Mining flame-proof and intrinsic safety type digital belt weigher instrument circuit

Abstract

The utility model relates to a mining flame-proof and intrinsic safety type digital belt weigher instrument circuit, and belongs to the field of belt weighers. The technical problem that the circuit performance of a digital belt scale instrument circuit is unstable is solved. According to the technical scheme, the mining flame-proof and intrinsic safety type digital belt weigher instrument circuit comprises a DC / DC isolation power supply circuit and a keyboard isolation circuit, the output end of the DC / DC isolation power supply circuit is connected with an overvoltage fusing protection circuit in series, the overvoltage fusing protection circuit is electrically connected with a dual overvoltage and overcurrent protection circuit, and the keyboard isolation circuit is electrically connected with the dual overvoltage and overcurrent protection circuit. The dual over-voltage and over-current protection circuit comprises a first positive power supply over-voltage and over-current protection module and a second positive power supply over-voltage and over-current protection module, and the input end of the first positive power supply over-voltage and over-current protection module is electrically connected with the output end of the over-voltage fusing protection circuit. The output end of the first positive power supply overvoltage and overcurrent protection module is connected to the input end of the second positive power supply overvoltage and overcurrent protection module, and the output end of the second positive power supply overvoltage and overcurrent protection module is electrically connected with the LED indicating lamp. The utility model is applied to the belt weigher.

Description

Technical Field

[0001] The utility model provides a mine-used flameproof and intrinsically safe digital belt scale instrument circuit, belonging to the field of belt scales. Background Art

[0002] The belt scale instrument is one of the main components of the belt scale system. The analog belt scale instrument collects analog signals and has poor anti-interference ability. Although the existing digital belt scale has overcome the problem of poor anti-interference ability, the instrument circuit performance is unstable and cannot meet the mining explosion-proof requirements of electrical products used in mines. Utility Model Content

[0003] In order to solve the technical problem of unstable circuit performance of digital belt scale instrument circuit, the utility model proposes a mine flameproof and intrinsically safe digital belt scale instrument circuit, and aims to improve the hardware structure of the digital belt scale instrument circuit to avoid danger when used in mines.

[0004] In order to solve the above technical problems, the technical solution adopted by the utility model is: a mine explosion-proof and intrinsically safe digital belt scale instrument circuit, including a DC / DC isolation power supply circuit and a keyboard isolation circuit, the output end of the DC / DC isolation power supply circuit is connected in series with a fuse F1 and then electrically connected to an overvoltage fuse protection circuit, and the overvoltage fuse protection circuit is electrically connected to a double overvoltage and overcurrent protection circuit;

[0005] The input end of the overvoltage fuse protection circuit is connected in parallel to the output end of the diode D1, the 2nd pin of the thyristor Q1, one end of the connector J7 and the test point TP5; the input end of the diode D1 is connected in parallel to one end of the resistor R2 and the 3rd pin of the thyristor Q1; the other end of the connector J7 is connected in parallel to the output end of the diode D2, the 2nd pin of the thyristor Q2, the test point TP6 and the output end of the overvoltage fuse protection circuit; the input end of the diode D2 is connected in parallel to one end of the resistor R3 and the 3rd pin of the thyristor Q2; the other end of the resistor R2, the 1st pin of the thyristor Q1, the other end of the resistor R3 and the 1st pin of the thyristor Q2 are connected in parallel to the test point TP7 and then grounded;

[0006] The dual overvoltage and overcurrent protection circuit includes a positive power supply overvoltage and overcurrent protection module, and the positive power supply overvoltage and overcurrent protection module includes a first positive power supply overvoltage and overcurrent protection module and a second positive power supply overvoltage and overcurrent protection module; the input end of the first positive power supply overvoltage and overcurrent protection module is electrically connected to the output end of the overvoltage fuse protection circuit, the output end of the first positive power supply overvoltage and overcurrent protection module is connected in series with the MOS tube Q3 and then connected to the input end of the second positive power supply overvoltage and overcurrent protection module, and the output end of the second positive power supply overvoltage and overcurrent protection module is connected in series with the MOS tube Q4 and the diode D3 and then electrically connected to the LED indicator light;

[0007] The keyboard isolation circuit comprises a keyboard interface, and the keyboard interface is connected in series with a plurality of optical couplers and then connected to a keyboard control interface on a belt scale mainboard.

[0008] Furthermore, the DC / DC isolation power supply circuit includes a first chip, pin 1 of the first chip is connected to the positive pole of capacitor EC1, the 12V interface of connector J11 and test point TP1, the negative pole of capacitor EC1 is connected to pin 2 of the DC / DC isolation power supply, the 0V interface of connector J11 and test point TP2, pin 3 of the DC / DC isolation power supply is connected to the 12V power supply, the positive pole of capacitor EC2, test point TP3 and the output end of the DC / DC isolation power supply circuit, and the negative pole of capacitor EC2 is connected to pin 4 of the DC / DC isolation power supply and test point TP4 and then grounded.

[0009] Further, the first positive power supply overvoltage and overcurrent protection module includes a second chip, wherein pin 1 of the second chip is connected to port 1 of connector J1, port 2 of connector J1, one end of resistor R101 and a power supply, pin 4 of the second chip is connected to port 3 of connector J1 and port 4 of connector J1 and then to ground, pin 8 of the second chip is connected to the other end of resistor R101, one end of resistor R31, a power supply end of comparator U2C, one end of resistor R21, one end of capacitor C11, port 1 of connector J22 and port 2 of connector J22, the other end of the resistor R31 is connected to the output end of comparator U2A, the inverting end of comparator U2C, the output end of comparator U2D, the output end of comparator U2B and pin 5 of the third chip; the inverting end of comparator U2A is connected in series with resistors R6 and R5 and then connected to pin 5 of the second chip, the output end of comparator U2C is connected to the other end of resistor R21, one end of resistor R4 and an input end of diode D11, ... The other end of capacitor C11, the other end of resistor R4 and the output end of diode D11 are connected to port 3 of connector J22; the inverting end of comparator U2D is electrically connected to the output end of the third chip, the in-phase end of comparator U2B is connected in parallel with one end of capacitor C4 and one end of resistor R11, the other end of resistor R11 is connected to the power supply, the other end of capacitor C4 is connected in parallel with the inverting end of comparator U2B and one end of resistor R14, the other end of resistor R14 is connected in parallel with one end of capacitor C5, one end of resistor R15 and one end of resistor R13, the other end of resistor R13 is connected in series with resistor R12 and then connected to the power supply, the other end of resistor R15 is connected in parallel with the other end of capacitor C5 and then grounded; pin 2 of the third chip is connected in parallel with one end of resistor R10 and one end of capacitor C3, the other end of resistor R10 is connected in parallel with pin 16 of the third chip and then connected to the power supply, the other end of capacitor C3 is connected in parallel with pin 1 of the third chip and pin 4 of the third chip and then grounded, and pin 3 of the third chip is connected to the power supply;

[0010] The non-inverting end of the comparator U2A, the non-inverting end of the comparator U2C, and the non-inverting end of the comparator U2D are all electrically connected to a 1.2V power supply;

[0011] The connector J1 is electrically connected to the input end of the first positive power supply overvoltage and overcurrent protection module, and the connector J22 is electrically connected to the output end of the first positive power supply overvoltage and overcurrent protection module.

[0012] Furthermore, the circuit structure of the second positive power supply overvoltage and overcurrent protection module is the same as that of the first positive power supply overvoltage and overcurrent protection module.

[0013] Further, the optical coupler includes a first optical coupler and a second optical coupler; the pin 1 of the first optical coupler is connected in series with a resistor R224, and then connected to one end of a fuse F13 and an output end of a voltage regulator D13; the input end of the voltage regulator D13 is connected in series with the pin 2 of the first optical coupler and the output end of a buffer; the input end of the buffer is connected to a keyboard control interface; the pin 4 of the first optical coupler is connected in series with a resistor R223, and then connected to the output end of a voltage regulator D14 and one end of a fuse F14; the other end of the fuse F14 is connected to a power supply; the input end of the voltage regulator D14 is connected in series with the pin 3 of the first optical coupler, and then connected to a high level end of the keyboard interface;

[0014] Pin 1 of the second optocoupler is connected in series with resistor R7 and then connected to a voltage regulator D16 and a fuse F15. The other end of the fuse F15 is connected to the low level end of the keyboard interface, the input end of the voltage regulator D16 is grounded, pin 2 of the second optocoupler and pin 3 of the second optocoupler are grounded, pin 4 of the second optocoupler is connected in series with resistor R8 and then connected to the output end of the voltage regulator D15 and one end of the fuse F16. The other end of the fuse F16 is connected in series with one end of a resistor R225 and then connected to the keyboard control interface, the input end of the voltage regulator D15 is grounded, and the other end of the resistor R225 is connected to a power supply.

[0015] Furthermore, the model of the optical coupler is EL817S; the model of the Zener diode D13, the Zener diode D14, the Zener diode D15 and the Zener diode D16 is 1N5339B; and the model of the buffer is SN74LVC07AD.

[0016] Furthermore, the models of the MOS transistor Q3 and the MOS transistor Q4 are IRFR5505TR.

[0017] Furthermore, the model of the first chip is CFDA10-24S12; the model of the capacitor EC1 and the capacitor EC2 is 25YXF330.

[0018] Furthermore, the diode D1 and the diode D2 are of type 1N4744A.

[0019] Furthermore, the models of the thyristor Q1 and the thyristor Q2 are BT151-800R.

[0020] The beneficial effects of the present invention compared with the prior art are as follows:

[0021] 1. The DC / DC isolated power supply circuit of the utility model is connected in series with an overvoltage fuse protection circuit and a double overvoltage and overcurrent protection circuit, which can effectively improve the stability of the instrument circuit. The setting of the keyboard isolation circuit further enhances the circuit performance of the instrument;

[0022] 2. The utility model ensures the stability of the instrument circuit through current limiting protection and overvoltage protection;

[0023] 3. The digital belt scale instrument circuit of the utility model is electrically connected to a flameproof power supply, which plays a dual role of explosion-proof and flameproof protection, and can be used in dangerous places such as mines. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The utility model is further described below in conjunction with the accompanying drawings:

[0025] Figure 1 It is a schematic diagram of the circuit structure of the utility model;

[0026] Figure 2 This is a schematic diagram of the circuit structure of the positive power supply overvoltage and overcurrent protection module of the utility model;

[0027] Figure 3 This is a schematic diagram of the structure of a DC / DC isolated power supply circuit of the utility model;

[0028] Figure 4 This is a schematic diagram of an overvoltage fuse protection circuit of the utility model;

[0029] Figure 5 This is a schematic diagram of a dual overvoltage and overcurrent protection circuit of the utility model;

[0030] Figure 6 This is a schematic diagram of the keyboard isolation circuit of the utility model;

[0031] Figure 7 This is a schematic diagram of the first optical coupler and its circuit connection relationship of the utility model;

[0032] Figure 8 This is a schematic diagram of the second optical coupler and its circuit connection relationship of the utility model;

[0033] Fig. 9 This is a schematic diagram of the keyboard interface of the present utility model. DETAILED DESCRIPTION

[0034] In the present invention, unless otherwise specified, the directional words used, such as "up, down, top, bottom", usually refer to the directions shown in the drawings, or to the components themselves in the vertical, perpendicular or gravity directions; similarly, for ease of understanding and description, "inside and outside" refer to the inside and outside relative to the outline of each component itself, but the above-mentioned directional words are not used to limit the present invention.

[0035] like Figures 1 to 9 As shown, the utility model provides a mine flameproof and intrinsically safe digital belt scale instrument circuit, including a DC / DC isolation power supply circuit and a keyboard isolation circuit. The output end of the DC / DC isolation power supply circuit is connected in series with a fuse F1 and then electrically connected to an overvoltage fuse protection circuit. The overvoltage fuse protection circuit is electrically connected to a double overvoltage and overcurrent protection circuit.

[0036] The input end of the overvoltage fuse protection circuit is connected in parallel to the output end of the diode D1, the 2nd pin of the thyristor Q1, one end of the connector J7 and the test point TP5; the input end of the diode D1 is connected in parallel to one end of the resistor R2 and the 3rd pin of the thyristor Q1; the other end of the connector J7 is connected in parallel to the output end of the diode D2, the 2nd pin of the thyristor Q2, the test point TP6 and the output end of the overvoltage fuse protection circuit; the input end of the diode D2 is connected in parallel to one end of the resistor R3 and the 3rd pin of the thyristor Q2; the other end of the resistor R2, the 1st pin of the thyristor Q1, the other end of the resistor R3 and the 1st pin of the thyristor Q2 are connected in parallel to the test point TP7 and then grounded.

[0037] The double overvoltage and overcurrent protection circuit includes a positive power supply overvoltage and overcurrent protection module, and the positive power supply overvoltage and overcurrent protection module includes a first positive power supply overvoltage and overcurrent protection module and a second positive power supply overvoltage and overcurrent protection module; the input end of the first positive power supply overvoltage and overcurrent protection module is electrically connected to the output end of the overvoltage fuse protection circuit, the output end of the first positive power supply overvoltage and overcurrent protection module is connected in series with the MOS tube Q3 and then connected to the input end of the second positive power supply overvoltage and overcurrent protection module, the output end of the second positive power supply overvoltage and overcurrent protection module is connected in series with the MOS tube Q4 and the diode D3 and then connected to the output end of the diode D4, one end of the capacitor C1, one end of the resistor R1, three ports of the connector J3, port 1 of the connector J4, two ports of the connector J2 and the power supply, the other end of the resistor R1 is connected in series with the input end of the LED lamp, the input end of the diode D4, the other end of the capacitor C1 and the output end of the LED lamp are connected in parallel and then grounded.

[0038] The DC / DC isolation power supply circuit includes a first chip, wherein pin 1 of the first chip is connected to the positive electrode of capacitor EC1, the 12V interface of connector J11 and test point TP1, the negative electrode of capacitor EC1 is connected to pin 2 of the DC / DC isolation power supply, the 0V interface of connector J11 and test point TP2, pin 3 of the DC / DC isolation power supply is connected to the 12V power supply, the positive electrode of capacitor EC2, test point TP3 and the output end of the DC / DC isolation power supply circuit, and the negative electrode of capacitor EC2 is connected to pin 4 of the DC / DC isolation power supply and test point TP4 and then grounded.

[0039] The first positive power supply overvoltage and overcurrent protection module includes a second chip, wherein pin 1 of the second chip is connected to port 1 of connector J1, port 2 of connector J1, one end of resistor R101 and a power supply, pin 4 of the second chip is connected to port 3 of connector J1 and port 4 of connector J1 and then grounded, pin 8 of the second chip is connected to the other end of resistor R101, one end of resistor R31, a power supply end of comparator U2C, one end of resistor R21, one end of capacitor C11, port 1 of connector J22 and port 2 of connector J22, the other end of resistor R31 is connected to the output end of comparator U2A, the inverting end of comparator U2C, the output end of comparator U2D, the output end of comparator U2B and pin 5 of the third chip; the inverting end of comparator U2A is connected in series with resistors R6 and R5 and then connected to pin 5 of the second chip, the output end of comparator U2C is connected to the other end of resistor R21, one end of resistor R4 and the input end of diode D11, The other end of capacitor C11, the other end of resistor R4 and the output end of diode D11 are connected to port 3 of connector J22; the inverting end of comparator U2D is electrically connected to the output end of the third chip, the inverting end of comparator U2B is connected in parallel to one end of capacitor C4 and one end of resistor R11, the other end of resistor R11 is connected to a power supply, the other end of capacitor C4 is connected in parallel to the inverting end of comparator U2B and one end of resistor R14, the other end of resistor R14 is connected in parallel to one end of capacitor C5, one end of resistor R15 and one end of resistor R13, the other end of resistor R13 is connected in series with resistor R12 and then connected to the power supply, the other end of resistor R15 is connected in parallel to the other end of capacitor C5 and then to ground; pin 2 of the third chip is connected in parallel to one end of resistor R10 and one end of capacitor C3, the other end of resistor R10 is connected in parallel to pin 16 of the third chip and then to the power supply, the other end of capacitor C3 is connected in parallel to pin 1 of the third chip and pin 4 of the third chip and then to ground, and pin 3 of the third chip is connected to the power supply. The non-inverting end of the comparator U2A, the non-inverting end of the comparator U2C, and the non-inverting end of the comparator U2D are all electrically connected to a 1.2V power supply. The connector J1 is electrically connected to the input end of the first positive power supply overvoltage and overcurrent protection module, and the connector J22 is electrically connected to the output end of the first positive power supply overvoltage and overcurrent protection module. The circuit structure of the second positive power supply overvoltage and overcurrent protection module is the same as that of the first positive power supply overvoltage and overcurrent protection module.

[0040] The keyboard isolation circuit includes a keyboard interface, which is connected in series with several optical couplers and then connected to the keyboard control interface on the belt scale mainboard. The optical coupler includes a first optical coupler and a second optical coupler; the 1-pin of the first optical coupler is connected in series with a resistor R224, and then connected to one end of the fuse F13 and the output end of the voltage regulator D13, the input end of the voltage regulator D13 is connected in series with the 2-pin of the first optical coupler and the output end of the buffer, and the input end of the buffer is connected to the keyboard control interface; the 4-pin of the first optical coupler is connected in series with a resistor R223, and then connected to the output end of the voltage regulator D14 and one end of the fuse F14, the other end of the fuse F14 is connected to the power supply, and the input end of the voltage regulator D14 is connected to the keyboard interface after being connected to the 3-pin of the first optical coupler. The high level end of the second optical coupler; the pin 1 of the second optical coupler is connected in series with the resistor R7 and then connected to the voltage regulator D16 and the fuse F15, the other end of the fuse F15 is connected to the low level end of the keyboard interface, the input end of the voltage regulator D16 is grounded, the pin 2 of the second optical coupler and the pin 3 of the second optical coupler are grounded, the pin 4 of the second optical coupler is connected in series with the resistor R8 and then connected to the output end of the voltage regulator D15 and one end of the fuse F16, the other end of the fuse F16 is connected in parallel with one end of the resistor R225 and then connected to the keyboard control interface, the input end of the voltage regulator D15 is grounded, and the other end of the resistor R225 is connected to the power supply;

[0041] The model of the optocoupler is EL817S;

[0042] The model of Zener diode D13, Zener diode D14, Zener diode D15 and Zener diode D16 is 1N5339B;

[0043] The model of the buffer is SN74LVC07AD;

[0044] The models of MOS tube Q3 and MOS tube Q4 are IRFR5505TR;

[0045] The model of the first chip is CFDA10-24S12;

[0046] The model of capacitor EC1 and capacitor EC2 is 25YXF330;

[0047] The diodes D1 and D2 are of the type 1N4744A;

[0048] The models of thyristor Q1 and thyristor Q2 are BT151-800R.

[0049] The instrument circuit setting of the utility model can effectively improve the circuit safety performance of the digital belt scale instrument. The digital belt scale instrument circuit of the utility model is electrically connected to the flameproof power supply or placed in a flameproof box, playing a dual role of explosion-proof and flameproof protection, and can be suitable for dangerous places such as mines.

[0050] Regarding the specific structure of the utility model, it should be explained that the connection relationship between the various component modules adopted in the utility model is definite and feasible. Except for special instructions in the embodiments, the specific connection relationship can bring corresponding technical effects and solve the technical problems raised by the utility model without relying on the execution of corresponding software programs. The components, modules, models of specific components and the connection methods between each other appearing in the utility model, as well as the conventional use methods and expected technical effects brought about by the above-mentioned technical features, except for specific instructions, all belong to the disclosed contents in patents, journal articles, technical manuals, technical dictionaries, and textbooks that can be obtained by technical personnel in this field before the application date, or belong to the existing technologies such as conventional technologies and common knowledge in this field, and there is no need to elaborate, so that the technical solution provided in this case is clear, complete and feasible, and the corresponding physical products can be reproduced or obtained according to the technical means.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A mine flameproof and intrinsically safe digital belt scale instrument circuit, characterized in that: It includes a DC / DC isolation power supply circuit and a keyboard isolation circuit, wherein the output end of the DC / DC isolation power supply circuit is connected in series with a fuse F1 and then electrically connected to an overvoltage fuse protection circuit, and the overvoltage fuse protection circuit is electrically connected to a double overvoltage and overcurrent protection circuit; The input end of the overvoltage fuse protection circuit is connected in parallel to the output end of the diode D1, the 2nd pin of the thyristor Q1, one end of the connector J7 and the test point TP5; the input end of the diode D1 is connected in parallel to one end of the resistor R2 and the 3rd pin of the thyristor Q1; the other end of the connector J7 is connected in parallel to the output end of the diode D2, the 2nd pin of the thyristor Q2, the test point TP6 and the output end of the overvoltage fuse protection circuit; the input end of the diode D2 is connected in parallel to one end of the resistor R3 and the 3rd pin of the thyristor Q2; the other end of the resistor R2, the 1st pin of the thyristor Q1, the other end of the resistor R3 and the 1st pin of the thyristor Q2 are connected in parallel to the test point TP7 and then grounded; The dual overvoltage and overcurrent protection circuit includes a positive power supply overvoltage and overcurrent protection module, and the positive power supply overvoltage and overcurrent protection module includes a first positive power supply overvoltage and overcurrent protection module and a second positive power supply overvoltage and overcurrent protection module; the input end of the first positive power supply overvoltage and overcurrent protection module is electrically connected to the output end of the overvoltage fuse protection circuit, the output end of the first positive power supply overvoltage and overcurrent protection module is connected in series with the MOS tube Q3 and then connected to the input end of the second positive power supply overvoltage and overcurrent protection module, and the output end of the second positive power supply overvoltage and overcurrent protection module is connected in series with the MOS tube Q4 and the diode D3 and then electrically connected to the LED indicator light; The keyboard isolation circuit comprises a keyboard interface, and the keyboard interface is connected in series with a plurality of optical couplers and then connected to a keyboard control interface on a belt scale mainboard.

2. The mine flameproof and intrinsically safe digital belt scale instrument circuit according to claim 1 is characterized in that: The DC / DC isolation power supply circuit includes a first chip, wherein pin 1 of the first chip is connected to the positive electrode of capacitor EC1, the 12V interface of connector J11 and test point TP1, the negative electrode of capacitor EC1 is connected to pin 2 of the DC / DC isolation power supply, the 0V interface of connector J11 and test point TP2, pin 3 of the DC / DC isolation power supply is connected to the 12V power supply, the positive electrode of capacitor EC2, test point TP3 and the output end of the DC / DC isolation power supply circuit, and the negative electrode of capacitor EC2 is connected to pin 4 of the DC / DC isolation power supply and test point TP4 and then grounded.

3. The mine flameproof and intrinsically safe digital belt scale instrument circuit according to claim 1 is characterized in that: The first positive power supply overvoltage and overcurrent protection module includes a second chip, wherein pin 1 of the second chip is connected to port 1 of connector J1, port 2 of connector J1, one end of resistor R101 and a power supply, pin 4 of the second chip is connected to port 3 of connector J1 and port 4 of connector J1 and then to ground, pin 8 of the second chip is connected to the other end of resistor R101, one end of resistor R31, a power supply end of comparator U2C, one end of resistor R21, one end of capacitor C11, port 1 of connector J22 and port 2 of connector J22, the other end of resistor R31 is connected to the output end of comparator U2A, the inverting end of comparator U2C, the output end of comparator U2D, the output end of comparator U2B and pin 5 of the third chip; the inverting end of comparator U2A is connected in series with resistors R6 and R5 and then connected to pin 5 of the second chip, the output end of comparator U2C is connected to the other end of resistor R21, one end of resistor R4 and an input end of diode D11, the capacitor C The other end of the resistor R11, the other end of the resistor R4 and the output end of the diode D11 are connected to the 3 port of the connector J22; the inverting end of the comparator U2D is electrically connected to the output end of the third chip, the in-phase end of the comparator U2B is connected in parallel with one end of the capacitor C4 and one end of the resistor R11, the other end of the resistor R11 is connected to the power supply, the other end of the capacitor C4 is connected in parallel with the inverting end of the comparator U2B and one end of the resistor R14, the other end of the resistor R14 is connected in parallel with one end of the capacitor C5, one end of the resistor R15 and one end of the resistor R13, the other end of the resistor R13 is connected in series with the resistor R12 and then connected to the power supply, the other end of the resistor R15 is connected in parallel with the other end of the capacitor C5 and then grounded; the 2 pin of the third chip is connected in parallel with one end of the resistor R10 and one end of the capacitor C3, the other end of the resistor R10 is connected in parallel with the 16 pin of the third chip and then connected to the power supply, the other end of the capacitor C3 is connected in parallel with the 1 pin of the third chip and the 4 pin of the third chip and then grounded, and the 3 pin of the third chip is connected to the power supply; The non-inverting end of the comparator U2A, the non-inverting end of the comparator U2C, and the non-inverting end of the comparator U2D are all electrically connected to a 1.2V power supply; The connector J1 is electrically connected to the input end of the first positive power supply overvoltage and overcurrent protection module, and the connector J22 is electrically connected to the output end of the first positive power supply overvoltage and overcurrent protection module.

4. The mine flameproof and intrinsically safe digital belt scale instrument circuit according to claim 1 is characterized by: The circuit structure of the second positive power supply overvoltage and overcurrent protection module is the same as that of the first positive power supply overvoltage and overcurrent protection module.

5. The mine flameproof and intrinsically safe digital belt scale instrument circuit according to claim 1 is characterized in that: The optical coupler includes a first optical coupler and a second optical coupler; the first optical coupler has a pin 1 connected in series with a resistor R224, and then connected to one end of a fuse F13 and an output end of a voltage regulator D13; the input end of the voltage regulator D13 is connected in series with the pin 2 of the first optical coupler and the output end of a buffer; the input end of the buffer is connected to a keyboard control interface; the first optical coupler has a pin 4 connected in series with a resistor R223, and then connected to the output end of a voltage regulator D14 and one end of a fuse F14; the other end of the fuse F14 is connected to a power supply; the input end of the voltage regulator D14 is connected in series with the pin 3 of the first optical coupler, and then connected to a high level end of the keyboard interface; Pin 1 of the second optocoupler is connected in series with resistor R7 and then connected to a voltage regulator D16 and a fuse F15. The other end of the fuse F15 is connected to the low level end of the keyboard interface, the input end of the voltage regulator D16 is grounded, pin 2 of the second optocoupler and pin 3 of the second optocoupler are grounded, pin 4 of the second optocoupler is connected in series with resistor R8 and then connected to the output end of the voltage regulator D15 and one end of the fuse F16. The other end of the fuse F16 is connected in series with one end of a resistor R225 and then connected to the keyboard control interface, the input end of the voltage regulator D15 is grounded, and the other end of the resistor R225 is connected to a power supply.

6. The mine flameproof and intrinsically safe digital belt scale instrument circuit according to claim 5 is characterized by: The model of the optical coupler is EL817S; the model of the Zener diodes D13, D14, D15 and D16 is 1N5339B; the model of the buffer is SN74LVC07AD.

7. The mine flameproof and intrinsically safe digital belt scale instrument circuit according to claim 1 is characterized by: The models of the MOS tube Q3 and the MOS tube Q4 are IRFR5505TR.

8. The mine flameproof and intrinsically safe digital belt scale instrument circuit according to claim 2 is characterized by: The model of the first chip is CFDA10-24S12; the model of the capacitor EC1 and the capacitor EC2 is 25YXF330.

9. The mine flameproof and intrinsically safe digital belt scale instrument circuit according to claim 1 is characterized by: The diode D1 and the diode D2 are of the type 1N4744A.

10. The mine flameproof and intrinsically safe digital belt scale instrument circuit according to claim 1 is characterized by: The models of the thyristor Q1 and the thyristor Q2 are BT151-800R.

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