[0047] Embodiment 4:
[0048] like Figure 1-2 As shown, as a preferred embodiment of the above embodiment, a hardware circuit compatible with both the NPN and PNP interfaces of a PLC includes an interface protection unit, a semiconductor execution unit and an isolation unit;
[0049] The interface protection unit is composed of passive components, including a gas discharge tube for surge protection, a varistor, an ESD clamp device for static protection, and a PTC device for short circuit protection; the interface protection unit is used to protect against short circuits caused by abnormal voltage misconnection or human operation;
[0050] The semiconductor execution unit includes an action execution unit and a polarity reversal unit; the semiconductor execution unit is used to achieve polarity reversal of the input signal and perform on-off operations according to the command signal of the sensor end;
[0051] The isolation unit is an optical coupler or a magnetic isolation device, which is used to isolate strong and weak electrical signals;
[0052] The interface protection unit is connected to the semiconductor execution unit, and the semiconductor execution unit is connected to the sensor control IO through the isolation unit; the circuit connection relationship of the polarity reversal unit is as follows: the external input DC signal or AC signal is converted into a DC or pulse DC signal with a determined polarity through a bridge rectifier array, the rectified positive electrode is connected to the drain of the power PMOS tube, and the rectified negative electrode is connected to the source of the power PMOS tube, and finally the gate and source voltages of the PMOS tube are controlled by the isolated power supply to achieve on and off.
[0053] The polarity reversal unit converts the level or alternating current of different connection methods into the direct current or pulse voltage required by the action execution unit.
[0054] Embodiment 5:
[0055] like Figure 1-2 As shown, as a preferred embodiment of the above embodiment, a hardware circuit compatible with both the NPN and PNP interfaces of a PLC includes an interface protection unit, a semiconductor execution unit and an isolation unit;
[0056] The interface protection unit is composed of passive components, including a gas discharge tube for surge protection, a varistor, an ESD clamp device for static protection, and a PTC device for short circuit protection; the interface protection unit is used to protect against short circuits caused by abnormal voltage misconnection or human operation;
[0057] The semiconductor execution unit includes an action execution unit and a polarity reversal unit; the semiconductor execution unit is used to achieve polarity reversal of the input signal and perform on-off operations according to the command signal of the sensor end;
[0058] The isolation unit is an optical coupler or a magnetic isolation device, which is used to isolate strong and weak electrical signals;
[0059] The interface protection unit is connected to the semiconductor execution unit, and the semiconductor execution unit is connected to the sensor control IO through the isolation unit; the isolation unit is an optical coupler or a magnetic isolation device.
[0060] The working principle of the utility model is as follows: the input protection unit mainly refers to the protection against short circuits caused by abnormal voltage misconnection or human operation, protecting the normal operation of the equipment body and the semiconductor actuator. The general structure is mainly realized by passive components, such as gas discharge tubes and varistors for surge protection, ESD clamping devices for electrostatic protection, PTC devices for short circuit protection, etc., which are realized according to a certain circuit structure.
[0061] The semiconductor execution unit mainly realizes the polarity reversal of the input signal, and then performs the on-off operation according to the instructions of the sensor end. The reason for the polarity reversal is mainly because for the NPN type connection, the negative power supply is the common terminal. For the PNP type connection, the power supply is the common terminal. When the two are in action, the current flows in opposite directions. For semiconductor devices, especially switching tubes, a stable "virtual ground" is required as a reference for the switch. Therefore, a special circuit must be used to achieve polarity reversal to achieve the purpose of semiconductor control.
[0062] The isolation unit is mainly used to isolate strong and weak electrical signals to protect the device when an accident occurs. The usual means is to isolate by light or magnetism. The optical isolation used in the present invention is relatively mature in technology and has lower cost.
[0063] The control signal flow is as follows: the sensor control IO is a low-level signal sent by a general sensor, such as a 3.3V or 5V controller signal. This signal is isolated through the isolation unit to achieve voltage isolation between the control and actuator. Generally, simple optical couples and magnetic isolation devices can easily achieve a voltage isolation of more than 2KV. The execution action unit acts as a switch, which can be compared to a passive relay. The polarity reversal is responsible for converting the levels of different connection methods or even AC into the DC or pulse voltage required by the execution unit. The interface protection unit is responsible for surge protection, external short circuit protection, etc., to protect the main body of the equipment from damage.
[0064] It should be noted that, in this article, the terms include, contain or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. Specific examples are used in this article to illustrate the principle and implementation of the technical solution of the utility model. The above examples are only used to help understand the method and core idea of the utility model. The above are only preferred implementations of the utility model. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, for ordinary technicians in this technical field, without departing from the principle of the utility model, several improvements, modifications or changes can be made, and the above technical features can also be combined in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the concept and technical solution of the utility model to other occasions without improvement, should be regarded as the protection scope of the utility model.
Claims
1. A hardware circuit compatible with both NPN and PNP interfaces of PLC, characterized in that: It includes an interface protection unit, a semiconductor execution unit and an isolation unit; The interface protection unit is composed of passive components, including a gas discharge tube for surge protection, a varistor, an ESD clamp device for static electricity protection, and a PTC device for short circuit protection; the interface protection unit is used to protect against short circuits caused by abnormal voltage misconnection or human operation; The semiconductor execution unit includes an action execution unit and a polarity reversal unit; the semiconductor execution unit is used to achieve polarity reversal of the input signal and perform on-off operations according to the command signal of the sensor end; The isolation unit is used to isolate strong and weak electrical signals; The interface protection unit is connected to a semiconductor execution unit, and the semiconductor execution unit is connected to a sensor control IO through an isolation unit.
2. A hardware circuit compatible with both NPN and PNP interfaces of PLC according to claim 1, characterized in that: The device circuit connection relationship of the interface protection unit is as follows: the output signal common end is connected to a varistor through a time-delay fuse, then connected in series with a PTC self-recovery fuse, and finally connected in parallel with a TVS tube to form a two-pole protection.
3. The hardware circuit compatible with both NPN and PNP interfaces of PLC according to claim 1, characterized in that: The action execution unit is a passive relay used for switching.
4. The hardware circuit compatible with both NPN and PNP interfaces of PLC according to claim 1, characterized in that: The circuit connection relationship of the polarity reversal unit is as follows: the external input DC signal or AC signal is converted into a DC or pulse DC signal with a determined polarity through a bridge rectifier array, the positive electrode after rectification is connected to the drain of the power PMOS tube, the negative electrode after rectification is connected to the source of the power PMOS tube, and finally the gate and source voltages of the PMOS tube are controlled by the isolated power supply to realize on and off; The polarity reversal unit converts the level or alternating current of different connection methods into the direct current or pulse voltage required by the action execution unit.
5. The hardware circuit compatible with both NPN and PNP interfaces of PLC according to claim 1, characterized in that: The isolation unit is an optical coupler or a magnetic isolation device.