Full-range smoke concentration detection system and method of photoelectric smoke detector

Abstract

The invention belongs to the technical field of aviation smoke detectors, and discloses a full-range smoke concentration detection system and method of a photoelectric smoke detector, which is based on a photoelectric smoke signal acquisition and conditioning technology, uses the full-range smoke concentration detection method, avoids the constraint of analog-to-digital conversion interface input voltage amplitude limit, and improves the smoke concentration detection accuracy. The smoke detector can detect the smoke concentration of (0-100)% / ft on the premise of ensuring the detection precision. The smoke detector adopting the scheme has the advantages of simple topological structure, controllable program, high flexibility, easy implementation of the method, high reliability and full-range concentration detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of aviation smoke detectors, and in particular relates to a full-range smoke concentration detection system and method for a photoelectric smoke detector. Background Art

[0002] Traditional photoelectric smoke detectors use a combination of light-emitting diodes and light-receiving diodes to detect smoke particles. When the light from the light-emitting diode is turned on and shines on the smoke particles, light scattering occurs. These scattered lights cannot be absorbed and reflected by the optical structure in large quantities due to their different directions and angles. As a result, the photocurrent generated on the light-receiving diode gradually increases. After being sampled and conditioned into a voltage signal, the mode conversion is performed, and the smoke concentration is determined by the microprocessor's recognition of the analog-to-digital conversion interface input voltage. At present, the mainstream smoke detector light transmittance is (93-97)% / ft, that is, the smoke concentration alarm threshold is (3-7)% / ft. In order to improve the product's sampling accuracy for smoke concentration, the resolution of the analog-to-digital conversion interface input voltage is maximized within the smoke concentration alarm threshold range. Therefore, the analog voltage enters saturation after reaching the analog-to-digital conversion interface input voltage limit, resulting in the smoke detector being unable to detect a smoke concentration of (7-100)% / ft.

[0003] It can be seen that for smoke with a higher concentration, it cannot be effectively identified and calibrated due to the upper limit of circuit design. Nowadays, with the gradual increase in the sensitivity and anti-interference requirements of smoke detectors for aircraft fire protection, the lower limit of smoke concentration that can be detected (light transmittance) for a single model of smoke detector is further increased, that is, the sensitivity requirements for smoke detection are getting higher and higher. Therefore, lower concentrations of smoke and interference sources (water vapor, dust, etc.) can make the collected analog voltage reach the upper limit of the voltage amplitude and saturate. This results in the inability of traditional photoelectric smoke detection methods to effectively identify high-concentration smoke and interference sources, resulting in an increase in the false alarm rate, which to a certain extent affects the accuracy and anti-interference ability of smoke detectors.

[0004] Patent 1: Application number CN202110760559.4 discloses a method and device for high-precision smoke detection. The invention belongs to the technical field of photoelectric smoke detectors. The device includes a photoelectric smoke detector, which includes a transmission control circuit, a transmission tube, a photosensitive receiving tube, a small signal amplifier circuit and an MCU. The MCU includes an ADC; the method includes placing the photoelectric smoke detector in a standard smoke concentration; the ADC collects the output value of the small signal amplifier circuit, and the MCU adjusts the amplification gain of the small signal amplifier circuit so that the output value of the small signal amplifier circuit is close to the preset alarm threshold; the calibration of the photoelectric smoke detector is completed, and the MCU records the alarm threshold and the gain adjustment value of the small signal amplifier circuit; the photoelectric smoke detector is installed in the workplace, and the gain value of the small signal amplifier circuit is set according to the parameters to perform smoke detection. The beneficial effects of the present invention are: it can eliminate the gain differences of the amplifier circuit caused by component differences and assembly errors, and improve the detection accuracy of the photoelectric smoke detector.

[0005] Patent 2: Application number CN201310751366.8 discloses a photoelectric smoke detector and a method for using the same. The invention provides a photoelectric smoke detector, wherein a signal processing unit amplifies according to a first or second gain value received from a calibration control unit, and the photoelectric smoke detector further comprises a long-term drift monitoring unit, wherein the long-term drift monitoring unit monitors the long-term drift of the signal output by the photoelectric smoke detection unit and outputs monitoring information to the calibration control unit, wherein the calibration control unit compensates the first gain value according to the monitoring information and sends the information to the signal processing unit. The present invention also provides a method for using such a detector. The photoelectric smoke detector and the method for using the same of the present invention can eliminate the influence of the rapid drift of the detector during each detection, and can eliminate the influence of the long-term drift by performing the long-term drift monitoring and compensation process at fixed intervals, thereby ensuring the accuracy and reliability of the detection results of the photoelectric smoke detector. Moreover, the circuit structure is simple and easy to implement.

[0006] Patent 3: Application number CN201310237553.4 discloses a variable gain small current pickup amplifier circuit. The invention includes a small current signal sampling circuit for collecting small current signals, whose output end is connected to the input end of a first-level precision operational amplifier circuit, the output end of the first-level precision operational amplifier circuit and the output end of the gain control circuit are both connected to the input end of a second-level variable gain operational amplifier circuit, and the output end of the second-level variable gain operational amplifier circuit is connected to a PC. The present invention can flexibly change the amplification factor, can be shared within a larger current sampling range, simplifies the analog signal processing of the detector, and has good versatility and stability.

[0007] Among the above three patents, Patent 1 improves the detection accuracy of photoelectric smoke detectors by eliminating the gain differences of the amplifier circuit caused by component differences and assembly errors, mainly to solve the inconsistency problem in the manufacturing process of smoke detectors. Patent 2 can eliminate the influence of long-term drift by performing long-term drift monitoring and compensation processes at fixed intervals, ensuring the accuracy and reliability of the detection results of photoelectric smoke detectors. It mainly solves the problem that the actual sensitivity of smoke detectors deviates from the established sensitivity after long-term operation. Patent 3 only describes the sampling and conditioning methods of tiny current signals, and does not involve the conversion of optical signals, current signals, and voltage signals. The acquisition device is only a PC, which is not suitable for airborne smoke detectors in the aviation field, and does not have the versatility of embedded products.

[0008] In order to ensure the sampling accuracy of the alarm smoke concentration range and avoid being constrained by the input voltage limit of the analog-to-digital conversion interface, the smoke detector can detect the smoke concentration of (0-100)% / ft while ensuring the detection accuracy, thereby improving the product's anti-interference and anti-false alarm capabilities. A full-range smoke concentration detection system and method for photoelectric smoke detectors are proposed. Summary of the invention

[0009] The present invention provides a full-range smoke concentration detection system and method for a photoelectric smoke detector, which avoids the constraint of input voltage limiting of an analog-to-digital conversion interface and enables the smoke detector to detect a smoke concentration of (0-100)% / ft while ensuring detection accuracy.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] A full-range smoke concentration detection system for a photoelectric smoke detector includes: a hardware circuit and a software control program. The hardware circuit consists of a light-emitting tube driving module, a light-receiving tube acquisition module, a signal amplification and filtering processing module and a microcontroller. The microcontroller controls the light-emitting diode to light up periodically through the light-emitting tube driving module. Smoke particles scatter the light, so that the light is irradiated to the light-receiving tube acquisition module, thereby generating a photocurrent on the light-receiving diode. After being converted into a voltage signal by IU, the gain is amplified by the signal amplification and filtering processing module to improve the signal output capability. Data processing and anti-interference judgment are performed according to a preset control program. The microcontroller dynamically adjusts the amplification gain according to the signal strength of the light-receiving tube acquisition module.

[0012] As a further technical solution of the present invention, the signal amplification and filtering processing module includes a first-stage amplification module, a first DC isolation filtering module, a second-stage amplification module, a second DC isolation filtering module, a third-stage amplification module and an AD interference filtering module connected in sequence.

[0013] As a further technical solution of the present invention, the light-emitting tube driving module includes: a blue light driving tube and a blue light LED tube, one end of the blue light driving tube is connected to the microcontroller, and the other end is connected to the blue light LED tube, and the microcontroller outputs a control signal to the blue light driving tube to realize the on and off of the light-emitting diode; the light-receiving tube acquisition module includes: a light-receiving diode, a sampling resistor and a filtering module, and the optical signal is converted into an electrical signal through the photoelectric effect of the light-receiving diode, and then converted into a voltage signal through the sampling resistor.

[0014] As a further technical solution of the present invention, the secondary amplification module includes a programmable operational amplifier, the gain of which is controllable and connected to the microcontroller. The microcontroller can adjust the gain multiple of the programmable operational amplifier by sending a corresponding control signal, thereby making the gain multiple of the secondary amplification module dynamically adjustable; the tertiary amplification module includes a digital potentiometer, which is equivalent to a resistor with adjustable resistance. It is used in the circuit as a gain matching resistor of the tertiary amplification module. By sending a control signal to the digital potentiometer by the microcontroller, the resistance value of the digital potentiometer can be continuously changed within a certain range, which is equivalent to the amplification multiple of the tertiary amplification module also changing with the change of the gain matching resistor value, thereby realizing dynamic adjustment of the gain multiple of the tertiary amplification module.

[0015] As a further technical solution of the present invention, the input signal of the microcontroller mainly includes the analog voltage signal of the three-stage amplification module, and the output signal of the microcontroller mainly includes the light-emitting control signal, the programmable operational amplifier gain adjustment control signal, and the digital potentiometer gain adjustment control signal.

[0016] A full range smoke concentration detection method for a photoelectric smoke detector comprises the following steps:

[0017] Based on the smoke signal acquisition and conditioning technology of photoelectric smoke detectors, smoke signal acquisition and conversion to electrical signals are realized;

[0018] Build a full range smoke concentration detection circuit topology for photoelectric smoke detectors;

[0019] The full-range smoke detection gain closed-loop control method of the photoelectric smoke detector is adopted to enable the smoke detector to achieve the calibration of the full-range smoke concentration.

[0020] As a further technical solution of the present invention, the smoke signal collection and conditioning technology specifically includes the following contents:

[0021] The photoelectric smoke detector uses a photoelectric smoke signal acquisition circuit composed of a microcontroller, a light emitting diode, and a light receiving diode as core electronic components;

[0022] The acquisition circuit includes a light-emitting tube driving module, a light-receiving tube acquisition module, a signal amplification and filtering processing module and a microcontroller;

[0023] The photoelectric smoke signal acquisition and conditioning technology is adopted to enable it to have the functions of light-emitting diode drive control and light-receiving diode current-voltage conversion;

[0024] The LED driving function mainly outputs control signals to the LED driving circuit through the microcontroller, and controls the on and off of the LED to control the light-emitting frequency of the LED tube;

[0025] The current-voltage conversion function of the light-receiving tube acquisition module mainly converts the current signal excited by the light-receiving diode after receiving the light signal into a voltage signal through the series connection of the sampling resistor and the light-receiving diode, and outputs it to the post-stage signal amplification and filtering processing module; after filtering and amplification, the voltage signal is calculated and processed by the analog-to-digital conversion and microcontroller for subsequent smoke alarm judgment.

[0026] As a further technical solution of the present invention, the detection circuit topology structure specifically includes the following contents:

[0027] The first-stage amplification module is composed of an operational amplifier and a gain matching resistor, the second-stage amplification module is composed of a program-controlled programmable operational amplifier, and the third-stage amplification module is composed of an operational amplifier and a digital potentiometer;

[0028] Between each stage of the amplification module, there is a DC isolation filter module with capacitors as the core device, which is used to eliminate the DC component in the photoelectric signal and improve the accuracy of the effective voltage signal;

[0029] Through the above-mentioned signal amplification and conditioning electrical cross-linking relationship, the first-stage amplification module, the second-stage amplification module, the third-stage amplification module, the DC isolation filter module, the AD interference filter module and the microcontroller constitute a full-range smoke concentration detection circuit topology structure for a photoelectric smoke detector.

[0030] As a further technical solution of the present invention, the full-range smoke detection gain closed-loop control method specifically includes the following contents:

[0031] The photoelectric smoke signal acquisition circuit with the light-emitting diode drive control function and the light-receiving diode current-voltage conversion function is integrated with the full-range smoke concentration detection circuit topology structure used for the photoelectric smoke detector to form a hardware platform capable of applying the full-range smoke detection gain closed-loop control method;

[0032] The microcontroller controls the periodic lighting of the light-emitting diode through the smoke collection drive function. The smoke particles scatter the light, causing the light to irradiate the light-receiving diode, thereby generating photocurrent on the light-receiving diode. After being converted into a voltage signal by IU, a first-level gain amplification is performed to improve the signal output capability and perform preliminary filtering of the signal.

[0033] The DC component of the voltage signal containing DC bias is isolated and filtered, leaving the effective AC component for secondary and tertiary gain amplification in turn;

[0034] The smoke concentration voltage signal output by the conditioning circuit is subjected to interference filtering of the analog-to-digital conversion interface, and finally input into the analog-to-digital conversion interface of the microcontroller, and the smoke concentration monitoring function is realized by monitoring the change of the analog voltage;

[0035] When the smoke concentration increases, the analog voltage increases and reaches a certain threshold value close to the input voltage limit of the analog-to-digital conversion interface, the microcontroller executes the programmable operational amplifier gain multiple switching function to reduce the gain of the secondary amplification, and the analog voltage signal will decrease proportionally. At this time, the microcontroller amplifies the smoke concentration response value in proportion to the reduction ratio of the analog voltage signal and calculates the actual smoke concentration response value;

[0036] At the moment of switching the gain multiple of the programmable operational amplifier, in order to ensure the continuity of the smoke concentration response value, the microcontroller adjusts the analog voltage signal through the digital potentiometer adjustment function, so that the analog voltage before and after switching the gain multiple has continuity;

[0037] On the contrary, when the smoke concentration decreases, the analog voltage decreases and reaches a certain threshold close to the input voltage limit of the analog-to-digital conversion interface, the microcontroller executes the corresponding smoke detection gain closed-loop control function.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The problem that the smoke concentration analog voltage of the traditional photoelectric smoke detector enters saturation after reaching the input voltage limit of the analog-to-digital conversion interface is solved, resulting in the smoke detector being unable to detect 100% / ft smoke concentration.

[0040] 2. The smoke detector using this solution has the advantages of simple topology, program controllable, high flexibility, easy implementation method, high reliability and full-range concentration detection.

[0041] 3. Through the full-range smoke concentration detection system and method of the photoelectric smoke detector, the constraint of the input voltage limit of the analog-to-digital conversion interface is avoided, and the smoke detector can detect the smoke concentration of (0-100)% / ft while ensuring the detection accuracy. This ensures that the smoke detector has the continuous collection and detection capability for smoke of higher concentrations, thereby improving the detection capability of the smoke detector and the accuracy of the smoke alarm. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying creative labor, other drawings obtained based on these drawings still belong to the scope of the present invention.

[0043] Figure 1 A schematic diagram of the smoke detection working principle of the photoelectric smoke detector of the present invention;

[0044] Figure 2 This is a schematic diagram of the smoke concentration acquisition circuit of the smoke detector of the present invention;

[0045] Figure 3 It is a circuit schematic diagram of a three-stage gain amplification module of the present invention;

[0046] Figure 4 The actual smoke concentration and the smoke concentration response value of the smoke detector of the present invention change curves over time;

[0047] Figure 5 The smoke detection software algorithm overall flow chart of the present invention;

[0048] Figure 6 The smoke detection full range software algorithm flow chart of the present invention;

[0049] Figure 7 A diagram showing the execution steps of the smoke detection software algorithm of the present invention;

[0050] Figure 8 This is a diagram of the execution steps of the full-range smoke detection software algorithm of the present invention. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] See also Figure 1-6 The present invention provides a full-range smoke concentration detection system and method for a photoelectric smoke detector, which includes: a hardware circuit and a software control program. The hardware circuit is composed of a light-emitting tube driving module, a light-receiving tube acquisition module, a signal amplification and filtering processing module and a microcontroller. The microcontroller controls the light-emitting diode to light up periodically through the light-emitting tube driving module. The smoke particles scatter the light, so that the light is irradiated to the light-receiving tube acquisition module, thereby generating a photocurrent on the light-receiving diode. After being converted into a voltage signal by IU, the gain is amplified by the signal amplification and filtering processing module to improve the signal output capability. Data processing and anti-interference judgment are performed according to a preset control program. The microcontroller dynamically adjusts the amplification gain according to the signal strength of the light-receiving tube acquisition module.

[0053] The signal amplification and filtering processing module includes a primary amplification module, a first DC isolation filtering module, a secondary amplification module, a second DC isolation filtering module, a tertiary amplification module and an AD interference filtering module which are connected in sequence.

[0054] The light-emitting tube driving module includes: a blue light driving tube and a blue light LED tube. One end of the blue light driving tube is connected to the microcontroller, and the other end is connected to the blue light LED tube. The microcontroller outputs a control signal to the blue light driving tube to realize the on and off of the light-emitting diode; the light-receiving tube acquisition module includes: a light-receiving diode, a sampling resistor and a filter module. The optical signal is converted into an electrical signal through the photoelectric effect of the light-receiving diode, and then converted into a voltage signal through the sampling resistor.

[0055] The two-stage amplification module includes a programmable operational amplifier, the gain of which is controllable. The programmable operational amplifier is connected to a microcontroller. The microcontroller can adjust the gain multiple of the programmable operational amplifier by sending corresponding control signals, thereby making the gain multiple of the two-stage amplification module dynamically adjustable; the three-stage amplification module includes a digital potentiometer, which is equivalent to a resistor with adjustable resistance. It is used in the circuit as a gain matching resistor of the three-stage amplification module. By sending a control signal to the digital potentiometer through the microcontroller, the resistance value of the digital potentiometer can be continuously changed within a certain range, which is equivalent to the amplification multiple of the three-stage amplification module also changing with the change of the gain matching resistor value, thereby realizing dynamic adjustment of the gain multiple of the three-stage amplification module.

[0056] The input signal of the microcontroller mainly includes the analog voltage signal of the three-stage amplification module, and the output signal of the microcontroller mainly includes the light-emitting control signal, the programmable operational amplifier gain adjustment control signal, and the digital potentiometer gain adjustment control signal.

[0057] The specific design process is:

[0058] Step 1: Smoke signal acquisition and conditioning technology based on photoelectric smoke detectors:

[0059] 1) The photoelectric smoke detector uses a photoelectric smoke signal acquisition circuit composed of a microcontroller, a light emitting diode, and a light receiving diode as core electronic components.

[0060] 2) The acquisition circuit includes a light-emitting tube driving module, a light-receiving tube acquisition module, a signal amplification and filtering processing module and a microcontroller.

[0061] 3) The photoelectric smoke signal acquisition and conditioning technology is used to enable it to have the light-emitting diode drive control function and the light-receiving diode current-voltage conversion function.

[0062] 4) The LED driving function mainly outputs control signals to the LED driving circuit through the microcontroller, and controls the on and off of the LED to control the light-emitting frequency of the LED tube. The main function of this function is to realize the light control function. When smoke enters the light-emitting area, it will scatter the light. The higher the smoke concentration, the stronger the scattered light.

[0063] 5) The current-voltage conversion function of the light-receiving tube acquisition module mainly converts the current signal excited by the light-receiving diode after receiving the light signal into a voltage signal by connecting the sampling resistor in series with the light-receiving diode, and outputs it to the post-stage signal amplification and filtering processing module. After filtering and amplification, the voltage signal is calculated and processed by analog-to-digital conversion and microcontroller for subsequent smoke alarm judgment.

[0064] 6) Through the smoke signal acquisition and conditioning technology, smoke signal acquisition and conversion to electrical signals are realized, so that the subsequent full-range smoke concentration detection can be achieved by calculating and analyzing the changes in the electrical signals.

[0065] Step 2: Build the full range smoke concentration detection circuit topology for photoelectric smoke detectors:

[0066] 1) An operational amplifier and a gain matching resistor are used to form a first-stage amplification module. This module realizes the primary amplification and filtering of the photoelectric signal. Its amplification factor is related to the gain matching resistor. Since the gain matching resistor is a fixed value, the amplification factor of the first-stage amplification module is also a fixed value, which is generally a common-mode amplification circuit.

[0067] 2) A program-controlled programmable operational amplifier is used to form a secondary amplifier module. The gain of the programmable operational amplifier is controllable. It is connected to a microcontroller. The microcontroller can adjust the gain multiple of the programmable operational amplifier by sending corresponding control signals, so that the gain multiple of the secondary amplifier module can be dynamically adjusted. The gain of the programmable operational amplifier is generally several fixed gears.

[0068] 3) An operational amplifier and a digital potentiometer are used to form a three-stage amplifier module. In this module, the digital potentiometer is equivalent to a resistor with adjustable resistance, which is used in the circuit as the gain matching resistor of the operational amplifier of the three-stage amplifier module. By sending a control signal to the digital potentiometer through the microcontroller, the resistance value of the digital potentiometer can be continuously changed within a certain range, which is equivalent to the amplification factor of the three-stage amplifier module also changing with the change of the gain matching resistor value, thereby realizing the dynamic adjustment of the gain factor of the three-stage amplifier module.

[0069] 4) A DC blocking filter module with capacitor as the core device is provided between each stage of the amplification gain module to eliminate the DC component in the photoelectric signal and improve the accuracy of the effective voltage signal.

[0070] 5) Through the above signal amplification and conditioning electrical cross-linking relationship, the first-stage amplification module, the second-stage amplification module, the third-stage amplification module, the DC isolation filter module, the AD interference filter module and the microcontroller constitute a full-range smoke concentration detection circuit topology structure for photoelectric smoke detectors.

[0071] 6) Among them, the microcontroller has analog-to-digital conversion function and program control device drive control function, so as to be able to perform analog voltage acquisition, as well as control of programmable operational amplifiers and digital potentiometers.

[0072] Step 3: Full range smoke detection gain closed loop control method using photoelectric smoke detectors:

[0073] 1) The photoelectric smoke signal acquisition circuit with light-emitting diode drive control function and light-receiving diode current-voltage conversion function is integrated with the full-range smoke concentration detection circuit topology structure for photoelectric smoke detectors to form a hardware platform that can apply the full-range smoke detection gain closed-loop control method.

[0074] 2) The microcontroller controls the periodic lighting of the light-emitting diode through the smoke collection drive function. The smoke particles scatter the light, causing the light to shine on the light-receiving diode, thereby generating photocurrent on the light-receiving diode. After being converted into a voltage signal by IU, a first-level gain amplification is performed to improve the signal output capability and perform preliminary filtering of the signal.

[0075] 3) The voltage signal containing DC bias is isolated and filtered for DC component, leaving the effective AC component for secondary and tertiary gain amplification.

[0076] 4) The smoke concentration voltage signal output by the conditioning circuit is subjected to interference filtering of the analog-to-digital conversion interface, and finally input into the analog-to-digital conversion interface of the microcontroller to realize the smoke concentration monitoring function by monitoring the change of the analog voltage.

[0077] 5) When the smoke concentration increases, the analog voltage increases and reaches a certain threshold close to the input voltage limit of the analog-to-digital conversion interface, the microcontroller executes the programmable operational amplifier gain multiple switching function, reduces the gain of the secondary amplifier, and the analog voltage signal will decrease proportionally. At this time, the microcontroller proportionally amplifies the smoke concentration response value according to the proportion of the reduction of the analog voltage signal, and calculates the actual smoke concentration response value.

[0078] 6) At the moment of switching the gain multiple of the programmable operational amplifier, in order to ensure the continuity of the smoke concentration response value, the microcontroller adjusts the analog voltage signal through the digital potentiometer adjustment function to ensure the continuity of the analog voltage before and after switching the gain multiple.

[0079] 7) On the contrary, when the smoke concentration decreases, the analog voltage decreases and reaches a certain threshold close to the input voltage limit of the analog-to-digital conversion interface, the microcontroller executes the corresponding smoke detection gain closed-loop control function.

[0080] 8) In addition to the circuit hardware platform, the above-mentioned full-range smoke detection gain closed-loop control method also includes the corresponding software control algorithm. The software control algorithm functions include the drive control of the light-emitting diode, the photoelectric signal acquisition and analog-to-digital conversion of the light-receiving diode, the secondary gain amplification adjustment, the tertiary gain amplification adjustment, the comprehensive logic judgment of the smoke alarm, etc. The software collects the smoke concentration signal through the analog input interface. If the smoke concentration is high, it adaptively switches to the lower programmable operational amplifier amplification factor to amplify the smoke concentration signal. If the smoke concentration is low, it adaptively switches to the higher programmable operational amplifier amplification factor to reduce the smoke concentration signal, thereby expanding the range of smoke concentration signal acquisition.

[0081] 9) The above process enables the smoke detector to maintain continuous changes in voltage value within the full range of smoke concentrations without full deviation, thereby enabling the smoke detector to achieve calibration of the full range of smoke concentrations and execute an algorithm for identifying interference sources.

[0082] Specific application examples:

[0083] The programmable operational amplifier used in the smoke detector has 1x, 4x, 8x, and 16x proportional method functions, and the digital potentiometer used is adjustable from 1Ω to 100kΩ. The circuit design is as follows: Figure 3 As shown, the specific implementation steps are as follows:

[0084] 1) After the product is initialized, the microcontroller outputs the LED drive signal to light up the LED, and at the same time the microcontroller starts to execute the light receiving diode collection function.

[0085] 2) The software calculates the smoke concentration response value based on the result of the smoke concentration voltage signal filtering and the programmable operational amplifier amplification factor.

[0086] 3) When the smoke concentration voltage signal reaches a certain value, the current circuit is considered to have reached saturation. At this time, the software adjusts the programmable op amp gain to adjust the signal gain of the sampling and conditioning circuit and the smoke concentration response value to expand the concentration range of smoke detection. Programmable op amps generally have multiple gain levels of +1, +4, +8, and +16. Programmable op amps with more gain levels can be selected according to actual needs. Here is just an example. The software should switch the programmable op amp gain according to the following conditions. The gain is divided into 4 levels of 1, 4, 8, and 16, and decreases step by step when it is reduced:

[0087] a) When the original voltage of the blue light smoke is greater than 4V, the secondary gain amplifier circuit is reduced by one level of amplification until the voltage is less than 4V or the amplification factor is 1 and the switching stops.

[0088] b) When the original voltage of the blue light smoke is less than 1V, the secondary gain amplifier circuit is amplified by one gear until the voltage is greater than 1V or the amplification factor is 16 times and the switching stops.

[0089] 4) After the adjustment of the gain multiple of the secondary operational amplifier is completed, the smoke concentration response value after the current reduction of the amplification factor is obtained through the calculation formula. At the same time, according to the algorithm, by adjusting the gain multiple (digital potentiometer) of the three-stage amplifier circuit, the continuous change of the smoke concentration value after analog-to-digital conversion is achieved.

[0090] 5) Digital potentiometers generally have multiple adjustable resistors, with a maximum value of 100kΩ and a minimum value of 1Ω for each channel. In actual use, it is connected in parallel with a fixed-resistance feedback resistor, and the adjustment range can be adjusted according to demand. Here is just an example to connect the digital potentiometer and the 825K resistor in parallel to achieve a three-level gain adjustment range of 1 to 9.9 times. The calculation formula for the resistance value of the digital potentiometer is given in the device chip manual, which is generally:

[0091]

[0092] Where RWB is the final resistance value, RAB is the fixed resistance value of the maximum adjustable range (100kΩ), RW is the minimum value of the fixed adjustable range (1Ω), and D is the control word instruction output by the microcontroller, which can achieve resistance adjustment with a minimum accuracy of 1 / 256.

[0093] 6) According to the currently adjusted smoke concentration response value, the smoke alarm comprehensive logic judgment algorithm is used to monitor the smoke alarm status and identify the interference source. The expanded smoke concentration detection range can identify high-concentration smoke and interference sources (water vapor, sand and dust), thereby reducing the false alarm rate of smoke detectors and improving the performance and reliability of smoke detectors.

[0094] The smoke detector performance test equipment was used to verify the smoke detection performance. Under normal temperature and pressure conditions, the smoke concentration was set to a smoke rising rate of about 2% / ft per minute, rising uniformly from 0% / ft to 18% / ft and then exhausting the smoke. The actual smoke concentration and the smoke concentration response value of the smoke detector change over time as shown in the figure. Figure 4 As shown. It can be seen from the figure that the non-full-range smoke response value using the scheme of the present application reaches a value close to the input voltage limit of the analog-to-digital conversion interface when the analog voltage is close to 5000mV, and the smoke concentration response value no longer changes with the actual smoke concentration, while the full-range smoke response value using the scheme of the present application is not constrained by the input voltage limit of the analog-to-digital conversion interface and can always change with the actual smoke concentration. Among them, when the smoke concentration is about 6% / ft and 12% / ft, the analog voltage reaches a certain threshold close to the input voltage limit of the analog-to-digital conversion interface, that is, 4000mV. At this time, the microcontroller executes the programmable operational amplifier gain multiple switching function and the digital potentiometer adjustment function, ensuring that the smoke concentration response value always increases continuously with the increase of the smoke concentration, thereby realizing the full-range smoke detection of the smoke detector.

[0095] So far, the purpose of the present invention has been achieved.

[0096] It will be apparent to those skilled in the art that the 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 features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A full range smoke concentration detection system for a photoelectric smoke detector, characterized in that ,include: Hardware circuit and software control program, the hardware circuit is composed of a light-emitting tube driving module, a light-receiving tube acquisition module, a signal amplification and filtering processing module and a microcontroller. The microcontroller controls the light-emitting diode to light up periodically through the light-emitting tube driving module. The smoke particles scatter the lit light, so that the light is irradiated to the light-receiving tube acquisition module, thereby generating photocurrent on the light-receiving diode. After being converted into a voltage signal by IU, the gain is amplified by the signal amplification and filtering processing module to improve the signal output capability. Data processing and anti-interference judgment are performed according to a preset control program. The microcontroller dynamically adjusts the amplification gain according to the signal strength of the light-receiving tube acquisition module.

2. A full range smoke concentration detection system of a photoelectric smoke detector according to claim 1, characterized in that: The signal amplification and filtering processing module comprises a primary amplification module, a first DC isolation filtering module, a secondary amplification module, a second DC isolation filtering module, a tertiary amplification module and an AD interference filtering module which are connected in sequence.

3. A full range smoke concentration detection system of a photoelectric smoke detector according to claim 2, characterized in that: The light-emitting tube driving module includes: a blue light driving tube and a blue light LED tube. One end of the blue light driving tube is connected to the microcontroller, and the other end is connected to the blue light LED tube. The microcontroller outputs a control signal to the blue light driving tube to realize the on and off of the light-emitting diode; the light-receiving tube acquisition module includes: a light-receiving diode, a sampling resistor and a filtering module. The optical signal is converted into an electrical signal through the photoelectric effect of the light-receiving diode, and then converted into a voltage signal through the sampling resistor.

4. A full range smoke concentration detection system of a photoelectric smoke detector according to claim 2, characterized in that: The secondary amplification module includes a programmable operational amplifier whose gain is controllable. The programmable operational amplifier is connected to the microcontroller. The microcontroller can adjust the gain multiple of the programmable operational amplifier by sending corresponding control signals, thereby making the gain multiple of the secondary amplification module dynamically adjustable.

5. A full range smoke concentration detection system for a photoelectric smoke detector according to claim 2, characterized in that: The three-stage amplification module includes a digital potentiometer, which is equivalent to a resistor with adjustable resistance. It is used in the circuit as a gain matching resistor of the three-stage amplification module. The microcontroller sends a control signal to the digital potentiometer, so that the resistance value of the digital potentiometer can change continuously within a certain range, which is equivalent to the amplification factor of the three-stage amplification module also changing with the change of the gain matching resistance value, thereby realizing dynamic adjustment of the gain factor of the three-stage amplification module.

6. A full range smoke concentration detection system for a photoelectric smoke detector according to claim 2, characterized in that: The input signal of the microcontroller mainly includes the analog voltage signal of the three-stage amplification module, and the output signal of the microcontroller mainly includes the light-emitting control signal, the programmable operational amplifier gain adjustment control signal, and the digital potentiometer gain adjustment control signal.

7. A method for detecting full-range smoke concentration of a photoelectric smoke detector, characterized in that: The steps include: Based on the smoke signal acquisition and conditioning technology of photoelectric smoke detectors, smoke signal acquisition and conversion to electrical signals are realized; Build a full range smoke concentration detection circuit topology for photoelectric smoke detectors; The full-range smoke detection gain closed-loop control method of the photoelectric smoke detector is adopted to enable the smoke detector to achieve the calibration of the full-range smoke concentration.

8. A full range smoke concentration detection system for a photoelectric smoke detector according to claim 7, characterized in that: The smoke signal collection and conditioning technology specifically includes the following contents: The photoelectric smoke detector uses a photoelectric smoke signal acquisition circuit composed of a microcontroller, a light emitting diode, and a light receiving diode as core electronic components; The acquisition circuit includes a light-emitting tube driving module, a light-receiving tube acquisition module, a signal amplification and filtering processing module and a microcontroller; The photoelectric smoke signal acquisition and conditioning technology is adopted to enable it to have the functions of light-emitting diode drive control and light-receiving diode current-voltage conversion; The LED driving function mainly outputs control signals to the LED driving circuit through the microcontroller, and controls the on and off of the LED to control the light-emitting frequency of the LED tube; The current-voltage conversion function of the light-receiving tube acquisition module mainly converts the current signal excited by the light-receiving diode after receiving the light signal into a voltage signal through the sampling resistor and the light-receiving diode in series, and outputs it to the post-stage signal amplification and filtering processing module; After filtering and amplification, the voltage signal is calculated and processed by analog-to-digital conversion and a microcontroller for subsequent smoke alarm judgment.

9. A full range smoke concentration detection system for a photoelectric smoke detector according to claim 8, characterized in that: The detection circuit topology structure specifically includes the following contents: The first-stage amplification module is composed of an operational amplifier and a gain matching resistor, the second-stage amplification module is composed of a program-controlled programmable operational amplifier, and the third-stage amplification module is composed of an operational amplifier and a digital potentiometer; Between each stage of the amplification module, there is a DC isolation filter module with capacitors as the core device, which is used to eliminate the DC component in the photoelectric signal and improve the accuracy of the effective voltage signal; Through the above-mentioned signal amplification and conditioning electrical cross-linking relationship, the first-stage amplification module, the second-stage amplification module, the third-stage amplification module, the DC isolation filter module, the AD interference filter module and the microcontroller constitute a full-range smoke concentration detection circuit topology structure for a photoelectric smoke detector.

10. A full range smoke concentration detection system for a photoelectric smoke detector according to claim 9, characterized in that: The full-range smoke detection gain closed-loop control method specifically includes the following contents: The photoelectric smoke signal acquisition circuit with the light-emitting diode drive control function and the light-receiving diode current-voltage conversion function is integrated with the full-range smoke concentration detection circuit topology structure used for the photoelectric smoke detector to form a hardware platform capable of applying the full-range smoke detection gain closed-loop control method; The microcontroller controls the periodic lighting of the light-emitting diode through the smoke collection drive function. The smoke particles scatter the light, causing the light to irradiate the light-receiving diode, thereby generating photocurrent on the light-receiving diode. After being converted into a voltage signal by IU, a first-level gain amplification is performed to improve the signal output capability and perform preliminary filtering of the signal. The DC component of the voltage signal containing DC bias is isolated and filtered, leaving the effective AC component for secondary and tertiary gain amplification in turn; The smoke concentration voltage signal output by the conditioning circuit is subjected to interference filtering of the analog-to-digital conversion interface, and finally input into the analog-to-digital conversion interface of the microcontroller, and the smoke concentration monitoring function is realized by monitoring the change of the analog voltage; When the smoke concentration increases, the analog voltage increases and reaches a certain threshold value close to the input voltage limit of the analog-to-digital conversion interface, the microcontroller executes the programmable operational amplifier gain multiple switching function to reduce the gain of the secondary amplification, and the analog voltage signal will decrease proportionally. At this time, the microcontroller amplifies the smoke concentration response value in proportion to the reduction ratio of the analog voltage signal and calculates the actual smoke concentration response value; At the moment of switching the gain multiple of the programmable operational amplifier, in order to ensure the continuity of the smoke concentration response value, the microcontroller adjusts the analog voltage signal through the digital potentiometer adjustment function, so that the analog voltage before and after switching the gain multiple has continuity; On the contrary, when the smoke concentration decreases, the analog voltage decreases and reaches a certain threshold close to the input voltage limit of the analog-to-digital conversion interface, the microcontroller executes the corresponding smoke detection gain closed-loop control function.

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