Fire detector

Abstract

The utility model provides a fire detector. The fire detector comprises a flame detection module, a peak detection circuit, a first comparison circuit, a frequency detection circuit, a second comparison circuit and a first AND gate circuit, the flame detection module is configured to detect a flame signal and output a corresponding voltage signal, an input end of the peak detection circuit is connected with an output end of the flame detection module, and an output end of the frequency detection circuit is connected with the first AND gate circuit. The output end of the peak detection circuit is connected to the first input end of the first comparison circuit, the second input end of the first comparison circuit is connected with a first reference voltage, the output end of the first comparison circuit is connected to the first input end of the first AND gate circuit, and the input end of the frequency detection circuit is connected with the output end of the flame detection module. The output end of the frequency detection circuit is connected to the first input end of the second comparison circuit, the output end of the second comparison circuit is connected to the second input end of the first AND gate circuit, and the output end of the first AND gate circuit is the output end of the fire detector. The flame detection precision can be improved.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of fire detection, and in particular to a fire detector. BACKGROUND

[0002] Fire detectors can detect fire signals in real time, reminding on-site personnel to take emergency evacuation measures at the initial stage of a fire to avoid casualties. Flame detectors (such as ultraviolet flame detectors and infrared flame detectors) can detect specific wavelengths of light emitted when a flame burns. For example, an ultraviolet flame detector can detect ultraviolet radiation generated when a flame burns, and when the intensity of the ultraviolet radiation received by the detector exceeds a set threshold, it is determined that a fire has occurred.

[0003] In some environments with strong background light, such as places directly exposed to sunlight or strong light, ultraviolet flame detectors may be disturbed and have difficulty in accurately distinguishing between ultraviolet signals and background light, thereby affecting their detection accuracy of the flame. CONTENT OF THE INVENTION

[0004] Embodiments of the present disclosure provide a fire detector to improve the accuracy of flame detection.

[0005] Embodiments of the present disclosure provide a fire detector, which includes a flame detection module, a peak detection circuit, a first comparison circuit, a frequency detection circuit, a second comparison circuit, and a first AND gate circuit,

[0006] The flame detection module is configured to detect a flame signal and output a corresponding voltage signal. The input end of the peak detection circuit is connected to the output end of the flame detection module. The output end of the peak detection circuit is connected to the first input end of the first comparison circuit. The second input end of the first comparison circuit is connected to a first reference voltage. The output end of the first comparison circuit is connected to the first input end of the first AND gate circuit,

[0007] The input end of the frequency detection circuit is connected to the output end of the flame detection module. The output end of the frequency detection circuit is connected to the first input end of the second comparison circuit. The second input end of the second comparison circuit is connected to a third reference voltage. The third input end of the second comparison circuit is connected to a fourth reference voltage. The output end of the second comparison circuit is connected to the second input end of the first AND gate circuit. The output end of the first AND gate circuit is the output end of the fire detector.

[0008] In an exemplary embodiment of the present disclosure, the frequency detection circuit includes a third comparison circuit and an F / V conversion circuit,

[0009] The first input end of the third comparison circuit is the input end of the frequency detection circuit, the second input end of the third comparison circuit is connected with the second reference voltage, the output end of the third comparison circuit is connected with the input end of the F / V conversion circuit, and the output end of the F / V conversion circuit is the output end of the frequency detection circuit.

[0010] In an exemplary embodiment of the present disclosure, the second comparison circuit comprises a comparator U1C, a comparator U1D and a second AND gate circuit, the non-inverting input end of the comparator U1C is the second input end of the second comparison circuit, the inverting input end of the comparator U1C is the first input end of the second comparison circuit, the non-inverting input end of the comparator U1D is connected with the inverting input end of the comparator U1C, the inverting input end of the comparator U1D is the third input end of the second comparison circuit,

[0011] the output end of the comparator U1C is connected with the first input end of the second AND gate circuit, the output end of the comparator U1D is connected with the second input end of the second AND gate circuit, and the output end of the second AND gate circuit is the output end of the second comparison circuit.

[0012] In an exemplary embodiment of the present disclosure, the first comparison circuit comprises a comparator U1A,

[0013] the non-inverting input end of the comparator U1A is the first input end of the first comparison circuit, the inverting input end of the comparator U1A is the second input end of the first comparison circuit, and the output end of the comparator U1A is the output end of the first comparison circuit.

[0014] In an exemplary embodiment of the present disclosure, the fire detector further comprises a resistor R5 and a potentiometer RP1, the first end of the resistor R5 is connected with the first power supply, the second end of the resistor R5 is connected with the first end of the potentiometer RP1, the second end of the potentiometer RP1 is grounded, the sliding end of the potentiometer RP1 is connected with the second end of the potentiometer RP1, and the first end of the potentiometer RP1 serves as the first reference voltage.

[0015] In an exemplary embodiment of the present disclosure, the F / V conversion circuit specifically adopts an F / V conversion chip U2.

[0016] In an exemplary embodiment of the present disclosure, the flame detection module comprises a photosensitive tube, a resistor R1 and a second power supply,

[0017] the first end of the photosensitive tube is connected with the second power supply, the second end of the photosensitive tube is grounded through the resistor R1, and the second end of the photosensitive tube is the output end of the flame detection module.

[0018] In an example embodiment of the present disclosure, a band-pass filter circuit is arranged between the output end of the flame detection module and the input end of the peak detection circuit.

[0019] In an example embodiment of the present disclosure, the fire detector further comprises:

[0020] An alarm circuit, a control end of the alarm circuit being connected with the output end of the first AND gate circuit.

[0021] The fire detector provided by the embodiments of the present disclosure has the following working principles and advantages:

[0022] In the embodiments of the present disclosure, the flame detection module is used to detect a flame signal and convert it into a corresponding voltage signal, the peak detection circuit is capable of extracting peak information in the voltage signal and capturing voltage fluctuation corresponding to the flame signal, the first comparison circuit is used to compare the peak voltage output by the peak detection circuit with a first reference voltage, and determine whether the intensity of the flame signal reaches a set threshold requirement.

[0023] The frequency detection circuit is used to extract the frequency of the voltage signal output by the flame detection module and convert the frequency into a corresponding voltage output, the output voltage of the frequency detection circuit is connected to the first input end of the second comparison circuit, compared with a third reference voltage and a fourth reference voltage, when the output voltage of the frequency detection circuit is between the third reference voltage and the fourth reference voltage, the second comparison circuit outputs a high-level signal, indicating that the flame detection module detects that the signal frequency falls within the typical frequency range (usually between 0.5Hz-20Hz) of the flame signal, otherwise, the second comparison circuit outputs a low-level signal.

[0024] Only when both the first comparison circuit and the second comparison circuit output high levels (i.e. the peak voltage reaches the requirement and the frequency is within a reasonable range), the first AND gate circuit can output a high-level signal, determining that a fire occurs.

[0025] The embodiments of the present disclosure can greatly improve the detection accuracy and avoid false positives by simultaneously detecting the voltage peak and frequency characteristics of the flame signal and combining the two for judgment, compared with the way of relying on only a single signal intensity to determine a fire. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative labor.

[0027] Figure 1is a circuit schematic diagram of a fire detector provided by an embodiment of the present disclosure.

[0028] Figure 2 is a circuit schematic diagram of an F / V conversion circuit provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0029] In order to enable persons skilled in the art to better understand the present scheme, the technical solutions in the embodiments of the present scheme will be clearly described below in combination with the drawings in the embodiments of the present scheme. Obviously, the described embodiments are part of the embodiments of the present scheme, rather than all the embodiments. Based on the embodiments in the present scheme, all other embodiments obtained by persons skilled in the art without creative labor should fall within the scope of protection of the present scheme.

[0030] The terms "include", and other any variations thereof, in the specification and claims of the present scheme and the above-mentioned drawings, refer to "include but not limited to", and are intended to cover non-exclusive inclusion, and are not limited to the examples listed in the text. In addition, the terms "first" and "second" and the like are used to distinguish different objects, rather than to describe a specific order.

[0031] The implementation of the present disclosure is described in detail below in combination with specific drawings:

[0032] Figure 1 is a principle block diagram of a fire detector provided by an embodiment of the present disclosure. Referring to Figure 1 , the fire detector includes a flame detection module, a peak detection circuit, a first comparison circuit, a frequency detection circuit, a second comparison circuit and a first AND gate circuit,

[0033] The flame detection module is configured to detect a flame signal and output a corresponding voltage signal. The input end of the peak detection circuit is connected with the output end of the flame detection module. The output end of the peak detection circuit is connected with the first input end of the first comparison circuit. The second input end of the first comparison circuit is connected with a first reference voltage. The output end of the first comparison circuit is connected with the first input end of the first AND gate circuit.

[0034] The input end of the frequency detection circuit is connected with the output end of the flame detection module. The output end of the frequency detection circuit is connected with the first input end of the second comparison circuit. The second input end of the second comparison circuit is connected with a third reference voltage. The third input end of the second comparison circuit is connected with a fourth reference voltage. The output end of the second comparison circuit is connected with the second input end of the first AND gate circuit. The output end of the first AND gate circuit is the output end of the fire detector.

[0035] In the embodiment, during the flame burning process, the voltage corresponding to the flame signal fluctuates, and the peak detection circuit can accurately capture the maximum value in the fluctuations. Specifically, the peak detection circuit is composed of a diode D7, a capacitor C3 and a resistor R8. When the output voltage of the flame detection module is greater than the conduction voltage of the diode D7, the output voltage of the flame detection module charges the capacitor C3, and the voltage across the capacitor C3 gradually rises until the peak value of the output voltage of the flame detection module; when the output voltage of the flame detection module is less than the conduction voltage of the diode D7, the diode D7 is cut off, and the capacitor C3 is discharged through the resistor R8 to prepare for the next charging. If repeated, the voltage across the capacitor C3 changes with the peak value of the output voltage of the flame detection module, that is, the voltage across the capacitor C3 is the output voltage of the flame detection module.

[0036] The flame detection module is used to detect the flame signal and convert it into a corresponding voltage signal, the peak detection circuit can extract the peak value information in the voltage signal, capture the voltage fluctuation corresponding to the flame signal, and the first comparison circuit is used to compare the peak voltage output by the peak detection circuit with the first reference voltage REF1 to determine whether the intensity of the flame signal meets the set threshold requirement.

[0037] The frequency detection circuit is used to extract the frequency of the voltage signal output by the flame detection module and convert the frequency into a corresponding voltage output. The output voltage of the frequency detection circuit is connected to the first input end of the second comparison circuit and compared with the third reference voltage REF3 and the fourth reference voltage REF4. When the output voltage of the frequency detection circuit is between the third reference voltage REF3 and the fourth reference voltage REF4, the second comparison circuit outputs a high-level signal, indicating that the flame detection module detects that the signal frequency falls within the typical frequency range (usually between 0.5 Hz - 20 Hz) of the flame signal, otherwise, the second comparison circuit outputs a low-level signal.

[0038] Only when the first comparison circuit and the second comparison circuit both output high levels (i.e., the peak voltage meets the requirement and the frequency is within a reasonable range), the first AND gate circuit U8A can output a high-level signal, determining that a fire occurs.

[0039] The embodiment of the present disclosure can greatly improve the detection accuracy and avoid false positives by simultaneously detecting the voltage peak and frequency characteristics of the flame signal and combining the two for judgment, compared with the way of relying only on a single signal intensity to judge the fire.

[0040] In an exemplary embodiment of the present disclosure, the frequency detection circuit includes a third comparison circuit and an F / V conversion circuit,

[0041] The first input end of the third comparison circuit is the input end of the frequency detection circuit, the second input end of the third comparison circuit is connected with the second reference voltage, the output end of the third comparison circuit is connected with the input end of the F / V conversion circuit, and the output end of the F / V conversion circuit is the output end of the frequency detection circuit. The second reference voltage is a pre-set voltage, and the specific value of the second reference voltage can be set according to actual needs by those skilled in the art.

[0042] In the embodiment, the third comparison circuit is composed of the comparator U1B. When the output voltage of the flame detection module is greater than the second reference voltage REF2, the comparator U1B outputs a high-level signal, otherwise, when the output voltage of the flame detection module is less than the second reference voltage REF2, the comparator U1B outputs a low-level signal. Therefore, through the setting of the comparator U1B, the output signal of the flame detection module is converted into a square wave pulse signal.

[0043] The square wave pulse output by the comparator U1B is connected with the F / V conversion circuit, and the F / V conversion circuit outputs a voltage signal VF which is proportional to the frequency of the square wave pulse. Therefore, the frequency of the output voltage of the flame detection module can be obtained by detecting the size of the voltage signal VF.

[0044] From the above, it can be seen that the frequency information of the flame signal is converted into a voltage signal output in the embodiment, which is convenient for the subsequent circuit to compare, analyze and judge the voltage signal.

[0045] In an exemplary embodiment of the present disclosure, the second comparison circuit comprises a comparator U1C, a comparator U1D and a second AND gate circuit, the non-inverting input end of the comparator U1C is the second input end of the second comparison circuit, the inverting input end of the comparator U1C is the first input end of the second comparison circuit, the non-inverting input end of the comparator U1D is connected with the inverting input end of the comparator U1C, the inverting input end of the comparator U1D is the third input end of the second comparison circuit,

[0046] The output end of the comparator U1C is connected with the first input end of the second AND gate circuit, the output end of the comparator U1D is connected with the second input end of the second AND gate circuit, and the output end of the second AND gate circuit is the output end of the second comparison circuit.

[0047] In the embodiment, the third comparison circuit is composed of the comparator U1C, the comparator U1D and the second AND gate circuit U8B, the third reference voltage REF3 is greater than the fourth reference voltage REF4, when the output voltage of the F / V conversion circuit is greater than the third reference voltage REF3, the comparator U1C outputs a low level, the comparator U1D outputs a high level, and the second AND gate circuit U8B outputs a low level, indicating that the flame detection module detects that the signal frequency is lower than the typical frequency range; when the output voltage of the F / V conversion circuit is between the third reference voltage REF3 and the fourth reference voltage REF4, the comparator U1C and the comparator U1D both output a high level, and the second AND gate circuit U8B outputs a high level, indicating that the flame detection module detects that the signal frequency falls within the typical frequency range of the flame signal; when the output voltage of the F / V conversion circuit is less than the fourth reference voltage REF4, the comparator U1C outputs a high level, the comparator U1D outputs a low level, and the second AND gate circuit U8B outputs a low level, indicating that the flame detection module detects that the signal frequency is higher than the typical frequency range.

[0048] As can be seen from the above, in the embodiment, the comparator U1C, the comparator U1D and the second AND gate circuit U8B are arranged, so that whether the flame detection module detects that the signal frequency falls within the typical frequency range of the flame signal can be effectively determined.

[0049] In an exemplary embodiment of the present disclosure, the first comparison circuit comprises a comparator U1A,

[0050] The non-inverting input terminal of the comparator U1A is the first input terminal of the first comparison circuit, the inverting input terminal of the comparator U1A is the second input terminal of the first comparison circuit, and the output terminal of the comparator U1A is the output terminal of the first comparison circuit.

[0051] In the embodiment, the first comparison circuit is composed of the comparator U1A, when the output voltage of the peak detection circuit is greater than the first reference voltage REF1, the comparator U1A outputs a high level signal, indicating that the flame signal intensity is greater than the set threshold. The first reference voltage REF1 is a preset voltage signal, and a person skilled in the art can design the specific value of the first reference voltage REF1 according to actual needs.

[0052] In an exemplary embodiment of the present disclosure, the fire detector further comprises a resistor R5 and a potentiometer RP1, the first end of the resistor R5 is connected with the first power supply, the second end of the resistor R5 is connected with the first end of the potentiometer RP1, the second end of the potentiometer RP1 is grounded, the sliding end of the potentiometer RP1 is connected with the second end of the potentiometer RP1, and the first end of the potentiometer RP1 serves as the first reference voltage.

[0053] In the embodiment, the resistor R5 and the potentiometer RP1 constitute a series voltage dividing circuit, the voltage division of the potentiometer RP1 serves as the first reference voltage REF1, and the circuit structure is simple and easy to implement.

[0054] Meanwhile, according to different requirements of the sensitivity of the fire detector in different use scenarios, the resistance value of the potentiometer can be adjusted to adjust the size of the first reference voltage REF1. If the sensitivity requirement of the detector is relatively high, the first reference voltage REF1 can be set to be relatively low. For example, it can be set to be in the order of millivolt (mV), so that an effective signal can be generated even under low light intensity.

[0055] As can be seen from the above, in the embodiment, the resistance R5 and the potentiometer RP1 are arranged to adjust the size of the first reference voltage REF1 according to actual needs, and the circuit structure is simple and convenient to operate.

[0056] In an exemplary embodiment of the present disclosure, the F / V conversion circuit specifically adopts an F / V conversion chip U2.

[0057] In the embodiment, the F / V conversion circuit specifically adopts an F / V conversion chip U2, and the specific model of the chip is AD651. The AD651 is an integrated circuit specially used for converting a frequency signal into a voltage signal, and can more accurately convert the frequency of the flame signal into a corresponding voltage signal.

[0058] In an exemplary embodiment of the present disclosure, the flame detection module includes a photosensitive tube, a resistor R1, and a second power supply,

[0059] The first end of the photosensitive tube is connected with the second power supply, the second end of the photosensitive tube is grounded through the resistor R1, and the second end of the photosensitive tube is an output end of the flame detection module.

[0060] In the embodiment, when the photosensitive tube is irradiated by ultraviolet light, under the electric field effect of the applied voltage (the second power supply), the cathode emits photoelectrons moving towards the anode. The high-speed moving photoelectrons collide with gas molecules in the tube to form ionization phenomenon. The cathode and the anode are filled with a large number of photoelectrons and ions, and present a conduction state. The resistor R1 has current passing through, so that a voltage drop is generated at both ends of the resistor R1. The voltage of the resistor R1 can be detected to detect the intensity of the flame signal.

[0061] In an exemplary embodiment of the present disclosure, a band-pass filter circuit is arranged between the output end of the flame detection module and the input end of the peak detection circuit.

[0062] In the embodiment, the voltage signal output by the flame detection module can contain various frequency components, in which there are not only the frequency components of the flame signal itself (for example, the flicker frequency of the flame is usually between 0.5 Hz - 20 Hz), but also other interference frequency components from the environment, such as high-frequency or low-frequency noise generated by electromagnetic interference, background light flicker, etc. By setting the band-pass filter, the flame signal can pass through smoothly, and the interference signals of other frequencies can be suppressed.

[0063] From the above, it can be concluded that the setting of the band-pass filter circuit in the embodiment can filter out the interference frequency components in the output signal of the flame detection module, and significantly improve the signal quality input to the peak value detection circuit and the third comparison circuit.

[0064] In an exemplary embodiment of the present disclosure, the fire detector further comprises:

[0065] An alarm circuit, a control end of the alarm circuit being connected with an output end of the first AND gate circuit.

[0066] In the embodiment, by setting the alarm circuit at the output end of the first AND gate circuit, the alarm circuit can be started to alarm when the first AND gate circuit outputs a high level (i.e. the peak voltage of the detected flame signal reaches the requirement and the frequency is in a reasonable range), so as to provide timely processing for the staff.

[0067] The above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than limit them; although the present disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features can be replaced equivalently; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A fire detector, characterized in that, It includes a flame detection module, a peak detection circuit, a first comparison circuit, a frequency detection circuit, a second comparison circuit, and a first AND gate circuit. The flame detection module is configured to detect flame signals and output corresponding voltage signals. The input terminal of the peak detection circuit is connected to the output terminal of the flame detection module. The output terminal of the peak detection circuit is connected to the first input terminal of the first comparison circuit. The second input terminal of the first comparison circuit is connected to a first reference voltage. The output terminal of the first comparison circuit is connected to the first input terminal of the first AND gate circuit. The input terminal of the frequency detection circuit is connected to the output terminal of the flame detection module. The output terminal of the frequency detection circuit is connected to the first input terminal of the second comparison circuit. The second input terminal of the second comparison circuit is connected to the third reference voltage. The third input terminal of the second comparison circuit is connected to the fourth reference voltage. The output terminal of the second comparison circuit is connected to the second input terminal of the first AND gate circuit. The output terminal of the first AND gate circuit is the output terminal of the fire detector.

2. The fire detector as described in claim 1, characterized in that, The frequency detection circuit includes a third comparator circuit and an F / V conversion circuit. The first input terminal of the third comparator circuit is the input terminal of the frequency detection circuit. The second input terminal of the third comparator circuit is connected to the second reference voltage. The output terminal of the third comparator circuit is connected to the input terminal of the F / V conversion circuit. The output terminal of the F / V conversion circuit is the output terminal of the frequency detection circuit.

3. The fire detector as described in claim 1, characterized in that, The second comparison circuit includes a comparator U1C, a comparator U1D, and a second AND gate. The non-inverting input of the comparator U1C is the second input of the second comparison circuit, the inverting input of the comparator U1C is the first input of the second comparison circuit, the non-inverting input of the comparator U1D is connected to the inverting input of the comparator U1C, and the inverting input of the comparator U1D is the third input of the second comparison circuit. The output of comparator U1C is connected to the first input of the second AND gate circuit, the output of comparator U1D is connected to the second input of the second AND gate circuit, and the output of the second AND gate circuit is the output of the second comparator circuit.

4. The fire detector as described in claim 1, characterized in that, The first comparison circuit includes comparator U1A, The non-inverting input of comparator U1A is the first input of the first comparator circuit, the inverting input of comparator U1A is the second input of the first comparator circuit, and the output of comparator U1A is the output of the first comparator circuit.

5. The fire detector as described in claim 4, characterized in that, It also includes a resistor R5 and a potentiometer RP1. The first end of the resistor R5 is connected to the first power supply, the second end of the resistor R5 is connected to the first end of the potentiometer RP1, the second end of the potentiometer RP1 is grounded, the sliding end of the potentiometer RP1 is connected to the second end of the potentiometer RP1, and the first end of the potentiometer RP1 serves as the first reference voltage.

6. The fire detector as described in claim 2, characterized in that, The F / V conversion circuit specifically uses the F / V conversion chip U2.

7. The fire detector as described in claim 1, characterized in that, The flame detection module includes a phototube, a resistor R1, and a second power supply. The first end of the phototube is connected to the second power supply, and the second end of the phototube is grounded through resistor R1. The second end of the phototube is the output end of the flame detection module.

8. The fire detector as described in claim 1, characterized in that, A bandpass filter circuit is provided between the output terminal of the flame detection module and the input terminal of the peak detection circuit.

9. The fire detector as described in claim 1, characterized in that, Also includes: An alarm circuit, wherein the control terminal of the alarm circuit is connected to the output terminal of the first AND gate circuit.

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