A bus water vending machine circuit protection device based on PPTC self-restoring fuse

Abstract

The utility model relates to a bus water vending machine circuit protection device based on PPTC self -restoring fuse, the device includes power input, anti -reversal circuit, power conversion module, MCU, data storage and transmission module and all sorts of function module. Its innovation lies in adopting the multistage protection framework that main protection unit and branch protection unit are combined: the main protection unit is composed of the PPTC1 of series connection and the parallel connection of pressure sensitive resistance RV, and the overvoltage, overcurrent and surge impact from the automobile power supply are effectively inhibited, the branch protection unit carries out independent overcurrent, overtemperature and short -circuit protection through PPTC2 to PPTC6 to point the money motor, find the make -up coin motor, send the bottle motor, electromagnetic valve and USB interface power supply circuit respectively. The utility model realizes comprehensive self -restoring type protection with very few components, has the advantages such as compact structure, maintenance -free, high reliability, low cost, significantly improves the adaptability and service life of vehicle-mounted water vending machine in the harsh electrical environment.

Description

Technical Field

[0001] This utility model relates to the technical field, and in particular to a circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse. Background Technology

[0002] With the development of competition and intelligence in public transportation, on-board water vending machines have emerged and developed rapidly. However, the on-board environment is subject to complex electromagnetic interference, such as peak voltage, pulse voltage, high voltage lightning waves, high voltage and high power back electromotive force generated by the start and stop of the engine (generator), and gap electromagnetic resonance peak voltage. In addition, the small motor and solenoid valve inside the water vending machine are prone to generating back electromotive force when working, which may break down the driving MOSFET. This places extremely high demands on the stability and reliability of the circuit.

[0003] Traditional vehicle-mounted water vending machine protection circuits have many defects:

[0004] Traditional solutions for overcurrent / short circuit protection have drawbacks: disposable glass fuses, 0Ω resistors, or PCB copper foil are commonly used at the PPTC1 position. The former two require manual replacement, and the latter is difficult to identify the model and cause of failure after disconnection. Some solutions use modular protection circuits, which include multiple units such as sampling, signal amplification, comparison, and execution drive, requiring dozens of components. This not only occupies a large amount of PCB area and installation space, but also causes the circuit distribution parameters to deteriorate due to the accumulation of component errors, making it susceptible to interference and damage, and even causing a chain of burnouts.

[0005] In terms of motor protection, issues such as stalled rotor and overheating require dual protection against overcurrent and overtemperature. Traditional temperature fuses are one-time devices, temperature switches have slow response, NTC sensors or thermocouples require complex circuits, and still have problems such as many components and low reliability. Relays have hidden dangers such as contact oxidation and arcing.

[0006] In summary, traditional protection circuits have many components, high cost, low reliability, large space occupation, and are difficult to maintain. Some manufacturers omit protection circuits to reduce costs, resulting in short product life and frequent quality disputes. Currently, there is a lack of ideal protection circuits with fewer components, high reliability, and the ability to prevent overvoltage, overcurrent, and overtemperature. Utility Model Content

[0007] The purpose of this invention is to provide a circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse. Through the innovative combination of a PPTC self-resetting fuse and a varistor, the device achieves overcurrent, overtemperature, overvoltage, and short-circuit protection for the water vending machine circuit system with fewer components, lower cost, and smaller size, while ensuring stable water vending function and improving product safety, reliability, and service life.

[0008] To achieve the above objectives, this utility model adopts the following technical solution: a circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse. This device includes a power input terminal, a reverse connection protection circuit, a power conversion module, a main control unit (MCU), a data storage and transmission module, and a coin acceptance module controlled by the MCU, a banknote counting motor (M1), a coin return motor (M2), a bottle feeding motor (M3), a solenoid valve, and a USB interface. Its distinguishing feature is that it further includes...

[0009] The main protection unit consists of a first resettable fuse PPTC1 and a varistor RV. The first resettable fuse PPTC1 is connected in series between the positive terminal of the vehicle power supply and the input terminal of the reverse connection protection circuit. The varistor RV is connected in parallel between the node between the first resettable fuse PPTC1 and the reverse connection protection circuit and ground.

[0010] Branch protection unit, including:

[0011] The second resettable fuse PPTC2 is connected in series in the power supply circuit of the banknote counting motor (M1); the third resettable fuse PPTC3 is connected in series in the power supply circuit of the change and return motor (M2).

[0012] The fourth resettable fuse PPTC4 is connected in series in the power supply circuit of the bottle feeding motor (M3); the fifth resettable fuse PPTC5 is connected in series in the power supply circuit of the solenoid valve.

[0013] The sixth resettable fuse, PPTC6, is connected in series in the power supply circuit of the USB interface.

[0014] As a further improvement of this utility model, the first self-resetting fuse PPTC1 to the sixth self-resetting fuse PPTC6 are all surface-mount packaged polymer-based positive temperature coefficient thermistors.

[0015] As a further improvement of this utility model, the varistor RV has a varistor voltage of 36V.

[0016] As a further improvement of this utility model, the reverse connection protection circuit is composed of four diodes (D1-D4) in a bridge structure, and a filter capacitor C1 is connected in parallel at its output terminal.

[0017] As a further improvement of this utility model, the power conversion module includes a DC-DC circuit that converts the input voltage to 5V and a linear voltage regulator circuit that converts 5V to 3.3V, which supply power for different operating voltages respectively.

[0018] As a further improvement of this utility model, the banknote counting motor (M1), the coin return motor (M2), the bottle feeding motor (M3), and the solenoid valve are driven by MOS transistors (Q1, Q2, Q3, Q4), and the gate of each MOS transistor (Q1-Q4) is connected in series with a driving resistor (R1, R3, R5, R7), and a discharge circuit composed of resistors (R2, R4, R6, R8) and diodes (D5, D6, D7, D8) is connected in parallel between its source and drain.

[0019] As a further improvement of this utility model, the data storage and transmission module includes a data memory connected to the MCU and a USB interface protected by the sixth self-resetting fuse PPTC6.

[0020] As a further improvement of this utility model, the coin-operated recognition module includes a purple light emitting LED1, a recognition camera CD2, and a coin-operated recognition processing unit.

[0021] As a further improvement of this utility model, it also includes a payment module, which includes a camera CD1 for face recognition and QR code recognition.

[0022] As a further improvement of this utility model, it also includes a status indicator LED2, which is connected to the MCU and is used to display standby and working status.

[0023] The beneficial effects of this utility model are:

[0024] 1. Comprehensive and reliable protection functions: Through the cooperation of PPTC1 and RV, overvoltage, overcurrent and overtemperature protection are achieved simultaneously. RV absorbs high voltage pulses, PPTC1 limits the large current when RV is turned on (to prevent RV from burning out), and prevents short circuits and overheating from damaging the car power supply; PPTC2-PPTC6 protect each motor, solenoid valve and USB interface respectively to avoid faults such as wire burning and fire caused by stalling, short circuit and overheating, and MOSFET explosion. Moreover, the protection action is early, which can avoid damage to the load and circuit.

[0025] 2. Simplified circuit and reduced cost: A single PPTC device replaces the traditional multi-component protection circuit, reducing the number of components by more than 80%, and reducing the PCB area to less than 1 / 24 of the traditional solution. This reduces procurement and production debugging costs and supports automated and large-scale production.

[0026] 3. Enhance product practicality: The water vending machine's casing is only 9cm thick (8.5cm internal space), allowing it to be installed flush against the vehicle wall without taking up passenger space; it supports multiple payment methods such as coins / banknotes, facial recognition, and mobile QR codes, catering to different user groups; data can be wirelessly transmitted to the upper control center or exported via USB interface, facilitating operation, maintenance, and auditing.

[0027] 4. Long lifespan and easy maintenance: PPTC devices are reusable and do not require frequent replacement; the circuit structure is simple, the troubleshooting is easy, the after-sales maintenance cost is reduced, and the product lifespan is extended by more than 3 times. Attached Figure Description

[0028] Figure 1 This is a circuit block diagram of the present invention. Detailed Implementation

[0029] To facilitate understanding of this utility model, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of this utility model are shown in the drawings. However, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this utility model.

[0030] It should be noted that when a component is said to be "fixed to" another component, it can be directly attached to the other component or there may be an intervening component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there may be an intervening component.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0032] The water vending machine's casing is relatively thin, only 9cm thick, with an internal space of 8.5cm. The outer diameter of a 555mL purified water plastic bottle is 6.3cm. The casing is fitted tightly against the vehicle wall without encroaching on passenger space. Various control circuits and actuators are installed in a very small space on the side of the casing, requiring a very compact design and installation. Furthermore, the onboard electromagnetic environment is complex, including sudden voltage spikes, pulse voltages, high-voltage lightning surges, high-voltage, high-power back electromotive force from engine (generator) start-up and shutdown, and gap electromagnetic resonance spike voltages. This places extremely high demands on the design of the onboard electronic circuitry, requiring high resistance to these interferences, high circuit stability, and high reliability. These design considerations extend beyond the selection of main circuit components; small motors and solenoid valves in the circuit can also generate high back electromotive force, potentially damaging their driving MOSFETs.

[0033] Please see Figure 1This utility model provides a circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse, including a power input terminal, a reverse connection protection circuit, a power conversion module, a main control unit (MCU), a data storage and transmission module, and a coin acceptance module controlled by the MCU, a banknote counting motor (M1), a coin return motor (M2), a bottle feeding motor (M3), a solenoid valve, and a USB interface. Its distinguishing feature is that it also includes...

[0034] The main protection unit consists of a first resettable fuse PPTC1 and a varistor RV connected in parallel and then in series to the positive terminal of the power supply. The first resettable fuse PPTC1 is connected in series between the positive terminal of the automotive power supply and the input terminal of the reverse connection protection circuit. The varistor RV is connected in parallel between the node between the first resettable fuse PPTC1 and the reverse connection protection circuit and ground, which is used to realize overcurrent and overvoltage protection of the input power supply.

[0035] Branch protection unit, including:

[0036] The second resettable fuse PPTC2 is connected in series in the power supply circuit of the banknote counting motor (M1); the third resettable fuse PPTC3 is connected in series in the power supply circuit of the change and coin return motor (M2).

[0037] The fourth resettable fuse PPTC4 is connected in series in the power supply circuit of the bottle feeding motor (M3); the fifth resettable fuse PPTC5 is connected in series in the power supply circuit of the solenoid valve.

[0038] The sixth resettable fuse, PPTC6, is connected in series in the power supply circuit of the USB interface. The USB interface is used to read water sales data stored in the data storage device.

[0039] Multiple resettable fuses are used to provide overcurrent, overtemperature and short-circuit protection for their respective branches.

[0040] The first settling fuse PPTC1 to the sixth settling fuse PPTC6 are all surface-mount polymer-based positive temperature coefficient thermistors. PPTC1 to PPTC6 are various models of different current ratings produced using the same materials and processes. PPTC itself is mainly made of polymer as the matrix, with nano-sized carbon powder mixed uniformly at high temperature, and then manufactured through special processes such as plate vulcanization, allowing the carbon powder particles to form conductive paths for normal operation. At room temperature, it has a low resistance in the mΩ range. When a large current flows through it or the surrounding environment is high-temperature, the polymer material of the PPTC will heat up due to the large current passing through the carbon powder or be exposed to ambient temperatures above 85°C. This sudden thermal expansion of the polymer material breaks the original conductive links between the carbon particles, causing most of the conductive paths in the carbon particles to break and become high-resistance, thus completing the current-limiting protection function. When power is cut off and the temperature drops to a certain value, the PPTC material contracts upon cooling, reconnecting the previously disconnected carbon particles and restoring normal conductivity with low resistance. This is the working principle of PPTC. From this principle, we can see that a large current causes the PPTC to heat up, resulting in thermal expansion, which increases the resistance and limits the current. The larger the current, the faster the sudden increase in heating, the greater the sudden increase in resistance, and the stronger the current-limiting effect. However, after current limiting, the current becomes very small, there is no heating, the temperature decreases, and the resistance also decreases. This decrease in resistance then leads to an increase in current, increased heating, and increased resistance, and so on, in one or more cycles, eventually reaching a thermal equilibrium point where heating and cooling are equal. This point is around 96℃. The normal operating temperature range of PPTC is -40℃ to +85℃. From the above working process of PPTC, we can see that PPTC itself will not be damaged by high temperatures because high temperatures result in high resistance and current limiting, preventing the temperature from rising and thus avoiding burnout. Therefore, using PPTC as a protection device is very reliable, as a single component performs overcurrent, short-circuit, and over-temperature protection functions. Using SMD surface-mount components further reduces the size.

[0041] Among them, PPTC1-PPTC6 are surface mount or through-hole type resettable fuses, made of polymer matrix doped with nano-sized carbon powder. Under normal operation, they have a low resistance in the mΩ range. When the circuit is overcurrent (current exceeds the rated value) or the ambient temperature exceeds 85℃ (PPTC1) and 90℃ (PPTC2-PPTC5), the thermal expansion of the polymer material causes the carbon powder conductive link to break, and the resistance suddenly becomes high, realizing current limiting protection. After the fault is cleared, the material cools and shrinks, the carbon powder link is restored, and the resistance returns to the low resistance state, and it can be reused. RV is a varistor with a varistor voltage of 36V and a diameter of φ10, used to absorb high voltage pulses in the input voltage.

[0042] The MCU processor is connected to the coin-operated change recognition module, the image recognition processing module, the MOS transistor of the execution drive unit, and the data memory to realize functional logic control and data processing.

[0043] The varistor RV has a varistor voltage of 36V and is used to absorb instantaneous high voltage pulses.

[0044] The reverse connection protection circuit consists of four diodes (D1-D4) in a bridge structure, with a filter capacitor C1 connected in parallel at its output.

[0045] The power conversion module includes a DC-DC circuit that converts the input voltage to 5V and a linear regulator circuit that converts 5V to 3.3V, providing power for different operating voltages.

[0046] The banknote counting motor (M1), the change / dispensing motor (M2), the bottle feeding motor (M3), and the solenoid valve are driven by MOSFETs (Q1, Q2, Q3, Q4), respectively. The gate of each MOSFET (Q1-Q4) is connected in series with a driving resistor (R1, R3, R5, R7), and the source and drain of each MOSFET are connected in parallel with a junction capacitance discharge circuit composed of resistors (R2, R4, R6, R8) and diodes (D5, D6, D7, D8).

[0047] The data storage and transmission module includes a data memory connected to the MCU and a USB interface protected by the sixth resettable fuse PPTC6.

[0048] The coin-operated recognition module includes a purple light emitting LED1, a recognition camera CD2, and a coin-operated recognition processing unit.

[0049] It also includes a payment module, which includes a camera CD1 for facial recognition and QR code recognition.

[0050] It also includes a status indicator LED2, which is connected to the MCU and is used to display standby and working status. The LED2 is always green when in standby mode and flashes red when in operation.

[0051] The workflow is as follows:

[0052] 1. Power Supply and Protection: The DC 12V / 24V power supply provided by the vehicle is fed into the reverse connection protection circuit via the first self-resetting fuse PPTC1 and the varistor RV. After passing through the reverse connection protection circuit composed of D1-D4 and filter capacitor C1, it provides DC power to each functional branch. If a high-voltage pulse occurs in the input voltage, the varistor RV will conduct momentarily to discharge the high voltage to ground. The first self-resetting fuse PPTC1 limits the large current when the varistor RV conducts, preventing the varistor RV from burning out. If the circuit experiences overcurrent or the ambient temperature exceeds 85℃, the resistance of PPTC1 will suddenly become high, cutting off the large current and protecting the subsequent circuits.

[0053] 2. Power Conversion: The voltage output by the reverse connection protection circuit is converted into 5V and 3.3V by the power conversion module, providing stable DC power to low-voltage devices such as the MCU processor, data memory, and image recognition processing module.

[0054] 3. Water sales function implemented:

[0055] Coin payment: Passengers insert coins / banknotes, the coin insertion and return recognition sensor detects the signal, the ultraviolet light recognition sensor (LED1 emits ultraviolet light, CD2 camera) recognizes the anti-counterfeiting information of the currency, and the signal is transmitted to the MCU. The MCU determines the amount through the coin insertion and return recognition module and controls Q2 to drive the coin return motor M2 to complete the change.

[0056] Electronic payment: Passengers scan their face or scan the QR code on the water vending machine. The CD1 camera captures the image, which is then processed by the image recognition and processing module and transmitted to the MCU. The MCU processor simultaneously processes the relevant data and stores it in the data storage device and wirelessly transmits it to the upper-level centralized processing and recognition system. After payment is confirmed, the payment is completed.

[0057] Water delivery and bottle dispensing: The MCU controls Q3 to drive the bottle delivery motor M3 to dispense 500ml-555ml bottles of water, and at the same time controls Q4 to drive the solenoid valve to open the bottle dispensing door, so that customers can easily take the bottle and get change. In this process, R1, R3, R5, and R7 provide drive switching signals to the corresponding MOSFETs, and diodes D4-D7 and resistors R2, R4, R6, and R8 form the discharge path for the junction capacitance of the corresponding MOSFETs.

[0058] 4. Branch Circuit Protection: If M1 is stalled or short-circuited, PPTC2 will limit the current due to overcurrent / overtemperature (90℃) resistor sudden change; PPTC3-PPTC5 will operate similarly in case of M2, M3, or solenoid valve failure; if a short circuit occurs when a USB flash drive is inserted into the USB interface, PPTC6 will limit the current to protect the MCU and the USB flash drive; PPTC2-PPTC5 are the overcurrent, short-circuit, and over-temperature protection circuits for the motor and solenoid valve, respectively. PPTC6 is for short-circuit protection applications of the USB interface.

[0059] 5. Data processing and status indication: The MCU stores data such as water sales quantity, payment / refund amount, time, and payment method in the data storage device and wirelessly transmits it to the upper control center; LED2 lights up green during standby time and flashes red when in operation.

[0060] The aforementioned coin-operated water dispenser is designed for elderly people who are not familiar with smartphones. For those who are smartphone users, payment can be completed via mobile payment code, facial recognition, or scanning the QR code on the surface of the water dispenser, utilizing the machine's intelligent image recognition (camera) processing and MCU processor system.

[0061] PPTC1 not only protects against and limits the large current generated by its downstream circuits, but also protects the system circuit by filtering external high voltage through the varistor RV. When other components on the circuit board (such as MOSFETs) overheat for an extended period, and the temperature around PPTC1 exceeds 85°C or is conducted through the PCB, PPTC1 will also change its resistance from low to high due to overheating, thus limiting the current and protecting its circuit. PPTC1 solves the problem of high voltage and high current from automotive power supply burning out the machine's circuitry, and also solves the problem of damage to the automotive power supply or interference with other circuits due to short circuits, overcurrent, and overheating. PPTC2 provides protection for the banknote counting motor in cases of stall, coil short circuit, jamming, overcurrent, and overheating. Its protection feature is also timely current limiting protection by changing its resistance from low to high after high current or overheating by 90°C, while also protecting MOSFET Q1 and system circuit equipment to prevent problems such as wire burnout and fire, and MOSFET Q1 short circuit and explosion. PPTC3 provides protection against high current in the coin return motor in cases of stall and jamming. The PPTC4 provides protection against overheating, winding coil cracking, arcing, and short circuits, while also protecting MOSFET Q2 and system circuitry to prevent issues such as wire burnout and fire, or MOSFET Q2 short-circuiting and exploding. The PPTC5 provides protection against high current during bottle delivery motor stall, overcurrent and overheating due to jamming, and winding coil cracking, arcing, and short circuits, while also protecting MOSFET Q3 and system circuitry to prevent wire burnout and fire, or MOSFET Q3 short-circuiting and exploding. The PPTC6 provides protection against cracking, arcing, and short circuits in the solenoid valve coil, while also protecting MOSFET Q4 and system circuitry to prevent wire burnout and fire, or MOSFET Q4 short-circuiting and exploding. The PPTC6 protects the USB interface. Since USB flash drives may be inserted at an angle, short circuits between interface nodes can occur, generating high currents that could burn out the MCU or its related control circuitry. PPTC6 effectively prevents the MCU circuitry and related control circuitry from burning out, and also protects the USB flash drive from damage.

[0062] In this embodiment, PPTC1 is a surface-mount type (1206 package) with a rated current of 5A and a trigger temperature of 85℃; PPTC2-PPTC5 are surface-mount types with a rated current of 2A and a trigger temperature of 90℃; and PPTC6 is a surface-mount type with a rated current of 1A and a trigger temperature of 85℃. RV is a through-hole type with a varistor voltage of 36V and a diameter of φ10. The MCU is an STM32 series microcontroller, and the power conversion module uses a DC-DC step-down chip. The space and PCB area occupied by a 3.2mm*1.6mm SMD1206 package PPTC is less than one-twenty-fourth the size of a 25mm*5mm high-power sampling resistor of a traditional circuit with a 0.01Ω / 3W resistor.

[0063] This invention enables automatic vending and payment collection for 500ml-555ml ordinary bottled water. It stores data such as the quantity sold, payment and refund data, payment and refund dates and times and methods (coin or banknote payment and refund, facial recognition payment, mobile phone QR code payment, mobile phone scanning of the QR code on the bus-specific water vending machine, etc.), refund data, and currency value lists in a data storage device and wirelessly transmits them to the upper-level control center database. The device's USB interface can also copy the aforementioned data tables for easy periodic inspection and auditing.

[0064] After actual testing and market application, this circuit has not experienced any problems such as protection failure or component burnout. Its safety, reliability and stability meet the requirements of the automotive environment and can be mass-produced and applied.

[0065] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse, comprising a power input terminal, a reverse connection protection circuit, a power conversion module, a main control unit (MCU), a data storage and transmission module, and a coin acceptance module, a banknote counting motor (M1), a coin return motor (M2), a bottle feeding motor (M3), a solenoid valve, and a USB interface controlled by the MCU, characterized in that: Also includes The main protection unit consists of a first resettable fuse PPTC1 and a varistor RV. The first resettable fuse PPTC1 is connected in series between the positive terminal of the vehicle power supply and the input terminal of the reverse connection protection circuit. The varistor RV is connected in parallel between the node between the first resettable fuse PPTC1 and the reverse connection protection circuit and ground. Branch protection unit, including: The second self-resetting fuse PPTC2 is connected in series in the power supply circuit of the banknote counting motor (M1); The third self-resetting fuse PPTC3 is connected in series in the power supply circuit of the coin return motor (M2); The fourth resettable fuse PPTC4 is connected in series in the power supply circuit of the bottle feeding motor (M3); The fifth self-resetting fuse PPTC5 is connected in series in the power supply circuit of the solenoid valve; The sixth resettable fuse, PPTC6, is connected in series in the power supply circuit of the USB interface.

2. The circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse according to claim 1, characterized in that: The first self-resetting fuse PPTC1 to the sixth self-resetting fuse PPTC6 are all surface-mount packaged polymer-based positive temperature coefficient thermistors.

3. The circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse according to claim 1, characterized in that: The varistor RV has a varistor voltage of 36V.

4. The circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse according to claim 1, characterized in that: The reverse connection protection circuit consists of four diodes (D1-D4) in a bridge structure, with a filter capacitor C1 connected in parallel at its output.

5. The circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse according to claim 1, characterized in that: The power conversion module includes a DC-DC circuit that converts the input voltage to 5V and a linear regulator circuit that converts 5V to 3.3V, providing power for different operating voltages.

6. The circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse according to claim 1, characterized in that: The banknote counting motor (M1), the change and return motor (M2), the bottle feeding motor (M3), and the solenoid valve are driven by MOSFETs (Q1, Q2, Q3, Q4), respectively. The gate of each MOSFET (Q1-Q4) is connected in series with a driving resistor (R1, R3, R5, R7), and a discharge circuit composed of resistors (R2, R4, R6, R8) and diodes (D5, D6, D7, D8) is connected in parallel between its source and drain.

7. The circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse according to claim 1, characterized in that... The data storage and transmission module includes a data storage device connected to the MCU and a USB interface protected by the sixth self-resetting fuse PPTC6.

8. The circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse according to claim 1, characterized in that... The coin-operated recognition module includes a purple light emitting LED1, a recognition camera CD2, and a coin-operated recognition processing unit.

9. The circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse according to claim 1, characterized in that... It also includes a payment module, which includes a camera CD1 for face recognition and QR code recognition.

10. The circuit protection device for a bus water vending machine based on a PPTC self-resetting fuse according to claim 1, characterized in that... It also includes a status indicator LED2, which is connected to the MCU and is used to display standby and working status.

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