A safety meter box

Abstract

This utility model discloses a safety meter box, belonging to the technical field of meter boxes. It solves the problem that while internal humidity is primarily regulated by slow, natural airflow, this slow flow can cause the meter box's internal structure to remain damp for an extended period. Even after the humidity is eventually reduced, the high internal humidity can still damage the structure before it is completely eliminated. The device includes a casing and a door hinged to the casing. The door has a mounting groove in which a connecting cylinder is installed. In use, a humidity detection module monitors the humidity inside and outside the casing. When the internal humidity is higher than the external humidity, the control circuit opens a solenoid valve and starts a motor to rotate forward and expel moisture. After the humidity balances, the motor reverses for a preset time, stops, and closes the solenoid valve, maintaining stable internal humidity and preventing damage to electrical components due to high humidity.

Description

Technical Field

[0001] This utility model relates to the field of meter box technology, and in particular to a safety meter box. Background Technology

[0002] A meter box is a device in a power system used to install electricity meters and related electrical components. It is typically made of metal or plastic and has protective, metering, and control functions. The main purpose of a meter box is to protect the meters and electrical components from damage caused by the external environment, while providing a centralized installation platform for energy metering and circuit control. Depending on their application and design, meter boxes can be divided into single-phase and three-phase types, suitable for circuits of different voltage levels. To ensure safe and stable operation, meter boxes require regular inspection and maintenance to avoid malfunctions caused by component aging, loose wiring, or environmental influences.

[0003] Currently, the inside of the meter box needs to be kept as dry as possible. However, the humidity inside is mainly regulated by the slow natural airflow. But the slow airflow will cause the structure inside the meter box to remain damp for a long time. Even if the humidity inside the meter box is eventually reduced, the high humidity inside will still damage the structure before it is completely reduced.

[0004] Therefore, a safety meter box is proposed to solve or alleviate the above problems. Utility Model Content

[0005] The purpose of this utility model is to address the shortcomings of existing technologies by proposing a safe electric meter box.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A safety meter box includes a chassis and a door hinged to the chassis. The door has a mounting groove, and a connecting cylinder is installed in the mounting groove. One end of the connecting cylinder facing the inside of the chassis is connected to a solenoid valve. The other end of the connecting cylinder facing the outside is fixedly connected to a motor via a connecting frame. The rotor shaft of the motor is fixedly connected to a fan blade. A plurality of filter sheets are filled between the connecting cylinder and the solenoid valve.

[0008] Preferably, the motor and the solenoid valve are coupled to a humidity electromechanical control circuit. When the humidity inside the chassis is higher than that outside, the humidity electromechanical control circuit opens the solenoid valve and starts the motor to rotate forward to discharge moisture. After the humidity inside and outside is balanced, the motor is switched to reverse operation for a preset time and then stops and closes the solenoid valve.

[0009] Preferably, the humidity electromechanical control circuit includes a power supply module, a humidity detection module, a comparator module, a logic control module, an execution module, and a protection module;

[0010] The output terminals of the power supply module are respectively connected to the power supply terminals of the humidity detection module, the comparator module, the logic control module, and the drive execution module. The internal and external humidity signal output terminals of the humidity detection module are respectively connected to the non-inverting input terminal and the inverting input terminal of the comparator module. The output terminals of the comparator module are respectively connected to the first input terminal of the logic control module, the forward drive terminal of the drive execution module, and the timing trigger terminal of the logic control module. The output terminal of the logic control module is connected to the valve drive terminal and the reverse drive terminal of the drive execution module. A mechanical interlock circuit is provided between the forward and reverse output terminals of the drive execution module, and its valve control terminal is synchronously switched on and off with the output terminal of the logic control module.

[0011] Preferably, the power supply module includes a first voltage regulator chip LM7812CT and a second voltage regulator chip AMS1117-5.0;

[0012] The input terminal of the first voltage regulator chip LM7812CT is connected to the positive terminal of a 24V power supply through a first input capacitor. The ground terminal of the first voltage regulator chip LM7812CT is grounded. The output terminal of the first voltage regulator chip LM7812CT outputs a 12V voltage to the execution module through a first output capacitor. The 12V voltage at the input terminal of the second voltage regulator chip AMS1117-5.0 is grounded through a filter capacitor. The output terminal of the second voltage regulator chip AMS1117-5.0 outputs a 5V logic voltage to the humidity detection module and the logic control module through a second output capacitor.

[0013] Preferably, the humidity detection module includes an internal humidity sensor, a first operational amplifier TL072, an external humidity sensor, and a second operational amplifier TL072;

[0014] The internal humidity sensor is located inside the chassis, and the external humidity sensor is located on the outer wall of the chassis. The Vdd pin of the internal humidity sensor is connected to a 5V logic voltage, and the Vout pin of the internal humidity sensor is connected to the non-inverting input of the first operational amplifier TL072. The GND pin of the internal humidity sensor is grounded. The Vdd pin of the external humidity sensor is connected to a 5V logic voltage, and the Vout pin of the external humidity sensor is connected to the non-inverting input of the second operational amplifier TL072. The GND pin of the external humidity sensor is grounded. The output of the first operational amplifier TL072 is connected to the non-inverting input of the comparator module via a low-pass filter, and the output of the second operational amplifier TL072 is connected to the inverting input of the comparator module via a low-pass filter.

[0015] Preferably, the comparator module includes an LM393 voltage comparator, a hysteresis resistor, a 1N4148 diode, a first resistor, and a first capacitor;

[0016] The non-inverting input of the LM393 voltage comparator is used to receive the internal humidity signal, and the inverting input of the LM393 voltage comparator is used to receive the external humidity signal. The output of the LM393 voltage comparator is connected to the non-inverting input of the LM393 voltage comparator through a series hysteresis resistor and a 1N4148 diode. The output of the LM393 voltage comparator is connected to the input of the logic control module through a first resistor and to the trigger of the logic control module through a first capacitor.

[0017] Preferably, the logic control module includes an OR gate chip CD4071, a monostable timer NE555, a pull-up resistor, a timing resistor, a timing capacitor, and a second resistor;

[0018] The first and second input terminals of the OR gate chip CD4071 are connected to the two output terminals of the comparator module. The output terminal of the OR gate chip CD4071 is connected to the input terminal of the execution module. The trigger terminal of the monostable timer NE555 is connected to a 12V voltage through a pull-up resistor. The threshold and discharge terminals of the monostable timer NE555 are connected to a timing resistor to a 12V voltage. The GND pin of the monostable timer NE555 is connected to a timing capacitor and then grounded. The output terminal of the monostable timer NE555 is connected to the input terminal of the OR gate chip CD4071 and the input terminal of the execution module.

[0019] Preferably, the execution module includes a Darlington transistor TIP122, a first transistor 2N2222, a forward relay, a second transistor 2N2222, and a reverse relay;

[0020] The base of the Darlington transistor TIP122 is connected to the output of the OR gate chip CD4071. The collector of the Darlington transistor TIP122 is connected in series with the solenoid valve and then energized. The emitter of the Darlington transistor TIP122 is grounded. The base of the first transistor 2N2222 is connected to the output of the comparator module. The collector of the first transistor 2N2222 is connected in series with a forward relay and then energized. The emitter of the first transistor 2N2222 is grounded. The base of the second transistor 2N2222 is connected to the output of the logic control module. The collector of the second transistor 2N2222 is connected in series with a reverse relay and then energized. The emitter of the second transistor 2N2222 is grounded. The normally closed contact of the forward relay is connected in series in the circuit where the reverse relay is located. The normally closed contact of the reverse relay is connected in series in the circuit where the forward relay is located.

[0021] Preferably, the protection module includes a freewheeling diode 1N4007, the anode of which is connected to the negative terminal of the solenoid valve, and the cathode of which is connected to the positive terminal of the solenoid valve.

[0022] This utility model has the following beneficial effects:

[0023] In use, the humidity detection module of this invention monitors the humidity inside and outside the chassis. When the humidity inside the chassis is higher than that outside, the control circuit opens the solenoid valve and starts the motor to rotate forward to expel moisture. After the humidity is balanced, the motor reverses for a preset time and then stops and closes the solenoid valve, maintaining stable humidity inside the chassis and preventing damage to electrical components due to high humidity. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of the structure of this utility model;

[0026] Figure 2 for Figure 1 Enlarged view of point A in the middle;

[0027] Figure 3 This is a structural block diagram of the humidity electromechanical control circuit in this utility model.

[0028] In the diagram: 1. Chassis; 2. Door; 3. Mounting slot; 4. Support slot; 5. Connecting cylinder; 6. Mounting block; 7. Guide slope; 8. Sealing strip; 9. Connecting frame; 10. Filter; 11. Power module; 12. Humidity detection module; 13. Comparator module; 14. Logic control module; 15. Execution module; 16. Protection module; 17. Fan blade. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0031] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0032] In the description of this utility model, it should be understood that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the utility model product is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this utility model and to simplify the description, and are not intended to indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0033] Furthermore, the terms "first," "second," and "third" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0034] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0035] A type of safety meter box, such as Figure 1 and Figure 2 As shown, the device includes a chassis 1 and a door 2 hinged to the chassis 1. The door 2 has a mounting groove 3, and a connecting cylinder 5 is installed in the mounting groove 3. The end of the connecting cylinder 5 facing the inside of the chassis 1 is connected to a solenoid valve. The end of the connecting cylinder 5 facing the outside is fixedly connected to a motor through a connecting frame 9. The rotor shaft of the motor is fixedly connected to a fan blade 17. Several filter sheets 10 are filled between the connecting cylinder 5 located between the connecting frame 9 and the solenoid valve.

[0036] like Figure 3As shown, the motor and solenoid valve are coupled to a humidity electromechanical control circuit. When the humidity inside the casing 1 is higher than that outside, the humidity electromechanical control circuit opens the solenoid valve and starts the motor to rotate forward to expel moisture. After the internal and external humidity are balanced, the motor switches to reverse operation for a preset time, then stops and closes the solenoid valve. The humidity electromechanical control circuit includes a power module 11, a humidity detection module 12, a comparator module 13, a logic control module 14, an execution module 15, and a protection module 16. The output terminal of the power module 11 is connected to the power supply terminal of the humidity detection module 12, the power supply terminal of the comparator module 13, the power supply terminal of the logic control module 14, and the drive. The power supply terminal of the execution module 15 and the internal and external humidity signal output terminals of the humidity detection module 12 are respectively connected to the non-inverting input terminal and the inverting input terminal of the comparator module 13. The output terminal of the comparator module 13 is respectively connected to the first input terminal of the logic control module 14, the forward drive terminal of the drive execution module 15, and the timing trigger terminal of the logic control module 14. The output terminal of the logic control module 14 is connected to the valve drive terminal and the reverse drive terminal of the drive execution module 15. A mechanical interlock circuit is set between the forward output terminal and the reverse output terminal of the drive execution module 15, and its valve control terminal is synchronously switched on and off with the output terminal of the logic control module 14.

[0037] The power supply module 11 includes a first voltage regulator chip LM7812CT and a second voltage regulator chip AMS1117-5.0. The input terminal of the first voltage regulator chip LM7812CT is connected to the positive terminal of a 24V power supply through a first input capacitor. The ground terminal of the first voltage regulator chip LM7812CT is grounded. The output terminal of the first voltage regulator chip LM7812CT outputs a 12V voltage to the execution module 15 through a first output capacitor. The 12V voltage at the input terminal of the second voltage regulator chip AMS1117-5.0 is grounded through a filter capacitor. The output terminal of the second voltage regulator chip AMS1117-5.0 outputs a 5V logic voltage to the humidity detection module 12 and the logic control module 14 through a second output capacitor.

[0038] The humidity detection module 12 includes an internal humidity sensor, a first operational amplifier TL072, an external humidity sensor, and a second operational amplifier TL072. The internal humidity sensor is installed inside the chassis 1, and the external humidity sensor is installed on the outer wall of the chassis 1. The Vdd pin of the internal humidity sensor is connected to a 5V logic voltage, and the Vout pin of the internal humidity sensor is connected to the non-inverting input of the first operational amplifier TL072. The GND pin of the internal humidity sensor is grounded. The Vdd pin of the external humidity sensor is connected to a 5V logic voltage, and the Vout pin of the external humidity sensor is connected to the non-inverting input of the second operational amplifier TL072. The GND pin of the external humidity sensor is grounded. The output of the first operational amplifier TL072 is connected to the non-inverting input of the comparator module 13 via a low-pass filter, and the output of the second operational amplifier TL072 is connected to the inverting input of the comparator module 13 via a low-pass filter.

[0039] The comparator module 13 includes an LM393 voltage comparator, a hysteresis resistor, a 1N4148 diode, a first resistor, and a first capacitor. The non-inverting input of the LM393 voltage comparator is used to receive the internal humidity signal, and the inverting input of the LM393 voltage comparator is used to receive the external humidity signal. The output of the LM393 voltage comparator is connected to the non-inverting input of the LM393 voltage comparator through the series hysteresis resistor and the 1N4148 diode. The output of the LM393 voltage comparator is connected to the input of the logic control module 14 through the first resistor and to the trigger terminal of the logic control module 14 through the first capacitor.

[0040] The logic control module 14 includes an OR gate chip CD4071, a monostable timer NE555, a pull-up resistor, a timing resistor, a timing capacitor, and a second resistor. The first and second input terminals of the OR gate chip CD4071 are connected to the two output terminals of the comparator module 13. The output terminal of the OR gate chip CD4071 is connected to the input terminal of the execution module 15. The trigger terminal of the monostable timer NE555 is connected to a 12V voltage through a pull-up resistor. The threshold and discharge terminals of the monostable timer NE555 are connected to a timing resistor to a 12V voltage. The GND pin of the monostable timer NE555 is connected to ground after being connected to the timing capacitor. The output terminal of the monostable timer NE555 is connected to the input terminal of the OR gate chip CD4071 and the input terminal of the execution module 15.

[0041] Execution module 15 includes a Darlington transistor TIP122, a first transistor 2N2222, a forward relay, a second transistor 2N2222, and a reverse relay. The base of Darlington transistor TIP122 is connected to the output of an OR gate chip CD4071. The collector of Darlington transistor TIP122 is connected in series with a solenoid valve and then energized. The emitter of Darlington transistor TIP122 is grounded. The base of the first transistor 2N2222 is connected to the output of comparator module 13. The collector of transistor 2N2222 is connected in series with a forward relay and then energized. The emitter of the first transistor 2N2222 is grounded. The base of the second transistor 2N2222 is connected to the output of logic control module 14. The collector of the second transistor 2N2222 is connected in series with a reverse relay and then energized. The emitter of the second transistor 2N2222 is grounded. The normally closed contact of the forward relay is connected in series in the circuit containing the reverse relay. The normally closed contact of the reverse relay is connected in series in the circuit containing the forward relay.

[0042] The protection module 16 includes a freewheeling diode 1N4007, the anode of which is connected to the negative terminal of the solenoid valve, and the cathode of which is connected to the positive terminal of the solenoid valve.

[0043] In actual use, the humidity detection module 12 detects the humidity inside and outside the chassis 1. When the humidity inside the chassis 1 is greater than the humidity outside the chassis 1, the humidity electromechanical control circuit controls the solenoid valve to open, controls the opening of the solenoid valve and starts the motor to rotate forward to discharge moisture. After the humidity inside and outside is balanced, the motor switches to reverse operation for a preset time and then stops and closes the solenoid valve. This allows the humidity inside the chassis 1 to maintain a relatively stable humidity level, avoiding the situation where the humidity inside the chassis 1 remains high for a long time, and preventing damage to the electrical components inside the chassis 1 caused by prolonged high humidity.

[0044] During the specific operation of the humidity electromechanical control circuit, when the voltage signal detected by the internal humidity sensor of the chassis 1 is higher than the signal of the external humidity sensor, the LM393 voltage comparator outputs a high-level signal. This signal drives the Darlington transistor TIP122 to conduct through the OR gate chip CD4071, causing the solenoid valve to open immediately. At the same time, it directly triggers the first transistor 2N2222 to drive the forward rotation relay to engage, and the fan starts to rotate forward to exhaust moisture.

[0045] When the internal and external humidity approaches equilibrium, the output level of the LM393 voltage comparator jumps low, and its falling edge triggers the monostable timer NE555. At this time, the OR gate chip CD4071 continues to conduct the solenoid valve under the high level maintained by the output of the monostable timer NE555. The forward relay is released due to de-energization, and the reverse relay is energized under the drive of the output of the monostable timer NE555, causing the fan to run in reverse. After a preset time constant, the output of the monostable timer NE555 is reset to low level, the solenoid valve closes, the reverse relay is disconnected, and the motor stops completely. During this period, the freewheeling diode continuously suppresses the reverse electromotive force of the solenoid valve, and the mechanical interlock structure ensures that the forward and reverse relays will not conduct at the same time.

[0046] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A safety meter box, characterized in that, The device includes a chassis (1) and a door (2) hinged to the chassis (1). The door (2) has an installation groove (3) and a connecting cylinder (5) is installed in the installation groove (3). The end of the connecting cylinder (5) facing the inside of the chassis (1) is connected to a solenoid valve. The end of the connecting cylinder (5) facing the outside is fixedly connected to a motor through a connecting frame (9). The rotor shaft of the motor is fixedly connected to a fan blade (17). Several filter sheets (10) are filled between the connecting cylinder (5) located between the connecting frame (9) and the solenoid valve. The motor and the solenoid valve are coupled to a humidity electromechanical control circuit. When the humidity inside the chassis (1) is higher than that outside, the humidity electromechanical control circuit opens the solenoid valve and starts the motor to rotate forward to discharge moisture. After the humidity inside and outside is balanced, the motor is switched to reverse operation for a preset time and then stopped and the solenoid valve is closed.

2. A safety meter box according to claim 1, characterized in that, The humidity electromechanical control circuit includes a power supply module (11), a humidity detection module (12), a comparator module (13), a logic control module (14), an execution module (15), and a protection module (16). The output terminal of the power module (11) is connected to the power supply terminal of the humidity detection module (12), the power supply terminal of the comparator module (13), the power supply terminal of the logic control module (14), and the power supply terminal of the drive execution module (15), respectively. The internal and external humidity signal output terminals of the humidity detection module (12) are connected to the non-inverting input terminal and the inverting input terminal of the comparator module (13), respectively. The output terminal of the comparator module (13) is connected to the first input terminal of the logic control module (14), the forward drive terminal of the drive execution module (15), and the timing trigger terminal of the logic control module (14), respectively. The output terminal of the logic control module (14) is connected to the valve drive terminal and the reverse drive terminal of the drive execution module (15). A mechanical interlock circuit is provided between the forward output terminal and the reverse output terminal of the drive execution module (15), and its valve control terminal and the output terminal of the logic control module (14) are kept synchronously on and off.

3. A safety meter box according to claim 2, characterized in that, The power module (11) includes a first voltage regulator chip LM7812CT and a second voltage regulator chip AMS1117-5.0; The input terminal of the first voltage regulator chip LM7812CT is connected to the positive terminal of the 24V power supply through the first input capacitor. The ground terminal of the first voltage regulator chip LM7812CT is grounded. The output terminal of the first voltage regulator chip LM7812CT outputs a 12V voltage to the execution module (15) through the first output capacitor. The 12V voltage at the input terminal of the second voltage regulator chip AMS1117-5.0 is grounded through the filter capacitor. The output terminal of the second voltage regulator chip AMS1117-5.0 outputs a 5V logic voltage to the humidity detection module (12) and the logic control module (14) through the second output capacitor.

4. A safety meter box according to claim 2, characterized in that, The humidity detection module (12) includes an internal humidity sensor, a first operational amplifier TL072, an external humidity sensor, and a second operational amplifier TL072; The internal humidity sensor is installed inside the chassis (1), and the external humidity sensor is installed on the outer wall of the chassis (1). The Vdd pin of the internal humidity sensor is connected to a 5V logic voltage, the Vout pin of the internal humidity sensor is connected to the non-inverting input of the first operational amplifier TL072, the GND pin of the internal humidity sensor is grounded, the Vdd pin of the external humidity sensor is connected to a 5V logic voltage, the Vout pin of the external humidity sensor is connected to the non-inverting input of the second operational amplifier TL072, the GND pin of the external humidity sensor is grounded, the output of the first operational amplifier TL072 is connected to the non-inverting input of the comparator module (13) via a low-pass filter, and the output of the second operational amplifier TL072 is connected to the inverting input of the comparator module (13) via a low-pass filter.

5. A safety meter box according to claim 2, characterized in that, The comparator module (13) includes an LM393 voltage comparator, a hysteresis resistor, a 1N4148 diode, a first resistor, and a first capacitor; The non-inverting input of the LM393 voltage comparator is used to receive the internal humidity signal, and the inverting input of the LM393 voltage comparator is used to receive the external humidity signal. The output of the LM393 voltage comparator is connected to the non-inverting input of the LM393 voltage comparator through a series hysteresis resistor and a 1N4148 diode. The output of the LM393 voltage comparator is connected to the input of the logic control module (14) through a first resistor and to the trigger of the logic control module (14) through a first capacitor.

6. A safety meter box according to claim 2, characterized in that, The logic control module (14) includes an OR gate chip CD4071, a monostable timer NE555, a pull-up resistor, a timing resistor, a timing capacitor, and a second resistor; The first and second input terminals of the OR gate chip CD4071 are connected to the two output terminals of the comparator module (13). The output terminal of the OR gate chip CD4071 is connected to the input terminal of the execution module (15). The trigger terminal of the monostable timer NE555 is connected to a 12V voltage through a pull-up resistor. The threshold and discharge terminals of the monostable timer NE555 are connected to a timing resistor to a 12V voltage. The GND pin of the monostable timer NE555 is connected to a timing capacitor and then grounded. The output terminal of the monostable timer NE555 is connected to the input terminal of the OR gate chip CD4071 and the input terminal of the execution module (15).

7. A safety meter box according to claim 2, characterized in that, The execution module (15) includes a Darlington transistor TIP122, a first transistor 2N2222, a forward relay, a second transistor 2N2222, and a reverse relay; The base of the Darlington transistor TIP122 is connected to the output of the OR gate chip CD4071. The collector of the Darlington transistor TIP122 is connected in series with the solenoid valve and then energized. The emitter of the Darlington transistor TIP122 is grounded. The base of the first transistor 2N2222 is connected to the output of the comparator module (13). The collector of the first transistor 2N2222 is connected in series with the forward relay and then energized. The emitter of the first transistor 2N2222 is grounded. The base of the second transistor 2N2222 is connected to the output of the logic control module (14). The collector of the second transistor 2N2222 is connected in series with the reverse relay and then energized. The emitter of the second transistor 2N2222 is grounded. The normally closed contact of the forward relay is connected in series in the circuit where the reverse relay is located. The normally closed contact of the reverse relay is connected in series in the circuit where the forward relay is located.

8. A safety meter box according to claim 2, characterized in that, The protection module (16) includes a freewheeling diode 1N4007, the anode of which is connected to the negative terminal of the solenoid valve, and the cathode of which is connected to the positive terminal of the solenoid valve.

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