Bidirectional electromagnetic drive test circuit

Abstract

The utility model discloses a bidirectional electromagnetic drive test circuit, which comprises a master control circuit, a capacitor charging circuit, a bridge type commutation circuit, a power supply step-down circuit, a key drive circuit and a voltage drop prevention circuit, and is characterized in that the output end of the power supply step-down circuit is electrically connected with the power supply input end of the key drive circuit; the output end of the key driving circuit is electrically connected with the main control circuit, the output end of the main control circuit is electrically connected with the commutation control end of the bridge type commutation circuit, the output end of the capacitor charging circuit is electrically connected with the input end of the bridge type commutation circuit, and the capacitor is controlled to be charged at regular time through the main control circuit. When power failure occurs or an open circuit occurs, the voltage drop prevention circuit acquires a signal to the main control circuit, and the main control circuit drives the electromagnet to operate, so that the problem that the electromagnet cannot be started due to power failure is avoided. The bidirectional electromagnetic drive test circuit provided by the utility model has the effect of completely simulating product functions for testing.

Description

Technical Field

[0001] The utility model belongs to the technical field of fire door closers, and in particular relates to a bidirectional electromagnetic drive test circuit. Background Art

[0002] The existing technology only tests a single function and cannot test the function and performance of the entire component in a linked manner. It is inefficient and the test parameters are not standard. This circuit equipment completely simulates the function of the product for testing. For example, in manual testing, first press the switch to charge the capacitor, then drive the electromagnetic to push left or right, and then drive the electromagnetic again to charge the capacitor. This circuit does not require manual charging of the capacitor, and can drive the electromagnet at the moment of power failure, which is a function that mechanical test equipment cannot achieve. Utility Model Content

[0003] In view of the above problems, a bidirectional electromagnetic drive test circuit is now provided to solve the problems existing in the prior art.

[0004] The specific technical solutions are as follows:

[0005] A bidirectional electromagnetic drive test circuit comprises a main control circuit, a capacitor charging circuit, a bridge commutation circuit, a power supply step-down circuit, a key drive circuit and an anti-voltage drop circuit, wherein the output end of the power supply step-down circuit is electrically connected to the power supply input end of the key drive circuit, the output end of the key drive circuit is electrically connected to the main control circuit, the output end of the main control circuit is electrically connected to the commutation control end of the bridge commutation circuit, the output end of the capacitor charging circuit is electrically connected to the input end of the bridge commutation circuit, and the output end of the anti-voltage drop circuit is electrically connected to the ADC acquisition end of the main control circuit.

[0006] The above-mentioned bidirectional electromagnetic drive test circuit also has the following characteristics: the power supply step-down circuit includes a resistor R39, a capacitor C5, a capacitor C4, a voltage stabilizing chip U2, a resistor R25, a resistor R23, an inductor L1, a capacitor C9 and a capacitor C6; the external 24V voltage is sequentially grounded through the resistor R39 and the capacitor C5; the common end of the resistor R39 and the capacitor C5 is electrically connected to the input end of the voltage stabilizing chip U2; the capacitor C4 is connected in parallel to both ends of the capacitor C5; the output end of the voltage stabilizing chip U2 is electrically connected to its control end through the resistor R23; the output end of the voltage stabilizing chip U2 is electrically connected to its control end through the inductor L1, the capacitor C9 and the resistor R25 in sequence; the capacitor C6 is connected in parallel to both ends of the capacitor C9; the common end of the capacitor C9 and the resistor R25 is grounded; the common end of the inductor L1 and the capacitor C9 is used as the output end to output a 3.3V voltage.

[0007] The above-mentioned bidirectional electromagnetic drive test circuit further has the following characteristics. The key drive circuit includes a resistor R38 and a switch SW1. The common terminal of the inductor L1 and the capacitor C9 is grounded sequentially through the resistor R38 and the switch SW1. The common terminal of the resistor R38 and the switch SW1 is used as a first output terminal and is electrically connected to the first control input terminal of the main control circuit.

[0008] The key drive circuit further includes a resistor R40 and a switch KY1. The common terminal of the inductor L1 and the capacitor C9 is grounded sequentially through the resistor R40 and the switch KY1. The common terminal of the resistor R40 and the switch KY1 is used as a second output terminal and is electrically connected to the second control input terminal of the main control circuit.

[0009] The capacitor charging circuit includes a terminal block CN2, a rectification chip U6, a resistor R4, a resistor R3, a resistor R1, a resistor R2, a triode Q1, a MOS transistor M5, a diode D2, a resistor R5, and a capacitor C1. The terminal block CN2 is electrically connected to the input terminal of the rectification chip U6. The output terminal of the rectification chip U6 is sequentially electrically connected to the collector of the triode Q1 through the resistor R4 and the resistor R3. The base of the triode Q1 is used as a power input terminal and is electrically connected to an external power supply after passing through the resistor R1. The base of the triode Q1 is also electrically connected to its emitter through the resistor R2. The emitter of the triode Q1 is grounded. The output terminal of the rectification chip U6 is also electrically connected to the drain of the MOS transistor M5. The gate of the MOS transistor M5 is electrically connected to the common terminal of the resistor R4 and the resistor R3. The source of the MOS transistor M5 is electrically connected to the anode of the diode D2. The cathode of the diode D2 is grounded sequentially through the resistor R5 and the capacitor C1. The common terminal of the resistor R5 and the capacitor C1 is used as an output terminal and is electrically connected to the input terminal of the bridge commutation circuit.

[0010] The above-mentioned bidirectional electromagnetic drive test circuit further has the following characteristics. The bridge commutation circuit includes a resistor R11, a resistor R13, a triode Q6, a resistor R14, a resistor R24, a resistor R18, a resistor R7, a MOS transistor M8, a MOS transistor M10, a TVS diode D3, a terminal block U4, a MOS transistor M9, a MOS transistor M11, a resistor R6, a resistor R15, a resistor R17, a triode Q7, a resistor R10, a resistor R8, and a resistor R16.

[0011] The common terminal of the resistor R5 and the capacitor C1 is sequentially electrically connected to the collector of the triode Q6 through the resistor R11 and the resistor R13. The base of the triode Q6 is electrically connected to its emitter through the resistor R24. The emitter of the triode Q6 is grounded. The base of the triode Q6 is electrically connected to the main control circuit as the first control signal input terminal after passing through the resistor R14;

[0012] The common terminal of the resistor R5 and the capacitor C1 is also electrically connected to the drain of the MOS transistor M8. The gate of the MOS transistor M8 is electrically connected to the common terminal of the resistor R11 and the resistor R13. The source of the MOS transistor M8 is electrically connected to the drain of the MOS transistor M10. The gate of the MOS transistor M10 is electrically connected to its source through the resistor R7. The gate of the MOS transistor M10 is electrically connected to the main control circuit as the second control signal input terminal after passing through the resistor R18;

[0013] The common terminal of the resistor R5 and the capacitor C1 is sequentially electrically connected to the collector of the triode Q7 through the resistor R15 and the resistor R17. The base of the triode Q7 is electrically connected to its emitter through the resistor R8. The emitter of the triode Q7 is grounded. The base of the triode Q7 is electrically connected to the main control circuit as the third control signal input terminal after passing through the resistor R10;

[0014] The common terminal of the resistor R5 and the capacitor C1 is electrically connected to the drain of the MOS transistor M9. The gate of the MOS transistor M9 is electrically connected to the common terminal of the resistor R15 and the resistor R17. The source of the MOS transistor M9 is electrically connected to the drain of the MOS transistor M11. The gate of the MOS transistor M11 is electrically connected to its source through the resistor R6. The gate of the MOS transistor M11 is also electrically connected to the main control circuit as the fourth control signal input terminal after passing through the resistor R16;

[0015] The sources of the MOS transistor M10 and the MOS transistor M11 are electrically connected and then grounded. The source of the MOS transistor M8 is electrically connected to one end of the TVS diode D3. The other end of the TVS diode D3 is electrically connected to the source of the MOS transistor M9. The sources of the MOS transistor M8 and the MOS transistor M9 are both electrically connected to an external electromagnet through the terminal block U4.

[0016] The above-mentioned bidirectional electromagnetic drive test circuit also has the following characteristics. The overvoltage protection circuit includes resistor R12, resistor R19, resistor R21, and capacitor C8. The external 24V voltage is grounded successively through resistor R12 and resistor R19. Resistor R21 and capacitor C8 are connected in series successively and then connected in parallel across both ends of resistor R19. The common terminal of resistor R21 and capacitor C8 serves as the output terminal and is electrically connected to the ADC acquisition terminal of the main control circuit.

[0017] In summary, the beneficial effects of this solution are:

[0018] In the bidirectional electromagnetic drive test circuit provided by the present invention, the main control circuit controls the capacitor to charge regularly. When the switch is pressed, the capacitor discharges to drive the electromagnet. When power is lost or an open circuit occurs, the overvoltage protection circuit collects signals and sends them to the main control circuit, and the main control circuit drives the electromagnet to operate, avoiding the problem that it cannot be turned on when power is lost. The bidirectional electromagnetic drive test circuit provided by the present invention has the effect of fully simulating the product function for testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the structural block diagram of the bidirectional electromagnetic drive test circuit of the present invention;

[0020] Figure 2 It is the circuit structure diagram of the power supply step-down circuit of the bidirectional electromagnetic drive test circuit of the present invention;

[0021] Figure 3 It is the circuit structure diagram of the key drive circuit of the bidirectional electromagnetic drive test circuit of the present invention;

[0022] Figure 4 It is the circuit structure diagram of the capacitor charging circuit of the bidirectional electromagnetic drive test circuit of the present invention;

[0023] Figure 5 It is the circuit structure diagram of the bridge commutation circuit of the bidirectional electromagnetic drive test circuit of the present invention;

[0024] Figure 6 It is the circuit structure diagram of the overvoltage protection circuit of the bidirectional electromagnetic drive test circuit of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] Next, the technical solutions in the embodiments of the present invention will be described clearly and completely in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the protection scope of the present invention.

[0026] It should be noted that, without conflict, the embodiments in the present utility model and the features in the embodiments can be combined with each other.

[0027] The present utility model will be further described below in conjunction with specific embodiments, but it is not limited to the present utility model.

[0028] Figure 1 is the structural block diagram of the bidirectional electromagnetic drive test circuit of the present utility model, Figure 2 is the circuit structure diagram of the power supply step-down circuit of the bidirectional electromagnetic drive test circuit of the present utility model, Figure 3 is the circuit structure diagram of the key drive circuit of the bidirectional electromagnetic drive test circuit of the present utility model, Figure 4 is the circuit structure diagram of the capacitor charging circuit of the bidirectional electromagnetic drive test circuit of the present utility model, Figure 5 is the circuit structure diagram of the bridge commutation circuit of the bidirectional electromagnetic drive test circuit of the present utility model, Figure 6 is the circuit structure diagram of the voltage drop prevention circuit of the bidirectional electromagnetic drive test circuit of the present utility model. As Figures 1-6 shown, the bidirectional electromagnetic drive test circuit provided in this embodiment includes a main control circuit, a capacitor charging circuit, a bridge commutation circuit, a power supply step-down circuit, a key drive circuit, and a voltage drop prevention circuit. The output end of the power supply step-down circuit is electrically connected to the power input end of the key drive circuit. The output end of the key drive circuit is electrically connected to the main control circuit. The output end of the main control circuit is electrically connected to the commutation control end of the bridge commutation circuit. The output end of the capacitor charging circuit is electrically connected to the input end of the bridge commutation circuit. The output end of the voltage drop prevention circuit is electrically connected to the ADC acquisition end of the main control circuit.

[0029] It should be noted that the main control circuit uses a main control chip with the model number HK32F030MF4P6 and its peripheral circuits.

[0030] In the above embodiment, the power supply step-down circuit includes a resistor R39, a capacitor C5, a capacitor C4, a voltage regulator chip U2, a resistor R25, a resistor R23, an inductor L1, a capacitor C9, and a capacitor C6. The external 24V voltage is grounded sequentially through the resistor R39 and the capacitor C5. The common end of the resistor R39 and the capacitor C5 is electrically connected to the input end of the voltage regulator chip U2. The capacitor C4 is connected in parallel across the capacitor C5. The output end of the voltage regulator chip U2 is electrically connected to its control end through the resistor R23. The output end of the voltage regulator chip U2 is sequentially electrically connected to its control end through the inductor L1, the capacitor C9, and the resistor R25. The capacitor C6 is connected in parallel across the capacitor C9. The common end of the capacitor C9 and the resistor R25 is grounded. The common end of the inductor L1 and the capacitor C9 is used as the output end to output 3.3V voltage.

[0031] It should be noted that the voltage regulator chip U2 uses a voltage regulator with the model number LM317G-MS.

[0032] In the above embodiment, the key driving circuit includes a resistor R38 and a switch SW1. The common terminal of the inductor L1 and the capacitor C9 is grounded sequentially through the resistor R38 and the switch SW1. The common terminal of the resistor R38 and the switch SW1 is used as the first output terminal and electrically connected to the first control input terminal of the main control circuit;

[0033] The key driving circuit further includes a resistor R40 and a switch KY1. The common terminal of the inductor L1 and the capacitor C9 is grounded sequentially through the resistor R40 and the switch KY1. The common terminal of the resistor R40 and the switch KY1 is used as the second output terminal and electrically connected to the second control input terminal of the main control circuit.

[0034] In the above embodiment, the capacitor charging circuit includes a terminal block CN2, a rectification chip U6, a resistor R4, a resistor R3, a resistor R1, a resistor R2, a triode Q1, a MOS transistor M5, a diode D2, a resistor R5, and a capacitor C1. The terminal block CN2 is electrically connected to the input terminal of the rectification chip U6. The output terminal of the rectification chip U6 is sequentially electrically connected to the collector of the triode Q1 through the resistor R4 and the resistor R3. The base of the triode Q1 is used as the power input terminal and electrically connected to an external power supply after passing through the resistor R1. The base of the triode Q1 is also electrically connected to its emitter through the resistor R2. The emitter of the triode Q1 is grounded. The output terminal of the rectification chip U6 is also electrically connected to the drain of the MOS transistor M5. The gate of the MOS transistor M5 is electrically connected to the common terminal of the resistor R4 and the resistor R3. The source of the MOS transistor M5 is electrically connected to the anode of the diode D2. The cathode of the diode D2 is grounded sequentially through the resistor R5 and the capacitor C1. The common terminal of the resistor R5 and the capacitor C1 is used as the output terminal and electrically connected to the input terminal of the bridge commutation circuit.

[0035] In the above embodiment, the bridge commutation circuit includes a resistor R11, a resistor R13, a triode Q6, a resistor R14, a resistor R24, a resistor R18, a resistor R7, a MOS transistor M8, a MOS transistor M10, a TVS diode D3, a terminal block U4, a MOS transistor M9, a MOS transistor M11, a resistor R6, a resistor R15, a resistor R17, a triode Q7, a resistor R10, a resistor R8, and a resistor R16;

[0036] The common terminal of the resistor R5 and the capacitor C1 is sequentially electrically connected to the collector of the triode Q6 through the resistor R11 and the resistor R13. The base of the triode Q6 is electrically connected to its emitter through the resistor R24. The emitter of the triode Q6 is grounded. The base of the triode Q6 is used as the first control signal input terminal and electrically connected to the main control circuit after passing through the resistor R14;

[0037] The common terminal of resistor R5 and capacitor C1 is also electrically connected to the drain of MOS transistor M8. The gate of MOS transistor M8 is electrically connected to the common terminal of resistor R11 and resistor R13. The source of MOS transistor M8 is electrically connected to the drain of MOS transistor M10. The gate of MOS transistor M10 is electrically connected to its source through resistor R7. The gate of MOS transistor M10 is used as the second control signal input terminal to be electrically connected to the main control circuit after passing through resistor R18;

[0038] The common terminal of resistor R5 and capacitor C1 is sequentially electrically connected to the collector of triode Q7 through resistor R15 and resistor R17. The base of triode Q7 is electrically connected to its emitter through resistor R8. The emitter of triode Q7 is grounded. The base of triode Q7 is used as the third control signal input terminal to be electrically connected to the main control circuit after passing through resistor R10;

[0039] The common terminal of resistor R5 and capacitor C1 is electrically connected to the drain of MOS transistor M9. The gate of MOS transistor M9 is electrically connected to the common terminal of resistor R15 and resistor R17. The source of MOS transistor M9 is electrically connected to the drain of MOS transistor M11. The gate of MOS transistor M11 is electrically connected to its source through resistor R6. The gate of MOS transistor M11 is also used as the fourth control signal input terminal to be electrically connected to the main control circuit after passing through resistor R16;

[0040] The sources of MOS transistor M10 and MOS transistor M11 are electrically connected and then grounded. The source of MOS transistor M8 is electrically connected to one end of TVS diode D3. The other end of TVS diode D3 is electrically connected to the source of MOS transistor M9. The sources of MOS transistor M8 and MOS transistor M9 are both electrically connected to an external electromagnet through terminal block U4.

[0041] In the above embodiment, the overvoltage protection circuit includes resistor R12, resistor R19, resistor R21 and capacitor C8. The external 24V voltage is sequentially grounded through resistor R12 and resistor R19. Resistor R21 and capacitor C8 are sequentially connected in series and then connected in parallel across resistor R19. The common terminal of resistor R21 and capacitor C8 is used as the output terminal to be electrically connected to the ADC acquisition terminal of the main control circuit.

[0042] Working principle: Using the main control circuit, a program is written to charge capacitor C1 regularly. When switch SW1 is pressed, the main control circuit receives the signal and outputs control signals from terminal L1 and terminal L2, causing the electromagnet to operate. At this time, the fire door opens to the left. When switch KY1 is pressed, the main control circuit receives the signal and outputs control signals from terminal R1 and terminal R2, causing the electromagnet to operate. At this time, the fire door opens to the right. When the external 24V voltage loses power or the system is open-circuited, the ADC acquisition terminal of the main control circuit acquires the corresponding signal, drives capacitor C1 to discharge, causing the electromagnet to operate, ensuring that the fire door opens.

[0043] The above are only the preferred embodiments of the present utility model, and do not limit the implementation manners and protection scope of the present utility model thereby. For those skilled in the art, it should be realized that all the solutions obtained by equivalent substitution and obvious changes made by using the content of the specification of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A bidirectional electromagnetic drive test circuit, characterized in that: It includes a main control circuit, a capacitor charging circuit, a bridge commutation circuit, a power supply step-down circuit, a key drive circuit and an anti-voltage drop circuit. The output end of the power supply step-down circuit is electrically connected to the power supply input end of the key drive circuit, the output end of the key drive circuit is electrically connected to the main control circuit, the output end of the main control circuit is electrically connected to the commutation control end of the bridge commutation circuit, the output end of the capacitor charging circuit is electrically connected to the input end of the bridge commutation circuit, and the output end of the anti-voltage drop circuit is electrically connected to the ADC acquisition end of the main control circuit.

2. A bidirectional electromagnetic drive test circuit according to claim 1, characterized in that: The power supply step-down circuit includes a resistor R39, a capacitor C5, a capacitor C4, a voltage stabilizing chip U2, a resistor R25, a resistor R23, an inductor L1, a capacitor C9 and a capacitor C6. The external 24V voltage is sequentially grounded through the resistor R39 and the capacitor C5. The common end of the resistor R39 and the capacitor C5 is electrically connected to the input end of the voltage stabilizing chip U2. The capacitor C4 is connected in parallel to both ends of the capacitor C5. The output end of the voltage stabilizing chip U2 is electrically connected to its control end through the resistor R23. The output end of the voltage stabilizing chip U2 is electrically connected to its control end through the inductor L1, the capacitor C9 and the resistor R25 in sequence. The capacitor C6 is connected in parallel to both ends of the capacitor C9. The common end of the capacitor C9 and the resistor R25 is grounded. The common end of the inductor L1 and the capacitor C9 serves as an output end to output a 3.3V voltage.

3. A bidirectional electromagnetic drive test circuit according to claim 2, characterized in that: The key driving circuit includes a resistor R38 and a switch SW1, the common end of the inductor L1 and the capacitor C9 is grounded in sequence through the resistor R38 and the switch SW1, and the common end of the resistor R38 and the switch SW1 is electrically connected to the first control input end of the main control circuit as a first output end; The key driving circuit also includes a resistor R40 and a switch KY1. The common end of the inductor L1 and the capacitor C9 is grounded in sequence through the resistor R40 and the switch KY1. The common end of the resistor R40 and the switch KY1 is electrically connected to the second control input end of the main control circuit as a second output end.

4. A bidirectional electromagnetic drive test circuit according to claim 3, characterized in that: The capacitor charging circuit includes a connection terminal CN2, a rectifier chip U6, a resistor R4, a resistor R3, a resistor R1, a resistor R2, a transistor Q1, a MOS tube M5, a diode D2, a resistor R5 and a capacitor C1. The connection terminal CN2 is electrically connected to the input end of the rectifier chip U6. The output end of the rectifier chip U6 is electrically connected to the collector of the transistor Q1 through the resistor R4 and the resistor R3 in sequence. The base of the transistor Q1 is electrically connected to the external power supply as a power input end after passing through the resistor R1. The base of the transistor Q1 is electrically connected to the external power supply as a power input end. The electrode is also electrically connected to the emitter of the transistor Q1 through the resistor R2, the emitter of the transistor Q1 is grounded, the output end of the rectifier chip U6 is also electrically connected to the drain of the MOS tube M5, the gate of the MOS tube M5 is electrically connected to the common end of the resistor R4 and the resistor R3, the source of the MOS tube M5 is electrically connected to the anode of the diode D2, the cathode of the diode D2 is grounded through the resistor R5 and the capacitor C1 in sequence, and the common end of the resistor R5 and the capacitor C1 is electrically connected to the input end of the bridge commutation circuit as an output end.

5. A bidirectional electromagnetic drive test circuit according to claim 4, characterized in that: The bridge commutation circuit includes a resistor R11, a resistor R13, a transistor Q6, a resistor R14, a resistor R24, a resistor R18, a resistor R7, a MOS tube M8, a MOS tube M10, a TVS diode D3, a terminal U4, a MOS tube M9, a MOS tube M11, a resistor R6, a resistor R15, a resistor R17, a transistor Q7, a resistor R10, a resistor R8 and a resistor R16; The common end of the resistor R5 and the capacitor C1 is electrically connected to the collector of the transistor Q6 through the resistor R11 and the resistor R13 in sequence, the base of the transistor Q6 is electrically connected to its emitter through the resistor R24, the emitter of the transistor Q6 is grounded, and the base of the transistor Q6 is electrically connected to the main control circuit as a first control signal input end after passing through the resistor R14; The common end of the resistor R5 and the capacitor C1 is also electrically connected to the drain of the MOS transistor M8, the gate of the MOS transistor M8 is electrically connected to the common end of the resistor R11 and the resistor R13, the source of the MOS transistor M8 is electrically connected to the drain of the MOS transistor M10, the gate of the MOS transistor M10 is electrically connected to its source through the resistor R7, and the gate of the MOS transistor M10 is electrically connected to the main control circuit as a second control signal input end after passing through the resistor R18; The common end of the resistor R5 and the capacitor C1 is electrically connected to the collector of the transistor Q7 through the resistor R15 and the resistor R17 in sequence, the base of the transistor Q7 is electrically connected to its emitter through the resistor R8, the emitter of the transistor Q7 is grounded, and the base of the transistor Q7 is electrically connected to the main control circuit as a third control signal input end after passing through the resistor R10; The common end of the resistor R5 and the capacitor C1 is electrically connected to the drain of the MOS transistor M9, the gate of the MOS transistor M9 is electrically connected to the common end of the resistor R15 and the resistor R17, the source of the MOS transistor M9 is electrically connected to the drain of the MOS transistor M11, the gate of the MOS transistor M11 is electrically connected to its source through the resistor R6, and the gate of the MOS transistor M11 is also electrically connected to the main control circuit as a fourth control signal input end after passing through the resistor R16; The source of the MOS tube M10 is electrically connected to the source of the MOS tube M11 and then grounded, the source of the MOS tube M8 is electrically connected to one end of the TVS diode D3, the other end of the TVS diode D3 is electrically connected to the source of the MOS tube M9, and the source of the MOS tube M8 and the source of the MOS tube M9 are both electrically connected to the external electromagnet through the wiring terminal U4.

6. A bidirectional electromagnetic drive test circuit according to claim 5, characterized in that: The anti-voltage drop circuit includes a resistor R12, a resistor R19, a resistor R21 and a capacitor C8. The external 24V voltage is grounded through the resistor R12 and the resistor R19 in sequence. The resistor R21 and the capacitor C8 are connected in series in sequence and then connected in parallel to both ends of the resistor R19. The common end of the resistor R21 and the capacitor C8 is electrically connected to the ADC acquisition end of the main control circuit as an output end.

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