Intelligent infrared gas sensor

Abstract

The application discloses an intelligent infrared gas sensor and belongs to the field of sensors.The intelligent infrared gas sensor comprises a light chamber reaction module, a signal conditioning module, a power supply module one, a power supply module two, an MCU module, a temperature and humidity detection module, a duty cycle adjustment module and a soft start module.The light chamber reaction module comprises a sensor and an infrared light source.The sensor is connected with the MCU module through the signal conditioning module.The MCU module is also connected with the temperature and humidity detection module, the power supply module one and the duty cycle adjustment module.The duty cycle adjustment module is also connected with the power supply module two and the soft start module.The soft start module is also connected with the infrared light source.The application increases the temperature and humidity sensor and the light source soft start driving function, flexibly adjusts the duty cycle, adjusts the duty cycle of the sensor in the case that the environmental humidity is relatively large and the temperature is relatively low, adapts to the environment, and greatly improves the sensor precision, service life and stability.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and in particular to an intelligent infrared gas sensor. Background Technology

[0002] Currently, most gas sensors based on the infrared NDIR principle have a fixed duty cycle. If the duty cycle is small, the infrared light source will be in a cold state, resulting in a large inrush current when the light is turned on, generally above 500mA. This inrush current also places high demands on the current output capability of the pre-amplifier power supply. Therefore, many solutions use a 50% duty cycle to keep the light in a hot state, thereby reducing the inrush current and making the sensor waveform more stable. However, the power consumption will also increase relatively. For example, the infrared absorption peak of methane gas is 3.3um. This band also has a large absorption of water, so it will greatly affect the accuracy of the sensor in high humidity environments.

[0003] The main drawback is:

[0004] A smaller duty cycle is beneficial for power consumption, but detrimental to the stability of the sensor waveform. A smaller duty cycle also reduces the heating effect on the air chamber, preventing moisture from dissipating. Furthermore, a smaller duty cycle can cause excessive inrush current, affecting the stability of the output of the pre-amplifier power supply and increasing the operating load of the pre-amplifier power supply. Summary of the Invention

[0005] The purpose of this invention is to provide an intelligent infrared gas sensor to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An intelligent infrared gas sensor includes a light chamber reaction module, a signal conditioning module, a power supply module one, a power supply module two, an MCU module, a temperature and humidity detection module, a duty cycle adjustment module, and a soft-start module. The light chamber reaction module includes a sensor and an infrared light source. The sensor is connected to the MCU module through the signal conditioning module. The MCU module is also connected to the temperature and humidity detection module, the power supply module one, and the duty cycle adjustment module. The duty cycle adjustment module is also connected to the power supply module two and the soft-start module. The soft-start module is also connected to the infrared light source.

[0008] As a further technical solution of the present invention: the MCU module is also connected to a communication output module.

[0009] As a further technical solution of the present invention: the duty cycle adjustment module is used to output waveforms of different frequencies and duty cycles to drive the soft-start power supply.

[0010] As a further technical solution of the present invention: the signal conditioning module is equipped with a signal amplifier.

[0011] As a further technical solution of the present invention: the signal conditioning module includes operational amplifiers U3A, U3B, U6A, U6B, and U7A. Port 6 of operational amplifier U3B is connected to resistors R11 and R8 and capacitor C6. Port 5 of operational amplifier U3B is connected to capacitor C10 and port 4 of thermopile probe P1. Port 7 of operational amplifier U3B is connected to the other end of capacitor C6, the other end of resistor R11, and capacitor C8. The other end of capacitor C8 is connected to resistor R12 and port 3 of operational amplifier U3A. Port 2 of operational amplifier U3A is connected to resistors R10 and R7 and capacitor C3. Port 1 of operational amplifier U3A is connected to the other end of capacitor C3, the other end of resistor R10, and resistor R13. The other end of resistor R13 is connected to capacitor C9. The other end of capacitor C9 is grounded. Port 6 of op-amp U6B is connected to resistor R15, resistor R17 and capacitor C12. Port 5 of op-amp U6B is connected to capacitor C19 and port 3 of thermopile probe P1. Port 7 of op-amp U6B is connected to the other end of capacitor C12, the other end of resistor R17 and capacitor C16. The other end of capacitor C16 is connected to resistor R19 and port 3 of op-amp U6A. Port 2 of op-amp U6A is connected to resistor R14, resistor R16 and capacitor C11. Port 1 of op-amp U6A is connected to the other end of capacitor C11, the other end of resistor R16 and resistor R20. The other end of resistor R20 is connected to capacitor C7. The other end of capacitor C17 is grounded. The model of chip U2 is STM32F051K6U6.

[0012] As a further technical solution of the present invention: the operational amplifiers U3A, U3B, U6A, U6B and U7A are operational amplifier modules inside the LM324 chip.

[0013] As a further technical solution of the present invention: the MCU module includes chip U2, resistor R6, resistor R9 and capacitor C7. Pin 31 of chip U2 is grounded through resistor R6, pin 4 of chip U2 is connected to resistor R9 and capacitor C7, the other end of capacitor C7 is grounded, and the other end of resistor R9 is connected to power supply VDD.

[0014] As a further technical solution of the present invention: the soft-start circuit includes chip U5, resistors R18, R21, R22, R23, R24, capacitors C13 and C21. Pin 8 of chip U5 is connected to capacitor C13 and power supply VCC. Pin 7 of chip U5 is connected to resistor R18. Pin 5 of chip U5 is connected to resistors R23 and R24. Pin 4 of chip U5 is grounded through capacitor C24. Pin 3 of chip U5 is grounded. Pin 2 of chip U5 is connected to resistors R21 and R22. The other end of resistor R21 is connected to pin 1 of chip U5, capacitors C14 and C15, and light source U4. The other end of capacitor C14 is connected to the other end of capacitor C15 and the ground terminal. The model of chip U5 is ADP7105.

[0015] A temperature and humidity acquisition and variable duty cycle method, based on the above-mentioned sensors, the sensors continuously acquire and monitor temperature and humidity, set the temperature threshold a and the humidity threshold b, when the temperature b, output the PWM signal W1; when the temperature b, output the PWM signal W2; when the temperature ≥ a and the humidity ≤ b, output the PWM signal W3; among which, the environment where the temperature b is relatively harsh, the environment when the temperature b is harsh; the environment when the temperature ≥ a and the humidity ≤ b is normal; in the normal environment, the lighting time is short, the duty cycle is small, and the period is small. In the relatively harsh environment, the output lighting time is medium, the duty cycle becomes larger, and the period is shortened. In the harsh environment, the maximum duty cycle is output and the lighting time is the longest.

[0016] As a further technical solution of the present invention: the duty cycle W2 > W1 > W3, the period W3 > W1 > W2, and W1, W2, and W3 are determined according to experimental tests.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] By adding a temperature and humidity sensor, adding a soft start drive function for the light source, and flexibly adjusting the duty cycle, the present invention enables the sensor to flexibly adjust the duty cycle to adapt to the environment when the environmental humidity is large and the temperature is low, greatly improving the accuracy, lifespan, and stability of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is the overall block diagram of the present invention.

[0020] Figure 2 It is a schematic diagram before duty cycle adjustment.

[0021] Figure 3 It is a schematic diagram after duty cycle adjustment.

[0022] Figure 4 It is a software control diagram for duty cycle adjustment.

[0023] Figure 5 It is the circuit diagram of the sensor signal conditioning module.

[0024] Figure 6 It is the circuit diagram of the sensor, MCU, and power supply. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] Example 1, as Figure 1-6 As shown, an intelligent infrared gas sensor mainly includes a light chamber reaction module, a signal conditioning module, a power supply module one, a power supply module two, an MCU module, a temperature and humidity detection module, a duty cycle adjustment module, and a soft-start module. Power supply module one is used to power the MCU, power supply module two is used to provide the soft-start power supply voltage, and the duty cycle adjustment module is used to output waveforms of different frequencies and duty cycles to drive the soft-start power supply. The sensor receives a chopped signal from the light source. Since the signal is very weak, it needs to be amplified by the signal conditioning circuit before being sent to the MCU for algorithm calculation. The waveform area is calculated and converted into the corresponding concentration value of the gas being measured.

[0027] Example 2, based on Example 1, includes operational amplifiers U3A, U3B, U6A, U6B, and U7A. Port 6 of operational amplifier U3B is connected to resistors R11 and R8 and capacitor C6. Port 5 of operational amplifier U3B is connected to capacitor C10 and port 4 of the thermopile probe P1. Port 7 of operational amplifier U3B is connected to the other end of capacitor C6, the other end of resistor R11, and capacitor C8. The other end of capacitor C8 is connected to resistor R12 and port 3 of operational amplifier U3A. Port 2 of operational amplifier U3A is connected to resistors R10 and R7 and capacitor C3. Port 1 of operational amplifier U3A is connected to the other end of capacitor C3, the other end of resistor R10, and resistor R13. The other end of resistor R13 is connected to capacitor C9, and the other end of capacitor C9 is grounded. Port 6 of op-amp U6B is connected to resistors R15 and R17 and capacitor C12. Port 5 of op-amp U6B is connected to capacitor C19 and port 3 of thermopile probe P1. Port 7 of op-amp U6B is connected to the other end of capacitor C12, the other end of resistor R17 and capacitor C16. The other end of capacitor C16 is connected to resistor R19 and port 3 of op-amp U6A. Port 2 of op-amp U6A is connected to resistors R14 and R16 and capacitor C11. Port 1 of op-amp U6A is connected to the other end of capacitor C11, the other end of resistor R16 and resistor R20. The other end of resistor R20 is connected to capacitor C7. The other end of capacitor C17 is grounded. Op-amps U3A, U3B, U6A, U6B and U7A are op-amp modules inside the LM324 chip.

[0028] The MCU module includes chip U2, resistors R6 and R9, and capacitor C7. Pin 31 of chip U2 is grounded through resistor R6, and pin 4 of chip U2 is connected to resistor R9 and capacitor C7. The other end of capacitor C7 is grounded, and the other end of resistor R9 is connected to power supply VDD.

[0029] The soft-start circuit includes chip U5, resistors R18, R21, R22, R23, and R24, capacitors C13 and C21. Pin 8 of chip U5 is connected to capacitor C13 and power supply VCC. Pin 7 of chip U5 is connected to resistor R18. Pin 5 of chip U5 is connected to resistors R23 and R24. Pin 4 of chip U5 is grounded through capacitor C24. Pin 3 of chip U5 is grounded. Pin 2 of chip U5 is connected to resistors R21 and R22. The other end of resistor R21 is connected to pin 1 of chip U5, capacitors C14 and C15, and light source U4. The other end of capacitor C14 is connected to the other end of capacitor C15 and ground.

[0030] The working principle is as follows:

[0031] Figure 2It is a schematic diagram before and after duty cycle adjustment. In the figure, in the PWM1 coordinate axis, t1 represents the lamp turning on. The turning-on time is t4 - t1, and the lamp turning-off time is t7 - t4. According to the pyroelectric principle, when there is a heat change, the pyroelectric output signal will change, and the magnitude of the heat change directly affects the magnitude of the change in the output waveform of the pyroelectric sensor. In the figure, the lamp starts to turn on at t1 of PWM1. The stage from t2 - t1 is the initial stage of the lamp turning on. According to the soft-start principle, the lamp source voltage does not directly rise to the maximum voltage, so the heat change is small, and the slope of the corresponding pyroelectric output waveform is small. The stage from t3 - t2 is the middle stage of the lamp turning on, where the heat change is the largest, and the slope of the pyroelectric output waveform is the largest. The stage from t4 - t3 is the later stage of the lamp turning on. At stage t3, the heat of the lamp source tends to be stable, so the heat change becomes smaller again, and the rising slope of the pyroelectric sensor also becomes smaller. The lamp starts to turn off at t4. At this time, the heat change is from hot to cold, and the change is the fastest. Therefore, the pyroelectric signal waveform drops the steepest from t5 - t4. The stage from t6 - t5 is the later stage of turning off the lamp, and the heat change is small. At this time, the pyroelectric output waveform changes from steep to gentle. After t6, the pyroelectric signal relaxation is completed. After t6, there is no heat change, and the waveform tends to zero. After t7, another cycle starts. The period of PWM1 is t7 - t1, and the duty cycle is (t4 - t1) / (t7 - t1). According to the product requirements, the time of t4 - t1 is the power consumption time. The duty cycle and the period directly affect the power consumption of the product and the lifespan of the sensor lamp source. Assume 1: t7 - t1 = 3s, t4 - t1 = 300ms, t6 = 600ms, t7 = 3s. At this time, the duty cycle is 300ms / 3s = 10%. According to the relaxation process of the sensor signal, after t6 = 600ms, the pyroelectric sensor signal relaxation is completed. At this time, changing the period does not affect the output waveform when the turning-on time remains unchanged. In the figure, S2 = S1. Therefore, the output time T3 of the PWM2 lamp source drive after duty cycle adjustment can be between 600ms - 3s. Assume T3 = t6 = 600ms, the period of PMW2 is 600ms, and the duty cycle is 300ms / 600ms = 50%. Therefore, when the turning-on time remains 300ms unchanged, the duty cycle can be flexibly adjusted between 10% - 50%. The actual duty cycle adjustment range needs to be determined according to specific sensor tests.

[0032] Figure 3 It is a software control diagram for sensor duty cycle adjustment. The sensor continuously collects temperature and humidity and monitors them. The temperature threshold a and the humidity threshold b are set. When the temperature b, the PWM signal W1 is output; when the temperature b, the PWM signal W2 is output; when the temperature ≥ a and the humidity ≤ b, the PWM signal W3 is output. Among them, the environment where the temperature b is relatively harsh, the environment where the temperature b is harsh, and the environment where the temperature ≥ a and the humidity ≤ b is normal.

[0033] Figure 5This is the sensor signal conditioning module. P1 is a thermopile gas sensor with a built-in NTC temperature sensor. The voltage is divided by resistor R2 and sent to the MCU for temperature calculation. The sensor outputs two small signals: a reaction signal channel and a reference signal channel. The reaction signal changes according to the gas concentration, while the reference signal channel does not change with the gas concentration. U3 and U6 are high-performance precision operational amplifiers, using a two-stage amplification topology. R10, R11, R16, and R17 are feedback amplification resistors. VREF is the reference power supply, typically set to 1 / 2VDDA to ensure signal output integrity. C6 and R11, C12 and R17, C3 and R7, and C11 and R14 form low-pass filter circuits, while C8 and R12, and C16 and R19 form high-pass filter circuits to keep the signal within the required frequency range and improve signal stability.

[0034] Figure 6 This is the sensor MCU and power supply circuit. U5 is a soft-start chip with output, which can effectively reduce the inrush current when the light source is turned on. C21 is a soft-start capacitor; adjusting the size of this capacitor adjusts the soft-start time. R21 and R22 are voltage divider resistors, which can adjust the output power supply voltage to keep the output light source energy at its optimal state. U1 is a humidity acquisition chip that sends the humidity signal to the MCU for calculation, and then the MCU outputs control U5 to adjust the duty cycle and period. U8 is the microcontroller power supply; separating the power supply for the infrared light source and the MCU effectively reduces the impact of lamp switch ripple on the MCU's power supply accuracy, thereby improving the AD sampling accuracy. U2 is the MCU, used for signal acquisition, outputting control signals, and converting the acquired signals into the concentration value of the gas being measured.

[0035] Under normal conditions, the lamp-on time is short, the duty cycle is small, and the period is short. This extends the sensor life and reduces power consumption while ensuring accuracy. Under harsher conditions, the output lamp-on time is moderate, the duty cycle increases, and the period shortens. This increases the internal temperature of the optical chamber, dissipates moisture, and maintains accuracy. Under extremely harsh conditions, the output has the maximum duty cycle and the lamp-on time is extended to maximize the heating of the optical chamber and maintain accuracy. Therefore, the duty cycle W2>W1>W3, and the period W3>W1>W2. W1, W2, and W3 are determined based on experimental testing.

[0036] This solution is a methane sensor based on the NDIR principle. It utilizes an external temperature and humidity sensor outside the light chamber to determine the appropriate duty cycle for the current environment. Based on actual testing and theory, the duty cycle can be flexibly adjusted according to the relaxation process of the detector signal without affecting the sensor's output waveform. The sensor's lamp driver includes a soft-start function, significantly reducing the inrush current when the duty cycle is low, thereby reducing device current surge losses and sensor power consumption. When the MCU determines that the humidity is too high or the temperature is too low, the sensor adjusts the duty cycle by shortening the cycle to increase the lamp's illumination frequency, thus increasing the temperature inside the light chamber. This significantly reduces the impact of moisture absorption on infrared radiation, raising the sensor's operating temperature and stabilizing sensor accuracy. When humidity is low, the sensor switches to a lower duty cycle output, ensuring accuracy while maintaining low power consumption and extending the lamp's lifespan.

[0037] This invention improves sensor accuracy, lifespan, and stability by adding a temperature and humidity sensor, a soft-start drive function for the light source, and a flexible duty cycle adjustment scheme. This allows the sensor to adapt to environments with high humidity and low temperature by flexibly adjusting the duty cycle.

[0038] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0039] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for adjusting the duty cycle of an intelligent infrared gas sensor based on temperature and humidity acquisition, characterized in that, Based on an intelligent infrared gas sensor, the intelligent infrared gas sensor includes a light chamber reaction module, a signal conditioning module, a power supply module 1, a power supply module 2, an MCU module, a temperature and humidity detection module, a duty cycle adjustment module, and a soft start module. It is characterized in that the light chamber reaction module includes a sensor and an infrared light source. The sensor is connected to the MCU module through the signal conditioning module. The MCU module is also respectively connected to the temperature and humidity detection module, the power supply module 1, and the duty cycle adjustment module. The duty cycle adjustment module is also respectively connected to the power supply module 2 and the soft start module. The soft start module is also connected to the infrared light source; The intelligent infrared gas sensor continuously collects and monitors temperature and humidity. Set the temperature threshold a and the humidity threshold b. When temperature < a and humidity ≤ b, or temperature ≥ a and humidity > b, output the first PWM signal W1; when temperature b, output the second PWM signal W2; when temperature ≥ a and humidity ≤ b, output the PWM signal W3; among them, the environment where temperature < a and humidity ≤ b, or temperature ≥ a and humidity > b is relatively harsh, the environment when temperature b is harsh, and the environment when temperature ≥ a and humidity ≤ b is normal. In a normal environment, the light-on time is short, the duty cycle is small, and the period is large. In a relatively harsh environment, the output light-on time is medium, the duty cycle becomes larger, and the period is shortened. In a harsh environment, the maximum duty cycle is output, the light-on time is lengthened, the temperature inside the light chamber is increased, moisture is dissipated, the temperature inside the light chamber is increased, and the accuracy is guaranteed. The duty cycle = light-on time / PWM period, and the duty cycle W2 > W1 > W3, the period W3 > W1 > W2, and W1, W2, and W3 are determined according to experimental tests.

2. The method for adjusting the duty cycle of an intelligent infrared gas sensor based on temperature and humidity acquisition according to claim 1, characterized in that, The MCU module is also connected to a communication output module.

3. A method for adjusting the duty cycle of an intelligent infrared gas sensor based on temperature and humidity acquisition according to claim 1, characterized in that, The duty cycle adjustment module is used to output waveforms with different frequencies and duty cycles to drive the soft start power supply.

4. A method for adjusting the duty cycle of an intelligent infrared gas sensor based on temperature and humidity acquisition according to claim 1, characterized in that, A signal amplifier is provided inside the signal conditioning module.

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