A water level sensing circuit for a tea bar machine

Abstract

This utility model discloses a water level sensing circuit for a tea bar machine, including a power supply circuit, a control unit, and an actuator. The control unit is electrically connected to the actuator. The power supply circuit is electrically connected to an overvoltage protection circuit, which is also electrically connected to the control unit. The control unit is electrically connected to an anti-interference water level detection circuit. This utility model, by combining a differential amplifier U1 with a multi-stage filtering network, significantly suppresses electromagnetic interference and signal noise caused by water surface fluctuations, solving the problem of accidental triggering, improving the stability and accuracy of the water level detection signal, greatly reducing the probability of malfunction, and enhancing the overall reliability and user experience. Furthermore, the overvoltage protection circuit can quickly cut off the power supply to subsequent stages when abnormally high voltage occurs, forming an effective protective barrier for the control unit and the anti-interference water level detection circuit, thus improving safety.

Description

Technical Field

[0001] This utility model relates to the field of tea bar machine technology, and in particular to a water level sensing circuit for a tea bar machine. Background Technology

[0002] As a common household and office water dispenser, one of the core functions of a tea bar machine is to automatically control the water level in the tank and heat the water. The accuracy and reliability of the water level sensor directly affect the user experience and safety of the equipment. Currently, many tea bar machines on the market are equipped with a water level sensing system to prevent dry burning and achieve automatic water filling. In existing technology, the water level detection of tea bar machines mostly uses an electrode-type (probe) sensor. Its basic principle is to utilize the conductivity of water. When the water level reaches the probe position, the circuit is turned on, generating a signal change; when the water level is lower than the probe, the circuit is turned off. The control unit determines the water level by detecting the on / off state of this signal, and then controls the action of actuators such as the water pump or heating element.

[0003] Traditional water level sensing technology used in tea bar machines has the following shortcomings during use: 1. Poor anti-interference capability: The heating element and water pump inside the tea bar machine are high-power inductive loads, which generate strong electromagnetic interference at the moment of start-up and shutdown. At the same time, slight fluctuations in the water surface can also cause unstable contact between the probe and the water. These interferences will be superimposed on the weak water level signal, producing signal jitter and glitches, which can easily lead to misjudgment and malfunction of the control unit; 2. Inadequate circuit protection: The tea bar machine is connected to the mains power supply, and voltage fluctuations and surges in the power grid occur frequently. Many existing designs lack dedicated power protection circuits, and excessively high voltages can easily directly impact the downstream control unit through the power path, causing permanent damage to components; In view of the above, this application proposes a water level sensing circuit for a tea bar machine. Utility Model Content

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a water level sensing circuit for a tea bar machine.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A water level sensing circuit for a tea bar machine includes a power supply circuit, a control unit, and an actuator. The control unit is electrically connected to the actuator. The power supply circuit is electrically connected to an overvoltage protection circuit, which is electrically connected to the control unit. The control unit is electrically connected to an anti-interference water level detection circuit.

[0007] Preferably, the anti-interference water level detection circuit includes a differential amplifier U1 and a comparator U2. Pin 1 of the differential amplifier U1 is electrically connected to one end of capacitor C1 and one end of resistor R2. Pin 2 of the differential amplifier U1 is electrically connected to one end of capacitor C2. The other end of capacitor C2, pin 2 of the differential amplifier U1, and pin 3 of the differential amplifier U1 are all grounded. The other end of resistor R2 is electrically connected to pin 3 of the differential amplifier U1. The other end of capacitor C1 is electrically connected to one end of resistor R1, one end of capacitor C5, and pin 1 of water level probe I. The other end of capacitor C5 is electrically connected to pin 1 of comparator U2. Pin 2 of comparator U2 and pin 2 of water level probe I are both grounded. Pin 3 of comparator U2 is electrically connected to one end of capacitor C4. The other end of capacitor C4 is electrically connected to the other end of resistor R1.

[0008] Preferably, the overvoltage protection circuit includes a transistor Q1. The base of transistor Q1 is electrically connected to one end of resistor R4. The other end of resistor R4 is electrically connected to one end of resistor R3 and the cathode of diode D1. The other end of resistor R3 and the emitter of transistor Q1 are both electrically connected to the output terminal of the power supply circuit. The collector of transistor Q1 is electrically connected to one end of capacitor C3. The other end of capacitor C3 is electrically connected to the anode of diode D2. The cathode of diode D2 and the anode of diode D1 are also connected. All terminals are grounded. The collector of transistor Q1 is electrically connected to one end of resistor R5. The other end of resistor R5 is electrically connected to the positive terminal of diode D2. One end of resistor R5 is electrically connected to pin 1 of MOSFET Q2. Pin 3 of MOSFET Q2 is electrically connected to the output terminal of the power supply circuit. Pin 1 of MOSFET Q2 is electrically connected to the collector of transistor Q1. Pin 2 of MOSFET Q2 is electrically connected to one end of resistor R6. The other end of resistor R6 is electrically connected to the power supply terminal of the control unit.

[0009] Preferably, the water level probe I is a multi-stage water level probe used to detect low, medium, and high water levels;

[0010] The capacitors C1, C2, C4, and C5, along with resistors R1 and R2, form a filter network used to filter out signal jitter and spikes caused by water ripples and electromagnetic interference from motor start-stop.

[0011] Preferably, the control unit is a microcontroller MCU, which is equipped with an ADC sampling pin and an I / O pin. The ADC sampling pin is electrically connected to pin 3 of the differential amplifier U1. The microcontroller MCU reads the water level status signal sent by the anti-interference water level detection circuit in real time through the ADC sampling pin.

[0012] Preferably, the actuator includes a relay for controlling the on / off state of the water pump, a relay for controlling the on / off state of the heating element, an alarm buzzer, and a status indicator LED. The actuator is used to receive low voltage and low current signals from the control unit to drive or disconnect high voltage and high current loads, thereby achieving isolation and control between strong and weak currents.

[0013] Preferably, the transistor Q1 and the MOSFET Q2 form a voltage monitoring and switching control circuit. When an overvoltage is detected, the voltage supplied to the subsequent circuit is cut off by the MOSFET Q2. The resistor R3, the resistor R4 and the diode D1 form a sampling network for sampling the power supply circuit voltage.

[0014] Compared with existing technologies, the beneficial effects of this utility model are:

[0015] This invention, by combining a differential amplifier U1 with a multi-stage filtering network, greatly suppresses electromagnetic interference and signal noise caused by water surface fluctuations, solves the problem of easy false triggering, improves the stability and accuracy of the water level detection signal, significantly reduces the probability of malfunction, enhances the overall reliability and user experience, and through the setting of the overvoltage protection circuit, can quickly cut off the power supply to the downstream stage when abnormal high voltage occurs, forming an effective protective barrier for the control unit and the anti-interference water level detection circuit, and improving the safety of use. Attached Figure Description

[0016] Figure 1 This is a connection block diagram of the water level sensing circuit for a tea bar machine proposed in this utility model;

[0017] Figure 2 The circuit diagram of the anti-interference water level detection circuit in the water level sensing circuit of the tea bar machine proposed in this utility model;

[0018] Figure 3 This is a circuit diagram of the overvoltage protection circuit in the water level sensing circuit of a tea bar machine proposed in this utility model. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0020] Reference Figure 1-3A water level sensing circuit for a tea bar machine includes a power supply circuit, a control unit, and an actuator. The control unit and the actuator are electrically connected. The actuator includes a relay for controlling the on / off of the water pump, a relay for controlling the on / off of the heating element, an alarm buzzer, and a status indicator LED. The actuator is used to receive low voltage and low current signals from the control unit to drive or cut off high voltage and high current loads, thereby achieving isolation and control of strong and weak currents.

[0021] The power supply circuit includes an AC-DC conversion module, a rectifier bridge BD1, a filter capacitor C0, and a linear regulator U3. The input of the AC-DC conversion module is connected to the mains power, and its output is rectified by the rectifier bridge BD1 and filtered by the filter capacitor C0 to output a DC voltage of about 12V. The input of the linear regulator U3 is electrically connected to the 12V DC voltage, and its output output is a stable 5V DC voltage, providing working power for the subsequent circuits.

[0022] The power supply circuit is electrically connected to an overvoltage protection circuit, which is electrically connected to the control unit. The control unit is electrically connected to an anti-interference water level detection circuit.

[0023] The anti-interference water level detection circuit includes a differential amplifier U1 and a comparator U2. Pin 1 of the differential amplifier U1 is electrically connected to one end of capacitor C1 and one end of resistor R2. Pin 2 of the differential amplifier U1 is electrically connected to one end of capacitor C2. The other end of capacitor C2, pin 2 of the differential amplifier U1, and pin 3 of the differential amplifier U1 are all grounded. The other end of resistor R2 is electrically connected to pin 3 of the differential amplifier U1. The other end of capacitor C1 is electrically connected to one end of resistor R1, one end of capacitor C5, and pin 1 of water level probe I. The other end of capacitor C5 is electrically connected to pin 1 of comparator U2. Pin 2 of comparator U2 and pin 2 of water level probe I are both grounded. Pin 3 of comparator U2 is electrically connected to one end of capacitor C4. The other end of capacitor C4 is electrically connected to the other end of resistor R1.

[0024] Water level probe I is a multi-stage water level probe used to detect low, medium, and high water levels;

[0025] Capacitors C1, C2, C4, and C5, along with resistors R1 and R2, form a filter network used to filter out signal jitter and spikes caused by water ripples and electromagnetic interference from motor start-up and shutdown.

[0026] The control unit is a microcontroller MCU, which is equipped with an ADC sampling pin and an I / O pin. The ADC sampling pin is electrically connected to pin 3 of the differential amplifier U1. The microcontroller MCU reads the water level status signal sent by the anti-interference water level detection circuit in real time through the ADC sampling pin.

[0027] The overvoltage protection circuit includes transistor Q1. The base of transistor Q1 is electrically connected to one end of resistor R4. The other end of resistor R4 is electrically connected to one end of resistor R3 and the cathode of diode D1. The other end of resistor R3 and the emitter of transistor Q1 are both electrically connected to the output terminal of the power supply circuit. The collector of transistor Q1 is electrically connected to one end of capacitor C3. The other end of capacitor C3 is electrically connected to the anode of diode D2. The cathode of diode D2 and the anode of diode D1 are both grounded. The collector of transistor Q1 is electrically connected to one end of resistor R5. The other end of resistor R5 is electrically connected to the anode of diode D2. One end of resistor R5 is electrically connected to pin 1 of MOSFET Q2. Pin 3 of MOSFET Q2 is electrically connected to the output terminal of the power supply circuit. Pin 1 of MOSFET Q2 is electrically connected to the collector of transistor Q1. Pin 2 of MOSFET Q2 is electrically connected to one end of resistor R6. The other end of resistor R6 is electrically connected to the power supply terminal of the control unit.

[0028] Among them, MOSFET Q2 is a P-MOS transistor, with pins 1, 2, and 3 corresponding to the gate (G), source (S), and drain (D) respectively. Under normal voltage, its gate-source voltage Vgs keeps MOSFET Q2 fully turned on. When an overvoltage occurs, transistor Q1 turns on and pulls up the gate voltage of MOSFET Q2, causing the absolute value of Vgs to decrease, thereby turning off P-MOS transistor Q2 and cutting off the voltage supplied to the subsequent circuit.

[0029] Transistor Q1 and MOSFET Q2 form a voltage monitoring and switching control circuit. When an overvoltage is detected, the voltage supplied to the subsequent circuit is cut off by MOSFET Q2. Resistors R3 and R4 and diode D1 form a sampling network to sample the power supply circuit voltage. The resistance ratio of resistors R3 and R4, together with the forward voltage drop of diode D1, sets the overvoltage protection threshold of the circuit. When the output voltage of the power supply circuit exceeds this threshold, transistor Q1 turns on.

[0030] This invention, by combining a differential amplifier U1 with a multi-stage filtering network, greatly suppresses electromagnetic interference and signal noise caused by water surface fluctuations, solves the problem of easy false triggering, improves the stability and accuracy of the water level detection signal, significantly reduces the probability of malfunction, enhances the overall reliability and user experience, and through the setting of the overvoltage protection circuit, can quickly cut off the power supply to the downstream stage when abnormal high voltage occurs, forming an effective protective barrier for the control unit and the anti-interference water level detection circuit, and improving the safety of use.

[0031] Working principle: When in use, after the power supply circuit is connected to the mains power, it first performs AC-DC conversion to output a stable low-voltage DC power. This DC power enters the overvoltage protection circuit. Under normal voltage, the voltage monitoring and switching control circuit composed of transistor Q1 and MOSFET Q2 makes MOSFET Q2 fully conduct, and the power is delivered to the subsequent circuit without obstruction. When the output voltage of the power supply circuit rises abnormally due to external reasons, the sampling network composed of resistor R3, resistor R4 and diode D1 will turn on transistor Q1, thereby pulling down the gate voltage of MOSFET Q2 and turning it off quickly to limit the output voltage. This cuts off the power supply to the subsequent control unit and the anti-interference water level detection circuit, protecting them from overvoltage damage and achieving an effective overvoltage protection effect during use.

[0032] During water level detection, multi-stage water level probes are installed at different heights in the water tank to detect low, medium, and high water levels. When the water level rises and contacts a certain probe, a conductive loop is formed between the probe and the ground, generating a weak electrical signal. This signal is first pre-filtered by a filter network consisting of capacitors C1, C2, C4, and C5, and resistors R1 and R2 to remove high-frequency glitches caused by water surface fluctuations or electromagnetic interference. Subsequently, the signal is amplified by differential amplifier U1. The characteristics of differential amplification effectively suppress common-mode interference, amplifying only the differential-mode signal representing the water level status, greatly improving the signal-to-noise ratio and measurement accuracy. Simultaneously, the amplified signal can be directly sent to the microcontroller MCU for analog-to-digital conversion via the ADC sampling pin. The microcontroller MCU accurately determines the water level height through software algorithms, achieving multi-stage water level control. The amplified signal is compared with a reference voltage by comparator U2, shaping the analog signal into a clean and stable digital level signal, which is then output to the MCU's I / O pin for simple water shortage detection and anti-dry-burning protection. The microcontroller (MCU) reads the processed water level signal in real time. The MCU's pre-stored control program performs logical judgments based on the current water level and user instructions, and outputs corresponding control signals. When water shortage is detected, the MCU immediately outputs a low level, cutting off the relay controlling the heating element to achieve anti-dry-burning protection. When the water level in the storage tank is low, the MCU outputs a high level, engaging the relay controlling the water pump to start the pump and fill the tank with water. The pump automatically stops when the tank is full. By effectively resisting interference during water level detection, the possibility of misjudgment and misoperation can be effectively reduced, improving the accuracy of water level detection.

[0033] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A water level sensing circuit for a tea bar machine, comprising a power supply circuit, a control unit, and an actuator, wherein the control unit is electrically connected to the actuator, characterized in that, The power supply circuit is electrically connected to an overvoltage protection circuit, which is electrically connected to the control unit. The control unit is electrically connected to an anti-interference water level detection circuit.

2. The water level sensing circuit of a tea bar machine according to claim 1, characterized in that, The anti-interference water level detection circuit includes a differential amplifier U1 and a comparator U2. Pin 1 of the differential amplifier U1 is electrically connected to one end of capacitor C1 and one end of resistor R2. Pin 2 of the differential amplifier U1 is electrically connected to one end of capacitor C2. The other end of capacitor C2, pin 2 of the differential amplifier U1, and pin 3 of the differential amplifier U1 are all grounded. The other end of resistor R2 is electrically connected to pin 3 of the differential amplifier U1. The other end of capacitor C1 is electrically connected to one end of resistor R1, one end of capacitor C5, and pin 1 of water level probe I. The other end of capacitor C5 is electrically connected to pin 1 of comparator U2. Pin 2 of comparator U2 and pin 2 of water level probe I are both grounded. Pin 3 of comparator U2 is electrically connected to one end of capacitor C4. The other end of capacitor C4 is electrically connected to the other end of resistor R1.

3. The water level sensing circuit of a tea bar machine according to claim 1, characterized in that, The overvoltage protection circuit includes a transistor Q1. The base of transistor Q1 is electrically connected to one end of resistor R4. The other end of resistor R4 is electrically connected to one end of resistor R3 and the cathode of diode D1. The other end of resistor R3 and the emitter of transistor Q1 are both electrically connected to the output terminal of the power supply circuit. The collector of transistor Q1 is electrically connected to one end of capacitor C3. The other end of capacitor C3 is electrically connected to the anode of diode D2. The cathode of diode D2 and the anode of diode D1 are both grounded. The collector of transistor Q1 is electrically connected to one end of resistor R5. The other end of resistor R5 is electrically connected to the anode of diode D2. One end of resistor R5 is electrically connected to pin 1 of MOSFET Q2. Pin 3 of MOSFET Q2 is electrically connected to the output terminal of the power supply circuit. Pin 1 of MOSFET Q2 is electrically connected to the collector of transistor Q1. Pin 2 of MOSFET Q2 is electrically connected to one end of resistor R6. The other end of resistor R6 is electrically connected to the power supply terminal of the control unit.

4. The water level sensing circuit for a tea bar machine according to claim 2, characterized in that, The water level probe I is a multi-stage water level probe used to detect low, medium, and high water levels. The capacitors C1, C2, C4, and C5, along with resistors R1 and R2, form a filter network used to filter out signal jitter and spikes caused by water ripples and electromagnetic interference from motor start-stop.

5. The water level sensing circuit for a tea bar machine according to claim 2, characterized in that, The control unit is a microcontroller MCU, which is equipped with an ADC sampling pin and an I / O pin. The ADC sampling pin is electrically connected to pin 3 of the differential amplifier U1. The microcontroller MCU reads the water level status signal sent by the anti-interference water level detection circuit in real time through the ADC sampling pin.

6. The water level sensing circuit of a tea bar machine according to claim 1, characterized in that, The actuator includes a relay for controlling the on / off state of the water pump, a relay for controlling the on / off state of the heating element, an alarm buzzer, and a status indicator LED. The actuator is used to receive low voltage and low current signals from the control unit to drive or cut off high voltage and high current loads, thereby achieving isolation and control between strong and weak currents.

7. The water level sensing circuit of a tea bar machine according to claim 3, characterized in that, The transistor Q1 and MOSFET Q2 form a voltage monitoring and switching control circuit. When an overvoltage is detected, the voltage supplied to the subsequent circuit is cut off through the MOSFET Q2. The resistors R3 and R4 and the diode D1 form a sampling network for sampling the power supply circuit voltage.

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