False detection prevention photoelectric liquid level sensor

Abstract

The invention discloses a photoelectric liquid level sensor capable of preventing false detection, which belongs to the technical field of liquid level sensors, and comprises a pipeline, a liquid level sensor, a liquid level sensor, a liquid level sensor and a liquid level sensor, the light emitting circuit is used for emitting light to the inner wall of the pipeline; the photosensitive circuit is used for receiving the light reflected by the inner wall of the pipeline and outputting a detection voltage signal according to the intensity of the light; the reference circuit is used for outputting a reference voltage signal; and the operational amplifier comparison circuit is used for comparing the detection voltage signal with the reference voltage signal and outputting a level signal according to a comparison result. The photoelectric liquid level sensor can be used for liquid level detection of liquid with viscosity, and the problem of false detection caused by the fact that the liquid adheres to the wall can be effectively solved.

Description

Technical Field

[0001] This invention relates to the field of liquid level sensor technology, and in particular to a photoelectric liquid level sensor that prevents false detection. Background Technology

[0002] In many household appliances or industrial equipment that use liquid storage tanks, it is necessary to detect whether the liquid level in the tank is low. Currently, floats or similar devices are commonly used to detect the liquid level, but such structures require a lot of space and are difficult to use in small household appliances or equipment. Small-sized pipe level sensors on the market use a prism to reflect light to detect the presence of liquid in the pipe. When conveying viscous liquids, the liquid tends to adhere to the inner wall of the sensor. The sensor works by recognizing that when liquid is present, light passes through the pipe's inner wall and enters the liquid, preventing the receiver from receiving it and thus outputting a signal indicating the presence of liquid and determining the level. Conversely, when the pipe is empty, the light emitted by the transmitter is reflected by the inner wall and received by the receiver, also indicating the absence of liquid. However, for viscous liquids, even when the pipe is empty, the viscous liquid adheres to the inner wall. In this case, the light emitted by the transmitter still passes through the inner wall and enters the liquid adhering to it. The light received by the receiver in this situation is weak, resulting in an output signal that is very close to the signal when liquid is present. This can lead to inaccurate liquid level detection. Summary of the Invention

[0003] The purpose of this invention is to provide a photoelectric liquid level sensor that prevents false detection, so as to solve the above-mentioned problems.

[0004] To achieve this objective, the present invention adopts the following technical solution:

[0005] A photoelectric liquid level sensor for preventing false detection, comprising:

[0006] A pipe, the interior of which has channels for conveying liquid;

[0007] A light-emitting circuit for emitting light towards the inner wall of the pipe;

[0008] A photosensitive circuit is used to receive light reflected from the inner wall of the pipe and output a detection voltage signal according to the intensity of the light.

[0009] A reference circuit is used to output a reference voltage signal.

[0010] The operational amplifier comparator circuit is used to compare the detected voltage signal and the reference voltage signal, and output a level signal based on the comparison result.

[0011] Preferably, the light emitting circuit includes an infrared emitting diode and a first resistor, one end of the first resistor is connected to a power supply, the other end is connected to the positive terminal of the infrared emitting diode, and the negative terminal of the infrared emitting diode is grounded;

[0012] The photosensitive circuit includes a second resistor, a phototransistor, a third resistor, and a fourth resistor; one end of the second resistor is connected to a power supply, and the other end is connected to the collector of the phototransistor, with the emitter of the phototransistor grounded; one end of the third resistor is connected to the emitter of the phototransistor, and the other end is the output terminal of the photosensitive circuit, used to output a detection voltage signal; one end of the fourth resistor is connected to one end of the third resistor, and the other end is grounded.

[0013] Preferably, the reference circuit includes a fifth resistor and a sixth resistor; one end of the fifth resistor is connected to the power supply, and the other end is the output terminal of the reference circuit for outputting a reference voltage signal; one end of the sixth resistor is connected to the other end of the fifth resistor, and the other end of the sixth resistor is grounded.

[0014] Preferably, the reference circuit further includes a first capacitor, one end of which is connected to the other end of the fifth resistor, and the other end of the first capacitor is grounded.

[0015] Preferably, the operational amplifier comparator circuit includes an operational amplifier chip and a seventh resistor. One end of the seventh resistor is connected to a power supply, and the other end is connected to the VCC pin of the operational amplifier chip. The GND pin of the operational amplifier chip is grounded. The non-inverting input pin and the inverting input pin of the operational amplifier chip are respectively connected to the output terminal of the photosensitive circuit and the output terminal of the reference circuit. The OUT pin of the operational amplifier chip is a detection signal output terminal, used to output a first level signal or a second level signal.

[0016] Preferably, the operational amplifier comparator circuit further includes a first Zener diode and a second capacitor. The positive terminal of the first Zener diode is grounded, and the negative terminal is connected to one end of the seventh resistor. One end of the second capacitor is grounded, and the other end of the second capacitor is connected to the other end of the seventh resistor.

[0017] Preferably, the output terminal of the reference circuit is connected to the inverting input pin of the operational amplifier chip, and the output terminal of the photosensitive circuit is connected to the non-inverting input pin of the operational amplifier chip.

[0018] It also includes a signal driving circuit, which comprises a PNP transistor, an eighth resistor, a ninth resistor, a tenth resistor, an eleventh resistor, and a twelfth resistor. One end of the eighth resistor is connected to the detection signal output terminal, and the other end of the eighth resistor is connected to the base of the PNP transistor. One end of the ninth resistor is connected to the base of the PNP transistor, and the other end is connected to the power supply. One end of the tenth resistor is connected to the other end of the ninth resistor, and the other end of the tenth resistor is connected to the emitter of the PNP transistor. One end of the eleventh resistor is connected to the collector of the PNP transistor, and the other end is grounded. One end of the twelfth resistor is connected to the collector of the PNP transistor, and the other end is the drive signal output terminal.

[0019] Preferably, the signal driving circuit further includes a second Zener diode, a third Zener diode, a third capacitor, and a fourth capacitor. The positive terminal of the second Zener diode is connected to one end of the twelfth resistor, and the negative terminal is connected to one end of the tenth resistor. The positive terminal of the third Zener diode is grounded, and the negative terminal is connected to one end of the twelfth resistor. One end of the third capacitor is connected to one end of the tenth resistor, and the other end of the third capacitor is grounded. One end of the fourth capacitor is connected to the other end of the twelfth resistor, and the other end of the fourth capacitor is grounded.

[0020] Preferably, the outer wall of the pipe is provided with a first prism and a second prism, the infrared emitting tube faces the first prism, and the phototransistor faces the second prism; the first prism is used to reflect the light emitted by the infrared emitting tube to the inner wall of the pipe; the second prism is used to reflect the light reflected by the inner wall of the pipe to the phototransistor.

[0021] Preferably, the internal channel of the pipe has a D-shaped structure, with one side of the plane facing the first prism and the second prism; the pipe is made of transparent material.

[0022] One embodiment of the present invention has the following beneficial effects:

[0023] By adding a reference circuit and an operational amplifier comparator circuit, the reference circuit outputs a reference voltage signal, and the reference voltage signal and the detection voltage signal output by the photosensitive circuit are input into the operational amplifier comparator circuit. The operational amplifier comparator circuit can amplify and compare the voltage difference, thereby distinguishing the detection voltage signal output when the pipe is full of liquid from the detection voltage signal output when the pipe is empty and the inner wall is covered with liquid. Based on the voltage comparison result between the detection voltage signal and the reference voltage signal, a level signal is output. The state of the pipe being full of liquid or empty can be determined by the level signal. Attached Figure Description

[0024] The accompanying drawings further illustrate the present invention, but the content of the drawings does not constitute any limitation on the present invention.

[0025] Figure 1 This is a three-dimensional structural schematic diagram of a photoelectric liquid level sensor according to one embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a circuit module according to one embodiment of the present invention;

[0027] Figure 3 This is a schematic diagram of a light emitting circuit and a photosensitive circuit according to one embodiment of the present invention;

[0028] Figure 4 This is a schematic diagram of a reference circuit according to one embodiment of the present invention;

[0029] Figure 5 This is a schematic diagram of an operational amplifier comparator circuit according to one embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of a signal driving circuit according to one embodiment of the present invention;

[0031] Figure 7 This is a cross-sectional structural schematic diagram of a photoelectric liquid level sensor according to one embodiment of the present invention;

[0032] In the attached diagram: 1-pipe, 11-channel, 12-first prism, 13-second prism, 2-light emitting circuit, IR1-infrared emitting tube, R1-first resistor, 3-photosensitive circuit, R2-second resistor, PT1-phototransistor, R3-third resistor, R4-fourth resistor, 4-reference circuit, R5-fifth resistor, R6-sixth resistor, C1-first capacitor, 5-operational amplifier comparator circuit, U1-operational amplifier chip, R7-seventh resistor, D1-first Zener diode, C2-second capacitor, 6-signal drive circuit, Q1-PNP transistor, R8-eighth resistor, R9-ninth resistor, R10-tenth resistor, R11-eleventh resistor, R12-twelfth resistor, D2-second Zener diode, D3-third Zener diode, U3-third capacitor, U4-fourth capacitor. Detailed Implementation

[0033] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. In the description of the present invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" 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, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0035] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0036] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0038] This embodiment provides a photoelectric liquid level sensor to prevent false detection, such as... Figures 1-7 As shown, it includes:

[0039] Pipe 1, wherein a channel 11 for conveying liquid is formed inside the pipe 1;

[0040] The light emitting circuit 2 is used to emit light into the inner wall of the pipe 1;

[0041] The photosensitive circuit 3 is used to receive light reflected from the inner wall of the pipe 1 and output a detection voltage signal according to the intensity of the light.

[0042] Reference circuit 4 is used to output a reference voltage signal;

[0043] Operational amplifier comparator circuit 5 is used to compare the detected voltage signal and the reference voltage signal, and output a level signal based on the comparison result.

[0044] The channel 11 inside pipe 1 is used to transport liquid. Pipe 1 can be installed at the outlet of the liquid storage tank or on the liquid delivery pipe from the liquid storage tank to the outside. The light emitting circuit 2 emits light towards the inner wall of pipe 1. When there is liquid in the liquid storage tank, the channel 11 inside pipe 1 will be filled with liquid, causing the light to refract. After refraction, the light shines into the liquid inside pipe 1. At this time, the photosensitive circuit 3 can hardly detect the light, thus outputting a corresponding detection voltage signal, such as a high level. However, when the liquid in the liquid storage tank is exhausted and the liquid level drops below the position of pipe 1, for low viscosity liquids... At this point, there is almost no liquid in pipe 1. The light emitted by the light emitting circuit 2 shines on the inner wall of pipe 1 and undergoes total internal reflection, reflecting the light to the photosensitive circuit 3. When the photosensitive circuit 3 senses the light, it outputs a corresponding detection voltage signal, such as a low level. By identifying whether the detection voltage signal is high or low, it is easy to determine whether pipe 1 is full of liquid. However, for viscous liquids, when the liquid level drops below the position of pipe 1, due to the viscosity of the liquid, some liquid will still adhere to the inner wall of pipe 1. At this time, the light emitted by the light emitting circuit 2 will be reflected back to the inner wall of pipe 1. The emitted light still passes through the inner wall of pipe 1 and refracts into the liquid adhering to the inner wall of pipe 1. Some of the light passes through the surface of the liquid and refracts into the air inside pipe 1, while some light is reflected at the surface of the liquid. Due to the shift in the reflected surface, the photosensitive circuit 3 can only detect weak light. At this time, the detection voltage signal output by the photosensitive circuit 3 is very close to the detection voltage signal when pipe 1 is full of liquid. Therefore, it is impossible to determine whether pipe 1 is full of liquid or empty by judging the level. This invention innovatively adds a reference circuit. 4. Operational amplifier comparison circuit 5, wherein a reference voltage signal is output through reference circuit 4, and the reference voltage signal and the detection voltage signal output by photosensitive circuit 3 are input into operational amplifier comparison circuit 5. Operational amplifier comparison circuit 5 can amplify and compare the voltage difference, thereby distinguishing the detection voltage signal output when the pipe 1 is full of liquid and the detection voltage signal output when the pipe 1 is empty and the inner wall is adhered with liquid. Based on the voltage comparison result between the detection voltage signal and the reference voltage signal, a level signal is output. The state of the pipe 1 being full of liquid or empty can be determined based on the level signal.

[0045] like Figure 3 As shown, the light emitting circuit 2 includes an infrared emitting diode IR1 and a first resistor R1. One end of the first resistor R1 is connected to the power supply, and the other end is connected to the positive terminal of the infrared emitting diode IR1. The negative terminal of the infrared emitting diode IR1 is grounded.

[0046] The photosensitive circuit 3 includes a second resistor R2, a phototransistor PT1, a third resistor R3, and a fourth resistor R4. One end of the second resistor R2 is connected to the power supply, and the other end is connected to the collector of the phototransistor PT1, with the emitter of the phototransistor PT1 grounded. One end of the third resistor R3 is connected to the emitter of the phototransistor PT1, and the other end is the output terminal of the photosensitive circuit 3, used to output a detection voltage signal. One end of the fourth resistor R4 is connected to one end of the third resistor R3, and the other end is grounded.

[0047] An infrared emitting diode IR1 is set in the light emitting circuit 2, which can emit light. When the photosensitive circuit 3 does not sense light, the phototransistor PT1 is completely off, and the output of the photosensitive circuit 3 is high. When the photosensitive circuit 3 senses light, the phototransistor PT1 is fully on. At this time, the fourth resistor R4 is short-circuited, the other end of the second resistor R2 is grounded, and the output of the photosensitive circuit 3 is pulled to a low level. When the photosensitive circuit 3 senses weak light, the phototransistor PT1 is not fully on. At this time, the phototransistor PT1 has a certain resistance. The phototransistor PT1 is connected in parallel with the fourth resistor R4. Therefore, the voltage at the other end of the second resistor R2 is pulled low. At this time, the photosensitive circuit 3 still outputs a high level, but the voltage is slightly lower than the high level output when the photosensitive circuit 3 does not sense light. The phototransistor PT1 has high sensitivity. Utilizing the photoelectric characteristics of the phototransistor PT1, the photocurrent increases with the increase of light intensity. Therefore, the photocurrent of the phototransistor PT1 is different when it cannot sense any light and when it senses a weak light. This characteristic enables the output terminal of the photosensitive circuit 3 to output different voltage values ​​in these two different states.

[0048] like Figure 4 As shown, the reference circuit 4 includes a fifth resistor R5 and a sixth resistor R6; one end of the fifth resistor R5 is connected to the power supply, and the other end is the output terminal of the reference circuit 4, used to output a reference voltage signal; one end of the sixth resistor R6 is connected to the other end of the fifth resistor R5, and the other end of the sixth resistor R6 is grounded.

[0049] The fifth resistor R5 and the sixth resistor R6 can act as a voltage divider. Changing the resistance values ​​of the fifth resistor R5 and the sixth resistor R6 can change the output voltage of the reference circuit 4. The resistance values ​​of the fifth resistor R5 and the sixth resistor R6 are calculated based on the required voltage of the reference circuit 4, so that the reference circuit 4 can accurately output a reference voltage signal. It should be noted that the voltage value of the reference voltage signal is higher than the voltage value of the detection voltage signal output by the photosensitive circuit 3 when liquid adheres to the inner wall of pipe 1, and lower than the voltage value of the detection voltage signal output by the photosensitive circuit 3 when the inner wall of pipe 1 is full of liquid.

[0050] Furthermore, the reference circuit 4 also includes a first capacitor C1, one end of which is connected to the other end of the fifth resistor R5, and the other end of the first capacitor C1 is grounded.

[0051] When the power supply of the reference circuit 4 fluctuates, the voltage output by the reference circuit 4 will also fluctuate. By setting the first capacitor C1, the voltage can be stabilized. When the voltage fluctuates, the first capacitor C1 can absorb and compensate, so that the reference voltage signal output by the reference circuit 4 can be stably maintained at a fixed voltage value and is not easily changed by the fluctuation of the electromagnetic wave.

[0052] like Figure 5 As shown, the operational amplifier comparator circuit 5 includes an operational amplifier chip U1 and a seventh resistor R7. One end of the seventh resistor R7 is connected to the power supply, and the other end is connected to the VCC pin of the operational amplifier chip U1. The GND pin of the operational amplifier chip U1 is grounded. The non-inverting input pin and the inverting input pin of the operational amplifier chip U1 are connected to the output terminal of the photosensitive circuit 3 and the output terminal of the reference circuit 4, respectively. The OUT pin of the operational amplifier chip U1 is the detection signal output terminal, used to output a first level signal or a second level signal.

[0053] The operational amplifier chip U1 has amplification and comparison functions. The output terminals of the photosensitive circuit 3 and the reference circuit 4 are respectively connected to the non-inverting input pin and the inverting input pin of the operational amplifier chip U1. That is, the output terminal of the photosensitive circuit 3 can be connected to the non-inverting input pin and the output terminal of the reference circuit 4 can be connected to the inverting input pin, or the output terminal of the photosensitive circuit 3 can be connected to the inverting input pin and the output terminal of the reference circuit 4 can be connected to the non-inverting input pin. The level signals output by the operational amplifier are exactly opposite in these two wiring methods.

[0054] Furthermore, the operational amplifier comparator circuit 5 also includes a first Zener diode D1 and a second capacitor C2. The positive terminal of the first Zener diode D1 is grounded, and the negative terminal is connected to one end of the seventh resistor R7. One end of the second capacitor C2 is grounded, and the other end of the second capacitor C2 is connected to the other end of the seventh resistor R7.

[0055] By setting the first Zener diode D1, the operational amplifier comparator circuit 5 can be protected. When a surge current occurs, the current can be quickly guided to ground through the reverse breakdown of the first Zener diode D1, thereby preventing the instantaneous current from being too large and breaking down the operational amplifier chip U1. The second capacitor C2 plays a voltage stabilizing role, making the operation of the operational amplifier chip U1 and the level signal output by the operational amplifier comparator circuit 5 more stable and reducing voltage fluctuations.

[0056] In one embodiment, the output terminal of the reference circuit 4 is connected to the inverting input pin of the operational amplifier chip U1, and the output terminal of the photosensitive circuit 3 is connected to the non-inverting input pin of the operational amplifier chip U1.

[0057] When there is liquid in pipe 1, light is refracted into the liquid through the inner wall of pipe 1. The photosensitive circuit 3 cannot detect the light, the phototransistor PT1 is in the off state, the photosensitive circuit 3 outputs a high level, and the output voltage is at its maximum. The voltage at the output terminal of the photosensitive circuit 3 is higher than the voltage at the output terminal of the reference circuit 4. At this time, the operational amplifier chip U1 outputs a high level.

[0058] When pipe 1 is empty and liquid adheres to the inner wall of pipe 1, the photosensitive circuit 3 senses weak light, the phototransistor PT1 is not fully conducting, and the photosensitive circuit 3 still outputs a high level. At this time, the output voltage is slightly less than the maximum output voltage of the photosensitive circuit 3. The voltage at the output terminal of the photosensitive circuit 3 is lower than the voltage at the output terminal of the reference circuit 4. At this time, the operational amplifier chip U1 outputs a low level.

[0059] When pipe 1 is empty and there is no liquid adhering to the inner wall of pipe 1, the photosensitive circuit 3 senses sufficient light, the phototransistor PT1 is fully turned on, the photosensitive circuit 3 outputs a low level, at this time the voltage at the output terminal of the photosensitive circuit 3 is lower than the voltage at the output terminal of the reference circuit 4, and the operational amplifier chip U1 outputs a low level.

[0060] Furthermore, it also includes a signal driving circuit 6, which includes a PNP transistor Q1, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, and a twelfth resistor R12. One end of the eighth resistor R8 is connected to the detection signal output terminal, and the other end of the eighth resistor R8 is connected to the base of the PNP transistor Q1. One end of the ninth resistor R9 is connected to the base of the PNP transistor Q1, and the other end is connected to the power supply. One end of the tenth resistor R10 is connected to the other end of the ninth resistor R9, and the other end of the tenth resistor R10 is connected to the emitter of the PNP transistor Q1. One end of the eleventh resistor R11 is connected to the collector of the PNP transistor Q1, and the other end is grounded. One end of the twelfth resistor R12 is connected to the collector of the PNP transistor Q1, and the other end is the drive signal output terminal.

[0061] The signal driving circuit 6 can drive external circuits according to the level signal output by the operational amplifier comparator circuit 5, providing strong driving capability and greater stability. Specifically, when the operational amplifier comparator circuit 5 outputs a high level, the base of the PNP transistor Q1 is at a high level, the emitter and collector of the PNP transistor Q1 are disconnected, and the output of the signal driving circuit 6 is low. When the operational amplifier comparator circuit 5 outputs a low level, the base of the PNP transistor Q1 is pulled low, the emitter and collector of the PNP transistor Q1 are connected, and the output of the signal driving circuit 6 is high.

[0062] Furthermore, the signal driving circuit 6 also includes a second Zener diode D2, a third Zener diode D3, a third capacitor U3, and a fourth capacitor U4. The positive terminal of the second Zener diode is connected to one end of the twelfth resistor R12, and the negative terminal is connected to one end of the tenth resistor R10. The positive terminal of the third Zener diode is grounded, and the negative terminal is connected to one end of the twelfth resistor R12. One end of the third capacitor U3 is connected to one end of the tenth resistor R10, and the other end of the third capacitor U3 is grounded. One end of the fourth capacitor U4 is connected to the other end of the twelfth resistor R12, and the other end of the fourth capacitor U4 is grounded.

[0063] By setting the second Zener diode D2 and the third Zener diode D3, the signal driving circuit 6 can be protected to prevent excessive instantaneous current; the third capacitor U3 and the fourth capacitor U4 play a voltage stabilizing role, which can make the output level signal of the signal driving circuit 6 more stable, less prone to fluctuation, and able to drive the external circuit more stably.

[0064] like Figure 1 and Figure 7 As shown, the outer wall of the pipe 1 is provided with a first prism 12 and a second prism 13. The infrared emitting tube IR1 faces the first prism 12, and the phototransistor PT1 faces the second prism 13. The first prism 12 is used to reflect the light emitted by the infrared emitting tube IR1 to the inner wall of the pipe 1. The second prism 13 is used to reflect the light reflected by the inner wall of the pipe 1 to the phototransistor PT1.

[0065] Infrared emitting tube IR1 emits light towards the first prism 12. After the light enters the first prism 12, the side wall of the first prism 12 reflects the light to the inner wall of the pipe 1. When there is no liquid in the pipe 1, the light transmission path is as follows: Figure 7As shown by the dotted line, the inner wall of pipe 1 reflects light to the second prism 13, and the light is then reflected again by the inner wall of the second prism 13 to the phototransistor PT1. When there is liquid in pipe 1, the light reflected to the inner wall of pipe 1 will be refracted into the liquid in pipe 1, and the phototransistor PT1 will not receive the light. When there is no liquid in pipe 1 and liquid adheres to the inner wall of pipe 1, the light reflected to the inner wall of pipe 1 will be refracted into the liquid adhering to the inner wall of pipe 1. Since the surface of the liquid adhering to the inner wall of pipe 1 is close to the inner wall of pipe 1, some light will be reflected back to the inner wall of pipe 1 and refracted by the inner wall of pipe 1 to the second prism 13, so that the phototransistor PT1 can sense the weak light.

[0066] like Figure 1 As shown, the internal channel 11 of the pipe 1 has a D-shaped structure, and one side of the plane faces the first prism 12 and the second prism 13; the pipe 1 is made of transparent material.

[0067] By designing the internal channel 11 of pipe 1 into a D-shaped structure, the inner wall of pipe 1 facing the first prism 12 and the second prism 13 is flat. This allows more light illuminating the inner wall of pipe 1 to be reflected to the second prism 13, resulting in a greater difference in the light sensed by the phototransistor PT1 when the inner wall of pipe 1 is filled with liquid and when it is not filled with liquid, thereby avoiding false detection.

[0068] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0069] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these equivalent variations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A false rejection proof optoelectronic liquid level sensor, characterized in that, The application relates to a liquid level detection device. The device comprises a pipeline, a light emitting circuit, a light sensing circuit, a reference circuit and an operational amplifier comparison circuit. The pipeline has a channel for conveying liquid. The light emitting circuit emits light to the inner wall of the pipeline. The light sensing circuit receives the reflected light and outputs a detection voltage signal according to the intensity of the light. The reference circuit outputs a reference voltage signal.

2. The false alarm resistant optoelectronic liquid level sensor of claim 1, wherein, The operational amplifier comparison circuit compares the detection voltage signal and the reference voltage signal and outputs a level signal according to the comparison result. The light emitting circuit comprises an infrared emitting tube and a first resistor.

3. The false alarm resistant optoelectronic liquid level sensor of claim 2, wherein, One end of the first resistor is connected to a power supply and the other end is connected to the positive electrode of the infrared emitting tube.

4. The false alarm resistant optoelectronic liquid level sensor of claim 3, wherein, The negative electrode of the infrared emitting tube is grounded.

5. The false alarm resistant optoelectronic liquid level sensor of claim 3, wherein, The light sensing circuit comprises a second resistor, a photosensitive triode, a third resistor and a fourth resistor.

6. A false alarm resistant optoelectronic liquid level sensor according to claim 5, characterized in that One end of the second resistor is connected to a power supply and the other end is connected to the collector of the photosensitive triode.

7. The false alarm resistant optoelectronic liquid level sensor of claim 5, wherein, The emitter of the photosensitive triode is grounded. One end of the third resistor is connected to the emitter of the photosensitive triode and the other end is the output end of the light sensing circuit for outputting the detection voltage signal. One end of the fourth resistor is connected to one end of the third resistor and the other end is grounded. The reference circuit comprises a fifth resistor and a sixth resistor. One end of the fifth resistor is connected to a power supply and the other end is the output end of the reference circuit for outputting the reference voltage signal. One end of the sixth resistor is connected to the other end of the fifth resistor and the other end of the sixth resistor is grounded. The reference circuit further comprises a first capacitor. One end of the first capacitor is connected to the other end of the fifth resistor and the other end of the first capacitor is grounded. The operational amplifier comparison circuit comprises an operational amplifier chip and a seventh resistor. One end of the seventh resistor is connected to a power supply and the other end is connected to the VCC pin of the operational amplifier chip. The GND pin of the operational amplifier chip is grounded. The non-inverting input pin and the inverting input pin of the operational amplifier chip are connected to the output end of the light sensing circuit and the output end of the reference circuit respectively. The OUT pin of the operational amplifier chip is the detection signal output end for outputting the first level signal or the second level signal. The operational amplifier comparison circuit further comprises a first zener diode and a second capacitor. The positive electrode of the first zener diode is grounded and the negative electrode is connected to one end of the seventh resistor. One end of the second capacitor is grounded and the other end of the second capacitor is connected to the other end of the seventh resistor. The output end of the reference circuit is connected to the inverting input pin of the operational amplifier chip and the output end of the light sensing circuit is connected to the non-inverting input pin of the operational amplifier chip. The signal driving circuit further comprises a second voltage stabilizing diode, a third voltage stabilizing diode, a third capacitor and a fourth capacitor, the positive pole of the second voltage stabilizing diode is connected with one end of the twelfth resistor, and the negative pole is connected with one end of the tenth resistor; the positive pole of the third voltage stabilizing diode is grounded, and the negative pole is connected with one end of the twelfth resistor; one end of the third capacitor is connected with one end of the tenth resistor, and the other end of the third capacitor is grounded; one end of the fourth capacitor is connected with the other end of the twelfth resistor, and the other end of the fourth capacitor is grounded.

8. The false alarm resistant optoelectronic liquid level sensor according to claim 7, characterized in that The outer wall of the pipeline is provided with a first prism and a second prism, the infrared emitter tube faces the first prism, and the photosensitive triode faces the second prism; the first prism is used for reflecting the light emitted by the infrared emitter tube to the inner wall of the pipeline; and the second prism is used for reflecting the light reflected by the inner wall of the pipeline to the photosensitive triode.

9. The false alarm resistant optoelectronic liquid level sensor of claim 2, wherein, The channel inside the pipeline is a D-shaped structure, and the planar side faces the first prism and the second prism; and the pipeline is of a transparent material.

10. The false alarm resistant optoelectronic liquid level sensor of claim 9, wherein, ​

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