Low power infrared gas detection alarm sensor

Abstract

The invention discloses a low-power infrared gas detection alarm sensor, comprising a gas chamber housing and a gas chamber bottom cover and a PCB circuit board that are mutually covered to form a gas sampling chamber; an infrared light source and an infrared gas sensor are arranged on the PCB circuit board; an air inlet and outlet are opened on the top surface of the gas chamber housing, and a microporous filter membrane is arranged on the air inlet and outlet; the microporous filter membrane is pressed on the air inlet and outlet through a light shielding pressing plate, and a light shielding membrane is also pressed between the light shielding pressing plate and the microporous filter membrane; a shielding cover is fixedly installed on the bottom of the gas chamber housing, and the shielding cover blocks the gas chamber bottom cover and the PCB circuit board in the gas chamber housing; an infrared photosensitive diode is arranged on the PCB circuit board; a reflection window is opened on the gas chamber bottom cover, and an arc-shaped reflection surface is formed in the gas chamber housing. The invention uses 2 to 3 batteries to work, has low power consumption and long service life, can be simply applied to gas detection alarms that have an absorption effect outside the red line and directly use a digital output interface as a gas sensor.

Description

Technical Field

[0001] The invention relates to the technical field of sensors, in particular to an infrared gas detection alarm sensor, specifically to a low-power infrared gas detection alarm sensor which can be powered by a battery for a long time. Background Art

[0002] The principle of infrared gas detection is to install an infrared light source and an infrared gas sensor in a gas detection room with good light conduction. The infrared gas sensor is used to receive light waves of a certain wavelength of the infrared spectrum that has an absorption effect on the target gas to be detected. The selectivity to gas is determined by the wavelength of the filter lens on the window of the infrared gas sensor. When the infrared light source is turned on, it emits infrared light waves with a wavelength of 0~5um, which are irradiated to the infrared gas sensor through space. After the infrared gas sensor is irradiated with infrared light of a specific wavelength, it outputs a voltage proportional to the amount of light. When the concentration of the target gas to be detected in the gas chamber increases, the amount of light of a specific wavelength irradiated on the infrared gas sensor is absorbed by the target gas to be detected and then reduced, and the output voltage of the receiving device is reduced proportionally. Infrared gas detection uses the infrared gas sensor to convert the infrared light amount of a specific wavelength and the absorption relationship of the target gas to a specific infrared wavelength into an electrical signal.

[0003] At present, commonly used infrared gas sensors are sensor modules that are assembled and directly output analog or digital values ​​of the target gas concentration. The goal of these sensor modules is to output the concentration data of the detected gas. In order to improve the resolution and accuracy of the output gas concentration data, the light source voltage usually uses a 3~5V voltage with a frequency of 2Hz to 6Hz for continuous power supply. The detection power consumption is relatively large. When used in gas detection alarms, the control circuit of the alarm processing function must be added before it can be used. In this way, the power consumption of the whole machine is added up, making it difficult to use battery power for a long time. Battery power is only used for some short-term working instruments and equipment, or for charging equipment, especially combustible gas detection alarms and carbon dioxide gas detection alarms that cannot use electrochemical sensors, which are almost all AC powered. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a low-power infrared gas detection alarm sensor which can be powered by battery DC and has low power consumption, long service life and stable and reliable operation.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] A low-power infrared gas detection alarm sensor comprises a gas chamber housing and a gas chamber bottom cover which are matched to form a gas sampling chamber, and a PCB circuit board which is closely mounted on the lower surface of the gas chamber bottom cover; The PCB circuit board is provided with an infrared light source extending through the bottom cover of the gas chamber into the gas sampling chamber and an infrared gas sensor for receiving reflected infrared light signals; the top surface of the gas chamber shell is provided with an inlet and outlet for the detected gas to enter the gas sampling chamber, and the inlet and outlet are provided with a microporous filter membrane; the microporous filter membrane is press-fitted and fixed on the inlet and outlet through a black light-shielding pressing plate, and a layer of black light-shielding film for preventing external light from entering the gas sampling chamber is also press-fitted between the light-shielding pressing plate and the microporous filter membrane; a shielding cover for shielding external interference radio waves is fixedly installed on the bottom of the gas chamber shell, and the shielding cover blocks the bottom cover of the gas chamber and the PCB circuit board in the gas chamber shell; the PCB circuit board is provided with an infrared photosensitive diode for receiving infrared light reflected from the inner wall of the gas sampling chamber; a reflection window for reflecting infrared light onto the infrared photosensitive diode is provided on the bottom cover of the gas chamber, and an arc-shaped reflection surface for reflecting infrared light and focusing it onto the receiving window of the infrared gas sensor is formed in the gas chamber shell.

[0007] To optimize the above technical solutions, the specific measures taken also include:

[0008] There are 15 functional output pins soldered on the above-mentioned PCB circuit board, and the 15 output pins include ground pin GND, positive pin VDD, test button pin SW, serial port sending pin TXD, serial port receiving pin RXD, single-line communication pin ODATA, reset pin RSET, pin NC, pin VOUT, pin LED_G, pin A / D, pin LED_R, pin LED_Y, pin SP and pin JOUT.

[0009] Four rectangular air inlets and outlets are opened in the middle of the top surface of the above-mentioned air chamber shell, and the four air inlets and outlets are arranged in two rows and two columns; a plug-in hole is formed on the air chamber shell, and a positioning pin is formed on the shading pressure plate. The shading pressure plate is installed on the air chamber shell through the positioning pin and the plug-in hole on the air chamber shell.

[0010] The inner surface of the air chamber shell and the upper surface of the air chamber bottom cover are both coated with a layer of electroplated film with good light-conducting and anti-oxidation properties; a light source hole for the infrared light source to pass through is opened near the left end of the air chamber bottom cover, and a sensor hole for the positioning sleeve infrared gas sensor is opened near the right end of the air chamber bottom cover. The reflection window is arranged on the inner side of the air chamber bottom cover adjacent to the sensor hole, and the above-mentioned arc-shaped reflection surface is obliquely located above the sensor hole.

[0011] The above-mentioned PCB circuit board is provided with an MCU chip and an LDO voltage regulator chip; the LDO voltage regulator chip and the infrared photosensitive diode together constitute an infrared light intensity stabilization control circuit arranged on the PCB circuit board for controlling the infrared light source; the MCU chip controls the infrared light source to light up as a gas qualitative detection signal in an intermittent power supply mode 1 to 2 times per minute through the infrared light intensity stabilization circuit. The infrared light source is lit up for 100 to 500mS each time. When the signal value obtained by the detection reaches the preset value, it is converted to continuously send out 3 to 5 detection signals each time as quantitative detection, and the rest of the time is in a dormant state.

[0012] The above-mentioned PCB circuit board is also provided with an infrared gas signal amplifying circuit connected to the MCU chip, a bee-cutting amplifying circuit, a light intensity reference circuit, a power supply voltage detection circuit, an infrared gas sensor temperature detection circuit, a fault detection circuit and an output interface circuit for connecting the output pins.

[0013] The above-mentioned MCU chip is a main control chip with a 12-bit ADC analog-to-digital input port and a 12-bit DAC digital-to-analog output port.

[0014] The above-mentioned PCB circuit board is formed with convex edges on both sides of the middle part, and the output pins are welded on the convex edges on both sides of the PCB circuit board. The shielding cover is provided with a long strip notch at the position corresponding to the convex edge of the PCB circuit board, through which the output pins can pass; four side air ports that match the corresponding air inlets and outlets are opened on the bottom cover of the air chamber at the positions corresponding to the four air inlets and outlets, and the two sides of the air chamber shell are formed with outward convex cavities for accommodating the convex edge of the PCB circuit board and the output pins.

[0015] Compared with the prior art, the present invention also presses a black light-shielding film on the air inlet and outlet through a light-shielding pressure plate, and the light-shielding film can prevent external light, especially sunlight containing infrared light waves, from irradiating into the gas sampling chamber from the air inlet and outlet. The present invention also uses a shielding cover to seal the bottom of the gas chamber shell, and the shielding cover prevents external interference with radio waves, thereby improving the working stability of the infrared gas detection alarm sensor. The PCB circuit board of the present invention is also equipped with an infrared photosensitive diode, and the infrared photosensitive diode can form an infrared light amount stabilization control circuit with the LDO voltage regulator chip on the PCB circuit board, thereby ensuring that the infrared light source can work stably when the battery voltage is the lowest. The present invention uses intermittent power supply to the infrared light source to make a gas qualitative detection signal, which can greatly reduce the loss of battery power without affecting the detection accuracy. The low-power infrared gas detection alarm sensor is powered by 2 1.5V batteries and has the functions of infrared gas detection and gas alarm.

[0016] The present invention is powered by 2 to 3 1.5V batteries, has low power consumption and long service life, can be simply applied to gas detection alarms that absorb outside the red line and can be directly used as gas sensors using a digital output interface. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is an exploded view of the present invention;

[0018] Figure 2 It is a schematic diagram of the assembly structure of the present invention;

[0019] Figure 3 It is a schematic diagram of the distribution state of the functional output pins of the present invention;

[0020] Figure 4 It is a circuit diagram of the infrared gas signal amplifying circuit of the present invention;

[0021] Figure 5 It is a circuit diagram of a bee-cutting amplifier circuit of the present invention;

[0022] Figure 6 It is a diagram of the output voltage waveform of the clipped bee amplifier circuit of the present invention;

[0023] Figure 7 It is a circuit diagram of the infrared light intensity stabilization control circuit and the light source voltage detection circuit of the present invention;

[0024] Figure 8 is a circuit diagram of a power supply voltage detection circuit of the present invention;

[0025] Fig. 9 It is a block diagram of the structure of the single / double window gas detection circuit of the present invention;

[0026] Fig.10 It is a block diagram of the structure of the high-precision gas detection circuit of the present invention;

[0027] Fig.11 It is a schematic diagram of temperature compensation of the infrared photosensitive diode (infrared gas probe) of the present invention. DETAILED DESCRIPTION

[0028] The embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0029] Figures 1 to 2 It is a structural schematic diagram of the present invention.

[0030] The accompanying drawings are marked as follows: infrared photosensitive diode G, gas sampling chamber K, infrared gas sensor Q, infrared light source Y, gas chamber shell 1, air inlet and outlet 1a, arc-shaped reflecting surface 1b, plug hole 1c, convex cavity 11, gas chamber bottom cover 2, reflecting window 2a, light source hole 2b, sensor hole 2c, side air port 21, PCB circuit board 3, convex edge 31, microporous filter membrane 4, shading pressure plate 5, positioning column 51, shading film 6, shielding cover 7, long strip notch 7a, output pin 8, bolt 9.

[0031] As shown in the figure, the present invention discloses a low-power infrared gas detection alarm sensor, which includes a gas chamber housing 1, a gas chamber bottom cover 2, a PCB circuit board 3, and an MCU chip, an infrared light source Y, and an infrared gas sensor Q installed on the PCB circuit board 3. The gas chamber bottom cover 2 is installed in the gas chamber housing 1, and is surrounded by the gas chamber housing 1 to form a gas sampling chamber K. The PCB circuit board 3 is also located in the gas chamber housing 1, and the PCB circuit board 3 is close to the bottom surface of the gas chamber bottom cover 2. The MCU chip on the PCB circuit board 3 is a main control chip with a 12-bit ADC analog quantity to digital quantity input port and a 12-bit DAC digital quantity to analog quantity output port. The MCU chip is the core processing unit of the low-power infrared gas detection alarm sensor, and the infrared light source Y and the infrared gas sensor Q are both controlled by it. The infrared light source Y can emit infrared light under the control of the MCU chip through the circuit, and the infrared gas sensor Q is used to receive the reflected infrared light signal for gas concentration detection. The infrared gas sensor Q can select the corresponding wavelength of the infrared wavelength according to the type of the detected gas. Of course, it can also select a single-channel infrared gas sensor Q for a single detected gas, or a dual-channel infrared gas sensor Q that can detect two gases, or a dual-channel infrared gas sensor Q with a reference channel for high-precision instruments and equipment according to functional requirements. These are all determined by the application or functional requirements. The infrared light source Y and the infrared gas sensor Q of the present invention are arranged on the PCB circuit board 3 on the left and right sides. Correspondingly, a light source hole 2b for the infrared light source Y to pass through is opened on the gas chamber bottom cover 2 near the left end, and a sensor hole 2c for the positioning sleeve infrared gas sensor Q is opened on the gas chamber bottom cover 2 near the right end. The infrared light source Y extends into the gas sampling chamber K through the light source hole 2b of the gas chamber bottom cover 2, and the infrared gas sensor Q is positioned and sleeved in the sensor hole 2c. The PCB circuit board 3 is fixed in the gas chamber housing 1 by two bolts 9. An air inlet and outlet 1a is opened in the middle of the top surface of the gas chamber housing 1 for allowing the detected gas to enter the gas sampling chamber K. A microporous filter membrane 4 is provided on the air inlet and outlet 1a. The main function of the microporous filter membrane 4 is to prevent water vapor from entering the gas sampling chamber K to prevent it from affecting the transmission of infrared light.

[0032] The main feature of the present invention is that the microporous filter membrane 4 is fixed on the air inlet and outlet 1a by a black light shielding pressing plate 5. Figure 1 It can be seen that the air chamber housing 1 is formed with a plug hole 1c at the air inlet and outlet 1a, and the light shielding plate 5 is formed with a positioning plug post 51, which can be positioned and plugged into the plug hole 1c, and the light shielding plate 1 and the air chamber housing 1 are connected by the plug-in connection of the column hole, so that the replacement and maintenance of the microporous filter membrane 4 can be convenient. At the same time, in order to prevent the external light, especially the sunlight containing infrared light waves from irradiating into the gas sampling chamber K from the air inlet and outlet, affecting the amount of light received by the infrared gas sensor Q, the present invention also presses a layer of black light shielding film 6 between the light shielding plate 5 and the microporous filter membrane 4. The light shielding plate 5 is provided with an air port corresponding to the air inlet and outlet 1a of the air chamber housing 1, so that the external gas to be measured can pass through the air port opened on the light shielding plate 5, and then pass through the light shielding film 6, the microporous filter membrane 4 and the air inlet and outlet 1a in sequence into the gas sampling chamber K.

[0033] In order to reduce the interference of external radio waves on the low-power infrared gas detection alarm sensor and improve the working stability of the low-power infrared gas detection alarm sensor, the present invention also uses two bolts 9 to fix a shielding cover 7 on the bottom port of the air chamber shell 1, and the shielding cover 7 blocks the air chamber bottom cover 2 and the PCB circuit board 3 in the air chamber shell 1.

[0034] The present invention also provides an infrared photosensitive diode G for stabilizing the amount of light on the PCB circuit board 3, and a reflection window 2a for reflecting infrared light onto the infrared photosensitive diode G is provided on the gas chamber bottom cover 2. The reflection window 2a is provided adjacent to the sensor hole 2c and is located on the inner side of the sensor hole 2c. The infrared photosensitive diode G receives infrared light through the reflection window 2a provided on the gas chamber bottom cover 2 through the inner wall of the gas sampling chamber K. An arc-shaped reflection surface 1b is formed in the gas chamber housing 1, and the arc-shaped reflection surface 1b is obliquely located above the sensor hole 2c. The infrared light of the infrared gas sensor Q is focused onto the receiving window of the infrared gas sensor Q by the arc-shaped reflection surface 1b formed on the gas chamber housing 1.

[0035] In order to improve light conductivity and reduce infrared light loss, the inner surface of the gas chamber shell 1 and the upper surface of the gas chamber bottom cover 2, or the surface of the gas sampling chamber K, are coated with a layer of electroplated film with good light-conducting and anti-oxidation properties.

[0036] As shown in the figure, in the present invention, four rectangular air inlets and outlets 1a are opened in the middle of the top surface of the air chamber shell 1, and the four air inlets and outlets 1a are arranged in two rows and two columns.

[0037] In the embodiment, the PCB circuit board 3 of the present invention is also provided with an LDO voltage stabilizing chip, and the LDO voltage stabilizing chip and the infrared photosensitive diode G together form an infrared light quantity stabilizing control circuit for controlling the infrared light source Y arranged on the PCB circuit board 3; the MCU chip controls the infrared light source Y to light up as a gas qualitative detection signal in an intermittent power supply mode 1 to 2 times per minute through the infrared light quantity stabilizing control circuit, and the infrared light source Y is lit for 100 to 500 mS each time. When the detected signal value reaches the preset value, it is converted to continuously send out 3 to 5 detection signals each time as quantitative detection, and the rest of the time is in a dormant state. This control method of the present invention can greatly reduce the loss of battery power without affecting the detection accuracy. The circuit of the present invention adopts LDO voltage stabilizing power supply, and can use the infrared light quantity stabilizing control circuit to ensure the normal operation of the infrared light source Y at the lowest voltage. The low-power infrared gas detection alarm sensor adopts 2 1.5V battery DC power supply, and can work normally when the voltage is as low as 2V.

[0038] The PCB circuit board 3 of the present invention is also provided with an infrared gas signal amplifying circuit connected to the MCU chip, a bee clipping amplifying circuit, a light illumination reference circuit, a power supply voltage detection circuit, an infrared gas sensor temperature detection circuit, a fault detection circuit and an output interface circuit. The infrared photodiode G also forms a signal reference quantity control with the bee clipping amplifying circuit to improve the detection accuracy.

[0039] The present invention combines infrared gas detection technology and gas alarm functions into a complete single-block infrared gas detection alarm component, and reduces the need for an external gas alarm function processing circuit unit, thereby greatly improving circuit utilization, reducing circuit power consumption, and facilitating use.

[0040] Depend on Figure 3It can be seen that the present invention has 15 functional output pins 8 welded on the PCB circuit board 3, and the 15 output pins include the ground pin GND, the positive pin VDD, the test button pin SW, the serial port sending pin TXD, the serial port receiving pin RXD, the single-line communication pin ODATA, the reset pin RSET, the pin NC, the pin VOUT, the pin LED_G, the pin A / D, the pin LED_R, the pin LED_Y, the pin SP and the pin JOUT. Among them: the ground pin GND is used to connect the negative pole of the power supply. The positive pin VDD is the positive power supply pin of the power supply, and the power supply voltage is 2.1~5.5V. The test button pin SW is the pin for the manual test button. The serial port sending pin TXD and the serial port receiving pin RXD are both used for RS232 communication and are suspended when not in use. The single-line communication pin ODATA is used to send gas concentration, power, and alarm status information, and can be connected to LCD and wireless communication. The reset pin RSET is used for manual button reset and is suspended when not in use. Pin NC is an empty pin and a program burning pin. Pin VOUT outputs a stable voltage used internally. Pin LED_G is a green power indicator light, and the output is low level to light up the indicator light. Pin A / D is a reserved spare port. Pin LED_R is a red alarm indicator light, and the output is low level to light up the indicator light. Pin LED_Y is a yellow fault indicator light, and the output is low level to light up the indicator light. Pin SP is an alarm sound audio output, and it outputs 3.0~3.4K audio pulses to drive the alarm sound device. Pin JOUT is a relay output control, which outputs a high level when an alarm occurs and a low level when the alarm is exited. It is left floating when not in use.

[0041] Figure 4This is the circuit diagram of the infrared gas signal amplification circuit of the present invention. As shown in the figure, infrared gas detection is actually the measurement of the infrared light exposure of a certain infrared spectrum band. The infrared thermopile inside the infrared gas sensor Q (i.e., the infrared sensor SEN1 in the figure) converts the infrared light into a nV level voltage signal and sends it to the U2 operational amplifier for voltage amplification. The resistors R21 and R27 are the gain control resistors of the operational amplifier circuit, and the amplification factor is controlled at 300 to 500 times. The capacitor C21 is mainly used to filter out signal clutter. The capacitor C24, the capacitor C17, and the inductor L3 are mainly used for anti-EMC high-frequency interference devices. The resistor R26 is mainly used to discharge SEN1 and C24 when the power is off. Since the signal is at the nV level, its resistance value is very large, between 6.2 and 10M. The operational amplifier reference voltage is provided by the PB0 port of the MCU chip through the resistor divider R19 and R18. In order to save energy, PB0 only outputs voltage during signal detection, and is closed at other times to output 0V voltage. R21 is mainly used for temperature detection in the double-window infrared gas probe. Since the negative terminals of the two infrared thermopiles of the double-window infrared gas probe and one of the pins of the internal NTC are connected to form a common pin, R21 uses a 0Ω resistor, and PC0 is set to an open-drain output mode. When PC0 is not closed, the other end of R21 is in a suspended state, which is equivalent to being vacant and non-existent, and has no effect on other work. When detecting the ambient temperature, turn off PC0 to ground, and the common pin of the double-window infrared gas probe is grounded by PC0 through a 0Ω resistor R21. The NTC and sampling resistor R7 form a temperature environment sampling circuit.

[0042] Figure 5This is the circuit diagram of the peak clipping amplifier circuit of the present invention. As shown in the figure, the working principle of the peak clipping amplifier circuit is: U2, R18, R16, C16, form a 200-300 times amplification circuit, and the output signal is sent to the ADC of the MCU through R19 and C14 for conversion processing. The peak cutting of the signal is determined by the "+" input terminal voltage of the AMP, and the peak cutting value is controlled by the DAC output voltage of the MCU. C15, R11, and R26 are the subdivision circuit of the DAC voltage. The infrared photosensitive diode G (photodiode D1) and R22 form a small-amplitude light stabilization circuit. Since the light of the D1 photodiode is not affected by the detected gas, the resistance of R22 is relatively large, between 1M and 6.2M. When the light intensity fluctuates due to some reason, the light intensity irradiated on D1 also fluctuates, causing the A_1 point Voltage changes. When the amount of light increases without the R22 resistor, the PB1 voltage drops because it is a negative signal, and the signal will be affected by fluctuations. After the R22 resistor is connected, when the amount of light increases or decreases, the gas signal voltage rises or falls, and the voltage at point A_1 also rises or falls at the same time. The voltage at point A_1 is divided by R22, R16 and R11 and sent to the "+" input of U2. Since the "+" input and "-" input of the operational amplifier rise or fall at the same time, the output signal amplitude can remain stable within a certain range.

[0043] Figure 7 It is a radio wave schematic diagram of the infrared light intensity stabilization control circuit of the present invention. As shown in the figure, the infrared light source voltage is not a constant voltage control, but a constant light control on the D1 irradiation surface. It is mainly controlled by the LDO voltage regulator chip U3 and turned on / off by the PB5 pin of the MCU. C22 is the filter capacitor of the input voltage, R13 and R14 are the maximum voltage limit of the light source. When there is no D1 and R23, it belongs to the voltage stabilization sampling control circuit, C18 is the high-frequency buffer capacitor of the LDO, C11 is the filter capacitor of the light source voltage, and LA1 is the infrared light. Source, R6 and R5 are sampling resistors for MCU to detect the light source voltage. D1 and R23 form constant light control, which is mainly used to maintain a constant amount of light on the surface of D1. When the LA1 light source ages and decays or the humidity is too high and the light is blocked by water vapor, causing the infrared light on the surface of D1 to decrease, the internal resistance of D1 becomes larger, the output voltage of U3 rises, and the infrared light of LA1 increases. When the infrared light on the surface of D1 increases for some reason, the internal resistance of D1 becomes smaller, the output voltage of U3 decreases, and the infrared light of LA1 weakens, always maintaining a relatively constant amount of light.

[0044] The open circuit and short circuit fault detection of the infrared gas sensor is that when the MCU light source controls the PB5 pin to turn on the light source, the light source voltage detected by the MCU's Adc2 pin after the voltage divider conversion by R6 and R5 must be between 1.6V and 2.2V. If the voltage is lower than 1.6V, the LDO should be faulty and the MCU will issue a fault warning. If it is 0V, it may be that the LA1 light source is short-circuited and the MCU will issue a fault warning.

[0045] When the light source is not turned on, the MCU first controls the DAC to increase from 0V until the MCU detects that the output voltage of the peak clipping amplifier is close to 1 / 2 of the power supply voltage, and then turns on the light source after recording the current voltage value. After the light source is turned on, if the light source voltage is detected to be normal, the output voltage of the infrared gas control head will definitely rise after being irradiated with infrared light. The voltage detected by the ADC input of the MCU's gas detection channel is definitely lower than the recorded voltage value when the light source is not turned on due to the final peak clipping. If the output voltage value of the gas signal channel detected after the light source is turned on does not change or changes very little from the voltage when the light source is turned off, there must be a fault in the infrared gas probe or the gas signal amplification channel, and the MCU issues a fault warning.

[0046] The fault warning is that the yellow-green fault light flashes twice in succession, and the buzzer (SP output audio) sounds two short sounds at the same time when the fault light flashes. A fault warning is issued at least once per minute. The method of fault warning is determined by the implemented alarm safety regulations.

[0047] Figure 8 This is a circuit diagram of the power supply voltage detection circuit of the present invention. As shown in the figure, the power supply voltage detection is the power detection by MCU to calculate the power value after detecting the power supply voltage. When the power supply is lower than 2.3V, a low voltage warning prompt will be issued. The low voltage warning prompt will emit at least one short sound per minute, and the yellow fault indicator light will flash once with the sound.

[0048] This prompt method is determined according to the implemented safety standards and regulations. If the safety standards are upgraded or changed, the low voltage warning prompt also needs to be changed accordingly.

[0049] R12 and R10 are the sampling voltage divider resistors of the power supply voltage, C7 is a capacitor to resist high-frequency interference. To reduce power consumption, R10 is connected to the ground by PB7 only when the power detection is performed. Since PB7 is set to open-drain floating mode, R10 is suspended at other times.

[0050] During power detection, PB7 is turned on to ground, and the power supply voltage is divided by R12 and R10 and sent to the MCU through the Adc10 / PD4 port for conversion and calculation of the power supply voltage value.

[0051] Common infrared gas sensors Q in the prior art include single-window probes, double-window probes, and four-window probes, of which the most commonly used are single-window and double-window probes. Double-window probes actually encapsulate two sets of infrared thermal stack devices in the same metal shell. Each set of infrared thermal stack devices has a corresponding window for configuring filters of different wavelengths. If the two windows of the double-window probe are configured with two different filters for gas detection, it can perform dual-gas detection functions. For example, the wavelength of one set of window filters is 3.375um, and the wavelength of the other set of window filters is 4.64um. The probe can detect propane and carbon monoxide gases at the same time. For example, the wavelength of one set of window filters is 3.375um, and the wavelength of the other set of window filters is 3.90um. The probe uses the 3.90um channel to the 3.375um channel as an environmental reference, which can be used for models requiring higher accuracy.

[0052] Fig.11 This is a schematic diagram of the temperature compensation of the infrared gas probe of the present invention. The temperature sensor is an NTC resistor encapsulated inside the infrared gas probe. The NTC resistor and R7 form a partial pressure sampling, which is sent to the Adc16 / Pb2 pin of the MCU through R3 and converted into corresponding temperature data according to the NTC's graduation list, and then software compensation is performed according to the temperature characteristics of the infrared gas probe.

[0053] The reference voltage for temperature detection is provided by PB6 of MCU. In order to reduce the power consumption of the circuit, PB6 turns on the output voltage only when temperature detection is performed, and is in a closed state at other times. When a single-window infrared probe is used, the NTC is directly connected to the shell end and grounded. Since the double-window infrared probe shares multiple pins, it is only grounded to the PC0 pin of MCU through a 0 ohm resistor R21 during temperature detection. At other times, PC0 is in a suspended state, which has no effect on the infrared detection signal.

[0054] The low-power infrared gas detection alarm sensor of the present invention is divided into three types: single-window single-gas detection type, double-window dual-gas detection type and high-precision gas detection type. It has the most basic functions required of a gas detector, a gas exceeding danger alarm function, a battery power detection function, a battery low power warning prompt function, a sensor open and short circuit fault warning function, a manual test function, and an information output function, and meets the standard characteristics of a gas detector.

[0055] The PCB circuit board 3 of the present invention is formed with convex edges 31 on both sides of the middle part, and the output pins 8 are welded on the convex edges 31 on both sides of the PCB circuit board 3. The shielding cover 7 is provided with a long strip notch 7a for the output pins 8 to pass through at the position corresponding to the convex edge 31 of the PCB circuit board 3; four side air ports 21 cooperating with the corresponding air inlets and outlets are opened on the air chamber bottom cover 2 at the positions corresponding to the four air inlets and outlets 1a, and the air chamber shell 1 is formed with convex edges 31 of the PCB circuit board 3 and outward convex cavities 11 for accommodating the output pins 8.

[0056] The working principle of the low-power infrared gas detection alarm sensor is as follows: when detecting gas, the MCU chip sends out an infrared light source voltage control LDO voltage to light up the infrared light source Y to emit infrared light. The infrared light is transmitted through the inner wall of the gas sampling chamber K and the space through the reflective window 2a on the bottom cover 2 of the gas chamber to irradiate the infrared photosensitive diode G. The infrared photosensitive diode G converts the infrared light into the corresponding amount of electrical information and then feeds back to the voltage sampling pin of the infrared light source voltage control LDO to control the infrared light illumination to obtain stable infrared light. The other way is sent to the peak clipping amplifier circuit for reference to improve the detection accuracy. The infrared light of the infrared light source Y with stable light illumination is focused on the receiving window of the infrared gas sensor Q through the arc-shaped reflective surface 1b of the gas chamber shell 1 and converted into the corresponding amount of electrical signal and then sent to the signal amplifier to amplify the signal. The amplified signal is sent to the peak clipping amplifier for peak removal, retaining the signal peak and amplifying it to the ADC port of the MCU for conversion and processing into the detection gas concentration information, the detection gas concentration and other electrical information, the fault information is output by the single-line digital information output pin and the serial port, and the MCU processes the gas alarm according to the detection gas concentration.

[0057] The best embodiment of the present invention has been described, and various changes or modifications made by those skilled in the art will not depart from the scope of the present invention.

Claims

1. A low-power infrared gas detection alarm sensor, comprising a gas chamber housing (1) and a gas chamber bottom cover (2) which are matched to form a gas sampling chamber (K), and a PCB circuit board (3) which is closely mounted on the lower surface of the gas chamber bottom cover; the PCB circuit board (3) is provided with an infrared light source (Y) which passes through the gas chamber bottom cover (2) and extends into the gas sampling chamber (K), and an infrared gas sensor (Q) for receiving reflected infrared light signals; the top surface of the gas chamber housing (1) is provided with an inlet and outlet (1a) for allowing the detected gas to enter the gas sampling chamber (K), and the inlet and outlet (1a) is provided with a microporous filter membrane (4); the characteristics are: The microporous filter membrane (4) is press-fitted and fixed on the gas inlet and outlet (1a) via a black light-shielding pressing plate (5), and a layer of black light-shielding film (6) is also press-fitted between the light-shielding pressing plate (5) and the microporous filter membrane (4) for preventing external light from entering the gas sampling chamber (K); a shielding cover (7) for shielding external interference radio waves is fixedly installed at the bottom of the gas chamber shell (1), and the shielding cover (7) blocks the gas chamber bottom cover (2) and the PCB circuit board (3) in the gas chamber shell (1); an infrared photosensitive diode (G) for receiving infrared light reflected by the inner wall of the gas sampling chamber (K) is provided on the PCB circuit board (3); a reflection window (2a) for reflecting infrared light onto the infrared photosensitive diode (G) is opened on the gas chamber bottom cover (2), and an arc-shaped reflection surface (1b) for reflecting infrared light and focusing it onto the receiving window of the infrared gas sensor (Q) is formed in the gas chamber shell (1); The middle part of the top surface of the air chamber shell (1) is provided with four air inlets and outlets (1a) of rectangular structure, and the four air inlets and outlets (1a) are arranged in two rows and two columns; the air chamber shell (1) is formed with a plug hole (1c), and the shading pressure plate (5) is formed with a positioning plug post (51), and the shading pressure plate (5) is installed on the air chamber shell (1) by plugging and matching with the plug hole (1c) on the air chamber shell (1) via the positioning plug post (51); The light shielding pressure plate (5) is provided with air ports corresponding to the air inlet and outlet ports (1a) of the air chamber housing (1); The inner surface of the gas chamber shell (1) and the upper surface of the gas chamber bottom cover (2) are both plated with a layer of electroplated film with good light-conducting and anti-oxidation properties; the gas chamber bottom cover (2) is provided with a light source hole (2b) near the left end for the infrared light source (Y) to pass through, and the gas chamber bottom cover (2) is provided with a sensor hole (2c) for the positioning sleeve infrared gas sensor (Q) near the right end; the reflection window (2a) is arranged on the inner side of the gas chamber bottom cover (2) adjacent to the sensor hole (2c), and the arc-shaped reflection surface (1b) is obliquely located above the sensor hole (2c); The PCB circuit board (3) is provided with an MCU chip and an LDO voltage stabilizing chip; the LDO voltage stabilizing chip and the infrared photosensitive diode (G) together form an infrared light intensity stabilizing control circuit arranged on the PCB circuit board (3) for controlling the infrared light source (Y); the MCU chip controls the infrared light source (Y) to light up as a gas qualitative detection signal in an intermittent power supply mode 1 to 2 times per minute through the infrared light intensity stabilizing control circuit, and the infrared light source (Y) is lit up each time for 100 to 500 milliseconds. When the signal value obtained by detection reaches a preset value, it is converted to continuously send out 3 to 5 detection signals each time as quantitative detection, and the rest of the time is in a dormant state; The MCU chip is a main control chip with a 12-bit ADC analog-to-digital input port and a 12-bit DAC digital-to-analog output port.

2. The low-power infrared gas detection alarm sensor according to claim 1 is characterized in that: The PCB circuit board (3) is welded with 15 functional output pins (8), and the 15 output pins include, in sequence, a ground pin GND, a positive pin VDD, a test button pin SW, a serial port transmission pin TXD, a serial port reception pin RXD, a single-line communication pin ODATA, a reset pin RSET, a pin NC, a pin VOUT, a pin LED_G, a pin A / D, a pin LED_R, a pin LED_Y, a pin SP, and a pin JOUT.

3. The low-power infrared gas detection alarm sensor according to claim 2 is characterized in that: The PCB circuit board (3) is also provided with an infrared gas signal amplifying circuit connected to the MCU chip, a shaved gas amplifying circuit, a light intensity reference circuit, a power supply voltage detection circuit, an infrared gas sensor temperature detection circuit, a fault detection circuit and an output interface circuit for connecting to an output pin (8).

4. The low-power infrared gas detection alarm sensor according to claim 3 is characterized in that: The PCB circuit board (3) is provided with convex edges (31) on both sides of the middle part, the output pins (8) are welded to the convex edges (31) on both sides of the PCB circuit board (3), and the shielding cover (7) is provided with a long strip-shaped notch (7a) at a position corresponding to the convex edge (31) of the PCB circuit board (3) through which the output pins (8) can pass; the air chamber bottom cover (2) is provided with four side air ports (21) corresponding to the four air inlets and outlets (1a) on the position corresponding to the four air inlets and outlets, and the air chamber shell (1) is provided with an outer convex cavity (11) on both sides for accommodating the convex edge (31) of the PCB circuit board (3) and the output pins (8).

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