Source type digital input device

Abstract

The utility model aims to provide the source type digital input device which is low in cost, good in compatibility and high in integration level, ensures stable current output and has stable signal transmission capability. The device comprises a DC / DC conversion module, a constant current source, a photoelectric coupling module, an overvoltage breakdown prevention module and a controller, an external power supply is connected to the constant current source through the DC / DC conversion module, the constant current source is connected to an anode input end of the photoelectric coupling module, a cathode input end of the photoelectric coupling module is connected to an external circuit through the overvoltage breakdown prevention module, and the controller is connected to the external circuit. And the output end of the photoelectric coupling module is connected with the controller. The PLC digital input device is applied to the technical field of PLC digital input.

Description

Technical Field

[0001] The utility model is applied to the technical field of PLC digital input, and particularly relates to a source type digital input device. Background Art

[0002] PLC refers to programmable logic controller; DC / DC refers to direct current to direct current converter; PNP refers to triode. PLC digital input is used for sensors, buttons, switches and other devices to receive external signals and convert them into logical states recognizable by PLC. Digital input modules can recognize external signals. Digital input modules require input voltage level DC 24V, source type digital input, and digital input modules are divided into separate component structure and single chip integrated structure from the degree of integration. The resistor used in the separate component structure can achieve current limiting to ensure that the PLC digital input electrical specification characteristics are met. However, the existing digital input module requires the voltage and current specifications of the PLC to be met. Although the single chip integrated structure has the advantages of high integration and easy use, it is difficult for cost-sensitive equipment to meet the cost reduction requirements. Most digital input modules are a combination of resistors and photocouplers. When the output state is 1, the output current will change greatly with the output voltage of the external circuit. In addition, if the input voltage is in the state of 0, it needs to be greater than 24V to completely prevent the current from flowing out. Therefore, it is necessary to provide a source type digital input device with low cost, good compatibility, high integration, stable current output, and stable signal transmission capability. Utility Model Content

[0003] The technical problem to be solved by the utility model is to overcome the deficiencies of the prior art and provide a source-type digital input device which has low cost, good compatibility, high integration, ensures stable current output and has stable signal transmission capability.

[0004] The technical solution adopted by the utility model is: the utility model includes a DC / DC conversion module, a constant current source, a photoelectric coupling module, an overvoltage breakdown protection module, and a controller; an external power supply is connected to the constant current source via the DC / DC conversion module; the constant current source is connected to the anode input end of the photoelectric coupling module; the cathode input end of the photoelectric coupling module is connected to the external circuit via the overvoltage breakdown protection module; and the output end of the photoelectric coupling module is connected to the controller.

[0005] It can be seen from the above scheme that the test cost of this application is relatively low, which can save 70% compared with the cost of a single power chip; it has a flexible range of material selection, which reduces procurement costs. Compared with the existing single power chip solution, the separation component solution has more replacement materials, which can reduce the risk of equipment shortages; it has a more stable signal transmission capability. The output current passing through the photoelectric coupling module affects the photoelectric conversion efficiency of the photoelectric coupling. Compared with the resistor and photoelectric coupler solution, the output current of this application is stable, which can ensure the stability of the signal transmitted to the controller. The DC / DC conversion module is equipped with a higher voltage-resistant diode and a wide voltage input range. Through the cooperation of the overvoltage breakdown protection module, it can be ensured that it can be recognized as a "0" state in the range of 12V-30V.

[0006] A preferred solution is that the photoelectric coupling module includes a photoelectric coupler, a first resistor, and a second resistor. The output end of the photoelectric coupler is divided into two paths, one path is grounded through the first resistor, and the other path is connected to the LAN9253_GPI1 pin of the controller through the second resistor.

[0007] A preferred solution is that the overvoltage breakdown protection module includes a diode, the anode of the diode is connected to the cathode input terminal of the photoelectric coupling module, and the cathode of the diode is connected to the IN_Y1 pin of the external circuit.

[0008] A preferred solution is that the DC / DC conversion module includes a DC-DC converter, an external power supply 24V is connected to the VIN terminal and EN terminal of the DC-DC converter, and the BS terminal and LX terminal of the DC-DC converter are both connected to the constant current source.

[0009] A preferred solution is that the constant current source includes a PNP transistor, a third resistor, and a fourth resistor, the BS terminal and the LX terminal of the DC-DC converter are connected to the E1 terminal and the B2 terminal of the PNP transistor via the third resistor, the C2 terminal and the B1 terminal of the PNP transistor are grounded via the fourth resistor, and the C1 terminal of the PNP transistor is connected to the anode input terminal of the photocoupler. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a structural block diagram of the utility model;

[0011] Figure 2 It is a principle block diagram of the utility model;

[0012] Figure 3 It is a circuit schematic diagram of the utility model;

[0013] Figure 4 is a circuit schematic diagram of the DC / DC conversion module. DETAILED DESCRIPTION

[0014] like Figures 1 to 3 As shown, in this embodiment, the utility model includes a DC / DC conversion module 1, a constant current source 2, a photoelectric coupling module 3, an overvoltage breakdown protection module 4, and a controller 5. The external power supply 6 is connected to the constant current source 2 via the DC / DC conversion module 1, the constant current source 2 is connected to the anode input end of the photoelectric coupling module 3, the cathode input end of the photoelectric coupling module 3 is connected to the external circuit 7 via the overvoltage breakdown protection module 4, and the output end of the photoelectric coupling module 3 is connected to the controller 5.

[0015] like Figures 1 to 3 As shown, in this embodiment, the photoelectric coupling module 3 includes a photoelectric coupler U1, a first resistor R3, and a second resistor R907. The output end of the photoelectric coupler U1 is divided into two paths, one of which is grounded through the first resistor R3, and the other is connected to the LAN9253_GPI1 pin of the controller 5 through the second resistor R907. The first pin and the second pin of the light-emitting diode of the photoelectric coupler U1 convert the electrical signal into an optical signal, and then convert the optical signal into an electrical signal through the third pin and the fourth pin. The photoelectric coupling module 3 can realize the conversion of the external signal input signal into an input signal that can be recognized by the PLC, and the signal high level is 3V and the low level is 0V.

[0016] like Figures 1 to 3 As shown, in this embodiment, the overvoltage breakdown protection module 4 includes a diode D1, the anode of the diode D1 is connected to the cathode input terminal of the photoelectric coupling module 3, and the cathode of the diode D1 is connected to the IN_Y1 pin of the external circuit 7. Since the reverse breakdown voltage of the photoelectric coupler U1 is low, the reverse breakdown voltage of the photoelectric coupler U1 is 6V. Without the diode D1, when the input voltage>18V, the photoelectric coupler U1 will be damaged. The diode D1 is added here, and the reverse breakdown voltage of the diode is 80V, which increases the maximum damage voltage of the digital input to 92V, effectively protecting the digital input.

[0017] like Figure 4 As shown, in this embodiment, the DC / DC conversion module 1 includes a DC-DC converter U2, and the external power supply 624V is connected to the VIN terminal and EN terminal of the DC-DC converter U2, and the BS terminal and LX terminal of the DC-DC converter U2 are both connected to the constant current source 2. The DC / DC conversion module 1 cooperates with the anti-overvoltage breakdown module 4 to achieve wider "0" state voltage recognition. The DC-DC converter U2 converts 24V to 12V, and 12V is used as the judgment voltage for the digital input 0 state and 1 state. When the power supply is higher than 12V, that is, state 0 Figure 2 Q1 and D1 in the reverse direction are cut off, and no current flows out of the digital input terminal. When the power supply is lower than 5V, that is, state 1, current flows out of the digital input terminal.

[0018] like Figures 1 to 3 As shown, in this embodiment, the constant current source 2 includes a PNP transistor Q1, a third resistor R1, and a fourth resistor R2. The BS terminal and the LX terminal of the DC-DC converter U2 are connected to the E1 terminal and the B2 terminal of the PNP transistor Q1 through the third resistor R1. The C2 terminal and the B1 terminal of the PNP transistor Q1 are grounded through the fourth resistor R2. The C1 terminal of the PNP transistor Q1 is connected to the anode input terminal of the photocoupler U1. The constant current source 2 utilizes the PN junction characteristics of the E2-B2 diode of the PNP transistor Q1, so that the output current of the third resistor R1 fluctuates in a small range of 2-3mA. When the temperature is constant, the PN junction voltage is constant, the output current is constant, and the output current is constant, so that the output current is constant.

Claims

1. A source type digital input device, characterized in that: It comprises a DC / DC conversion module (1), a constant current source (2), a photoelectric coupling module (3), an overvoltage breakdown prevention module (4), and a controller (5); an external power source (6) is connected to the constant current source (2) via the DC / DC conversion module (1); the constant current source (2) is connected to the anode input end of the photoelectric coupling module (3); the cathode input end of the photoelectric coupling module (3) is connected to an external circuit (7) via the overvoltage breakdown prevention module (4); and the output end of the photoelectric coupling module (3) is connected to the controller (5).

2. A source type digital input device according to claim 1, characterized in that: The photoelectric coupling module (3) comprises a photoelectric coupler (U1), a first resistor (R3), and a second resistor (R907); the output end of the photoelectric coupler (U1) is divided into two paths, one path is connected to the ground via the first resistor (R3), and the other path is connected to the LAN9253_GPI1 pin of the controller (5) via the second resistor (R907).

3. A source type digital input device according to claim 1, characterized in that: The overvoltage breakdown prevention module (4) comprises a diode (D1), the anode of the diode (D1) is connected to the cathode input terminal of the photoelectric coupling module (3), and the cathode of the diode (D1) is connected to the IN_Y1 pin of the external circuit (7).

4. A source type digital input device according to claim 2, characterized in that: The DC / DC conversion module (1) comprises a DC-DC converter (U2), an external power supply (6) of 24V is connected to the VIN terminal and EN terminal of the DC-DC converter (U2), and the BS terminal and LX terminal of the DC-DC converter (U2) are both connected to the constant current source (2).

5. A source type digital input device according to claim 4, characterized in that: The constant current source (2) comprises a PNP transistor (Q1), a third resistor (R1), and a fourth resistor (R2); the BS terminal and the LX terminal of the DC-DC converter (U2) are connected to the E1 terminal and the B2 terminal of the PNP transistor (Q1) via the third resistor (R1); the C2 terminal and the B1 terminal of the PNP transistor (Q1) are grounded via the fourth resistor (R2); and the C1 terminal of the PNP transistor (Q1) is connected to the anode input terminal of the photoelectric coupler (U1).

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