CN211927781U

CN211927781U - Gas detection circuit and charging support

Info

Publication number: CN211927781U
Application number: CN201920720038.4U
Authority: CN
Inventors: 谢高庆
Original assignee: Shenzhen Dayu Wujiang Technology Development Co ltd
Current assignee: Shenzhen Dayu Wujiang Technology Development Co ltd
Priority date: 2019-05-16
Filing date: 2019-05-16
Publication date: 2020-11-13
Anticipated expiration: 2029-05-16

Abstract

The utility model relates to the technical field of auxiliary appliances, in particular to a gas detection circuit and a charging support, wherein the gas detection circuit comprises a semiconductor gas sensor, an operational amplification circuit with temperature compensation and an isolation circuit, and the reliability and the accuracy of detection are improved by a series of measures such as sensitivity adjustment, temperature compensation, operational amplification, the isolation circuit and voltage clamping; the charging support containing the gas detection circuit is novel in concept, reasonable in design and convenient to use, integrates the charging support for supporting the mobile phone and the circuit for detecting air, enables the charging support to have the air quality detection function, displays and sends out an alarm function, reduces cost and saves space.

Description

Gas detection circuit and charging support

Technical Field

The utility model relates to an auxiliary appliances technical field especially relates to a gaseous detection circuitry and support that charges.

Background

Formaldehyde, chemical formula HCHO or CHO, also known as formaldehyde. Colorless and has stimulating effect on eyes and nose. Is easily soluble in water and ethanol. Indoor air pollution has become a cause of various diseases, and formaldehyde is a main aspect of indoor air pollution. Sources of formaldehyde: the related articles comprise: clothing-Children, easy-care shirts; food-instant noodles, rice flour, water-soaked squid, sea cucumber, beef tripe and shrimp meat; live-furniture, wood floor; go-car. It is easy to see that clothes, food, live and go, the most important four things in our lives, formaldehyde is all dyed and means that formaldehyde is worried about everywhere.

VOC is a short term for Volatile Organic Compounds (VOCs), but because of the wide variety of VOCs, it is impossible to include all the VOCs in monitoring and supervision, so that indexes such as VOCs, TVOC, non-methane total hydrocarbons and hydrocarbons are used in China to characterize VOCs.

The initial objective of the VOCs index is to analyze the sum of various components by analyzing the VOC components. VOCs and VOCs are indeed the same class of materials, and since volatile organic compounds are generally more than one component, VOCs are more accurate.

TVOC is an indicator of the summation of common VOCs in a room, and researchers of indoor air quality generally refer to all indoor Organic gaseous substances they sample for analysis as TVOC, which is an abbreviation of the first letter of the three words of vollate Organic Compound, and the various VOCs being measured are collectively referred to as total Volatile Organic TVOC (Total Volatile Organic Compounds).

The gas sensor is a sensor for detecting specific gas, which can sense the gas to be detected, detect specific components in the gas and convert the specific components into output signals convenient for observation and analysis. The gas sensor is used for leakage alarm of combustible explosive gas at the earliest time, and production and life safety is guaranteed. Through gradual popularization and application, the method has very important application value in the fields of air pollution monitoring, industry, national defense, food safety, medical detection and the like.

Gas sensors are mainly classified into chemical reaction type, thermal conduction type, optical type, electrochemical type, contact combustion type, semiconductor type, and the like, depending on the analytical detection method. The formaldehyde sensors used in the market are mainly semiconductor type and electrochemical type gas sensors, and the VOC sensors used are mainly classified into semiconductor type and PID type sensors (photoionization detectors):

semiconductor type formaldehyde sensor: under a certain temperature condition, when a gas to be detected reaches the surface of a semiconductor sensitive material, the gas to be detected chemically reacts with oxygen adsorbed on the surface of the semiconductor sensitive material, the resistance of the semiconductor sensitive material is changed, the resistance change rate of the semiconductor sensitive material is in an exponential relation with the concentration of the gas to be detected, and the concentration of the gas can be detected by measuring the change of the resistance. The method can realize limited identification of gas in a known environment through selective catalysis, physics and the like. The semiconductor sensor can realize qualitative detection, has low cost and long service life, and is convenient for use of portable products for civil families.

Electrochemical formaldehyde sensor: the method is characterized in that the redox reaction of the tested environmental gas in the electrochemical sensor system is utilized, and charges are released to form current, and the generated current is in direct proportion to the concentration of the tested gas. I.e. the higher the gas concentration the greater the output current. The electrochemical sensor can realize quantitative detection, has excellent repeatability and stability, and is generally applied to high-end commercial products mostly due to the complex cost and process.

Semiconductor type VOC sensor: the conductivity of the sensor changes when the gas to be detected is present in the ambient air, and the higher the concentration of the gas, the higher the conductivity of the sensor. This change in conductivity can be converted into an output signal corresponding to the gas concentration using a simple circuit. The sensor has the characteristics of high sensitivity, quick response and recovery time, small volume, good stability and the like for organic gases such as toluene, benzene, formaldehyde and the like.

PID formula VOC sensor: consists of an ultraviolet light source and a gas chamber. The ultraviolet light emitting principle is the same as that of a fluorescent tube, but the frequency is high and the energy is large. After the gas to be measured reaches the gas chamber, the ultraviolet light emitted by the ultraviolet lamp is ionized to generate charge flow, the gas concentration is positively correlated with the charge flow, and the gas concentration can be measured by measuring the charge flow.

PID can detect most VOCs, except for low molecular weight hydrocarbons. Each VOC has a photon energy that when light is directed at the VOC, it breaks down into ions, which are the ionization potential or IP. VOCs are ionized (i.e., detected) if photon energies greater than IP interact with the sample gas.

PID has excellent sensitivity and large dynamic range, and can measure the VOC concentration of low ppb under the background of higher inorganic gas concentration. The device has the advantages of high sensitivity and high resolution, small volume, high test stability and strong anti-interference capability, is mainly applied to outdoor VOC gas pollution detection, and is widely applied to portable and fixed gas detectors and various occasions and equipment needing VOC gas detection.

As described above, the semiconductor sensor can detect formaldehyde and VOC at the same time, and thus is widely used. In addition, the semiconductor gas sensor is favored by people because of its advantages of high sensitivity, fast response speed, small volume, light weight, easy compatibility with Si-based semiconductor process, etc. The sensor is widely applied to the application fields of daily life, urban exhaust gas, propane gas and the like, has high sensitivity and simple structure and circuit, but is easy to influence the linearity of signal output and gas concentration. Functionally, semiconductor gas sensors are moving toward "detecting multiple gases without affecting the measurement accuracy".

With the development of the automobile industry, the automobile not only can be used as a vehicle and completely integrated into daily trips of people, but also can bear other functions such as mobile phone charging due to the fact that people are in the automobile for a long time. Meanwhile, the interior decoration material of the automobile can generate a great amount of harmful gases, such as formaldehyde, Total Volatile Organic Compounds (TVOC), carbon monoxide emitted from automobile exhaust and other external harmful gases, which can damage the health of people and also need to be treated in time.

In addition, with the development progress of automobile functions, the number of internal auxiliary functional accessories is increased, such as a driving recorder, an air purifier, a vehicle-mounted charger, a teacup holder and the like. The accessories cause complexity in the automobile cab and increase economic cost, so that the accessories are reasonably and organically combined or fused, the purchase trouble is reduced for an automobile owner, the economic cost is reduced, and the cleanliness in the cabin is greatly improved.

SUMMERY OF THE UTILITY MODEL

To the not enough of prior art, the utility model provides a gaseous detection circuitry and support that charges, its concrete scheme as follows:

in a first aspect, the present invention provides a gas detection circuit, including: the gas sensor comprises a semiconductor gas sensor, an operational amplifier circuit with temperature compensation and an isolation circuit; the output end of the semiconductor gas sensor is electrically connected with the input end of the operational amplifier circuit with temperature compensation, the output end of the operational amplifier circuit with temperature compensation is electrically connected with the input end of the isolation circuit, and the isolation circuit outputs a detection signal.

Preferably, the operational amplifier circuit with temperature compensation comprises a first operational amplifier (A1), a variable resistor (R)_T) The gas sensor comprises a semiconductor gas sensor, a first resistor (R1) and a first capacitor (C1), wherein the positive input end of the first operational amplifier (A1) is electrically connected with the output end of the semiconductor gas sensor, a parallel circuit consisting of the first capacitor (C1) and the first resistor (R1) is connected between the negative input end and the output end in a bridging mode, and the negative input end of the first operational amplifier (A1) also passes through the variable resistor (R1)_T) And (4) grounding.

Preferably, when the internal resistance of the semiconductor gas sensor is in a direct proportion to the ambient temperature, the variable resistance is a thermistor in a direct proportion to the ambient temperature; or, when the internal resistance of the semiconductor gas sensor is inversely proportional to the ambient temperature, the variable resistance is a thermistor inversely proportional to the ambient temperature.

Preferably, the isolation circuit comprises a second operational amplifier (A2) and a second resistor (R2), wherein the negative input end of the second operational amplifier (A2) is short-circuited with the output end, and the positive input end is electrically connected with the output end of the operational amplifier (A1) through the second resistor (R2).

Preferably, the model of the semiconductor gas sensor is TGS 812.

Preferably, the gas sensor further comprises a sensitivity adjusting circuit consisting of an adjustable resistor (Rp), wherein the adjustable resistor (Rp) is arranged between the positive input end of the first operational amplifier (A1) and the output end of the semiconductor gas sensor; the adjustable resistor is a self-locking organic solid potentiometer.

Preferably, the circuit further comprises a clamping circuit, the clamping circuit is composed of a first diode (D1) and a second diode (D2), the cathode of the first diode (D1) is electrically connected with the output end of the isolating circuit, the anode of the first diode is grounded, the anode of the second diode (D2) is electrically connected with the output end of the isolating circuit, and the cathode of the second diode is connected with a power supply.

In a second aspect, the present invention provides a charging stand, comprising a central processing unit, a power circuit, the gas detection circuit of the first aspect, and a stand body (1), wherein the central processing unit, the power circuit, and the gas detection circuit are electrically connected to each other; the left side and the right side of the support main body (1) are provided with clamping arms (2) for clamping a mobile phone, the lower part of the support main body is provided with a supporting plate (3) for supporting the mobile phone, and the upper part of the support main body is also provided with an LCD display screen (4); the central processing unit converts an analog detection signal output by the gas detection circuit and collected by a built-in integrated digital-to-analog converter into a digital signal; the central processing unit compares the digital signal converted by the digital-to-analog converter with a preset threshold value stored in advance; the central processor displays the comparison result through an LCD display screen (4); the model of the central processor is AT89C 51.

Preferably, the monitoring device further comprises a PM2.5 sensor, a carbon monoxide sensor and an alarm which are all electrically connected with the central processing unit, wherein the PM2.5 detection circuit is of a model PMSA003, and the carbon monoxide sensor is of a model TGS 5141; the bracket main body (1) comprises a front shell plate (1a) arranged at the front part and a back shell plate (1b) arranged at the rear part, and a cavity is formed between the front shell plate (1a) and the back shell plate (1 b); the supporting plates (3) are arranged at the lower part of the face shell plate (1a), and the number of the supporting plates (3) is two; the LCD display screen (4) is arranged on the face shell plate (1a) and is positioned below the supporting plate (3).

Preferably, the middle part of the front surface of the panel (1a) is provided with a mobile phone supporting protrusion (5), the panel (1a) is provided with a plurality of through holes (1aa), the through holes (1aa) are in a strip shape, the through holes (1aa) are distributed around the supporting protrusion (5) and are in a radiating shape with the center facing outwards, the middle part of the rear surface of the back panel (1b) is provided with a fixing part (6) used for being installed on a vehicle, and the fixing part (6) is provided with threads.

Has the advantages that: the gas detection circuit of the utility model improves the reliability and accuracy of detection through a series of measures such as sensitivity adjustment, temperature compensation, operational amplification, an isolation circuit and voltage clamping; the charging support comprising the gas detection circuit is novel in concept, reasonable in design and convenient to use, and integrates the charging support for supporting the mobile phone and the circuit for detecting air, so that the charging support has the functions of detecting air quality, displaying and giving an alarm, the cost is reduced, and the space is saved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and the embodiments in the drawings do not constitute any limitation to the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without any creative efforts.

Fig. 1 is a schematic diagram of an embodiment of the gas detection circuit of the present invention.

Fig. 2 is a circuit diagram of an embodiment of the gas detection circuit of the present invention.

Fig. 3 is a schematic diagram of an embodiment of the present invention including the gas detection circuit.

Fig. 4 is a schematic structural view of an embodiment of the charging stand of the present invention.

Fig. 5 is a schematic structural view of the second embodiment of the charging stand of the present invention.

Detailed Description

The technical solution of the present invention will be described in further detail with reference to the accompanying drawings and embodiments, which are preferred embodiments of the present invention. It is to be understood that the described embodiments are merely a subset of the embodiments of the invention, and not all embodiments; it should be noted that, in the present invention, the embodiments and features of the embodiments may be combined with each other without conflict. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

Example one

An embodiment of the utility model provides a gas detection circuit, as shown in FIG. 1, specifically can include following module: the gas sensor comprises a semiconductor gas sensor, an operational amplifier circuit with temperature compensation and an isolation circuit for avoiding the coupling effect between circuits, wherein the semiconductor gas sensor, the operational amplifier circuit with temperature compensation and the isolation circuit are sequentially and electrically connected, and the isolation circuit outputs a detection signal.

Common gas sensors include contact combustion gas sensors, electrochemical gas sensors, semiconductor gas sensors, and the like. The semiconductor gas sensor is the semiconductor class sensor of detectable VOC, formaldehyde to have like the advantage of background art, therefore, the utility model discloses a gas sensor adopts the gas sensor of semiconductor class. The semiconductor sensor mainly uses a semiconductor as a sensitive material, changes the carrier concentration or distribution in the semiconductor material under the action of various physical quantities, and realizes gas sensitivity by detecting the changes of the physical properties. If the gas contacts the heated metal oxide or other semiconductor material, the resistance of the semiconductor substrate increases or decreases, and the gas is identified by the amount of change in the electrical signal.

As shown in fig. 2, in the present embodiment, the operational amplifier circuit with temperature compensation includes a first operational amplifier (a1), a variable resistor (R)_T) The gas sensor comprises a semiconductor gas sensor, a first resistor (R1) and a first capacitor (C1), wherein the positive input end of the first operational amplifier (A1) is electrically connected with the output end of the semiconductor gas sensor, a parallel circuit consisting of the first capacitor (C1) and the first resistor (R1) is connected between the negative input end and the output end in a bridging mode, and the negative input end of the first operational amplifier (A1) also passes through the variable resistor (R1)_T) And (4) grounding.

As described above, the semiconductor gas sensor distinguishes gases by the amount of change in electrical signal of the semiconductor substrate due to increase or decrease in resistance, and even if the gas concentration is the same, the semiconductor substrate of the semiconductor gas sensor has a resistance value in the gas that varies with different ambient humidity temperatures, i.e., the magnitude of the resistance value of the semiconductor gas sensor is related to the humidity temperature: the resistance value is smaller when the temperature and the humidity are higher. Therefore, temperature compensation is required for suppressing temperature drift of the detection signal of the semiconductor gas sensor.

In practical application, the variable resistor (R) for temperature compensation is used according to the relation between the internal resistance of different semiconductor gas sensors and the ambient temperature_T) There are two different options:

first, when the internal resistance of the semiconductor gas sensor is in a proportional relationship with the ambient temperature, the variable resistance is a thermistor in a proportional relationship with the ambient temperature.

Second, when the internal resistance of the semiconductor gas sensor is inversely proportional to the ambient temperature, the variable resistance is a thermistor inversely proportional to the ambient temperature.

As a preferred embodiment of the utility model, we choose the model of the semiconductor gas sensor as TGS812, the

ports

2 and 3 of the semiconductor gas sensor TGS812 are connected with the power supply, and the port 4 is grounded; a thermistor which is in direct proportion to the ambient temperature is selected as the variable resistor.

In this embodiment, the isolation circuit includes a second operational amplifier (a2) and a second resistor (R2), the negative input terminal of the second operational amplifier (a2) is shorted with the output terminal, and the positive input terminal is electrically connected to the output terminal of the operational amplifier (a1) through the second resistor (R2).

In an alternative example, the gas detection circuit further comprises a sensitivity adjustment circuit consisting of an adjustable resistor (Rp) disposed between the positive input terminal of the first operational amplifier (a1) and the output terminal of the semiconductor gas sensor.

The sensitivity of a sensor is the ratio of the output value to the measured input value when the output signal tends to stabilize, and is usually determined by the techniques involved in the sensor structure. Generally, the higher the sensitivity of the sensor, the higher the accuracy of its output signal. However, the sensitivity is too high, which may cause the output stability of the sensor to be reduced, and therefore, a sensitivity adjusting circuit is added between the output end and the load in practical application. In particular, the adjustable resistor may be a self-locking organic solid potentiometer.

In another alternative example, the gas detection circuit further comprises a clamping circuit, the clamping circuit is composed of a first diode (D1) and a second diode (D2), the cathode of the first diode (D1) is electrically connected with the output end of the isolation circuit, the anode is grounded, the anode of the second diode (D2) is electrically connected with the output end of the isolation circuit, and the cathode is connected with the power supply.

The clamp circuit limits the voltage output by the isolation circuit within the allowable input voltage range of the central processing circuit, avoids the damage to the central processing circuit when the voltage output by the isolation circuit is overhigh, ensures the normal work of the circuit, and improves the reliability and the stability of the work of equipment.

The detailed working principle in this example is: the semiconductor gas sensor TGS812 port 1 outputs the induction electric signal with the intensity corresponding to TVOC and formaldehyde to the temperature compensation operational amplification circuit for temperature compensation and signal amplification through the sensitivity adjustment of the adjustable resistor (Rp) of the sensitivity adjustment circuit, and provides a measurement signal for the central processing unit through the isolation circuit and the clamping circuit in sequence. Normally, the internal resistance between the

pins

1 and 2 of the TGS812 is high, and when harmful gas is detected, the internal resistance is reduced along with the detection concentration, and the output signal intensity is increased and increased along with the increase of temperature. Variable resistance (R) when temperature rises_T) The resistance of the thermistor (proportional to the ambient temperature) is increased by the variable resistor (R)_T) The variable resistor (R) is known by a voltage division circuit formed by the first resistor (R1)_T) The division of (A) is increased, as can be seen from the comparison amplifier principle, so that the amplification factor of the first operational amplifier (A1) is reduced, thereby enabling the first operational amplifier to perform the first operationThe output signal Uo of the amplifier (a1) becomes smaller as the input signal Ui increases. The variable resistor (R)_T) The temperature compensation circuit can be a platinum thermal resistor, and the platinum thermal resistor has good linearity in the temperature range of 0-100 ℃ (the resistance value of the platinum thermal resistor increases along with the rise of the temperature), so the platinum thermal resistor can play a good compensation role when being used in the temperature compensation circuit. Thus, a variable resistor (R) is used_T) The resistance value of the gas detection circuit is increased along with the increase of the temperature, so that the signal of the gas detection circuit is reduced, the processed output signal can correctly reflect the actual situation, and the reliability and the accuracy of detection are improved.

Example two

In a second aspect, the present invention provides a charging stand, as shown in fig. 3, 4 and 5, which specifically includes the following modules: a central processing unit, a power supply circuit, the gas detection circuit of the first aspect and a holder body (1), the central processing unit, the power supply circuit and the gas detection circuit being electrically connected to each other; the left side and the right side of the support main body (1) are provided with clamping arms (2) for clamping a mobile phone, the lower part of the support main body is provided with a supporting plate (3) for supporting the mobile phone, and the upper part of the support main body is also provided with an LCD display screen (4); the central processing unit converts an analog detection signal output by the gas detection circuit and collected by a built-in integrated digital-to-analog converter into a digital signal; the central processing unit compares the digital signal converted by the digital-to-analog converter with a preset threshold value stored in advance; the central processor displays the comparison result through an LCD display screen (4); the model of the central processor is AT89C 51.

In an optional embodiment, the system further comprises a PM2.5 sensor, a carbon monoxide sensor and an alarm which are all electrically connected with the central processing unit, wherein the model of the PM2.5 detection circuit is PMSA003, and the model of the carbon monoxide sensor is TGS 5141; the bracket main body (1) comprises a front shell plate (1a) arranged at the front part and a back shell plate (1b) arranged at the rear part, and a cavity is formed between the front shell plate (1a) and the back shell plate (1 b); the supporting plates (3) are arranged at the lower part of the face shell plate (1a), and the number of the supporting plates (3) is two; the LCD display screen (4) is arranged on the face shell plate (1a) and is positioned below the supporting plate (3).

Specifically, the middle part of the front surface of the face shell plate (1a) is provided with a mobile phone supporting protrusion (5), the face shell plate (1a) is provided with a plurality of through holes (1aa), the through holes (1aa) are in a strip shape, the through holes (1aa) are distributed around the supporting protrusion (5) and are in a radiating shape with the center facing outwards, the middle part of the rear surface of the back shell plate (1b) is provided with a fixing part (6) used for being installed on a vehicle, and the fixing part (6) is provided with threads.

In the specific implementation process, the support main body (1) is formed by connecting and assembling a face shell plate (1a) and a back shell plate (1b), a cavity is formed between the face shell plate and the back shell plate, and the support main body is mainly used for arranging all circuits. When the mobile phone needs to be clamped, the mobile phone is clamped and placed on the front face of the whole support main body (1), namely the front face of the panel (1a) in the embodiment, through the clamping arm (2) and the supporting plate (3). A central processing unit and a peripheral circuit thereof are arranged in a cavity between the face shell plate 1a and the back shell plate 1 b.

In the embodiment, in order to clamp the mobile phone, especially mobile phones with different sizes, the width between the two clamping arms (2) is adjusted to clamp the mobile phone. Specifically, a pressing block (7) is arranged below each clamping arm (2), the pressing block (7) extends into a cavity formed between the face shell plate (1a) and the back shell plate (1b), and is connected to the clamping arm (2) on the opposite side through a rigid connecting rod (not shown in the figure) in the inner part, so that when one hand presses the two pressing blocks (7) simultaneously, the two clamping arms (2) are outwards opened, a return spring is arranged in the inner part, when the force pressing the pressing blocks (7) disappears, the pressing blocks (7) reset under the action of the return spring, and meanwhile, the two clamping arms (2) are folded towards the middle, so that the clamping and fixing of the mobile phone are completed.

To sum up, the embodiment of the present invention provides a gas detection circuit and a charging stand, wherein a semiconductor gas sensor TGS812 port 1 outputs an induced electrical signal with corresponding strength to TVOC and formaldehyde to a calculation amplifying circuit with temperature compensation for temperature compensation and signal amplification through the sensitivity adjustment of an adjustable resistor (Rp) of a sensitivity adjusting circuit, and provides a measurement signal for a central processing unit through an isolation circuit and a clamping circuit in sequence; the central processing unit converts an analog detection signal output by the gas detection circuit and collected by a built-in integrated digital-to-analog converter into a digital signal; the central processing unit compares the digital signal converted by the digital-to-analog converter with a preset threshold value stored in advance; and the central processor displays the comparison result through an LCD display screen (4).

Normally, the internal resistance between the

pins

1 and 2 of the TGS812 is high, and when harmful gas is detected, the internal resistance is reduced along with the detection concentration, and the output signal intensity is increased and increased along with the increase of temperature. Variable resistance (R) when temperature rises_T) The resistance of the thermistor (proportional to the ambient temperature) is increased by the variable resistor (R)_T) The variable resistor (R) is known by a voltage division circuit formed by the first resistor (R1)_T) The division voltage of the first operational amplifier (a1) is increased, and the amplification factor of the first operational amplifier (a1) is decreased according to the comparison amplifier principle, so that the output signal Uo of the first operational amplifier (a1) is decreased along with the increase of the input signal Ui. The variable resistor (R)_T) The temperature compensation circuit can be a platinum thermal resistor, and the platinum thermal resistor has good linearity in the temperature range of 0-100 ℃ (the resistance value of the platinum thermal resistor increases along with the rise of the temperature), so the platinum thermal resistor can play a good compensation role when being used in the temperature compensation circuit. Thus, a variable resistor (R) is used_T) The resistance value of the gas detection circuit is increased along with the increase of the temperature, so that the signal of the gas detection circuit is reduced, the processed output signal can correctly reflect the actual situation, and the reliability and the accuracy of detection are improved.

The charging support has the advantages of novel concept, reasonable design and convenience in use, and the charging support supporting the mobile phone is integrated with a circuit used for detecting air, so that the charging support has the air quality detection function, the alarm function is displayed and sent, the cost is reduced, and the space is saved. In the application aspect of products, although the application is originally developed to be applied to the interior of an automobile cab, the practical application is also suitable for various environments, such as factories, mining rooms, indoor places and other scenes needing to combine the support and the air detection function. It should be noted that the support of the present invention can be used as a mobile phone support, and can also be used to support other accessories, such as a recorder, as long as the support can be effectively installed on the device.

It should be noted that all the directional indicators (such as upper, lower, left, right, front and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the motion situation, etc. in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indicator is changed accordingly.

In addition, the descriptions related to "first", "second", etc. in the present invention are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicit ly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions in the embodiments may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should not be considered to exist, and is not within the protection scope of the present invention.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention.

Claims

1. A gas detection circuit, comprising: the gas sensor comprises a semiconductor gas sensor, an operational amplifier circuit with temperature compensation and an isolation circuit; the output end of the semiconductor gas sensor is electrically connected with the input end of the operational amplifier circuit with temperature compensation, the output end of the operational amplifier circuit with temperature compensation is electrically connected with the input end of the isolation circuit, and the isolation circuit outputs a detection signal:

wherein the operational amplifier circuit with temperature compensation comprises a first operational amplifier (A1), a variable resistor (R)_T) The gas sensor comprises a semiconductor gas sensor, a first resistor (R1) and a first capacitor (C1), wherein the positive input end of a first operational amplifier (A1) is electrically connected with the output end of the semiconductor gas sensor, a parallel circuit composed of the first capacitor (C1) and a first resistor (R1) is bridged between the negative input end and the output end of the first operational amplifier (A1), and the negative input end of the first operational amplifier (A1) also passes through the variable resistor (R1)_T) And (4) grounding.

2. The gas detection circuit of claim 1, wherein when the internal resistance of the semiconductor gas sensor is in direct proportion to the ambient temperature, the variable resistance is a thermistor in direct proportion to the ambient temperature; or, when the internal resistance of the semiconductor gas sensor is inversely proportional to the ambient temperature, the variable resistance is a thermistor inversely proportional to the ambient temperature.

3. The gas detection circuit of claim 1, wherein the isolation circuit comprises a second operational amplifier (a2) and a second resistor (R2), the negative input terminal of the second operational amplifier (a2) being shorted to the output terminal, the positive input terminal being electrically connected to the output terminal of the first operational amplifier (a1) through a second resistor (R2).

4. The gas detection circuit of claim 1, wherein the semiconductor gas sensor model is TGS 812.

5. A gas detection circuit according to any of claims 1 to 3, further comprising an adjustable resistor (R)_p) A sensitivity adjusting circuit composed ofAdjustable resistance (R)_p) Is arranged between the positive input end of the first operational amplifier (A1) and the output end of the semiconductor gas sensor; the adjustable resistor is a self-locking organic solid potentiometer.

6. The gas detection circuit according to any one of claims 1-4, further comprising a clamping circuit, wherein the clamping circuit comprises a first diode (D1) and a second diode (D2), the cathode of the first diode (D1) is electrically connected to the output terminal of the isolation circuit, the anode is grounded, the anode of the second diode (D2) is electrically connected to the output terminal of the isolation circuit, and the cathode is connected to a power supply.

7. A charging stand comprising a central processor, a power supply circuit, characterized by further comprising a gas detection circuit according to any one of claims 1 to 6 and a stand body (1), the central processor, the power supply circuit and the gas detection circuit being electrically connected to each other; the left side and the right side of the support main body (1) are provided with clamping arms (2) for clamping a mobile phone, the lower part of the support main body is provided with a supporting plate (3) for supporting the mobile phone, and the upper part of the support main body is also provided with an LCD display screen (4); the central processing unit converts the acquired analog detection signal output by the gas detection circuit into a digital signal by using a built-in integrated digital-to-analog converter; the central processing unit compares the digital signal converted by the digital-to-analog converter with a preset threshold value stored in advance; the central processor displays the comparison result through an LCD display screen (4); the model of the central processor is AT89C 51.

8. The charging stand of claim 7, further comprising a PM2.5 sensor, a carbon monoxide sensor and an alarm, all electrically connected to the central processor, wherein the PM2.5 detection circuit is model PMSA003, the carbon monoxide sensor is model TGS 5141; the bracket main body (1) comprises a front shell plate (1a) arranged at the front part and a back shell plate (1b) arranged at the rear part, and a cavity is formed between the front shell plate (1a) and the back shell plate (1 b); the supporting plates (3) are arranged at the lower part of the face shell plate (1a), and the number of the supporting plates (3) is two; the LCD display screen (4) is arranged on the face shell plate (1a) and is positioned below the supporting plate (3).

9. The charging support according to claim 8, wherein a mobile phone supporting protrusion (5) is disposed in the middle of the front surface of the panel (1a), the panel (1a) is provided with a plurality of through holes (1aa), the through holes (1aa) are in a strip shape, the through holes (1aa) are arranged around the supporting protrusion (5) and are in a radial shape with the center facing outwards, a fixing member (6) for being mounted on a vehicle is disposed in the middle of the rear surface of the back panel (1b), and a thread is disposed on the fixing member (6).