Gas sensor device

Abstract

The utility model discloses a gas sensor device, which belongs to the technical field of semiconductor gas detection and is characterized in that a main circuit board is arranged in a shell, a reference resistor is fixed on the outer surface of the shell through a reference resistor base, and a gas sensitive sensor is fixed on the outer surface of the shell through a sensor base; the main circuit board comprises a universal serial bus interface circuit, a serial port data processing circuit, a main control chip, an analog-to-digital converter, a reference resistor switching circuit and a gas-sensitive sensor interface, the main control chip controls switching of reference resistors through the reference resistor switching circuit, the reference resistors are connected with the gas-sensitive sensor, and the gas-sensitive sensor interface is connected with the analog-to-digital converter. The analog-to-digital converter measures the midpoint voltage of the reference resistor and the gas-sensitive sensor, the main control chip reads the midpoint voltage obtained by the analog-to-digital converter, and the main control chip is externally connected with an upper computer through the serial port data processing circuit and the universal serial bus interface circuit. The device is good in stability, high in collection real-time performance, less in external interference and capable of detecting the gas concentration around a worker at any time.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of semiconductor gas detection, especially relates to a small -size gas sensor device of remote detection. BACKGROUND

[0002] Gas sensors are mainly divided into handheld sensors and fixed sensors. Fixed sensors have better resistance to external interference and vibration, can realize continuous monitoring of environmental data, and do not need manual continuous intervention. However, fixed sensors also have some limitations, mainly manifested in that they must be installed in a specific position, and special installation equipment is required, which limits their mobility and flexibility. This means that when it is necessary to temporarily monitor the gas concentration of an area and carry out work, the user cannot quickly install the fixed sensor, and needs to face the problem of disassembly after the completion of the later work, which increases the inconvenience and cost of use, and the maintenance and maintenance of the fixed sensor are relatively complicated, and because the sensor is in a fixed position for a long time, it is easily affected by dust, moisture and other external environments, and needs to be cleaned and calibrated regularly, and the manual maintenance cost is high.

[0003] Common metal oxide sensors can only perform gas-sensitive tests on the characteristics of a single metal oxide, and cannot adapt to complex situations in reality. UTILITY MODEL CONTENTS

[0004] The utility model aims at seeking to design a small -size gas sensor device and method of remote detection, and provides a more flexible and convenient gas monitoring solution for users.

[0005] In order to achieve the above-mentioned purpose, the utility model relates to a kind of gas sensor device, including shell, main circuit board, reference resistance, reference resistance pedestal, gas-sensitive sensor and sensor pedestal, main circuit board is built into shell, reference resistance is fixed on the outer surface of shell by reference resistance pedestal, gas-sensitive sensor is fixed on the outer surface of shell by sensor pedestal;Wherein, main circuit board includes universal serial bus interface circuit, serial data processing circuit, main control chip, analog-digital converter, reference resistance switching circuit and gas-sensitive sensor interface;Main control chip is connected with reference resistance switching circuit, reference resistance switching circuit is connected with multiple reference resistances respectively, main control chip controls reference resistance switching by reference resistance switching circuit, reference resistance and gas-sensitive sensor interface are connected, gas-sensitive sensor is connected with gas-sensitive sensor interface by sensor pedestal, analog-digital converter is connected with the midpoint of reference resistance and gas-sensitive sensor connecting line, for measuring the midpoint voltage of reference resistance and gas-sensitive sensor, main control chip is connected with analog-digital converter, for reading the midpoint voltage obtained by analog-digital converter, main control chip and serial data processing circuit are connected, serial data processing circuit is connected with universal serial bus interface circuit, universal serial bus interface circuit is externally connected with host computer.

[0006] The main circuit board further comprises a power supply circuit, a 3.3V voltage stabilizing circuit, a 5V voltage stabilizing circuit, a rectifier circuit and a reference voltage source circuit; the input end of the 5V voltage stabilizing circuit is connected with the output end of the power supply circuit, and is used for converting the voltage input by the power supply circuit into a stable 5V voltage output; the input end of the rectifier circuit is connected with the output end of the 5V voltage stabilizing circuit, and is used for outputting a 5V voltage with low bottom noise; the output end of the rectifier circuit is connected with an analog-digital converter, a reference resistance switching circuit, a gas sensor interface and the reference voltage source circuit respectively; the output end of the rectifier circuit is connected with the analog-digital converter through the reference voltage source circuit; the input end of the 3.3V voltage stabilizing circuit is connected with the output end of the power supply circuit, and the output end of the 3.3V voltage stabilizing circuit is connected with a serial port data processing circuit and a master control chip.

[0007] It should be noted that: the reference resistance switching circuit comprises a P-channel enhancement mode field effect transistor Q4, a P-channel enhancement mode field effect transistor Q5, a P-channel enhancement mode field effect transistor Q6, a resistor R32, a resistor R33 and a resistor R34; the reference resistance comprises a reference resistor R35, a reference resistor R36 and a reference resistor R37, the reference resistor R35, the reference resistor R36 and the reference resistor R37 have different resistance values, and the analog-digital converter comprises an ADC chip; the gate of the P-channel enhancement mode field effect transistor Q4 is connected with the IO25 pin of the master control chip and one end of the resistor R32 respectively, the other end of the resistor R32 is grounded, one end of the reference resistor R35 is connected with the drain of the P-channel enhancement mode field effect transistor Q4, and the source of the P-channel enhancement mode field effect transistor Q4 is connected with the 3rd pin of the sliding switch SW7; the gate of the P-channel enhancement mode field effect transistor Q5 is connected with the IO32 pin of the master control chip and one end of the resistor R33 respectively, the other end of the resistor R33 is grounded, one end of the reference resistor R36 is connected with the drain of the P-channel enhancement mode field effect transistor Q5, and the source of the P-channel enhancement mode field effect transistor Q5 is connected with the 3rd pin of the sliding switch SW7; the gate of the P-channel enhancement mode field effect transistor Q6 is connected with the IO21 pin of the master control chip and one end of the resistor R34 respectively, the other end of the resistor R34 is grounded, one end of the reference resistor R37 is connected with the drain of the P-channel enhancement mode field effect transistor Q6, and the source of the P-channel enhancement mode field effect transistor Q6 is connected with the 3rd pin of the sliding switch SW7; the other ends of the reference resistor R35, the reference resistor R36 and the reference resistor R37 are connected with the gas sensor interface, and the AINP pin of the ADC chip is connected on the line between the reference resistor R35, the reference resistor R36 or the reference resistor R37 and the gas sensor interface.

[0008] Specifically, the gas sensor interface includes a pad U8, the 4th pin of the pad U8 is grounded, the pad U8 is connected to the sensor base 4 through a flying wire, the other ends of the reference resistors R35, R36 and R37 are connected to the 3rd pin of the pad U8, the AINP pin of the ADC chip is connected to one end of the capacitor C20, the connection lines of the reference resistors R35, R36 and R37 and the 3rd pin of the pad U8 are connected to the other end of the capacitor C20, and the AINGND pin of the ADC chip is connected to the other end of the capacitor C20 and grounded.

[0009] It should be noted that the IO12, IO13 and IO14 pins of the main control chip 203 are respectively connected to the SDO-0, SCLK and SDI pins of the ADC chip.

[0010] It should be noted that the serial port data processing circuit includes a serial port data processing chip U9, the D+ and D- pins of the serial port data processing chip U9 are differentially connected to the DP1, DP2, DN1 and DN2 pins of the universal serial bus interface circuit 201, the TXD and RXD pins of the serial port data processing chip U9 are respectively connected to the TXD0 and RXD0 pins of the main control chip, the main control chip has a built-in wireless communication unit, and the wireless communication unit is used for communication with a terminal device.

[0011] It should be noted that the reference voltage source circuit includes a reference voltage chip U1, a capacitor C2 and a capacitor C4, the two ends of the capacitor C2 are respectively connected to the VIN and GND pins of the reference voltage chip U1, the TRIM / NR pin of the reference voltage chip U1 is connected to one end of the capacitor C4, the other end of the capacitor C4 is grounded, the GND pin of the reference voltage chip U1 is grounded, the VOUT pin of the reference voltage chip U1 is connected to the REFIO pin of the ADC chip, the REFIO pin of the ADC chip is connected to one end of the resistor R5, the other end of the resistor R5 is connected to the capacitor C12, and the other end of the capacitor C12 is grounded.

[0012] As an implementation manner, the 3.3V voltage stabilizing chip circuit includes a voltage stabilizing chip U5, the GND pin of the voltage stabilizing chip U5 is grounded, the VOUT pin of the voltage stabilizing chip U5 is connected to the serial port VDD33 of the main control chip, the serial port VCC of the serial port data processing chip U9, the DVDD and RST# pins of the ADC chip, the VIN pin of the voltage stabilizing chip U5 is connected to an output end of a power supply circuit.

[0013] As an implementation form, the 5V voltage stabilizing chip circuit comprises a voltage stabilizing chip U72, a diode D74, an inductor L75, a capacitor C78, a capacitor C738, a resistor R72 and a resistor R74, the SW pin of the voltage stabilizing chip U72 is connected with the anode of the diode D74 and one end of the inductor L75 respectively, the VIN pin of the voltage stabilizing chip U72 is connected with the other end of the inductor L75, one end of the capacitor C78 and the capacitor C738 parallel circuit and the output end of the power supply circuit 207 respectively, the GND pin of the voltage stabilizing chip U72 is connected with the other end of the capacitor C78 and the capacitor C738 parallel circuit and one end of the resistor R74 respectively, and the other end of the resistor R74 is connected with one end of the resistor R72 and the FB pin of the voltage stabilizing chip U72, and the other end of the resistor R72 is connected with the cathode of the diode D74 and then connected with the input end of the rectifier circuit 210.

[0014] As an implementation form, the rectifier circuit comprises a rectifier chip U4, a resistor R6, a resistor R15 and a capacitor C18, the IN and EN pins of the rectifier chip U4 are connected with the output end of the 5V voltage stabilizing circuit 209, the NR / SS pin of the rectifier chip U4 is connected with one end of the capacitor 18, the other end of the capacitor 18 is grounded, the PwPd and GND pins of the rectifier chip U4 are grounded, the resistor R6 and the resistor R15 are connected to form a series circuit, the other end of the resistor R15 is grounded, the other end of the resistor R6 is connected with the OUT pin of the rectifier chip U4, and the OUT pin of the rectifier chip U4 is connected with the 2nd pin of the sliding switch SW7 of the reference resistor switching circuit 205, the VIN pin of the reference voltage stabilizing chip U1 and the AVDD and RST# pins of the analog-digital converter 204.

[0015] The main circuit board is divided into a digital circuit part and an analog circuit measurement part, and a 0-ohm resistor is connected between the digital ground plane and the analog ground plane to reduce the influence of digital noise on analog measurement.

[0016] The power supply circuit of the embodiment is connected with an AC power supply through a universal serial bus interface or connected with a built-in battery, the shell comprises an upper support plate, a rectangular frame and a bottom plate, the upper support plate is fixed at the upper opening of the rectangular frame, the bottom plate is fixed at the lower opening of the rectangular frame, two through holes are formed in the upper support plate, a reference resistor base and a sensor base are fixedly arranged on the through holes respectively, the reference resistor is fixed on the reference resistor base, the sensor is installed on the sensor base, the main circuit board is installed in the cavity surrounded by the rectangular frame, the reference resistor and the sensor are connected with the main circuit board through the through holes below respectively, and the battery is fixed in the rectangular frame and located on the lower side of the main circuit board.

[0017] Compared with the prior art, the utility model has the following beneficial effects: (1) the sensor base and side wall are smooth, can be fixed on the wall or placed on the ground, need not rely on fixed sensor, the structure is small and exquisite, convenient to carry, maintenance and maintenance cost is low, can use as fixed sensor also can use as mobile handheld sensor;(2) good stability, strong real-time performance of acquisition, less by outside interference, can detect gas concentration situation around staff at any time;(3) through wireless communication module and terminal equipment connection, convenient for detection personnel to check detection result in time outdoors, convenient for the detection of toxic gas;(4) interdigital electrode piece is placed outside sensor shell, when using, the sensor material is attached to interdigital electrode piece, and the detection of different gas can be realized by replacing different gas sensitive sensor material, convenient to replace, and strong universality;(5) power supply circuit can be powered by universal serial bus interface also can be connected with battery, convenient to use. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 It is a three-dimensional structure diagram of a small gas sensor device for remote detection related to embodiment 1.

[0019] Figure 2 It is the structure explosion map of Figure 1 .

[0020] Figure 3 It is the main circuit board circuit diagram related to embodiment 1.

[0021] Figure 4 It is the gas sensitive sensor interface circuit diagram related to embodiment 1.

[0022] Figure 5 It is the reference resistance switching circuit circuit diagram related to embodiment 1.

[0023] Figure 6 It is the ESP32 master control chip circuit diagram related to embodiment 1.

[0024] Figure 7 It is the analog-digital converter chip circuit diagram related to embodiment 1.

[0025] Figure 8 It is the universal serial bus interface circuit and serial data processing circuit 202 circuit diagram related to embodiment 1.

[0026] Figure 9 It is the reference voltage source circuit circuit diagram related to embodiment 1.

[0027] Figure 10 It is the 5V voltage stabilizing circuit circuit diagram related to embodiment 1.

[0028] Figure 11 It is the rectifier circuit circuit diagram related to embodiment 1.

[0029] Figure 12 Circuit diagram of 3.3V voltage stabilizing circuit involved in example 1. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, rather than all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the utility model.

[0031] As Figures 1-3 The utility model relates to a kind of gas sensor devices, including shell 1, main circuit board 2, reference resistance, reference resistance pedestal 5, gas sensor and sensor pedestal 4, main circuit board 2 is built into shell 1, reference resistance is fixed on the outer surface of shell 1 by reference resistance pedestal 5, gas sensor is fixed on the outer surface of shell 1 by sensor pedestal 4;

[0032] Wherein, main circuit board 2 includes universal serial bus interface circuit 201, serial port data processing circuit 202, main control chip 203, analog-digital converter 204, reference resistance switching circuit 205 and gas sensor interface 206;

[0033] Main control chip 203 is connected with reference resistance switching circuit 205, reference resistance switching circuit 205 is connected with multiple reference resistances respectively, main control chip 203 controls reference resistance switching by reference resistance switching circuit 205, reference resistance and gas sensor interface 206 are connected, gas sensor is connected with gas sensor interface 206 by sensor pedestal 4, analog-digital converter 204 is connected with the midpoint of reference resistance and gas sensor connecting line, for measuring the midpoint voltage of reference resistance and gas sensor, main control chip 203 is connected with analog-digital converter 204, for reading the midpoint voltage obtained by analog-digital converter 204, main control chip 203 is connected with serial port data processing circuit 202, serial port data processing circuit 202 is connected with universal serial bus interface circuit 201, universal serial bus interface circuit 201 is connected with host computer, and data interaction is realized with host computer.

[0034] As Figure 3As shown, the main circuit board 2 further comprises a power supply circuit 207, a 3.3V voltage stabilizing circuit 208, a 5V voltage stabilizing circuit 209, a rectifier circuit 210 and a reference voltage source circuit 211; the input end of the 5V voltage stabilizing circuit 209 is connected with the output end of the power supply circuit 207, for converting the voltage input by the power supply circuit 207 into a stable 5V voltage output, the input end of the rectifier circuit 210 is connected with the output end of the 5V voltage stabilizing circuit 209, for outputting a 5V voltage with low bottom noise, the output end of the rectifier circuit 210 is connected with the analog-digital converter 204, the reference resistance switching circuit 205, the gas sensor interface 206 and the reference voltage source circuit 211 respectively, for providing power supply for them; the output end of the rectifier circuit 210 is connected with the analog-digital converter 204 through the reference voltage source circuit 211, for providing a reference voltage 4.096V for quantization level division for the analog-digital converter 204; the input end of the 3.3V voltage stabilizing circuit 208 is connected with the output end of the power supply circuit 207, and the output end of the 3.3V voltage stabilizing circuit 208 is connected with the serial port data processing circuit 202 and the main control chip 203, for providing power supply for them.

[0035] It should be noted that: the main control chip 203 connected with the reference resistance switching circuit 205, the reference resistance switching circuit 205 connected with the reference resistance, the main control chip 203 controls the reference resistance switching through the reference resistance switching circuit 205, the reference resistance connected with the gas sensor interface 206, the gas sensor connected with the gas sensor interface 206 through the sensor base 4, the analog-digital converter 204 connected with the midpoint of the connection line between the reference resistance and the gas sensor interface 206, for measuring the midpoint voltage of the reference resistance and the gas sensor, specifically: Figures 4-7As shown, the reference resistance switching circuit 205 includes a P-channel enhancement-mode field effect transistor Q4, a P-channel enhancement-mode field effect transistor Q5, a P-channel enhancement-mode field effect transistor Q6, a resistor R32, a resistor R33, a resistor R34, the reference resistance includes a reference resistance R35, a reference resistance R36 and a reference resistance R37, the reference resistance R35, the reference resistance R36 and the reference resistance R37 have different resistance values, and the analog-digital converter 204 includes an ADC chip (for example, ADS8681); the gate of the P-channel enhancement-mode field effect transistor Q4 is connected to the IO25 pin of the master control chip 203 and one end of the resistor R32 respectively, the other end of the resistor R32 is grounded, one end of the reference resistance R35 is connected to the drain of the P-channel enhancement-mode field effect transistor Q4, and the source of the P-channel enhancement-mode field effect transistor Q4 is connected to the 3rd pin of the sliding switch SW7; the gate of the P-channel enhancement-mode field effect transistor Q5 is connected to the IO32 pin of the master control chip 203 and one end of the resistor R33 respectively, the other end of the resistor R33 is grounded, one end of the reference resistance R36 is connected to the drain of the P-channel enhancement-mode field effect transistor Q5, and the source of the P-channel enhancement-mode field effect transistor Q5 is connected to the 3rd pin of the sliding switch SW7; the gate of the P-channel enhancement-mode field effect transistor Q6 is connected to the IO21 pin of the master control chip 203 and one end of the resistor R34 respectively, the other end of the resistor R34 is grounded, one end of the reference resistance R37 is connected to the drain of the P-channel enhancement-mode field effect transistor Q6, and the source of the P-channel enhancement-mode field effect transistor Q6 is connected to the 3rd pin of the sliding switch SW7; the other ends of the reference resistance R35, the reference resistance R36 and the reference resistance R37 are connected to the gas sensor interface 206, and the AINP pin of the ADC chip is connected on the line between the reference resistance R35, the reference resistance R36 or the reference resistance R37 and the gas sensor interface 206.

[0036] Specifically, the gas sensor interface 206 includes a pad U8, the 4th pin of the pad U8 is grounded, the pad U8 is connected to the sensor base 4 through a flying wire, the other ends of the reference resistance R35, the reference resistance R36 and the reference resistance R37 are connected to the 3rd pin of the pad U8, the AINP pin of the ADC chip is connected to one end of the capacitor C20, the line between the reference resistance R35, the reference resistance R36 and the reference resistance R37 and the 3rd pin of the pad U8, the AINGND pin of the ADC chip is connected to the other end of the capacitor C20 and grounded, that is, connected to the midpoint of the line between the gas sensor and the reference resistance switching circuit 205. The capacitor C20 is used to filter the noise of the midpoint voltage. The ADC chip measures the midpoint voltage IOMID between the reference resistance and the gas sensor to be measured through the AINP and AINGND pins of the analog end.

[0037] The pin IO25, IO32 and IO21 of the master control chip 203 in the embodiment respectively control a field effect transistor. When the pin of the master control chip 203 outputs a high level, the voltage exceeds the threshold voltage 1.3V of the field effect transistor, so that the circuit is turned on, and the current can pass through the reference resistor with different resistance. The fourth pin of the pad U8 is grounded. After the gas sensor detects the target gas, the device resistance will change, and the midpoint voltage formed between the device resistance and the reference resistance can reflect the response change of the device resistance. The resistance of the gas sensor is obtained by the measured value of the reference resistance, so that the concentration of the gas to be measured can be accurately known.

[0038] It should be noted that the master control chip 203 in the embodiment is connected with the analog-to-digital converter 204, which is used to read the midpoint voltage obtained by the analog-to-digital converter 204. Specifically, the IO12, IO13 and IO14 pins of the master control chip 203 are respectively connected with the SDO-0, SCLK and SDI pins of the ADC chip. The master control chip 203 uses the SPI protocol to communicate with the SDO-0, SCLK and SDI pins of the ADC chip through the IO12, IO13 and IO14 pins.

[0039] The master control chip 203 in the embodiment is connected with the serial data processing circuit 202, the serial data processing circuit 202 is connected with the universal serial bus interface circuit 201, the universal serial bus interface circuit 201 is externally connected with the host computer, and the data interaction between the host computer and the master control chip 203 is realized. Specifically, the serial data processing circuit 202 includes a serial data processing chip U9 (such as CH340), the D+ and D- pins of the serial data processing chip U9 are differentially connected with the DP1, DP2, DN1 and DN2 pins of the universal serial bus interface circuit 201, the TXD and RXD pins of the serial data processing chip U9 are respectively connected with the TXD0 and RXD0 pins of the master control chip 203 for communication, so that the host computer in the external environment can be connected with the master control chip 203 for communication.

[0040] The master control chip 203 in the embodiment is built-in with a wireless communication unit, such as a Bluetooth module, which communicates with a terminal device such as a mobile phone through the wireless communication unit. The terminal device is installed with a corresponding application program, and the application program integrates functions such as signal strength test, ADC raw data acquisition, voltage calculation, data fluctuation prompt, abnormal data analysis, real-time chart drawing and CSV format data.

[0041] As an implementation manner, the host computer or the terminal device obtains the resistance value of the gas sensor based on the midpoint voltage, queries a calibrated data reference table, and obtains the concentration value of the gas to be measured in the current environment.

[0042] The reference voltage source circuit 211 involved in the embodiment is connected with the analog-digital converter 204, and provides a reference voltage 4.096V for quantization stage division. Specifically, the reference voltage source circuit 211 includes a reference voltage chip U1 (such as REF5040), a capacitor C2 and a capacitor C4. The capacitor C2 is connected with the VIN and GND pins of the reference voltage chip U1 respectively, the TRIM / NR pin of the reference voltage chip U1 is connected with one end of the capacitor C4, the other end of the capacitor C4 is grounded, the GND pin of the reference voltage chip U1 is grounded, the VOUT pin of the reference voltage chip U1 is connected with the REFIO pin of the ADC chip, the REFIO pin of the ADC chip is connected with one end of the resistor R5, the other end of the resistor R5 is connected with the capacitor C12, and the other end of the capacitor C12 is grounded. This part of the circuit serves as a low-pass filter to filter high-frequency noise.

[0043] The AGND and DGND pins of the ADC chip are connected and grounded.

[0044] The REFGND pin of the ADC chip is connected with one end of the capacitor C16 and the capacitor C17 in parallel, and then grounded. The REFCAP pin of the ADC chip is connected with one end of the resistor R10, and the other end of the resistor R10 is connected with the other end of the capacitor C16 and the capacitor C17 in parallel. This part of the circuit constitutes a buffer decoupling capacitor for filtering the reference voltage input of the ADC chip.

[0045] As an implementation manner, the 3.3V voltage stabilizing chip circuit involved in the embodiment includes a voltage stabilizing chip U5 (such as AMS1117). The GND pin of the voltage stabilizing chip U5 is grounded, the VOUT pin of the voltage stabilizing chip U5 is connected with the serial port VDD33 of the master control chip 203, the serial port VCC of the serial data processing chip U9, the DVDD and RST# pins of the ADC chip, the VIN pin of the voltage stabilizing chip U5 is connected with the output end of the power supply circuit 207. The voltage stabilizing chip U5 is used to adjust the voltage of the digital circuit part to 3.3V, and then the digital end of the master control chip 203, the serial data processing chip U9 and the ADC chip are input through the VOUT pin to provide power for them.

[0046] As an implementation manner, the 5V voltage stabilizing chip circuit in the embodiment includes a voltage stabilizing chip U72 (such as XL6008E1), a diode D74, an inductor L75, a capacitor C78, a capacitor C738, a resistor R72 and a resistor R74, the SW pin of the voltage stabilizing chip U72 is connected with the anode of the diode D74 and one end of the inductor L75 respectively, the VIN pin of the voltage stabilizing chip U72 is connected with the other end of the inductor L75, one end of the capacitor C78 and the capacitor C738 parallel circuit and the output end of the power supply circuit 207 respectively, the GND pin of the voltage stabilizing chip U72 is connected with the other end of the capacitor C78 and the capacitor C738 parallel circuit and one end of the resistor R74 respectively, and is grounded at the same time, the other end of the resistor R74 is connected with one end of the resistor R72 and the FB pin of the voltage stabilizing chip U72 respectively, and the other end of the resistor R72 is connected with the cathode of the diode D74 and then connected with the input end of the rectifier circuit 210.

[0047] As an implementation manner, the rectifier circuit 210 in the embodiment includes a rectifier chip U4 (such as TPS7A4901), a resistor R6, a resistor R15 and a capacitor C18, the IN and EN pins of the rectifier chip U4 are connected with the output end of the 5V voltage stabilizing circuit 209, the NR / SS pin of the rectifier chip U4 is connected with one end of the capacitor 18, the other end of the capacitor 18 is grounded, the PwPd and GND pins of the rectifier chip U4 are grounded, the resistor R6 and the resistor R15 are connected to form a series circuit, the other end of the resistor R15 is grounded, the other end of the resistor R6 is connected with the OUT pin of the rectifier chip U4, and the OUT pin of the rectifier chip U4 is connected with the 2nd pin of the sliding switch SW7 of the reference resistor switching circuit 205, the VIN pin of the reference voltage stabilizing chip U1 and the AVDD and RST# pins of the analog-digital converter 204. The rectifier chip U4 supplies power to the analog end of the ADC chip.

[0048] The IN pin of the rectifier chip U4 inputs 5V voltage, the resistor R6 and the resistor R15 connected in series between the OUT pin and the ground, and a voltage difference is caused between the OUT pin and the FB pin. The FB pin of the rectifier chip U4 is connected with the midpoint of the two resistors, and through the ratio of the two resistors, the rectifier chip U4 outputs a low noise 3.3V voltage, and through the connection of the OUT pin with the VIN pin of the reference voltage stabilizing chip U1 and the 2nd pin of the sliding switch SW7 of the reference resistor switching circuit 205, the low noise 3.3V voltage is delivered to the reference voltage source circuit 211 and the reference resistor switching circuit 205.

[0049] The power supply circuit 207 in the embodiment is a lithium battery charging and dual power switching circuit, and the power supply circuit 207 is connected with the AC power supply through the universal serial bus interface and is also connected with the battery.

[0050] The interdigital electrode sheet is welded on the sensor base 4, and different gas sensitive sensor materials are coated on the interdigital electrode sheet for measuring the concentration of different gases. When used, different gas sensitive sensor materials are replaced to realize the detection of different gases. When detecting NO2, the sensor can be the three-dimensional porous graphene quantum dot composite material disclosed in the patent with the publication number CN114113238A and the invention name of a gas sensitive sensor based on three-dimensional porous graphene quantum dot composite material and a preparation method thereof. The material solution is dropped on the electrode sheet and dried.

[0051] The main circuit board adopts a 4-layer epoxy printed circuit board, and from top to bottom, it is a top layer, a digital ground layer, a power supply layer and a bottom layer. The through holes are used to connect the positions required by the circuit.

[0052] The main circuit board is divided into two parts, namely a digital circuit part and an analog circuit measurement part. The digital circuit part includes a lithium battery charging and dual power switching circuit 207, a universal serial bus interface circuit 201, a serial data processing circuit 202, a master control chip 203 and a 3.3V voltage stabilizing circuit 208. The analog circuit measurement part includes a 5V voltage stabilizing circuit 209, a rectifier circuit 210, a reference resistance switching circuit 205, a gas sensitive sensor interface 206 and a reference voltage source circuit 211. A 0 ohm resistor is used to connect the digital ground plane and the analog ground plane to reduce the influence of digital noise on analog measurement. The 0 ohm resistor is placed far away from the important voltage measurement chip 101 and the resistor and the measured element interface 102. The universal serial bus interface and the processing chip use equal length differential design, which helps to reduce interference and improve communication speed and quality between the serial port and the master control chip.

[0053] The shell 1 includes an upper support plate 101, a rectangular frame 102 and a bottom plate 103. The upper support plate 101 is fixed at the upper opening of the rectangular frame 102, and the bottom plate 103 is fixed at the lower opening of the rectangular frame 102. Two through holes are formed in the upper support plate 101, and a reference resistance base 5 and a sensor base 4 are respectively fixed on the through holes. The reference resistance is fixed on the reference resistance base 5, and the sensor is installed on the sensor base 4. The main circuit board 2 is installed in the cavity surrounded by the rectangular frame 102, and the reference resistance and the sensor are connected with the main circuit board 2 through the through holes below.

[0054] The small gas sensor device for remote detection according to the embodiment includes a battery 3, which is connected with the input end of the power supply circuit 207. The battery 3 is fixed in the rectangular frame 102 and located on the lower side of the main circuit board 2.

[0055] The sensor system of the embodiment takes ESP32 chip as the core controller and is composed of a control board based on a printed circuit board. The ESP32 chip exchanges data with an ADC chip ADS8681 based on SPI protocol through the circuit on the circuit board. The analog quantity measurement interface of the ADC chip measures the midpoint voltage of the reference resistor and the gas sensitive sensor through the matching circuit, and calculates the resistance of the gas sensitive sensor by using the resistance value of the reference resistor, queries the calibrated data comparison table, and thus obtains the concentration of the target gas in the current environment.

Claims

1. A gas sensor device, characterized in that, The system includes a housing, a main circuit board, a reference resistor, a reference resistor base, a gas sensor, and a sensor base. The main circuit board is built into the housing. The reference resistor is fixed to the outer surface of the housing via the reference resistor base, and the gas sensor is fixed to the outer surface of the housing via the sensor base. The main circuit board includes a universal serial bus interface circuit, a serial port data processing circuit, a main control chip, an analog-to-digital converter (ADC), a reference resistor switching circuit, and a gas sensor interface. The main control chip is connected to the reference resistor switching circuit, which is connected to multiple reference resistors. The main control chip controls the switching of the reference resistors through the reference resistor switching circuit. The reference resistors are connected to the gas sensor interface, and the gas sensor is connected to the gas sensor interface via the sensor base. The ADC is connected to the midpoint of the connection line between the reference resistor and the gas sensor to measure the midpoint voltage between them. The main control chip is also connected to the ADC to read the midpoint voltage obtained by the ADC. The main control chip is connected to the serial port data processing circuit, which is connected to the universal serial bus interface circuit. The universal serial bus interface circuit is externally connected to a host computer.

2. The gas sensor device according to claim 1, characterized in that, The main circuit board also includes a power supply circuit, a 3.3V voltage regulator circuit, a 5V voltage regulator circuit, a rectifier circuit, and a reference voltage source circuit. The input of the 5V voltage regulator circuit is connected to the output of the power supply circuit to convert the input voltage of the power supply circuit into a stable 5V voltage output. The input of the rectifier circuit is connected to the output of the 5V voltage regulator circuit to output a low-noise 5V voltage. The output of the rectifier circuit is connected to the analog-to-digital converter, the reference resistor switching circuit, the gas sensor interface, and the reference voltage source circuit, respectively. The output of the rectifier circuit is connected to the analog-to-digital converter through the reference voltage source circuit. The input of the 3.3V voltage regulator circuit is connected to the output of the power supply circuit, and the output of the 3.3V voltage regulator circuit is connected to the serial port data processing circuit and the main control chip.

3. The gas sensor device according to claim 2, characterized in that, The reference resistor switching circuit includes P-channel enhancement-mode MOSFETs Q4, Q5, and Q6, resistors R32, R33, and R34, and reference resistors R35, R36, and R37, with different resistance values ​​for each. The analog-to-digital converter includes an ADC chip. The gate of P-channel enhancement-mode MOSFET Q4 is connected to the IO25 pin of the main control chip and one end of resistor R32, with the other end of resistor R32 grounded. The drain of P-channel enhancement-mode MOSFET Q4 is connected to one end of reference resistor R35, and the source of P-channel enhancement-mode MOSFET Q4 is connected to pin 3 of the slide switch SW7. The gate of the P-channel enhancement-mode MOSFET Q5 is connected to the IO32 pin of the main control chip and one end of the resistor R33. The other end of the resistor R33 is grounded. The drain of the P-channel enhancement-mode MOSFET Q5 is connected to one end of the reference resistor R36. The source of the P-channel enhancement-mode MOSFET Q5 is connected to the third pin of the slide switch SW7. The gate of the P-channel enhancement-mode MOSFET Q6 is connected to the IO21 pin of the main control chip and one end of resistor R34, respectively. The other end of resistor R34 is grounded. The drain of the P-channel enhancement-mode MOSFET Q6 is connected to one end of reference resistor R37. The source of the P-channel enhancement-mode MOSFET Q6 is connected to the third pin of the slide switch SW7. The other ends of reference resistors R35, R36, and R37 are all connected to the gas sensor interface. The AINP pin of the ADC chip is connected to the connection line between reference resistors R35, R36, or R37 and the gas sensor interface.

4. The gas sensor device according to claim 3, characterized in that, The IO12, IO13, and IO14 pins of the main control chip 203 are connected to the SDO-0, SCLK, and SDI pins of the ADC chip, respectively.

5. The gas sensor device according to claim 4, characterized in that, The serial port data processing circuit includes a serial port data processing chip U9. The D+ and D- pins of the serial port data processing chip U9 are differentially connected to the DP1, DP2, DN1, and DN2 pins of the universal serial bus interface circuit 201. The TXD and RXD pins of the serial port data processing chip U9 are connected to the TXD0 and RXD0 pins of the main control chip, respectively. The main control chip has a built-in wireless communication unit, which communicates with the terminal device.

6. The gas sensor device according to claim 5, characterized in that, The reference voltage source circuit includes a reference voltage chip U1, capacitor C2, and capacitor C4. The two ends of capacitor C2 are connected to the VIN and GND pins of reference voltage chip U1, respectively. The TRIM / NR pin of reference voltage chip U1 is connected to one end of capacitor C4, and the other end of capacitor C4 is grounded. The GND pin of reference voltage chip U1 is grounded. The VOUT pin of reference voltage chip U1 is connected to the REFIO pin of ADC chip. The REFIO pin of ADC chip is connected to one end of resistor R5, and the other end of resistor R5 is connected to capacitor C12. The other end of capacitor C12 is grounded.

7. The gas sensor device according to claim 6, characterized in that, The 3.3V voltage regulator chip circuit includes voltage regulator chip U5. The GND pin of voltage regulator chip U5 is grounded. The VOUT pin of voltage regulator chip U5 is connected to the serial port VDD33 of the main control chip, the serial port VCC of the serial data processing chip U9, and the DVDD and RST# pins of the ADC chip. The VIN pin of voltage regulator chip U5 is connected to the output terminal of the power supply circuit.

8. The gas sensor device according to claim 6, characterized in that, The 5V voltage regulator chip circuit includes a voltage regulator chip U72, a diode D74, an inductor L75, a capacitor C78, ​​a capacitor C738, a resistor R72, and a resistor R74. The SW pin of the voltage regulator chip U72 is connected to the anode of the diode D74 and one end of the inductor L75. The VIN pin of the voltage regulator chip U72 is connected to the other end of the inductor L75, one end of the parallel circuit of capacitors C78 and C738, and the output terminal of the power supply circuit 207. The GND pin of the voltage regulator chip U72 is connected to the other end of the parallel circuit of capacitors C78 and C738 and one end of the resistor R74, and is also grounded. The other end of the resistor R74 is connected to one end of the resistor R72 and the FB pin of the voltage regulator chip U72. The other end of the resistor R72 is connected to the cathode of the diode D74 and then connected to the input terminal of the rectifier circuit 210. The rectifier includes rectifier chip U4, resistors R6 and R15, and capacitor C18. The IN and EN pins of rectifier chip U4 are connected to the output of 5V voltage regulator circuit 209. The NR / SS pin of rectifier chip U4 is connected to one end of capacitor C18, and the other end of capacitor C18 is grounded. The PwPd and GND pins of rectifier chip U4 are grounded. Resistors R6 and R15 are connected to form a series circuit. The other end of resistor R15 is grounded. The other end of resistor R6 is connected to the OUT pin of rectifier chip U4. The OUT pin of rectifier chip U4 is externally connected to the second pin of the sliding switch SW7 of reference resistor switching circuit 205, the VIN pin of reference voltage regulator chip U1, and the AVDD and RST# pins of analog-to-digital converter 204.

9. The gas sensor device according to claim 7 or 8, characterized in that, The main circuit board is divided into a digital circuit section and an analog circuit measurement section. A 0-ohm resistor is used to connect the digital ground plane and the analog ground plane to reduce the impact of digital noise on analog measurement.

10. The gas sensor device according to claim 9, characterized in that, The power supply circuit is connected to external AC power through a universal serial bus interface, or the power supply circuit is connected to the built-in battery. The housing includes an upper support plate, a rectangular frame, and a bottom plate. The upper support plate is fixed at the upper opening of the rectangular frame, and the bottom plate is fixed at the lower opening of the rectangular frame. Two through holes are opened on the upper support plate, and a reference resistor base and a sensor base are fixedly installed on the through holes respectively. The reference resistor is fixed on the reference resistor base, and the sensor is installed on the sensor base. The main circuit board is installed in the cavity enclosed by the rectangular frame. The reference resistor and the sensor are connected to the main circuit board through the through holes below. The battery is fixed inside the rectangular frame and located below the main circuit board.

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