Food freshness monitoring device and monitoring method
By combining the pulse sampling circuit and the heating control circuit, the problems of high power consumption and susceptibility to environmental influences of the gas sensor module are solved, and the stability and accuracy are improved.
Patent Information
- Application Number
- CN202511125146.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-12
- Publication Date
- 2025-10-17
AI Technical Summary
Existing gas sensor modules consume large amounts of power, are easily affected by environmental parameters, have unstable performance, and produce inaccurate detection results.
By combining a pulse sampling circuit with a heating control circuit, the microprocessor MCU controls the working state of the gas sensor to achieve intermittent sampling and temperature control, reduce power consumption and improve stability.
The working performance stability of the gas sensor is improved, the power consumption is reduced, and the accuracy of the detection results is greatly improved.
Smart Images
Figure CN120801439A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of refrigerator preservation, in particular to a food freshness monitoring device and a monitoring method. BACKGROUND
[0002] With the improvement of living standards, people have higher and higher requirements for the preservation function of refrigerators. Traditional refrigerators mainly delay food deterioration by controlling temperature, but cannot accurately judge the freshness change of food inside.
[0003] Because food will release specific gases during the deterioration process, such as trimethylamine of meat and methyl mercaptan of fish, in related technologies, using gas sensors to detect these characteristic gases to evaluate food freshness has become an effective detection method.
[0004] However, the existing gas sensor module at least has the following defects: first, the sampling method is unreasonable, the continuous sampling power consumption is large, and the sensor performance is unstable; second, the sensor performance is easily affected by environmental parameters and fluctuates, resulting in inaccurate detection results. SUMMARY
[0005] The purpose of the present application is to overcome the above technical deficiencies, and to provide a food freshness monitoring device and a monitoring method, which solves the technical problems of large power consumption, easy to be affected by environmental parameters, unstable performance and inaccurate detection results of the gas sensor module in the prior art.
[0006] To achieve the above technical purpose, the present application adopts the following technical scheme: In a first aspect, the present application provides a food freshness monitoring device, comprising: a gas sensor, the gas sensor comprising a sensitive element and a heating element; a pulse sampling circuit connected to the sensitive element, for sampling a gas concentration voltage signal; a heating control circuit connected to the heating element, for controlling the heating power of the heating element; and a control module connected to the pulse sampling circuit, the heating control circuit and an external power supply device, for controlling the pulse sampling circuit and the heating control circuit.
[0007] In some embodiments, the pulse sampling circuit comprises: a gas concentration sampling voltage output end connected to the detection signal output end of the gas sensor, for outputting a voltage signal varying with the gas concentration; and a voltage dividing resistor, one end of which is connected to the detection signal output end of the gas sensor through the gas concentration sampling voltage output end, and the other end is grounded, for forming a series voltage dividing circuit with the sensitive element of the gas sensor.
[0008] In some embodiments, the pulse sampling circuit further comprises: a pulse signal generator configured to generate a periodic pulse signal; and a pulse switch element configured to control the pulse sampling circuit to be turned on or turned off according to the periodic pulse signal. The pulse switch element comprises a control end and a passage end. The control end is electrically connected to an output end of the pulse signal generator, and the passage end is connected in series between a detection signal output end of the gas sensor and the voltage dividing resistor.
[0009] In some embodiments, the heating control circuit comprises: a power supply end and a ground end configured to be connected to an external power supply device and a ground, respectively; a filter module comprising a first capacitor and a second capacitor connected in parallel between the power supply end and the ground end, configured to filter high-frequency noise introduced by the power supply; and a first current-limiting resistor having one end connected to an output end of the filter module and the other end connected to a heating signal input pin of the gas sensor, configured to limit the current flowing into the heating element.
[0010] In some embodiments, the monitoring device further comprises an NTC sensor sampling circuit electrically connected to the control module, the NTC sensor sampling circuit comprising: a power supply end configured to be connected to an external power supply device; a temperature sampling voltage output end configured to output a temperature sampling voltage signal; a second current-limiting resistor having one end connected to the power supply end and the other end connected to the temperature sampling voltage output end; a thermistor having one end connected to the other end of the second current-limiting resistor away from the power supply end and the other end grounded and close to the gas sensor, configured to form a voltage dividing circuit with the second current-limiting resistor; a third capacitor connected in parallel to the thermistor, configured to filter high-frequency noise of the temperature sampling voltage signal.
[0011] In some embodiments, the monitoring device further comprises an ESD protection circuit, and the power supply ends of the gas sensor, the pulse sampling circuit, the heating control circuit, and the control module are connected to an external power supply device through the ESD protection circuit.
[0012] In some embodiments, the gas sensor is a metal oxide semiconductor gas sensor, the probe of the gas sensor has a porous structure, and the probe is coated with a filter membrane on the outside.
[0013] In some embodiments, the control module is a microprocessor MCU, which is attached with the chip of the gas sensor in the monitoring device on two different planes vertically or horizontally.
[0014] In some embodiments, the monitoring device further comprises a state indicating lamp, which is electrically connected with the control module, for indicating the working state of the monitoring device.
[0015] In a second aspect, the application further provides a food freshness monitoring method, which applies the food freshness monitoring device described above, comprising: determining the working parameters of the gas sensor, and adjusting the working temperature of the gas sensor according to the working parameters; determining the sampling frequency of the gas sensor, and intermittently obtaining the characteristic gas concentration data according to the sampling frequency; obtaining the actual working temperature of the gas sensor, and performing temperature compensation on the characteristic gas concentration data according to the actual working temperature, to obtain the final gas concentration data; according to the final gas concentration data, rating the current food freshness according to the preset rating rules, and displaying the rating result.
[0016] Compared with the prior art, the food freshness monitoring device and monitoring method provided by the application connect the sensitive element on the gas sensor through the pulse sampling circuit, and connect the heating element on the gas sensor through the heating control circuit, and control the pulse sampling circuit and the heating control circuit by means of the control module, which not only can realize flexible control of the working state of the gas sensor, avoid continuous sampling of the gas sensor, but also can control the heating power of the heating element on the gas sensor through the heating control circuit, to control the working temperature of the gas sensor. In this way, not only the stability of the working performance of the sensor can be improved, the power consumption can be reduced, but also the influence of environmental parameters on the gas sensor can be reduced, and the accuracy of the detection result can be greatly improved. BRIEF DESCRIPTION OF DRAWINGS
[0017] Figure 1 is the overall structure schematic diagram of the food freshness monitoring device in one embodiment of the application; Figure 2 is the circuit structure block diagram of the food freshness monitoring device in one embodiment of the application; Figure 3 is the circuit principle diagram of the pulse sampling circuit and the heating control circuit in one embodiment of the application; Figure 4 is the circuit principle diagram of the NTC sensor sampling circuit in one embodiment of the application; Figure 5 is the circuit principle diagram of the MCU peripheral circuit in one embodiment of the application; Figure 6 is a circuit schematic diagram of a voltage conversion circuit in one embodiment of the present application; Figure 7 is a circuit schematic diagram of an ESD protection circuit in one embodiment of the present application; Figure 8 is a flowchart of a food freshness monitoring method in one embodiment of the present application. DETAILED DESCRIPTION
[0018] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.
[0019] In order to solve the above technical problems, the present application provides a food freshness monitoring device and a monitoring method, which can not only improve the stability of sensor working performance and reduce power consumption, but also reduce the influence of environmental parameters on the gas sensor 200, greatly improving the accuracy of the detection result.
[0020] Please refer to Figures 1-2 The present application provides a food freshness monitoring device, which can be applied to real-time monitoring of food freshness in a refrigerator, and comprises a shell 100, a plurality of air inlet holes 110 are arranged on the shell 100; an integrated circuit board is arranged inside the shell 100, and a gas sensor 200, a pulse sampling circuit 300, a heating circuit and a control module are arranged on the integrated circuit board.
[0021] The gas sensor 200 is provided with a sensitive element and a heating element, and the sensitive element and the heating element correspond to a sensitive circuit and a heating circuit on the gas sensor 200 respectively, and the sensitive circuit and the heating circuit are connected to the pulse sampling circuit 300 and the heating control circuit 400 respectively, and the pulse sampling circuit 300 and the heating control circuit 400 can be further connected to the control module.
[0022] In the above manner, the pulse sampling circuit 300 can sample the gas concentration voltage signal fed back by the gas sensor 200, and the heating control circuit 400 can control the heating power of the heating element, so as to control the working temperature of the gas sensor 200 within a suitable temperature range.
[0023] In the present embodiment, the above-mentioned gas sensor 200 can be a metal oxide semiconductor gas sensor 200 (i.e. MEMS MOX sensor), the sensitive element on the gas sensor 200 can be made of a metal oxide semiconductor (MOX) with high sensitivity, and the heating element thereon can be a heating electrode, which is not specifically limited.
[0024] When the sensitive element adsorbs characteristic gas (such as trimethylamine, methyl mercaptan, and ethylene), the sensitive element will react with the characteristic gas, resulting in a change in the resistance characteristics of the sensitive element. Based on the resistance change characteristics of the sensitive element, the concentration of the characteristic gas can be detected by using a related circuit.
[0025] Since the sensitive element is a MOX sensitive material, the MOX sensitive material has specific requirements for the working temperature. Therefore, the heating power of the heating element is controlled by the heating control circuit 400 to be fixed at a set value, which helps to keep the MOX sensitive material in a stable and suitable working temperature range, thereby ensuring that the adsorption and reaction characteristics of the sensitive element to the characteristic gas remain stable, so as to improve the detection accuracy and stability.
[0026] On this basis, in order to further improve the detection sensitivity, the probe of the gas sensor 200 can be provided with a porous structure, and the pore size can be flexibly designed according to requirements, which can not be specifically limited. By providing the probe surface with a porous structure, the contact area between the sensitive element and the gas can be increased, which helps the sensitive element to adsorb the characteristic gas and react with it.
[0027] Meanwhile, the probe of the gas sensor 200 can also be coated with a filter film (not shown in the figure), which can be made of a high polymer composite material (such as a polytetrafluoroethylene composite material, a polyvinylidene fluoride composite material, a polypropylene composite microfiltration membrane, etc.). It has a microporous structure and chemical stability, can allow trimethylamine, methyl mercaptan, and other characteristic gases to pass through, and block water vapor, dust, oil stains, and other impurities in the refrigerator, play a waterproof and breathable role, protect the probe from the influence of the external harsh environment, thereby prolonging the service life of the probe.
[0028] Please refer to Figure 3 In the embodiment, the pulse sampling circuit 300 is connected to the sensitive element on the gas sensor 200, and can output a gas concentration voltage signal.
[0029] Specifically, the pulse sampling circuit 300 includes a gas concentration sampling voltage output end H_V and a voltage dividing resistor R15. The gas concentration sampling voltage output end H_V is connected to the detection signal output end H2 of the gas sensor 200, and can be used to output a voltage signal that changes with the gas concentration. One end of the voltage dividing resistor R15 is connected to the detection signal output end H2 of the gas sensor 200 through the gas concentration sampling voltage output end H_V, and the other end is grounded and connected in series with the sensitive element on the gas sensor 200 to form a voltage dividing circuit.
[0030] In another embodiment, the pulse sampling circuit 300 can further include a pulse signal generator and a pulse switch element. The pulse signal generator can be used to generate a periodic pulse signal, and the pulse switch element can be controlled according to the periodic signal to turn on or turn off the pulse sampling circuit 300. Specifically, the pulse switch element can include a control end and a passage end; wherein the control end can be electrically connected with the output end of the pulse signal generator, and the passage end can be connected in series between the detection signal output end H2 of the gas sensor 200 and the voltage dividing resistor R15.
[0031] It should be noted that the parameters of the pulse signal generator can include a pulse width t1 and a pulse period T; wherein the pulse width t1 can be used to define the duration of a single sampling, and the pulse period T can be used to define the time interval t2 between two samplings, i.e. T = t1 + t2.
[0032] The pulse switch element can be an N-channel MOS tube or an analog switch, and its control end (i.e. gate or enable end) can be electrically connected with the output end of the pulse signal generator, and its passage end can be connected in series in the signal path of the pulse signal sampling circuit, which can control the pulse signal sampling circuit to turn on or turn off according to the pulse signal.
[0033] In this way, in one embodiment, when the pulse signal generator outputs a high-level pulse, the pulse switch element is turned on, the pulse sampling circuit 300 forms a passage, and the sensitive element on the gas sensor 200 and the voltage dividing resistor R15 can form a series voltage dividing circuit, and the gas concentration sampling voltage output end H_V can output a voltage signal corresponding to the gas concentration, realizing single sampling start, and the duration is t1. When the pulse signal generator outputs a low-level pulse, the pulse switch element is turned off, and the gas concentration sampling voltage output end H_V has no effective voltage output, i.e. sampling is stopped, and the interval time is t2.
[0034] By periodically repeating the process, intermittent sampling according to the set time interval T and single sampling time t1 can be realized, so that the probe on the gas sensor 200 can work intermittently, avoiding performance degradation caused by long-time continuous work, reducing overall power consumption, and improving sampling stability and accuracy.
[0035] On this basis, different pulse parameters can be set for different types of food, for example, for meat, vegetable or fish detection, the pulse frequency can be controlled at 1 Hz, and the duty cycle is 1%, which can ensure the accuracy and timeliness of the detection of trimethylamine gas and methyl mercaptan gas, while reducing power consumption.
[0036] It should be noted that, for the gas concentration sampling voltage signal output by the gas concentration sampling voltage output end H_V, a post-stage circuit connected with the gas concentration sampling voltage output end H_V can be further arranged on the integrated circuit board, which can include an ADC analog-digital conversion circuit, an amplification filter circuit, etc., to realize analog-digital conversion and amplification filtering of the gas concentration sampling voltage signal, and the post-stage circuit can be further connected with the control module, which will not be described here.
[0037] Please refer to Figure 3 In the embodiment, the heating control circuit 400 is connected with the heating element on the gas sensor 200, and can be used to control the heating power of the heating loop to control the working temperature of the sensitive element on the gas sensor 200.
[0038] Specifically, the heating control circuit 400 can include a power supply end and a ground end, the power supply end can be used to connect an external power supply device 900, and the ground end can be used for grounding.
[0039] Meanwhile, the heating control circuit 400 further includes a filtering module and a current limiting resistor R11 (i.e., a first current limiting resistor). The filtering module can include a capacitor C3 (i.e., a first capacitor) and a capacitor C8 (i.e., a second capacitor), which can be connected in parallel between the power supply end and the ground end, and can be used to filter out high-frequency noise introduced by the power supply; one end of the current limiting resistor R11 can be connected to the output end of the filtering module, and the other end can be connected to the heating signal input pin S1 on the gas sensor 200, which can be used to limit the current flowing into the heating loop.
[0040] Please refer to Figure 4 In the embodiment, the food freshness monitoring device can further include an NTC (Negative Temperature Coefficient) sensor sampling circuit 600 connected with the control module, which can be used to sample the temperature voltage signal of the gas sensor 200, so as to realize temperature compensation for the detection data of the gas sensor 200 in cooperation with the control module.
[0041] Specifically, the NTC sensor sampling circuit 600 can include a power supply end and a temperature sampling voltage output end NTC_W; the power supply end can be used to connect an external power supply device 900, and the temperature sampling voltage output end NTC_W can be used to output a temperature sampling voltage signal.
[0042] Meanwhile, the NTC sensor sampling circuit 600 further includes a current limiting resistor R7 (i.e., a second current limiting resistor), a thermistor R9, and a filtering capacitor C9 (i.e., a third capacitor).
[0043] One end of the current-limiting resistor R7 is connected to the power supply end, and the other end is connected to the temperature sampling voltage output end. One end of the thermistor R9 is connected to the end of the current-limiting resistor R7 away from the power supply end, and the other end can be grounded. The filter capacitor C9 can be connected in parallel with the thermistor R9 to filter high-frequency noise in the temperature sampling voltage signal.
[0044] It should be noted that the thermistor R9 is preferably an NTC thermistor, that is, a thermistor with a negative temperature coefficient (NTC) whose resistance decreases exponentially with temperature. It can be a semiconductor ceramic made of two or more metal oxides of manganese, copper, silicon, cobalt, iron, nickel, and zinc, which are fully mixed, molded, and sintered. This is not limited in detail. In actual application, the thermistor R9 can be placed near the gas sensor 200 to accurately sense the temperature at the location of the gas sensor 200.
[0045] Please refer to Figure 5 In this embodiment, the control module can be a microprocessor MCU 500 to automatically control the pulse sampling circuit 300 and the heating control circuit 400.
[0046] To achieve the above purpose, the microprocessor MCU 500 in this embodiment is provided with an MCU peripheral circuit, which can include a communication interface module, a reset circuit module, and a power management module.
[0047] The communication interface module includes a sending end TXD1 pin and a receiving end RXD1 pin. The microprocessor MCU 500 can connect the corresponding ports of the pulse sampling circuit 300, the heating control circuit 400, and the NTC sensor sampling circuit 600 through the TXD1 pin and the RXD1 pin to realize the transmission and reception of instructions.
[0048] The reset circuit module includes an NRST reset pin that can be connected to a reset circuit to realize the reset function of the microprocessor MCU 500. The reset circuit can use existing circuit structures as needed, and will not be described here.
[0049] The power management module includes a power supply pin 10 that can be connected to an external power supply device 900 through a filter module composed of capacitors C15 and C16 to ensure that the voltage of the power supply pin 10 of the microprocessor MCU 500 is pure and avoid interfering with the internal logic.
[0050] It should be noted that in the embodiment, the TXD1 pin and the RXD1 pin of the MCU peripheral circuit can be connected to the corresponding ports of the pulse sampling circuit 300 and the heating control circuit 400; the voltage signals (such as the gas concentration sampling voltage signal and the temperature sampling voltage signal) collected by each circuit can be input to the microprocessor MCU 500 through the RXD1 pin after analog-to-digital conversion, amplification and filtering, and the microprocessor MCU 500 can perform data analysis and processing.
[0051] Meanwhile, the microprocessor MCU 500 can send control instructions (such as adjusting the heating power and the sampling frequency) to each circuit through the TXD1 pin, so as to realize dynamic regulation and control of the pulse sampling circuit 300, the heating control circuit 400 and the NTC sensor sampling circuit 600, and ensure the accuracy of voltage signal collection.
[0052] In this process, the microprocessor MCU 500 can determine the current working temperature of the gas sensor 200 according to the temperature sampling voltage signal sampled by the NTC sensor sampling circuit 600, and perform temperature compensation on the detected gas concentration data according to the working temperature and the built-in temperature compensation algorithm, so as to correct and eliminate the influence of temperature change on the detection result, thereby improving the accuracy of the monitoring device in detecting the characteristic gas.
[0053] In addition, in the embodiment, the microprocessor MCU 500 and the chip of the gas sensor 200 in the shell 100 can be assembled by using a patch assembly method, but the microprocessor MCU 500 and the chip of the gas sensor 200 are preferably arranged on two different planes, which can be perpendicular or parallel, and the two different planes are not limited.
[0054] In order to facilitate the user to master the running status of each circuit, a status indicator light (not shown in the figure) can also be arranged on the integrated circuit board, which can be an LED indicator light. The LED indicator light can be electrically connected to the microprocessor MCU 500. When a fault occurs, the microprocessor MCU 500 can control the status indicator light to flash at a specified frequency, so as to facilitate the user to judge whether the monitoring device is normally running.
[0055] In the embodiment, the microprocessor MCU 500 can also have a pre-built food freshness rating algorithm model. When the microprocessor MCU 500 receives the sampling signal from the pulse sampling circuit 300 and the temperature signal from the NTC sensor sampling circuit 600, the microprocessor MCU 500 can rate the current freshness of the food in the refrigerator according to the algorithm model.
[0056] It should be noted that the temperature compensation algorithm described above is prior art in the field and is not the focus of the present application, and therefore will not be described here. The food freshness rating algorithm model described above can grade the freshness of food according to the concentration of characteristic gas.
[0057] For example, the concentration of characteristic gas can be divided into low, medium and high concentration ranges according to the concentration values from low to high. Among them, the low concentration can correspond to freshness levels 0-3, the medium concentration can correspond to freshness levels 4-6, and the high concentration can correspond to freshness levels 7-9. In this way, the current freshness of food can be divided into 0-9 levels according to the concentration of characteristic gas, and output and display, so that users can understand the current freshness of food in the refrigerator.
[0058] Please refer to Figure 6 In this embodiment, the monitoring device can further include a voltage conversion circuit 700, which can realize voltage conversion and provide stable DC voltage for the pulse sampling circuit 300, the heating control circuit 400, the NTC sensor sampling circuit 600 and the microprocessor MCU 500.
[0059] Specifically, the voltage conversion circuit 700 includes a linear voltage regulator chip U1, which is provided with an IN pin (input voltage end), a GND pin (ground end), an EN pin, a BYP pin (bypass pin) and an OUT pin (output voltage end).
[0060] In one embodiment, the IN pin can be connected to a +5V DC power supply to provide input power for the linear voltage regulator chip U1; the GND pin can provide a circuit reference ground to ensure stable operation of the linear voltage regulator chip U1; the EN pin can be always on by default; the BYP pin can be connected to a small capacity capacitor C17 to filter high frequency noise in the linear voltage regulator chip U1 and optimize output ripple; and the OUT pin can output a stabilized +3.3V voltage to power the subsequent circuit (such as the pulse sampling circuit 300, the heating control circuit 400 and the NTC sensor sampling circuit 600).
[0061] On this basis, the OUT pin can be further connected to an output filtering module, which can include capacitors C5, C6, C7 and inductor L1. Among them, capacitors C5, C6 and C7 are all filtering capacitors, one end of which is connected to the OUT pin, and the other end is grounded, forming a parallel structure; high-frequency noise will be shorted to ground by capacitors C5, C6 and C7 to reduce the ripple of the output voltage, making the +3.3V voltage output more stable. Inductor L1 cooperates with each of the filtering capacitors (C5, C6, C7) to form a pi-type filtering network, further enhancing the filtering effect to make the output DC voltage present low impedance, reduce loss and maintain pure output.
[0062] In this way, when the input voltage from the external power supply device 900 is +5V DC voltage, the +5V DC voltage is input to the linear voltage regulator chip U1, which reduces and stabilizes the voltage and outputs a preliminary +3.3V DC voltage. After filtering by inductor L1 and capacitors C5, C6 and C7, the preliminary +3.3V DC voltage is stably output at +3.3V DC voltage, which can power the subsequent circuit.
[0063] Please refer to Figure 7 In this embodiment, to ensure that the monitoring device can operate reliably and stably in a complex electromagnetic environment, the monitoring device can further include an ESD protection circuit 800, which can be placed at a designated location as needed to achieve protection effect on the subsequent circuit.
[0064] It should be noted that in this embodiment, the ESD protection circuit 800 can use any existing electrostatic discharge protection circuit, which can include TVS tubes (transient voltage suppression diodes), field effect tubes, resistors, capacitors, inductors, etc. will not be repeated here.
[0065] By setting the ESD protection circuit 800, on the one hand, it can provide an electrostatic discharge protection power input for the subsequent circuit, protecting the related circuit and components, and on the other hand, it can also resist ESD transient interference and improve the stability of signal sampling and transmission.
[0066] For example, in one embodiment, the ESD protection circuit 800 can be placed between the voltage conversion circuit 700 and the microprocessor MCU 500. The ESD protection circuit 800 is connected to the output voltage end of the voltage conversion circuit 700 on the one hand, and can also be connected to the power supply pin 10 on the microprocessor MCU 500 on the other hand. Therefore, after the DC voltage is converted by the voltage conversion circuit 700, it needs to pass through the ESD protection circuit 800 to output to the microprocessor MCU 500. In this way, the ESD protection circuit 800 can play a power protection role for the microprocessor MCU 500, protecting the microprocessor MCU 500.
[0067] In another embodiment, the signal output end of the ESD protection circuit 800 can be connected to the TXD1 pin of the microprocessor MCU 500, and the signal input end of the ESD protection circuit 800 can be connected to the RXD1 pin of the microprocessor MCU 500. In this way, when ESD interference is introduced from the outside, the ESD protection circuit 800 can discharge and clamp the interference before the signal enters the microprocessor MCU 500, thereby protecting the communication module and internal logic of the microprocessor MCU 500.
[0068] It can be understood that the ESD protection circuit 800 can provide power and / or communication protection for specified circuits or components. In this way, by reasonably setting the position of the ESD protection circuit 800, the pulse signal sampling circuit, the heating control circuit 400, the NTC sensor sampling circuit 600, and the MCU peripheral circuit can be protected from ESD, ensuring the normal operation of power supply, communication, sensor data acquisition, and other functions.
[0069] Please refer to Figure 8 Based on the above food freshness monitoring device, the application further provides a food freshness monitoring method, comprising: determining the working parameters of the gas sensor 200, and adjusting the working temperature of the gas sensor 200 according to the working parameters; determining the sampling frequency of the gas sensor 200, and intermittently obtaining the characteristic gas concentration data according to the sampling frequency; obtaining the actual working temperature of the gas sensor 200, and performing temperature compensation on the characteristic gas concentration data according to the actual working temperature to obtain final gas concentration data; According to the final gas concentration data, the current food freshness is rated according to the preset rating rule, and the rating result is displayed.
[0070] Specifically, the above "determining the working parameters of the gas sensor 200, and adjusting the working temperature of the gas sensor 200 according to the working parameters" includes: The technical manual of the corresponding gas sensor 200 can be consulted to understand the working temperature of the gas sensor 200. According to the working temperature, the heating power of the heating element on the gas sensor 200 can be controlled by the heating control circuit 400, so that the working temperature of the gas sensor 200 is maintained within a suitable temperature range.
[0071] The above "determining the sampling frequency of the gas sensor 200, and intermittently obtaining the characteristic gas concentration data according to the sampling frequency" includes: The sampling frequency of the probe on the gas sensor 200 can be controlled by the microprocessor MCU 500 and the pulse sampling circuit 300 according to the relationship between the working performance and service life of the gas sensor 200 and the sampling frequency, so that the probe on the gas sensor 200 works intermittently, thereby avoiding performance degradation of the gas sensor 200 due to long-term continuous work and reducing power consumption. During work, the microprocessor MCU 500 can determine the concentration of the characteristic gas in the environment through the gas concentration sampling voltage signal output by the pulse sampling circuit 300, which facilitates the judgment of the freshness of the food.
[0072] On this basis, the above-mentioned "obtaining the actual working temperature of the gas sensor 200, and temperature compensating the characteristic gas concentration data according to the actual working temperature to obtain the final gas concentration data" includes: The microprocessor MCU 500 can obtain the actual working temperature of the gas sensor 200 through the NTC sensor sampling circuit 600, and then temperature compensate and correct the obtained gas concentration data based on the built-in temperature compensation algorithm, thereby obtaining the final gas concentration data.
[0073] Based on the above-mentioned final gas concentration data, the above-mentioned "rating the current food freshness according to the preset rating rules based on the final gas concentration data, and displaying the rating result" includes: Through the obtained final gas concentration data, the microprocessor MCU 500 can determine the specific concentration of the characteristic gas, and then can determine which interval range the current concentration of the characteristic gas is in through the built-in food freshness rating algorithm model, and can rate the current freshness of the food according to 0-9 according to the specific concentration value. The final rating result can be output to the display device connected thereto through the output interface on the microprocessor MCU 500, which facilitates the user to understand the current freshness level of the food.
[0074] In the description of the present application, it should be noted that the positions or location relationships indicated by the terms "upper" and "lower" are based on the positions or location relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. Unless otherwise specified and limited, the terms "mounting", "connection" and "connection" should be interpreted broadly, for example, it can be fixed connection, or detachable connection, or integral connection; it can be mechanical connection, or electrical connection; it can be direct connection, or indirect connection through an intermediate medium, or internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.
[0075] It should be noted that, in the present application, the relational terms such as "first" and "second", and the like, are used solely to distinguish one entity or action from another, without necessarily requiring or implying any actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.
[0076] The specific embodiments of the present application described above are not meant to be limiting. Various other changes and modifications to the present application will be apparent to those skilled in the art from the foregoing description, and such changes and modifications are intended to fall within the scope of the claims.
Claims
1. A food freshness monitoring device, characterized in that: include: A gas sensor, wherein the gas sensor is provided with a sensitive element and a heating element; A pulse sampling circuit, connected to the sensitive element, for sampling a gas concentration voltage signal; a heating control circuit connected to the heating element and used to control the heating power of the heating element; as well as A control module is connected to the pulse sampling circuit, the heating control circuit and an external power supply device, and is used to control the pulse sampling circuit and the heating control circuit.
2. The food freshness monitoring device according to claim 1, characterized in that: The pulse sampling circuit comprises: A gas concentration sampling voltage output terminal connected to the detection signal output terminal of the gas sensor, for outputting a voltage signal that varies with the gas concentration; and A voltage divider resistor, one end of which is connected to the detection signal output end of the gas sensor through the gas concentration sampling voltage output end, and the other end is grounded, and is used to form a series voltage divider circuit with the sensitive element of the gas sensor.
3. The food freshness monitoring device according to claim 2, characterized in that: The pulse sampling circuit further includes: a pulse signal generator, configured to generate a periodic pulse signal; and A pulse switch element, used for controlling the pulse sampling circuit to be turned on or off according to the periodic pulse signal; The pulse switch element includes a control end and a path end; the control end is electrically connected to the output end of the pulse signal generator, and the path end is connected in series between the detection signal output end of the gas sensor and the voltage divider resistor.
4. The food freshness monitoring device according to claim 1, characterized in that: The heating control circuit includes: The power supply terminal and the ground terminal are used to connect to the external power supply device and the ground respectively; a filtering module, the filtering module comprising a first capacitor and a second capacitor, the first capacitor and the second capacitor being connected in parallel between the power supply terminal and the ground terminal, for filtering high-frequency noise introduced by the power supply; and A first current limiting resistor has one end connected to the output end of the filter module and the other end connected to the heating signal input pin of the gas sensor, and is used to limit the current flowing into the heating element.
5. The food freshness monitoring device according to claim 1, characterized in that: The monitoring device further includes an NTC sensor sampling circuit electrically connected to the control module, and the NTC sensor sampling circuit includes: Power supply terminal, used for connecting to an external power supply device; Temperature sampling voltage output terminal, used for outputting temperature sampling voltage signal; a second current limiting resistor, one end of which is connected to the power supply end, and the other end of which is connected to the temperature sampling voltage output end; a thermistor, one end of which is connected to the end of the second current-limiting resistor away from the power supply end, the other end of which is grounded and close to the gas sensor, and is used to form a voltage divider circuit with the second current-limiting resistor; The third capacitor is connected in parallel with the thermistor and is used to filter out high-frequency noise of the temperature sampling voltage signal.
6. The food freshness monitoring device according to claim 1, characterized in that: The monitoring device further includes an ESD protection circuit, and the gas sensor, the pulse sampling circuit, the heating control circuit, and the power supply end of the control module are all connected to an external power supply device through the ESD protection circuit.
7. The food freshness monitoring device according to any one of claims 1 to 6, characterized in that: The gas sensor is a metal oxide semiconductor gas sensor, the probe of the gas sensor is a porous structure, and the outside of the probe is covered with a filter membrane.
8. The food freshness monitoring device according to any one of claims 1 to 6, characterized in that: The control module is a microprocessor MCU, and the microprocessor MCU and the chip of the gas sensor are mounted on two different perpendicular or parallel planes in the monitoring device.
9. The food freshness monitoring device according to any one of claims 1 to 6, characterized in that: The monitoring device further comprises a status indicator light, which is electrically connected to the control module and is used to indicate the working status of the monitoring device.
10. A method for monitoring food freshness, characterized in that: The food freshness monitoring device according to any one of claims 1 to 9 comprises: determining operating parameters of the gas sensor, and adjusting the operating temperature of the gas sensor according to the operating parameters; Determining a sampling frequency of the gas sensor, and intermittently acquiring characteristic gas concentration data according to the sampling frequency; Acquiring an actual operating temperature of the gas sensor, and performing temperature compensation on the characteristic gas concentration data according to the actual operating temperature to obtain final gas concentration data; Based on the final gas concentration data, the current food freshness is rated according to preset rating rules, and the rating results are displayed.