A photoelectric smoke detector system and method for full-range smoke concentration detection

Abstract

This invention belongs to the technical field of aviation smoke detectors, and discloses a full-range smoke concentration detection system and method for photoelectric smoke detectors. Based on photoelectric smoke signal acquisition and conditioning technology, it uses a full-range smoke concentration detection method to avoid the constraints of analog-to-digital conversion interface input voltage limiting, enabling the smoke detector to detect smoke concentrations of (0-100)% / ft while ensuring detection accuracy. The smoke detector using this solution has the advantages of simple topology, controllable program, high flexibility, easy implementation, high reliability, and full-range concentration detection.

Description

Technical Field

[0001] This invention belongs to the field of aviation smoke detector technology, specifically relating to a photoelectric smoke detector system and method for full-range smoke concentration detection. Background Technology

[0002] Traditional photoelectric smoke detectors use a combination of light-emitting diodes (LEDs) and photodiodes (PDDs) to detect smoke particles. When the light from the LED is lit and shines on the smoke particles, light scattering occurs. Because this scattered light has different directions and angles, it cannot be largely absorbed or reflected by the optical structure. As a result, the photocurrent generated on the PDD gradually increases. After sampling and conditioning into a voltage signal, a mode conversion is performed. The microprocessor identifies the input voltage of the analog-to-digital converter (ADC) interface to determine the smoke concentration. Currently, the transmittance of mainstream smoke detectors is (93–97)% / ft, meaning the smoke concentration alarm threshold is (3–7)% / ft. To improve the sampling accuracy of smoke concentration, the resolution of the ADC input voltage is maximized within the smoke concentration alarm threshold range. Therefore, the analog voltage saturates after reaching the ADC input voltage limit, resulting in the smoke detector being unable to detect smoke concentrations of (7–100)% / ft.

[0003] This shows that for higher concentrations of smoke, the circuit design limits its effectiveness in identification and calibration. Currently, with the increasing demands on the sensitivity and anti-interference capabilities of smoke detectors for applications such as aircraft fire prevention, the lower limit of smoke concentration (light transmittance) that a single model of smoke detector can detect has further increased. This means that the sensitivity requirements for smoke detection are becoming increasingly stringent. Therefore, even lower concentrations of smoke and interfering sources (water vapor, dust, etc.) can cause the collected analog voltage to reach its upper voltage amplitude limit and saturate. This results in traditional photoelectric smoke detection methods being unable to effectively identify high concentrations of smoke and interfering sources, leading to a higher false alarm rate and impacting the accuracy and anti-interference capabilities of smoke detectors to some extent.

[0004] Patent 1: Application No. CN202110760559.4 discloses a method and device for high-precision smoke detection. This invention belongs to the field of photoelectric smoke detector technology. The device includes a photoelectric smoke detector, which comprises a transmission control circuit, a transmitting tube, a photosensitive receiving tube, a small signal amplification circuit, and an MCU. The MCU includes an ADC. The method includes placing the photoelectric smoke detector in a standard smoke concentration; the ADC acquiring the output value of the small signal amplification circuit; the MCU adjusting the amplification gain of the small signal amplification circuit to make the output value of the small signal amplification circuit close to a preset alarm threshold; completing the calibration of the photoelectric smoke detector; the MCU recording the alarm threshold and the gain adjustment value of the small signal amplification circuit; installing the photoelectric smoke detector in the workplace, setting the gain value of the small signal amplification circuit according to parameters, and performing smoke detection. The beneficial effects of this invention are: it can eliminate the gain difference of the amplification circuit caused by component differences and assembly errors, thus improving the detection accuracy of the photoelectric smoke detector.

[0005] Patent 2: Application No. CN201310751366.8 discloses a photoelectric smoke detector and its usage method. This invention provides a photoelectric smoke detector whose signal processing unit amplifies the signal based on a first or second gain value received from a calibration control unit. The photoelectric smoke detector also includes a long-term drift monitoring unit, which monitors the long-term drift of the signal output by the photoelectric smoke detection unit and outputs monitoring information to the calibration control unit. The calibration control unit compensates for the first gain value based on the monitoring information and then sends it to the signal processing unit. This invention also provides a method for using this detector. The photoelectric smoke detector and its usage method of this invention can eliminate the influence of rapid drift in each detection. By performing a long-term drift monitoring and compensation process at fixed intervals, the influence of long-term drift can be eliminated, ensuring the accuracy and reliability of the detection results of the photoelectric smoke detector. Furthermore, the circuit structure is simple and easy to implement.

[0006] Patent 3: Application No. CN201310237553.4 discloses a variable gain small current pickup amplifier circuit. This invention includes a small current signal sampling circuit for acquiring small current signals. Its output is connected to the input of a first-stage precision operational amplifier circuit. The output of the first-stage precision operational amplifier circuit and the output of the gain control circuit are both connected to the input of a second-stage variable gain operational amplifier circuit. The output of the second-stage variable gain operational amplifier circuit is connected to a PC. This invention allows for flexible adjustment of the amplification factor, enabling shared use over a large current sampling range. It simplifies the analog signal processing of the detector and exhibits good versatility and stability.

[0007] Of the three patents mentioned above, Patent 1 improves the detection accuracy of the photoelectric smoke detector by eliminating differences in amplifier circuit gain caused by component variations and assembly errors, mainly addressing inconsistencies in the smoke detector manufacturing process. Patent 2 eliminates the effects of long-term drift by performing long-term drift monitoring and compensation at fixed intervals, ensuring the accuracy and reliability of the photoelectric smoke detector's detection results, primarily addressing the issue of deviation between the actual sensitivity and the predetermined sensitivity after prolonged operation. Patent 3 only describes the sampling and conditioning method for minute current signals, without involving the conversion of optical, current, or voltage signals, and the acquisition device is limited to a PC, making it unsuitable for airborne smoke detectors in the aviation field, and lacking the versatility of embedded products.

[0008] To ensure the sampling accuracy of the alarm smoke concentration range while avoiding the constraint of the analog-to-digital converter interface input voltage limit, and to enable the smoke detector to detect smoke concentrations of (0~100)% / ft while ensuring detection accuracy, thereby improving the product's anti-interference and false alarm prevention capabilities, a full-range smoke concentration detection system and method for photoelectric smoke detectors is proposed. Summary of the Invention

[0009] This invention provides a full-range smoke concentration detection system and method for photoelectric smoke detectors, avoiding the constraint of input voltage limitation of analog-to-digital conversion interface, and enabling the smoke detector to detect smoke concentrations of (0~100)% / ft while ensuring detection accuracy.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A full-range smoke concentration detection system for a photoelectric smoke detector includes: hardware circuitry and software control program. The hardware circuitry consists of a light-emitting diode (LED) driving module, a light-receiving diode acquisition module, a signal amplification and filtering module, and a microcontroller. The microcontroller controls the LED to periodically light up through the LED driving module. Smoke particles scatter the lit light, causing it to illuminate the light-receiving diode acquisition module, thereby generating a photocurrent on the LED. After being converted into a voltage signal by IU, the signal is amplified by the signal amplification and filtering 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 based on the signal strength of the light-receiving diode 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 blocking filter module, a second-stage amplification module, a second DC blocking filter module, a third-stage amplification module, and an AD interference filter module connected in sequence.

[0013] As a further technical solution of the present invention, the light-emitting diode driving module includes: a blue light driving diode and a blue light LED. One end of the blue light driving diode is connected to the microcontroller, and the other end is connected to the blue light LED. The microcontroller outputs a control signal to the blue light driving diode to realize the conduction and shutdown of the light-emitting diode. The light-receiving diode acquisition module includes: a light-receiving diode, a sampling resistor, and a filtering module. The light 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 is connected to the microcontroller. The microcontroller can adjust the gain of the programmable operational amplifier by sending corresponding control signals, thereby making the gain of the secondary amplification module dynamically adjustable. The tertiary amplification module includes a digital potentiometer, which is equivalent to an adjustable resistor. It is used as the gain matching resistor of the tertiary amplification module in the circuit. By sending control signals to the digital potentiometer through the microcontroller, the resistance value of the digital potentiometer can be continuously changed within a certain range. This means that the amplification factor of the tertiary amplification module also changes with the change of the gain matching resistor value, thereby realizing the dynamic adjustment of the gain 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 emission control signal, the programmable operational amplifier gain adjustment control signal, and the digital potentiometer gain adjustment control signal.

[0016] A method for detecting smoke concentration across the entire range using a photoelectric smoke detector, comprising the following steps:

[0017] Smoke signal acquisition and conditioning technology based on photoelectric smoke detectors enables the acquisition of smoke signals and their conversion into electrical signals.

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

[0019] By adopting a closed-loop control method for the full-range smoke detection gain of a photoelectric smoke detector, the smoke detector can achieve calibration of smoke concentration across the entire range.

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

[0021] The photoelectric smoke detector uses a photoelectric smoke signal acquisition circuit composed of microcontrollers, light-emitting diodes, and light-absorbing diodes as core electronic components.

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

[0023] It employs photoelectric smoke signal acquisition and conditioning technology to enable it to have LED driving control function and LED current-to-voltage conversion function;

[0024] The LED driving function mainly involves the microcontroller outputting control signals to the LED driving circuit, thereby controlling the LED's emission frequency by controlling its on / off state.

[0025] The current-to-voltage conversion function of the light-receiving diode 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 subsequent signal amplification and filtering processing module. After filtering and amplification, the voltage signal is calculated and processed by analog-to-digital converter and microcontroller for subsequent smoke alarm judgment.

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

[0027] An operational amplifier and a gain matching resistor are used to form a first-stage amplification module; a programmable operational amplifier controlled by a program is used to form a second-stage amplification module; and an operational amplifier and a digital potentiometer are used to form a third-stage amplification module.

[0028] Each amplification module is equipped with a DC blocking filter module with capacitors as the core component, which is used to eliminate the DC component in the photoelectric signal and improve the accuracy of the effective voltage signal.

[0029] By amplifying and conditioning the electrical interconnection relationship described above, a full-range smoke concentration detection circuit topology for photoelectric smoke detectors is constructed by combining a first-stage amplification module, a second-stage amplification module, a third-stage amplification module, a DC blocking filter module, an AD interference filter module, and a microcontroller.

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

[0031] The photoelectric smoke signal acquisition circuit with LED driving control function and LED current-to-voltage conversion function is integrated with the full-range smoke concentration detection circuit topology for photoelectric smoke detectors to form a hardware platform that can apply the full-range smoke detection gain closed-loop control method.

[0032] The microcontroller controls the periodic lighting of the light-emitting diodes (LEDs) through the smoke collection drive function. The smoke particles scatter the light, causing it to shine on the LEDs and generate a photocurrent. This photocurrent is converted into a voltage signal by the IU (induction generator) and then amplified by the gain stage to improve the signal output capability and perform preliminary filtering of the signal.

[0033] The voltage signal containing DC bias is isolated by DC component filtering, and the effective AC component is then subjected to two-stage and three-stage amplification for gain adjustment.

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

[0035] When the smoke concentration increases, the analog voltage increases and reaches a certain threshold that is close to the input voltage limit of the analog-to-digital converter interface, the microcontroller executes the programmable operational amplifier gain switching function to reduce the gain of the second-stage amplifier. The analog voltage signal will decrease proportionally. At this time, the microcontroller amplifies the smoke concentration response value proportionally according to the reduction of the analog voltage signal and calculates the actual smoke concentration response value.

[0036] When switching the gain 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 is continuous.

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

[0038] Compared with the prior art, the beneficial effects of the present invention are:

[0039] 1. This solves the problem that the analog voltage of smoke concentration in traditional photoelectric smoke detectors saturates after reaching the input voltage limit of the analog-to-digital conversion interface, thus preventing the smoke detector from detecting 100% / ft of smoke concentration.

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

[0041] 3. By using a full-range smoke concentration detection system and method for photoelectric smoke detectors, the limitations of the input voltage of the analog-to-digital converter interface are avoided, enabling the smoke detector to detect smoke concentrations of (0~100)% / ft while ensuring detection accuracy. This ensures that the smoke detector has the ability to continuously collect and detect smoke of higher concentrations, thereby improving the detection capability and accuracy of smoke alarms. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0043] Figure 1 This is a schematic diagram illustrating the working principle of the photoelectric smoke detector of the present invention.

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

[0045] Figure 3 This is a schematic diagram of the three-stage gain amplifier module of the present invention;

[0046] Figure 4 The curves showing the actual smoke concentration and the smoke detector's smoke concentration response value over time are from the present invention.

[0047] Figure 5 This is the overall flowchart of the smoke detection software algorithm of the present invention;

[0048] Figure 6 This is a flowchart of the full-range smoke detection software algorithm of the present invention;

[0049] Figure 7 This is a diagram illustrating the execution steps of the smoke detection software algorithm of the present invention;

[0050] Figure 8 This diagram illustrates the execution steps of the full-range smoke detection software algorithm of the present invention. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Please see Figure 1-6 This invention provides a full-range smoke concentration detection system and method for a photoelectric smoke detector, comprising: hardware circuitry and software control program. The hardware circuitry consists of a light-emitting diode (LED) driving module, a light-receiving diode acquisition module, a signal amplification and filtering module, and a microcontroller. The microcontroller controls the LED to periodically light up through the LED driving module. Smoke particles scatter the lit light, causing it to illuminate the light-receiving diode acquisition module, thereby generating a photocurrent on the LED. After being converted into a voltage signal by IU, the gain is amplified by the signal amplification and filtering 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 based on the signal strength of the light-receiving diode acquisition module.

[0053] The signal amplification and filtering module includes a first-stage amplification module, a first DC blocking filter module, a second-stage amplification module, a second DC blocking filter module, a third-stage amplification module, and an AD interference filter module connected in sequence.

[0054] The LED driving module includes a blue LED driver and a blue LED. One end of the blue LED driver is connected to a microcontroller, and the other end is connected to the blue LED. The microcontroller outputs a control signal to the blue LED driver to turn the LED on and off. The light receiving module includes a light receiving diode, a sampling resistor, and a filtering module. The light receiving diode converts the light signal into an electrical signal through the photoelectric effect, and then converts it into a voltage signal through the sampling resistor.

[0055] The second-stage amplification module includes a programmable operational amplifier (PAP), whose gain is controllable. It is connected to a microcontroller, which, by sending corresponding control signals, adjusts the PAP gain, thus making the gain of the second-stage amplification module dynamically adjustable. The third-stage amplification module includes a digital potentiometer, which acts as an adjustable resistor, serving as the gain matching resistor for the third-stage amplification module. By sending control signals from the microcontroller to the digital potentiometer, its resistance value can be continuously varied within a certain range. This means the amplification factor of the third-stage amplification module changes accordingly with the change in the gain matching resistor value, thereby achieving dynamic adjustment of the third-stage amplification module's gain.

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

[0057] The specific design process is as follows:

[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 microcontrollers, light-emitting diodes, and light-absorbing diodes as core electronic components.

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

[0061] 3) It adopts photoelectric smoke signal acquisition and conditioning technology to enable it to have LED driving control function and LED current-voltage conversion function.

[0062] 4) The LED driving function mainly uses the microcontroller to output control signals to the LED driving circuit. By controlling the on / off state of the LED, the light emission frequency and other parameters of the LED are controlled. The main function of this function is to achieve light emission control. 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-to-voltage conversion function of the light-receiving diode acquisition module mainly converts the current signal generated by the light-receiving diode after receiving the light signal into a voltage signal through a sampling resistor connected in series with the light-receiving diode. This voltage signal is then output to the subsequent signal amplification and filtering module. After filtering and amplification, the voltage signal is calculated and processed by an analog-to-digital converter and a microcontroller for subsequent smoke alarm judgment.

[0064] 6) Through this smoke signal acquisition and conditioning technology, smoke signals are acquired and converted into electrical signals. Then, by calculating and analyzing the changes in the electrical signals, subsequent full-range smoke concentration detection can be achieved.

[0065] Step 2: Construct 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 construct a primary amplification module. This module performs primary amplification and filtering of photoelectric signals. Its amplification factor is related to the gain matching resistor. Since the gain matching resistor is a fixed value, the amplification factor of this primary amplification module is also a fixed value. It is generally a non-inverting amplifier circuit.

[0067] 2) A programmable operational amplifier (PAP) is used to construct a two-stage amplification module. The gain of the PAP is controllable and it is connected to a microcontroller. The microcontroller can adjust the gain of the PAP by sending corresponding control signals, thus making the gain of the two-stage amplification module dynamically adjustable. The gain of the PAP is typically set to several fixed levels.

[0068] 3) A three-stage amplification module is constructed using operational amplifiers and digital potentiometers. In this module, the digital potentiometer acts as an adjustable resistor, serving as the gain matching resistor for the operational amplifier in the three-stage amplification module. By sending control signals to the digital potentiometer via a microcontroller, the resistance value of the digital potentiometer can be continuously varied within a certain range. This means that the amplification factor of the three-stage amplification module also changes with the value of the gain matching resistor, thereby achieving dynamic adjustment of the gain factor of the three-stage amplification module.

[0069] 4) Each stage of amplification gain module is equipped with a DC blocking filter module with capacitors as the core component, which is used to eliminate the DC component in the photoelectric signal and improve the accuracy of the effective voltage signal.

[0070] 5) By amplifying and conditioning the electrical cross-linking relationship as described above, the first-stage amplification module, the second-stage amplification module, the third-stage amplification module, the DC blocking filter module, the AD interference filter module, and the microcontroller are combined to form a full-range smoke concentration detection circuit topology for photoelectric smoke detectors.

[0071] 6) The microcontroller has analog-to-digital conversion and programmable device drive control functions, so as to be able to acquire analog voltages and control programmable operational amplifiers and digital potentiometers.

[0072] Step 3: Employing a closed-loop control method for the full-range smoke detection gain of a photoelectric smoke detector:

[0073] 1) Integrate the photoelectric smoke signal acquisition circuit with LED driving control function and LED current-to-voltage conversion function with the full-range smoke concentration detection circuit topology 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 diodes through the smoke collection drive function. The smoke particles scatter the light, causing the light to shine on the light-collecting diodes, thereby generating a photocurrent on the light-collecting diodes. After being converted into a voltage signal by IU, it undergoes a first-stage amplification to improve the signal output capability and perform preliminary filtering of the signal.

[0075] 3) Isolate the DC component of the voltage signal containing DC bias and filter it to leave the effective AC component for secondary and tertiary amplification.

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

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

[0078] 6) When switching the gain 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 is continuous.

[0079] 7) Conversely, when the smoke concentration decreases, the analog voltage decreases and reaches a certain threshold that is 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 a corresponding software control algorithm. The software control algorithm functions include driving control of the LEDs, acquiring and converting the photoelectric signal from the LEDs to analog-to-digital conversion, adjusting the second-level gain amplification factor, adjusting the third-level gain amplification factor, and making comprehensive logic judgments for smoke alarms. The software acquires the smoke concentration signal through an analog input interface. If the smoke concentration is high, it adaptively switches to the lower-level programmable operational amplifier amplification factor to amplify the smoke concentration signal; if the smoke concentration is low, it adaptively switches to the higher-level programmable operational amplifier amplification factor to reduce the smoke concentration signal, thus expanding the range of smoke concentration signal acquisition.

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

[0082] Specific application examples:

[0083] The smoke detector uses a programmable operational amplifier with scaling capabilities of 1x, 4x, 8x, and 16x, and its digital potentiometer is adjustable from 1Ω to 100kΩ. Its circuit design is as follows: Figure 3 As shown, the specific implementation steps are as follows:

[0084] 1) After the product completes initialization, the microcontroller outputs a light-emitting diode drive signal to light up the light-emitting diode, and at the same time the microcontroller starts to execute the light-receiving diode acquisition function.

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

[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 amplification factor of the programmable operational amplifier to adjust the signal amplification factor of the sampling conditioning circuit and the smoke concentration response value, thereby expanding the concentration range of smoke detection. Programmable operational amplifiers generally have multiple amplification gain levels of +1, +4, +8, and +16. Depending on actual needs, more gain levels of programmable operational amplifiers can be selected. This is just an example; the software should switch the amplification factor of the programmable operational amplifier according to the following conditions. The amplification factor is divided into four levels: 1, 4, 8, and 16, decreasing progressively with each level:

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

[0088] b) When the original voltage of the blue light smoke is less than 1V, the secondary gain amplifier circuit will increase the amplification factor by one level until the voltage is greater than 1V or the amplification factor is 16 times, at which point the switching will stop.

[0089] 4) After the gain of the second-stage operational amplifier is adjusted, the smoke concentration response value after reducing the amplification factor is obtained through the calculation formula. At the same time, according to the algorithm, the gain factor of the third-stage amplifier circuit (digital potentiometer) is adjusted to realize the continuous change of the smoke concentration value after analog-to-digital conversion.

[0090] 5) Digital potentiometers typically have multiple adjustable resistors, each with a maximum value of 100kΩ and a minimum of 1Ω. In practical applications, they are connected in parallel with a fixed-value feedback resistor. The adjustment range can be adjusted according to requirements. For example, connecting a digital potentiometer in parallel with an 825K resistor achieves a three-stage gain adjustment range of 1 to 9.9 times. The specific formula for calculating the resistance value of a digital potentiometer is given in the device chip datasheet, and is generally as follows:

[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 precision of 1 / 256.

[0093] 6) Based on the adjusted smoke concentration response value, the smoke alarm status is monitored and interference sources are identified through a comprehensive logic judgment algorithm. The expanded smoke concentration detection range enables the identification of high-concentration smoke and interference sources (water vapor, dust), thereby reducing the false alarm rate of the smoke detector and improving its performance and reliability.

[0094] Smoke detection performance was verified using smoke detector performance testing equipment. Under normal temperature and pressure conditions, the smoke concentration was set at a rising rate of approximately 2% / ft / minute, uniformly increasing from 0% / ft to 18% / ft before being discharged. The changes in actual smoke concentration and the smoke detector's smoke concentration response value over time are shown below. Figure 4 As shown in the figure, the non-full-range smoke response value of the proposed solution reaches near the input voltage limit of the analog-to-digital converter interface when the analog voltage approaches 5000mV, at which point the smoke concentration response value no longer changes with the actual smoke concentration. In contrast, the full-range smoke response value of the proposed solution is not constrained by the input voltage limit of the analog-to-digital converter interface and can always change with the actual smoke concentration. Specifically, when the smoke concentration is approximately 6% / ft and 12% / ft, the analog voltage reaches a threshold close to the input voltage limit of the analog-to-digital converter interface, namely 4000mV. At this point, the microcontroller executes the programmable operational amplifier gain switching function and the digital potentiometer adjustment function, ensuring that the smoke concentration response value continuously increases with the increase of smoke concentration, thereby achieving full-range smoke detection of the smoke detector.

[0095] Thus, the objective of this invention has been achieved.

[0096] 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 its spirit or essential characteristics. 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, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A photoelectric smoke detector's full-range smoke concentration detection system, characterized in that, include: The hardware circuit and software control program, wherein the hardware circuit consists of a light-emitting diode driving module, a light-receiving diode acquisition module, a signal amplification and filtering processing module, and a microcontroller; The microcontroller controls the LED to light up periodically through the LED driver module. Smoke particles scatter the lit light, causing it to shine on the light-collecting module, thereby generating a photocurrent on the light-collecting LED. After being converted into a voltage signal by the IU, the signal is amplified and filtered by the signal amplification and filtering module to improve the signal output capability and perform preliminary filtering of the signal. The voltage signal containing DC bias is isolated by DC component filtering, and the effective AC component is then subjected to two-stage and three-stage amplification for gain adjustment. The output smoke concentration voltage signal is filtered by the analog-to-digital conversion interface and then input to the analog-to-digital conversion interface of the microcontroller. The smoke concentration monitoring function is realized by monitoring the changes in analog voltage. When the smoke concentration increases, the analog voltage increases and reaches a certain threshold that is close to the input voltage limit of the analog-to-digital converter interface, the microcontroller executes the programmable operational amplifier gain switching function to reduce the gain of the second-stage amplifier. The analog voltage signal will decrease proportionally. At this time, the microcontroller amplifies the smoke concentration response value proportionally according to the reduction of the analog voltage signal and calculates the actual smoke concentration response value. When switching the gain 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 is continuous; conversely, 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 converter interface, the microcontroller executes the corresponding smoke detection gain closed-loop control function.

2. The full-range smoke concentration detection system for a photoelectric smoke detector according to claim 1, characterized in that, The signal amplification and filtering processing module includes a first-stage amplification module, a first DC blocking filter module, a second-stage amplification module, a second DC blocking filter module, a third-stage amplification module, and an AD interference filter module connected in sequence.

3. The full-range smoke concentration detection system for a photoelectric smoke detector according to claim 2, characterized in that, The light-emitting diode driving module includes a blue light-emitting diode and a blue light-emitting LED. One end of the blue light-emitting diode is connected to the microcontroller, and the other end is connected to the blue light-emitting LED. The microcontroller outputs a control signal to the blue light-emitting diode to realize the conduction and switching off of the light-emitting diode. The light-receiving diode acquisition module includes a light-receiving diode, a sampling resistor, and a filtering module. The light 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. The full-range smoke concentration detection system for a photoelectric smoke detector according to claim 3, characterized in that, The secondary amplification module includes a programmable operational amplifier with controllable gain. It is connected to the microcontroller, which can adjust the gain of the programmable operational amplifier by sending corresponding control signals, thereby making the gain of the secondary amplification module dynamically adjustable.

5. A full-range smoke concentration detection system for a photoelectric smoke detector according to claim 4, characterized in that, The three-stage amplification module includes a digital potentiometer, which is equivalent to an adjustable resistor. It is used as the gain matching resistor of the three-stage amplification module in the circuit. 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. This means that the amplification factor of the three-stage amplification module also changes with the change of the gain matching resistor value, thereby realizing the dynamic adjustment of the gain factor of the three-stage amplification module.

6. The full-range smoke concentration detection system for a photoelectric smoke detector according to claim 5, characterized in that, The input signals of the microcontroller mainly include the analog voltage signals of the three-stage amplification module, and the output signals of the microcontroller mainly include the light emission control signal, the programmable operational amplifier gain adjustment control signal, and the digital potentiometer gain adjustment control signal.

7. A method for detecting smoke concentration across the entire range using a photoelectric smoke detector, characterized in that, The calibration of the full-range smoke concentration detection system based on the photoelectric smoke detector of claim 1 includes the following steps: Smoke signal acquisition and conditioning technology based on photoelectric smoke detectors enables the acquisition of smoke signals and their conversion into electrical signals. Construct a full-range smoke concentration detection circuit topology for photoelectric smoke detectors; By adopting a closed-loop control method for the full-range smoke detection gain of a photoelectric smoke detector, the smoke detector can achieve calibration of smoke concentration across the entire range.

8. A full-range smoke concentration detection system for a photoelectric smoke detector according to claim 7, characterized in that, The smoke signal acquisition and conditioning technology specifically includes the following: The photoelectric smoke detector uses a photoelectric smoke signal acquisition circuit composed of microcontrollers, light-emitting diodes, and light-absorbing diodes as core electronic components. The acquisition circuit includes a light-emitting diode driving module, a light-receiving diode acquisition module, a signal amplification and filtering processing module, and a microcontroller; It employs photoelectric smoke signal acquisition and conditioning technology to enable it to have LED driving control function and LED current-to-voltage conversion function; The LED driving function mainly involves the microcontroller outputting control signals to the LED driving circuit, thereby controlling the LED's emission frequency by controlling its on / off state. The current-to-voltage conversion function of the light-receiving diode 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 then outputs it to the subsequent signal amplification and filtering processing module. After filtering and amplification, the voltage signal is then processed by analog-to-digital converter and 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 specifically includes the following: An operational amplifier and a gain matching resistor are used to form a first-stage amplification module; a programmable operational amplifier controlled by a program is used to form a second-stage amplification module; and an operational amplifier and a digital potentiometer are used to form a third-stage amplification module. Each amplification module is equipped with a DC blocking filter module with capacitors as the core component, which is used to eliminate the DC component in the photoelectric signal and improve the accuracy of the effective voltage signal. By amplifying and conditioning the electrical interconnection relationship described above, a full-range smoke concentration detection circuit topology for photoelectric smoke detectors is constructed by combining a first-stage amplification module, a second-stage amplification module, a third-stage amplification module, a DC blocking filter module, an AD interference filter module, and a microcontroller.

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: The photoelectric smoke signal acquisition circuit with LED driving control function and LED current-to-voltage conversion function is integrated with the full-range smoke concentration detection circuit topology for photoelectric smoke detectors to form a hardware platform that can apply the full-range smoke detection gain closed-loop control method. The microcontroller controls the periodic lighting of the light-emitting diodes (LEDs) through the smoke collection drive function. The smoke particles scatter the light, causing it to shine on the LEDs and generate a photocurrent. This photocurrent is converted into a voltage signal by the IU (induction generator) and then amplified by the gain stage to improve the signal output capability and perform preliminary filtering of the signal. The voltage signal containing DC bias is isolated by DC component filtering, and the effective AC component is then subjected to two-stage and three-stage amplification for gain adjustment. The smoke concentration voltage signal output by the conditioning circuit is subjected to interference filtering by the analog-to-digital conversion interface, and finally input to the analog-to-digital conversion interface of the microcontroller. The smoke concentration monitoring function is realized by monitoring the change of analog voltage. When the smoke concentration increases, the analog voltage increases and reaches a certain threshold that is close to the input voltage limit of the analog-to-digital converter interface, the microcontroller executes the programmable operational amplifier gain switching function to reduce the gain of the second-stage amplifier. The analog voltage signal will decrease proportionally. At this time, the microcontroller amplifies the smoke concentration response value proportionally according to the reduction of the analog voltage signal and calculates the actual smoke concentration response value. When switching the gain 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 is continuous; conversely, 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 converter interface, the microcontroller executes the corresponding smoke detection gain closed-loop control function.

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