CN114993894B - Forward scattering-based dual-wavelength modulated light smoke sensor - Google Patents
Forward scattering-based dual-wavelength modulated light smoke sensor Download PDFInfo
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- CN114993894B CN114993894B CN202210589884.3A CN202210589884A CN114993894B CN 114993894 B CN114993894 B CN 114993894B CN 202210589884 A CN202210589884 A CN 202210589884A CN 114993894 B CN114993894 B CN 114993894B
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- 239000000779 smoke Substances 0.000 title claims abstract description 37
- 238000001514 detection method Methods 0.000 claims abstract description 28
- 230000003287 optical effect Effects 0.000 claims abstract description 20
- 239000002245 particle Substances 0.000 claims abstract description 16
- 230000035945 sensitivity Effects 0.000 claims abstract description 6
- 230000009977 dual effect Effects 0.000 claims abstract 3
- 229910052710 silicon Inorganic materials 0.000 claims description 29
- 239000010703 silicon Substances 0.000 claims description 29
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 28
- 230000003750 conditioning effect Effects 0.000 claims description 16
- 238000001914 filtration Methods 0.000 claims description 7
- 238000000034 method Methods 0.000 claims description 4
- 230000008569 process Effects 0.000 claims description 4
- 230000004044 response Effects 0.000 claims description 4
- 230000008859 change Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 206010000369 Accident Diseases 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 230000010485 coping Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
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Abstract
The invention provides a forward scattering-based dual-wavelength modulated light smoke sensor, which belongs to the technical field of photoelectric sensing, adopts dual light sources to detect smoke particles, can directly eliminate external natural light interference, omits an optical labyrinth structure, greatly reduces the volume of the smoke sensor, can eliminate interference of external fluctuation factors while improving the detection performance of the smoke sensor in a small particle size range, improves the fire detection accuracy and sensitivity, and has good popularization value.
Description
Technical Field
The invention belongs to the technical field of photoelectric sensing, and particularly relates to a dual-wavelength modulated light smoke sensor based on forward scattering.
Background
With the continuous improvement of national living standard, household appliances and various electronic products are gradually popularized. Because of the influence of many factors such as abnormal use, environmental change, etc. for electrical appliance fire accident frequently takes place, has caused great loss to people's personal safety and property, consequently, people often install the fire detector in order to make timely early warning to the conflagration condition to make relevant emergency treatment measure, reduce the loss. Current fire detectors can be classified into five types according to signal characteristics: smoke sensing, temperature sensing, sound sensing, light sensing, and gas sensing are the most responsive detection tools in the early stage of fire because of the large amount of solid or liquid particle clusters discharged at the moment of combustion of most fires. Smoke detectors are also classified into ionic and photoelectric types, and photoelectric type smoke detectors are advantageous in practical applications because of the radioactivity of the ionic type smoke sensor and the short plate with limited life.
Current photoelectric smoke sensors often have an optical maze in the optical front-end structure, so that natural light is attenuated in the optical maze and blocked outside the detection area of the optical front-end. The problem that this structure set up produces is that the optics maze has taken up great space, is unfavorable for the integrated application, and simultaneously, the optics maze has prolonged the smog particle and has arrived the time that the optical front end structure took for system detection efficiency is low, and response speed is slow. In addition, the existing smoke sensing technology adopts a monochromatic light source, smoke particles enter a cavity at the initial stage of a fire disaster, scatter monochromatic light, a photodiode detects light signal changes to respond, and a change signal is transmitted to a rear-end conditioning circuit.
Disclosure of Invention
In order to meet the above defects or improvement needs of the prior art, the invention provides a dual-wavelength modulated light smoke sensor based on forward scattering, and aims to improve the sensitivity while improving the fire detection accuracy.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
The dual-wavelength modulated light smoke sensor based on forward scattering comprises an optical front end and a conditioning circuit, wherein the conditioning circuit comprises a pulse signal generating circuit, a differential amplifying circuit, a filtering circuit and an alarm circuit of an alarm, a base of the optical front end is of a square structure, at least two light emitting diodes with different wavelengths and the same technological parameters and two identical silicon photocells are arranged on the base, the two light emitting diodes emit red light and orange light respectively, response sensitivity of the two silicon photocells to the light emitting diodes with the two wavelengths is the same, one photoelectric detection pair is formed by one light emitting diode and one silicon photocell, the other light emitting diode and the other silicon photocell form the other photoelectric detection pair, each photoelectric detection pair is in forward scattering arrangement, the back parts of the two silicon photocells are arranged in a staggered manner, the two silicon photocells are positioned in the center of the base, and the light emitting diodes in the corresponding detection pairs are positioned on the top points of the base pair;
The conditioning circuit is arranged in the base and positioned at the bottom of the optical front end, the two light emitting diodes are respectively connected with the output end of the pulse signal generating circuit in the conditioning circuit, the pulse signal generating circuit comprises a timer, the timer can generate pulse square wave signals, and the two light emitting diodes are driven to emit light so as to generate modulated light signals with specific frequencies;
The two silicon photocells are respectively connected with the input end of a differential amplifying circuit in the conditioning circuit and are used for respectively receiving light signals directly emitted by the two light emitting diodes and scattered light signals formed by scattering the modulated light signals by smoke particles so as to generate photocurrent signals,
The differential amplifying circuit utilizes a triode to construct a differential pair, amplifies the difference between photocurrent signals generated by the two silicon photocells, and the amplified differential mode signals have the same frequency as the modulating signals and are continuously transmitted to the filtering circuit;
the filter circuit is constructed into a fourth-order active band-pass filter by utilizing an operational amplifier, filters the amplified differential mode signal, continuously amplifies the differential mode signal, and transmits the differential mode signal to the alarm;
The alarm consists of a voltage comparator and a buzzer, and when the peak value of the filtering signal is larger than the threshold value signal, the voltage comparator outputs high level to drive the buzzer to alarm.
Compared with the prior art, the invention has the beneficial effects that:
1. The sensor adopts the modulated signal to drive the light source, and then the external interference light is removed through the filter, so that only the photoelectric signal with the same frequency as the modulated signal is reserved, the optical labyrinth structure carried by the traditional smoke sensor is omitted, the time for smoke to enter the detector is shortened, the volume of the sensor is reduced, and the detection efficiency is improved; the smoke detection device has the advantages of eliminating interference of natural light and other environmental factors on the smoke detection process under the condition of removing the optical maze, being small in occupied volume, being capable of being integrally applied to miniaturized equipment, being good in stability, long in service life and high in detection precision, and being particularly suitable for detecting low-concentration smoke in smoldering stage;
2. The sensor adopts double light beams as light sources, and utilizes the difference of light sources with different wavelengths on scattered light of particles to detect smoke, so that the detection sensitivity of the sensor on small-particle-size smoke particles in smoldering stage is improved. The influence of external light noise and direct light of the light source can be eliminated by utilizing the geometric symmetrical structure of the double light beams and the topological symmetrical structure of the differential amplifying circuit. The difference of the scattering of the smoke particles by the light with two different wavelengths (red light and orange light) is amplified, so that the smoke particles with small particle size in the smoldering stage can be sensitively reacted, and sufficient time is provided for coping with fire.
Drawings
FIG. 1 is a schematic view of the basic structure of an optoelectronic smoke sensor of the present invention;
fig. 2 is a schematic circuit configuration of the photoelectric smoke sensor of the present invention;
FIG. 3 is a schematic workflow diagram of the photoelectric smoke sensor of the present invention;
Wherein, 1-light gathering diode (emitting red light), 2-light gathering diode (emitting orange light), 3, 4-silicon photocell, 5-photoelectric detection pair, 6-base, 7-photoelectric front end, 8-conditioning circuit.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It should be noted that, if directional indications (such as up, down, left, right, front, and rear … …) are included in the embodiments of the present invention, the directional indications are merely used to explain the relative positional relationship, movement conditions, etc. between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indications are correspondingly changed.
As shown in fig. 1-3, the present invention provides a dual-wavelength modulated light smoke sensor based on forward scattering, which is composed of an optical front end and a conditioning circuit, the conditioning circuit includes a pulse signal generating circuit, a differential amplifying circuit, a filtering circuit and an alarm circuit of an alarm, wherein a base 6 of the optical front end 7 is in a square structure, preferably a square structure, on which at least two light emitting diodes 1,2 with different wavelengths and the same other process parameters and two identical silicon photocells 3, 4 are arranged, the light emitted by the two light emitting diodes 1,2 is preferably red light and orange light, the response sensitivity of the two silicon photocells 3, 4 to the light emitting diodes 1,2 with two wavelengths is the same, one light emitting diode 1 and one silicon photocell 3 form one photoelectric detection pair 5, the other light emitting diode 2 and the other silicon photocell 4 form the other photoelectric detection pair 5, each photoelectric detection pair 5 is in forward scattering arrangement (i.e. the angle formed by the light emitting diode and the silicon photocell is greater than 90 degrees), the two silicon photocells 3, 4 are arranged side by side, the back of the two silicon photocells are arranged side, the center pairs are located on the base 6 in the corresponding pairs, and the base is located at the top of the center pairs;
the conditioning circuit 8 is arranged in the base 6 and is positioned at the bottom of the optical front end 7, the two light emitting diodes 1 and 2 are respectively connected with the output end of the pulse signal generating circuit in the conditioning circuit 8, and the pulse signal generating circuit comprises a timer which can generate pulse square wave signals through the timer so as to drive the two light emitting diodes 1 and 2 to emit light to generate modulated light signals with specific frequency;
The two silicon photocells 3 and 4 are respectively connected with the input end of a differential amplifying circuit in the conditioning circuit 8, and are used for respectively receiving the direct light signals of the two light emitting diodes 1 and 2 and the scattered light signals formed by scattering the modulated light signals by smoke particles so as to generate photocurrent signals, the differential amplifying circuit utilizes triodes to construct differential pairs, amplifies the difference between the photocurrent signals generated by the two silicon photocells 3 and 4, and the amplified differential mode signals have the same frequency as the modulated signals and are continuously transmitted to the filter circuit; the filter circuit is constructed into a fourth-order active band-pass filter by utilizing an operational amplifier, filters the amplified differential mode signal, continuously amplifies the differential mode signal, and transmits the differential mode signal to the alarm;
the alarm consists of a voltage comparator and a buzzer, and when the peak value of the filtering signal is larger than the threshold value signal, the voltage comparator outputs high level to drive the buzzer to alarm. The voltage comparator and the buzzer circuit together form an alarm circuit of the alarm.
Examples
The pulse signal generating circuit adopts an NE555 square wave generator to generate pulse signals with the duty ratio of 75%, the frequency of 8-10 kHz and the Vpp of 15V, and a diode in the optical front end is driven to generate modulated light;
The optical front end adopts a base with the size of 3cm x 3cm, high-light-gathering orange light and red light diodes with the wavelengths of 600nm and 900nm respectively, a silicon photocell with the chip size of 2.8mm x 3.2mm, and the included angle between the light emitting diode and the silicon photocell in each detection pair is 120 degrees;
The differential amplifying circuit adopts two BJT triodes with the model of 2N2222A to construct the differential amplifying circuit to amplify the difference between photoelectric signals generated by two silicon photocells;
the filter adopts two OP07 amplifier chips to form a fourth-order band-pass active filter, noise signals in differential mode signals are filtered, the bandwidth is about 8kHz, and the gain is about 6dB;
the alarm adopts an LM339DG chip as a voltage comparator, and when the peak value of the output signal of the filter is larger than the set threshold voltage, the comparator outputs 15V bias voltage to drive the buzzer to give an alarm.
The working process of the invention is as follows:
S1, a pulse signal generating circuit modulates a light source, and drives two light emitting diodes 1 and 2 with different wavelengths in a forward scattering structure detection pair, namely a photoelectric detection pair 5 to generate modulated light;
S2, smoke particles generated in the early stage of a fire disaster scatter a modulated light signal, and two silicon photocells 3 and 4 of a forward scattering structure detection pair respectively receive the light signals directly emitted by two light emitting diodes 1 and 2 and scattered light signals formed by scattering the modulated light signal by the smoke particles so as to generate a photocurrent signal;
S3, amplifying the generated two paths of photocurrent signals by a differential amplifier circuit, and further amplifying the difference of particle scattering light signals generated when the double light sources pass through the detection area;
S4, the differential mode signal is filtered by the filter circuit and then enters a voltage comparator of the alarm, and when the differential mode signal is not smaller than the threshold value of the alarm, the buzzer is driven to carry out fire alarm.
The foregoing description of the preferred embodiments of the present invention should not be construed as limiting the scope of the invention, but rather utilizing equivalent structural changes made in the present invention description and drawings or directly/indirectly applied to other related technical fields are included in the scope of the present invention.
Claims (3)
1. A dual-wavelength modulated light smoke sensor based on forward scattering is characterized by comprising an optical front end and a conditioning circuit, wherein the conditioning circuit comprises a pulse signal generating circuit, a differential amplifying circuit, a filter circuit and an alarm circuit of an alarm,
The base of the optical front end is of a square structure, at least two light emitting diodes with different wavelengths and the same other process parameters and two identical silicon photocells are arranged on the base, the response sensitivity of the two silicon photocells to the light emitting diodes with the two wavelengths is the same, one photoelectric detection pair is formed by one light emitting diode and one silicon photocell, the other photoelectric detection pair is formed by the other light emitting diode and the other silicon photocell, each photoelectric detection pair is in forward scattering arrangement, the back parts of the two silicon photocells are arranged side by side in a staggered manner and are positioned in the center of the base, and the light emitting diodes in the corresponding detection pairs are positioned on the top of the base pair;
The conditioning circuit is arranged in the base and positioned at the bottom of the optical front end, the two light emitting diodes are respectively connected with the output end of the pulse signal generating circuit in the conditioning circuit, the pulse signal generating circuit comprises a timer, the timer can generate pulse square wave signals, and the two light emitting diodes are driven to emit light so as to generate modulated light signals with specific frequencies; the two silicon photocells are respectively connected with the input end of the differential amplifying circuit in the conditioning circuit and are used for respectively receiving light signals directly emitted by the two light emitting diodes and scattered light signals formed by scattering the modulated light signals by smoke particles so as to generate photocurrent signals; the differential amplifying circuit utilizes a triode to construct a differential pair, amplifies the difference between photocurrent signals generated by the two silicon photocells, and the amplified differential mode signals have the same frequency as the modulating signals and are continuously transmitted to the filtering circuit; the filter circuit is constructed into a fourth-order active band-pass filter by utilizing an operational amplifier, filters the amplified differential mode signal, continuously amplifies the differential mode signal, and transmits the differential mode signal to the alarm; the alarm consists of a voltage comparator and a buzzer, and when the peak value of the filtering signal is larger than the threshold value signal, the voltage comparator outputs high level to drive the buzzer to alarm.
2. The forward scatter based dual wavelength modulated light smoke sensor as defined in claim 1, wherein the base of the optical front end has a square configuration.
3. The forward scatter based dual wavelength modulated light smoke sensor as defined in claim 1, wherein the two leds emit red and orange light, respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210589884.3A CN114993894B (en) | 2022-05-26 | Forward scattering-based dual-wavelength modulated light smoke sensor |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210589884.3A CN114993894B (en) | 2022-05-26 | Forward scattering-based dual-wavelength modulated light smoke sensor |
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| CN114993894A CN114993894A (en) | 2022-09-02 |
| CN114993894B true CN114993894B (en) | 2024-06-28 |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN216670897U (en) * | 2021-11-22 | 2022-06-03 | 华中师范大学 | Smoke detector |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN216670897U (en) * | 2021-11-22 | 2022-06-03 | 华中师范大学 | Smoke detector |
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