Universal detection circuit and device for PLC source drain type digital quantity output module

Abstract

The invention provides a general detection circuit and device for a PLC source-drain type digital quantity output module, and the circuit is characterized in that a first terminal and a second terminal are connected to a common terminal, a power supply terminal, a first resistor, a first diode and the second terminal of the PLC source-drain type digital quantity output module to form a drain type current path; the second terminal, the second diode, the second resistor, the NPN type triode and the grounding terminal form a source type current path, and when the general detection circuit is connected with the common terminal of the drain type digital quantity output module, the general detection circuit can be automatically switched to a drain type current path to be conducted. When the general detection circuit is connected with the common end of the source type digital quantity output module, the general detection circuit can be automatically switched to the source type current path for conduction. According to the invention, a general detection function of a single detection circuit and device for PLC source type and drain type digital quantity output modules can be realized.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial control automation, and in particular relates to a universal detection circuit and device for a PLC source-drain type digital quantity output module. Background Art

[0002] In PLC (Programmable Logic Controller), digital output modules are usually divided into two types: source type and sink type. The source type digital output module can provide current to the load, that is, the current flows out from the common end of the PLC, passes through the load and returns to the negative pole of the external power supply or the ground wire. The sink type digital output module is the opposite. It can receive current from the load, that is, the current flows from the positive pole of the external power supply through the load and flows into the common end of the PLC.

[0003] In order to measure the load capacity of the PLC digital output module, a detection device is often connected to the common end of the PLC digital output module for direct measurement. However, under the existing technology, the conventional PLC digital output module detection device includes a source-type digital output module detection device and a leakage-type digital output module detection device, which correspond to the detection operations of the source-type digital output module and the leakage-type digital output module respectively, and the two are not interchangeable. When the PLC device has a source-type digital output module and a leakage-type digital output module, and shares a common end, two detection devices need to be prepared to cope with the measurement requirements of different types of digital output modules. The disassembly and assembly process is cumbersome, and the measurement operation efficiency is low. Summary of the invention

[0004] The present invention aims to provide a universal detection circuit and device for a PLC source-drain type digital output module to solve the technical problem that conventional PLC digital output module detection circuits and devices cannot realize the universal detection function of source type digital output modules and drain type digital output modules under the prior art.

[0005] To solve the above problems, the technical solution of the present invention is: a universal detection circuit of a PLC source-drain type digital output module, comprising: an NPN transistor, a first diode, a second diode, a first resistor and a second resistor; The base of the NPN transistor is connected to the first terminal, the collector of the NPN transistor is connected to the power supply terminal, the emitter of the NPN transistor is connected to the ground terminal, and the first terminal and the second terminal are connected to the common terminal of the PLC source and / or sink digital output module; The first diode and the second diode are arranged in parallel, the cathode of the first diode is connected to the second terminal, the anode of the first diode is connected to the first end of the first resistor, the second end of the first resistor is connected to the collector of the NPN transistor, the power supply end, the first resistor, the first diode to the second terminal, to form a leakage current path; the anode of the second diode is connected to the second terminal, the cathode of the second diode is connected to the first end of the second resistor, the second end of the second resistor is connected to the collector of the NPN transistor, the second terminal, the second diode, the second resistor, the NPN transistor to the ground terminal, to form a source current path; When the first terminal and the second terminal are configured to be connected to the common terminal of the PLC digital output module, the universal detection circuit is based on the low level output by the PLC leakage-type digital output module, and the NPN-type transistor is cut off, and the current flows from the power supply end through the first resistor and the first diode in sequence to the second terminal, and the leakage-type current path is turned on, which is used to measure the load performance of the PLC leakage-type digital output module; the universal detection circuit is based on the high level output by the PLC source-type digital output module, and the NPN-type transistor is turned on, and the current flows from the second terminal through the second diode, the second resistor, and the NPN-type transistor in sequence to the ground terminal, and the source-type current path is turned on, which is used to measure the load performance of the PLC source-type digital output module.

[0006] Preferably, the leakage current path includes a first branch and a second branch, a first common node of the first branch and the second branch is connected to the collector of the NPN transistor, and a second common node of the first branch and the second branch is connected to the anode of the first diode; The first resistor is connected in series in the first branch, and the third resistor and the first light-emitting diode are connected in series in the second branch. The first end of the third resistor is connected to the first common node of the first branch and the second branch, the second end of the third resistor is connected to the anode of the first light-emitting diode, and the cathode of the first light-emitting diode is connected to the second common node of the first branch and the second branch.

[0007] Preferably, the source current path includes a third branch and a fourth branch, a third common node of the third branch and the fourth branch is connected to the collector of the NPN transistor, and a fourth common node of the third branch and the fourth branch is connected to the cathode of the second diode; The second resistor is connected in series in the third branch, and the fourth resistor and the second light-emitting diode are connected in series in the fourth branch. The first end of the fourth resistor is connected to the third common node of the third branch and the fourth branch, the second end of the fourth resistor is connected to the cathode of the second light-emitting diode, and the anode of the second light-emitting diode is connected to the fourth common node of the third branch and the fourth branch.

[0008] Preferably, a fifth resistor is connected in series between the power supply end and the collector of the NPN transistor, and the fifth resistor is used to limit the current amplitude transmitted from the power supply end to the collector of the NPN transistor.

[0009] Preferably, the resistance value of the first resistor is limited to 100Ω, the resistance value of the fifth resistor is limited to 100Ω, and the resistance value of the third resistor is limited to 5KΩ.

[0010] Preferably, the resistance value of the second resistor is limited to 200Ω, and the resistance value of the fourth resistor is limited to 10KΩ.

[0011] Preferably, an acceleration capacitor is connected in parallel between the base and the emitter of the NPN transistor, and the acceleration capacitor is used to increase the charge discharge efficiency of the NPN transistor during the switching process between the leakage current path and the source current path.

[0012] Preferably, a sixth resistor is connected in series between the first wiring terminal and the base of the NPN transistor, and the sixth resistor is used to limit the current amplitude transmitted from the first wiring terminal to the base of the NPN transistor.

[0013] Based on the same concept, the present invention also provides a universal detection device for a PLC source-drain type digital output module, which is equipped with a universal detection circuit for a PLC source-drain type digital output module as described in any one of the above, and is used to realize a universal load detection function for a PLC source-type or drain-type digital output module.

[0014] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: The present invention provides a universal detection circuit and device for a PLC source-drain type digital quantity output module. A source type current path and a drain type current path are constructed by an NPN type transistor, a first diode, a second diode, a first resistor and a second resistor. When a first terminal and a second terminal are connected to a common terminal of a PLC digital quantity output module, if the digital quantity output module is a drain type at this time, the first terminal and the second terminal output a low level, the NPN type transistor is cut off, and the current can only flow out from the power supply end, flow unidirectionally through the first resistor and the first diode in the drain type current path, and finally flow into the second terminal. On the contrary, if the digital quantity output module is a source type at this time, the first terminal and the second terminal output a high level, the NPN type transistor is turned on, and the current flows out from the second terminal, flows unidirectionally through the second diode in the source type current path, and flows through the second resistor and the collector to the emitter of the NPN type transistor, and finally flows into the ground terminal. Therefore, through the present invention, the PLC digital output module detection circuit and device can realize a universal detection function for source-type digital output modules and leakage-type digital output modules. It can automatically switch the detection circuit according to the output level of the PLC common terminal, and there is no need to repeatedly disassemble and assemble the measuring device to complete the load measurement operation, thereby effectively improving the measurement operation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic structural diagram of a universal detection circuit of a PLC source-drain type digital quantity output module provided by the present invention; Figure 2 Schematic diagram of current flow in the measurement circuit of source digital output module; Figure 3 Schematic diagram of the current flow in the measurement circuit of a sink-type digital output module. DETAILED DESCRIPTION

[0016] The following is a further detailed description of a universal detection circuit and device for a PLC source-drain digital output module proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims.

[0017] First embodiment See also Figure 1 This embodiment provides a universal detection circuit for a PLC source-drain type digital output module, which is used to implement a universal detection function for the output load of a PLC source-type or drain-type digital output module.

[0018] Specifically, a first terminal U1 and a second terminal U2 are provided at both ends of the universal detection circuit of the PLC source-drain type digital output module, and the first terminal U1 and the second terminal U2 are actually maintained in a commonly connected state, that is, when the universal detection circuit provided in this embodiment is connected to the common end of the PLC source type and / or drain type digital output module, the level signal output by the PLC source type and drain type digital output module is synchronously transmitted to the first terminal U1 and the second terminal U2.

[0019] The universal detection circuit for the PLC source-drain type digital output module is internally provided with an NPN transistor, a first diode D1, a second diode D2, a first resistor R1 and a second resistor R2. The base of the NPN transistor is connected to the first terminal U1, the collector of the NPN transistor is connected to the power supply terminal VCC, and the emitter of the NPN transistor is connected to the ground terminal. In this embodiment, the power supply terminal VCC can maintain an output voltage of +24V.

[0020] The first diode D1 and the second diode D2 are arranged in parallel, the cathode of the first diode D1 is connected to the second terminal U2, the anode of the first diode D1 is connected to the first end of the first resistor R1, the second end of the first resistor R1 is connected to the collector of the NPN transistor, the power supply terminal VCC, the first resistor R1, the first diode D1 to the second terminal U2, to form a leakage current path. The anode of the second diode D2 is connected to the second terminal U2, the cathode of the second diode D2 is connected to the first end of the second resistor R2, the second end of the second resistor R2 is connected to the collector of the NPN transistor, the second terminal U2, the second diode D2, the second resistor R2, the NPN transistor to the ground terminal, to form a source current path.

[0021] For the NPN transistor, when its base input is high level, the NPN transistor is turned on, and the current can be transmitted from its collector to the emitter. Conversely, when its base input is low level, the NPN transistor is turned off, and the current path from its collector to the emitter is cut off. For the first diode D1 and the second diode D2, they can allow current to be input from their anode end, conduct unidirectionally, and output from their cathode end.

[0022] See also Figure 2-Figure 3 In the conventional source-drain digital quantity output module detection circuit of PLC, since the source type digital quantity output module outputs a high level, the main design of the measurement circuit of the source type digital quantity output module is as follows: Figure 2 As shown in the figure, the wiring terminal on one side of the measurement circuit is connected to the common terminal of the source type digital output module, and the wiring terminal on the other side of the measurement circuit is grounded. On the contrary, the output of the leakage type digital output module is low level, so the main design of the measurement circuit of the leakage type digital output module is as follows: Figure 3As shown, the wiring terminal on one side of the measuring circuit is connected to the common terminal of the leakage type digital output module, and the wiring terminal on the other side of the measuring circuit is connected to the power supply terminal.

[0023] In the present embodiment, a measurement circuit common to source-type digital quantity output modules and sink-type digital quantity output modules is provided. Based on the above circuit structure, when the universal detection circuit is connected to the common terminal of the sink-type digital quantity output module, since the common terminal output of the sink-type digital quantity output module is at a low level, that is, at this time, the first terminal U1 and the first terminal U2 are both at a low level, the NPN transistor is cut off, and the power supply terminal VCC outputs current, and the current is transmitted to the second terminal U2 through the first resistor R1 and the first diode D1 in the sink-type current path. When the universal detection circuit is connected to the common terminal of the source-type digital quantity output module, since the common terminal output of the source-type digital quantity output module is at a high level, that is, at this time, the first terminal U1 and the first terminal U2 are at a high level, the NPN transistor is turned on, and the first terminal U2 outputs current, and the current is transmitted to the collector of the NPN transistor through the second diode D2 and the second resistor R2 in the source current path, and then transmitted to the ground terminal through the collector-to-emitter current path of the NPN transistor.

[0024] In summary, the present embodiment provides a universal detection circuit for a PLC source-drain type digital output module, which can automatically select and switch the current to flow through a leakage type current path or a source type current path according to the high and low levels output by the common end of the connected PLC digital output module, thereby simultaneously meeting the measurement circuit wiring requirements of the leakage type digital output module and the source type digital output module in a single measurement circuit, thereby realizing a universal measurement function for the leakage type digital output module and the source type digital output module.

[0025] The specific structure of a universal detection circuit of a PLC source-drain type digital output module provided by this embodiment will be described in further detail below: Preferably, in this embodiment, the leakage current path includes a first branch and a second branch, the first common node of the first branch and the second branch is connected to the collector of the NPN transistor, and the second common node of the first branch and the second branch is connected to the anode of the first diode D1, that is, the first branch and the second branch are in parallel.

[0026] Among them, a first resistor R1 is provided in series in the first branch, a second resistor R3 and a first light-emitting diode LED1 are provided in series in the second branch, a first end of the third resistor R3 is connected to a first common node of the first branch and the second branch, a second end of the third resistor R3 is connected to an anode of the first light-emitting diode LED1, and a cathode of the first light-emitting diode LED1 is connected to a second common node of the first branch and the second branch. Therefore, when the leakage current path is turned on, current can flow in from the anode of the first light-emitting diode LED1 and flow out from the cathode of the first light-emitting diode LED1, enabling the first light-emitting diode LED1 to emit light, which is used to indicate that the leakage current path is in the on state at this time, that is, the PLC digital output module detected by the universal detection circuit at this time is a leakage digital output module. The third resistor R3 is used to limit the current amplitude flowing through the second branch to prevent the first light-emitting diode LED1 from being damaged due to excessive current flowing through it.

[0027] Similarly, the source current path includes a third branch and a fourth branch, the third common node of the third branch and the fourth branch is connected to the collector of the NPN transistor, and the fourth common node of the third branch and the fourth branch is connected to the cathode of the second diode D2, that is, the third branch and the fourth branch are in parallel.

[0028] Among them, a second resistor R2 is provided in series in the third branch, a fourth resistor R4 and a second light emitting diode LED2 are provided in series in the fourth branch, a first end of the fourth resistor R4 is connected to a third common node of the third branch and the fourth branch, a second end of the fourth resistor R4 is connected to a cathode of the second light emitting diode LED2, and an anode of the second light emitting diode LED2 is connected to a fourth common node of the third branch and the fourth branch. Therefore, when the source current path is turned on, current can flow in from the anode of the second light emitting diode LED2 and flow out from the cathode of the second light emitting diode LED2, enabling the first light emitting diode LED2 to emit light, indicating that the source current path is in the on state at this time, that is, the PLC digital output module detected by the universal detection circuit at this time is a source digital output module. The fourth resistor R4 is used to limit the current amplitude flowing through the fourth branch to prevent the second light emitting diode LED2 from being damaged due to excessive current flowing through it.

[0029] Preferably, in this embodiment, a fifth resistor R5 is connected in series between the power supply terminal VCC and the collector of the NPN transistor. When the leakage current path is turned on, the power supply terminal VCC outputs current, and the current first flows through the fifth resistor R5, then flows through the first resistor R1 and the second resistor R2 arranged in parallel, and finally is transmitted to the second terminal U2. By measuring the voltage between the fifth resistor R5 and the first resistor R1, the actual current flowing through the fifth resistor R5 to the first resistor R1 can be calculated according to Ohm's law, and then the load capacity and performance of the PLC leakage digital output module can be evaluated and verified. At the same time, when the source current path is turned on, in addition to the second terminal U2 outputting current, the power supply terminal VCC also outputs current. Therefore, a fifth resistor R5 is connected in series between the power supply terminal VCC and the collector of the NPN transistor, which can be used to limit the current size of the power supply terminal VCC flowing into the collector of the NPN transistor to prevent the NPN transistor from being burned due to excessive current.

[0030] Specifically, in this embodiment, the resistance value of the first resistor R1 is selected as 100Ω, the resistance value of the fifth resistor R5 is selected as 100Ω, and the resistance value of the third resistor R3 is 5KΩ. The first resistor R1 and the fifth resistor R5 with smaller resistance values ​​are used in conjunction with the +24V voltage output by the power supply terminal VCC, so that a larger measurement current can be generated in the leakage current path, thereby improving the load measurement accuracy of the PLC leakage digital output module. At the same time, the third resistor R3 with a larger resistance value is selected to limit the current passing through the first light-emitting diode LED1 to prevent the first light-emitting diode LED1 from being damaged due to overcurrent.

[0031] Similarly, the resistance value of the second resistor is selected to be 200Ω, and the resistance value of the fourth resistor is selected to be 10KΩ, so as to improve the load measurement accuracy of the PLC source digital output module and prevent the second light emitting diode LED2 from being damaged due to overcurrent.

[0032] Preferably, in the present embodiment, an acceleration capacitor C1 is provided in parallel between the base and the emitter of the NPN transistor, and the capacitance value of the acceleration capacitor C1 is selected to be 100pF. During the on-off switching process of the NPN transistor, a certain charge will accumulate between the base and the emitter of the NPN transistor. The accumulation and release process of the charge will affect the switching speed of the NPN transistor. Therefore, the acceleration capacitor C1 is provided to provide an additional path for the charge discharge of the NPN transistor, improve the switching speed of the NPN transistor, increase the switching efficiency of the source digital output module detection and the sink digital output module detection, and at the same time prevent the NPN transistor from generating voltage spikes during the switching process, thereby protecting the general detection circuit from damage.

[0033] Preferably, a sixth resistor R6 is connected in series between the power supply end and the base of the NPN transistor. The resistance value of the sixth resistor R6 is selected to be 1KΩ. The sixth resistor R6 is used to limit the maximum current flowing from the first terminal U1 into the base of the NPN transistor to prevent excessive base current from damaging the NPN transistor.

[0034] Second embodiment Based on the same concept, the present invention also provides a universal detection device for a PLC source-drain type digital output module, which is internally equipped with a universal detection circuit for a PLC source-drain type digital output module as described in any one of the first embodiments. The device can evaluate and verify the actual load capacity and performance of the PLC source-type or drain-type digital output module by measuring the voltage values ​​across the load resistor of the drain current path and the source current path in the universal detection circuit, and further calculating the actual current flowing through the load resistor according to Ohm's law.

[0035] Through this embodiment, universal detection of the load function of the source-type digital output module and the sink-type digital output module can be realized. There is no need to provide two corresponding sets of detection devices specifically for the source-type digital output module and the sink-type digital output module. The automatic measurement function of the PLC source-type or sink-type digital output module when switching output can be realized, which effectively improves the measurement operation efficiency and reduces the use cost.

[0036] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they still fall within the protection scope of the present invention.

Claims

1. A universal detection circuit for a PLC source-drain type digital output module, characterized in that: include: NPN transistor, a first diode, a second diode, a first resistor and a second resistor; The base of the NPN transistor is connected to the first terminal, the collector of the NPN transistor is connected to the power supply terminal, the emitter of the NPN transistor is connected to the ground terminal, and the first terminal and the second terminal are connected to the common terminal of the PLC source and / or sink digital output module; The first diode and the second diode are arranged in parallel, the cathode of the first diode is connected to the second terminal, the anode of the first diode is connected to the first end of the first resistor, the second end of the first resistor is connected to the collector of the NPN transistor, the power supply end, the first resistor, the first diode to the second terminal, to form a leakage current path; the anode of the second diode is connected to the second terminal, the cathode of the second diode is connected to the first end of the second resistor, the second end of the second resistor is connected to the collector of the NPN transistor, the second terminal, the second diode, the second resistor, the NPN transistor to the ground terminal, to form a source current path; When the first terminal and the second terminal are configured to be connected to the common terminal of the PLC digital output module, the universal detection circuit is based on the low level output by the PLC leakage-type digital output module, and the NPN-type transistor is cut off, and the current flows from the power supply end through the first resistor and the first diode in sequence to the second terminal, and the leakage-type current path is turned on, which is used to measure the load performance of the PLC leakage-type digital output module; the universal detection circuit is based on the high level output by the PLC source-type digital output module, and the NPN-type transistor is turned on, and the current flows from the second terminal through the second diode, the second resistor, and the NPN-type transistor in sequence to the ground terminal, and the source-type current path is turned on, which is used to measure the load performance of the PLC source-type digital output module.

2. The universal detection circuit of the PLC source-drain type digital output module according to claim 1, characterized in that: The leakage current path includes a first branch and a second branch, a first common node of the first branch and the second branch is connected to the collector of the NPN transistor, and a second common node of the first branch and the second branch is connected to the anode of the first diode; The first resistor is connected in series in the first branch, and the third resistor and the first light-emitting diode are connected in series in the second branch. The first end of the third resistor is connected to the first common node of the first branch and the second branch, the second end of the third resistor is connected to the anode of the first light-emitting diode, and the cathode of the first light-emitting diode is connected to the second common node of the first branch and the second branch.

3. The universal detection circuit of the PLC source-drain type digital output module according to claim 1, characterized in that: The source current path includes a third branch and a fourth branch, a third common node of the third branch and the fourth branch is connected to the collector of the NPN transistor, and a fourth common node of the third branch and the fourth branch is connected to the cathode of the second diode; The second resistor is connected in series in the third branch, and the fourth resistor and the second light-emitting diode are connected in series in the fourth branch. The first end of the fourth resistor is connected to the third common node of the third branch and the fourth branch, the second end of the fourth resistor is connected to the cathode of the second light-emitting diode, and the anode of the second light-emitting diode is connected to the fourth common node of the third branch and the fourth branch.

4. The universal detection circuit of the PLC source-drain type digital output module according to claim 1, characterized in that: A fifth resistor is provided in series between the power supply end and the collector of the NPN transistor, and the fifth resistor is used to limit the current amplitude transmitted from the power supply end to the collector of the NPN transistor.

5. The universal detection circuit of the PLC source-drain type digital output module according to claim 4, characterized in that: The resistance value of the first resistor is limited to 100Ω, the resistance value of the fifth resistor is limited to 100Ω, and the resistance value of the third resistor is limited to 5KΩ.

6. The universal detection circuit of the PLC source-drain type digital output module according to claim 3, characterized in that: The resistance value of the second resistor is limited to 200Ω, and the resistance value of the fourth resistor is limited to 10KΩ.

7. The universal detection circuit of the PLC source-drain type digital output module according to claim 1, characterized in that: An acceleration capacitor is connected in parallel between the base and the emitter of the NPN transistor, and the acceleration capacitor is used to increase the charge discharge efficiency of the NPN transistor during the switching process between the leakage current path and the source current path.

8. The universal detection circuit of the PLC source-drain type digital output module according to claim 1, characterized in that: A sixth resistor is provided in series between the first wiring terminal and the base of the NPN transistor, and the sixth resistor is used to limit the current amplitude transmitted from the first wiring terminal to the base of the NPN transistor.

9. A universal detection device for a PLC source-drain type digital output module, characterized in that: A universal detection circuit equipped with a PLC source-drain type digital quantity output module as described in any one of claims 1 to 8 is used to realize a universal load detection function for a PLC source-type or sink-type digital quantity output module.

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