A detection method and circuit for a smoke detector with adjustable range

Abstract

The present invention discloses a detection method and circuit for a smoke detector with adjustable range. Infrared light is emitted by a transmitting circuit, and a receiving circuit receives the infrared light scattered by the smoke and converts the optical signal into an electrical signal. A signal processing circuit provides a reference voltage and adjusts and outputs a final electrical signal according to the reference voltage. A controller adjusts the range according to the final electrical signal and calculates and outputs the smoke concentration. This realizes dynamic adjustment of the detector range and solves the technical problem in the prior art that the detector range is fixed and cannot be adjusted, which limits the range of the smoke alarm response threshold and makes the applicable scenarios of the smoke detector relatively limited.

Description

Technical Field

[0001] The present invention relates to the technical field of smoke detection, and in particular to a detection method and circuit of a smoke detector. Background Art

[0002] Smoke concentration is typically detected using photoelectric smoke detectors, which work based on the principle of light scattering when it encounters smoke particles. This detection is typically done using an infrared emitter. When infrared light strikes a cloud of smoke particles, it is diffusely reflected. This reflection increases with increasing smoke particle concentration. An infrared receiver receives this reflected light and converts the analog light intensity signal into a discrete digital signal that can be processed by a microprocessor. Using an algorithm running on the microprocessor, the smoke detector measures the smoke concentration and, when a threshold is reached, issues a fire alarm.

[0003] However, the current photoelectric smoke detectors have a fixed range and a maximum detectable smoke concentration that cannot be adjusted. The smoke alarm response threshold is also limited, which restricts the application scenarios of the smoke detectors. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a detection method and circuit for a smoke detector with adjustable range, wherein the detection range is dynamically adjustable, the resolution is maintained unchanged over the entire range, and the detection accuracy is high.

[0005] The object of the present invention is achieved through the following technical measures: A detection method of a smoke detector comprises the following steps:

[0006] Step 1: The controller pre-enters the detector's response voltage range (Vmin-Vmax), the initial smoke concentration range (0-T) corresponding to the response voltage range, the detector's resolution (K), and the unit smoke concentration change (M). The smoke detector's reference voltage is pre-divided into N levels, and the level corresponding to the initial range is set to level N0.

[0007] Step 2: The detector detects the fire smoke concentration, converts the smoke concentration signal into a voltage value V, and outputs it to the controller. The controller also records the current level N of the reference voltage. The controller determines whether V falls within the range of Vmin-Vmax. If so, it establishes a smoke concentration calculation model, calculates and outputs the current smoke concentration value. Otherwise, it determines whether V≥Vmax or V≤Vmin.

[0008] Step 3: If V≥Vmax, increase the reference voltage level by one, i.e., N=N+1. The detector re-detects the smoke concentration and outputs a voltage value V. The controller determines whether V falls within the range of Vmin-Vmax. If so, the controller calculates and outputs the current smoke concentration value according to the smoke concentration calculation model in step 2. Otherwise, repeat step 3.

[0009] Step 4: If V≤Vmin, reduce the reference voltage by one level, i.e., N=N-1. The detector re-detects the smoke concentration and outputs a voltage value V. The controller determines whether V falls within the range of Vmin-Vmax. If so, it calculates and outputs the current smoke concentration value according to the smoke concentration calculation model in step 2. Otherwise, repeat step 4.

[0010] The smoke concentration calculation model in step 2 is: , where Q is the maximum smoke concentration corresponding to the current gear N, and its calculation model is .

[0011] Furthermore, the reference voltage increment or decrement corresponding to each increase or decrease of one gear of the reference voltage is the same.

[0012] Furthermore, the resolution K is , and the resolution is the same in each gear.

[0013] Furthermore, the value of M is less than or equal to the value of T.

[0014] A smoke detector circuit includes a controller, a transmitting circuit, a receiving circuit, and a signal processing circuit. The transmitting circuit is used to emit infrared light, the receiving circuit is used to receive the infrared light and convert the optical signal into an electrical signal, the signal processing circuit is used to provide a reference voltage and adjust and output a final electrical signal based on the reference voltage, and the controller is used to control the transmitting circuit and the signal processing circuit.

[0015] Furthermore, it also includes an amplification circuit, which includes a first operational amplifier, a first feedback resistor and a first matching resistor, the non-inverting input terminal of the first operational amplifier is connected to the receiving circuit, the inverting input terminal of the first operational amplifier is connected to one end of the first matching resistor, the other end of the first matching resistor is grounded, the output terminal of the first operational amplifier is connected to the signal processing circuit, one end of the first feedback resistor is connected to the inverting input terminal of the first operational amplifier, and the other end of the first feedback resistor is connected to the output terminal of the first operational amplifier.

[0016] Furthermore, the signal processing circuit includes a second operational amplifier, a second feedback resistor, a second matching resistor, a third matching resistor and a fourth matching resistor, the non-inverting input terminal of the second operational amplifier is connected to one end of the second matching resistor, the other end of the second matching resistor is connected to the receiving circuit, the non-inverting input terminal of the second operational amplifier is also connected to one end of the fourth matching resistor, the other end of the fourth matching resistor is grounded, the inverting input terminal of the second operational amplifier is connected to one end of the third matching resistor, the other end of the third matching resistor is connected to a reference voltage, the output terminal of the second operational amplifier is connected to the controller, one end of the second feedback resistor is connected to the inverting input terminal of the second operational amplifier, the other end of the second feedback resistor is connected to the output terminal of the second operational amplifier, the second matching resistor and the third matching resistor have the same resistance value, and the second feedback resistor and the fourth matching resistor have the same resistance value.

[0017] Furthermore, the transmitting circuit includes an infrared emitting tube and a transistor, one end of the infrared emitting tube is connected to the power supply voltage, the other end of the infrared emitting tube is connected to the first end of the transistor, the second end of the transistor is grounded, and the control end of the transistor is connected to the controller.

[0018] Furthermore, the receiving circuit includes an infrared receiving tube and a sampling resistor, one end of the infrared receiving tube is connected to the power supply voltage, the other end of the infrared receiving tube is connected to one end of the sampling resistor, and the other end of the sampling resistor is grounded.

[0019] Compared to the prior art, the present invention provides the following advantages: The smoke detector detection method and circuit thereof achieve dynamic adaptive adjustment of the detector range by adjusting the reference voltage level during the detection process, thereby resolving the issues of limited smoke alarm response thresholds and the limited application scenarios of smoke detectors. Furthermore, the detector resolution in the present application always remains the same as the initial range resolution K, extending the range without reducing its resolution, thus maintaining a consistently high resolution and achieving high detection accuracy.

[0020] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of the smoke detector circuit.

[0022] Figure 2 is the schematic diagram of the smoke detector circuit.

[0023] Figure 3 This is a graph showing the change in voltage with smoke concentration.

[0024] Among them, 1. controller, 2. infrared emitting tube, 3. transistor, 4. infrared receiving tube, 5. sampling resistor, 6. first matching resistor, 7. first feedback resistor, 8. first operational amplifier, 9. reference voltage, 10. second matching resistor, 11. third matching resistor, 12. fourth matching resistor, 13. second operational amplifier, 14. second feedback resistor. DETAILED DESCRIPTION

[0025] like Figures 1 to 3 As shown, a detection method of a smoke detector includes the following steps:

[0026] Step 1: The controller 1 pre-inputs the detector's response voltage range (Vmin-Vmax), the initial smoke concentration range (T) corresponding to the response voltage range, the detector's resolution (K), and the unit smoke concentration change (M). The smoke detector's reference voltage 9 (Vref) is pre-divided into N levels, and the level corresponding to the initial range (T) is set to level N0. Specifically, the response voltage range (Vmin-Vmax) is set based on the operating voltage of the second operational amplifier 13 in the detector's signal processing circuit. The initial range is the smoke concentration range corresponding to Vmin-Vmax. The unit smoke concentration change (M) is determined based on the detector's application scenario and required detection accuracy. For example, if the detector's application scenario has a wide smoke concentration range and requires low detection accuracy, the unit smoke concentration change (M) can be set to a larger value. If the detector's application scenario has a narrow smoke concentration range and requires high detection accuracy, the unit smoke concentration change (M) can be set to a smaller value. Vref is divided into levels based on the unit smoke concentration change (M). Specifically, each additional level of Vref increases the smoke concentration measured by the detector by a range of M.

[0027] Step 2: The detector detects the smoke concentration of the fire, converts the smoke concentration signal into a voltage value V and outputs it to the controller 1. At the same time, the controller 1 records the current gear position N of Vref. The controller 1 determines whether V falls within Vmin-Vmax. If so, it means that the range corresponding to the current gear position N can meet the detector's detection of the current smoke concentration. The controller 1 establishes a smoke concentration calculation model, calculates and outputs the current smoke concentration value; otherwise, it determines whether V≥Vmax or V≤Vmin. The smoke concentration calculation model is , where Q is the maximum smoke concentration in the range corresponding to the current gear N, and its calculation model is .

[0028] Step 3: If V≥Vmax, it means that the current smoke concentration to be detected exceeds the maximum value of the range corresponding to the current gear N, and the range of the detector needs to be expanded. The gear of Vref is increased by one gear, that is, N=N+1. The detector re-detects the smoke concentration and outputs the voltage value V. The controller 1 determines whether V falls within Vmin-Vmax. If so, it calculates and outputs the current smoke concentration value according to the smoke concentration calculation model in step 2. Otherwise, it continues to increase the gear of Vref and re-detect the smoke concentration, outputs the voltage value V and determines whether V falls within Vmin-Vmax. This is repeated until V falls within Vmin-Vmax, and the current smoke concentration value is calculated and output.

[0029] Step 4: If V≤Vmin, it means that the current smoke concentration to be detected is lower than the minimum value of the range corresponding to the current gear N. The range of the detector needs to be reduced, so the gear of Vref is reduced by one gear, that is, N=N-1. The detector re-detects the smoke concentration and outputs the voltage value V. The controller 1 determines whether V falls within Vmin-Vmax. If so, it calculates and outputs the current smoke concentration value according to the smoke concentration calculation model in step 2. Otherwise, it continues to reduce the gear of Vref and re-detect the smoke concentration, outputs the voltage value V and determines whether V falls within Vmin-Vmax. This is repeated until V falls within Vmin-Vmax, and the current smoke concentration value is calculated and output.

[0030] The increment or decrement of Vref corresponding to each increase or decrease of one gear is the same. Vref is divided into N gear levels, and the voltage value of Vref corresponding to each gear level increases step by step. For example, when the gear increases, if the reference voltage 9 corresponding to the N0 gear is Vref0, the reference voltage 9 corresponding to the N0+1 gear is Vref1, and the reference voltage 9 corresponding to the N0+2 gear is Vref2, then Vref1-Vref0=Vref2-Vref1. Specifically, a detector equipped with a transmitting circuit, a receiving circuit and an amplifying circuit is placed in a smoke box, and the smoke concentration in the smoke box is gradually increased. The controller 1 collects the voltage output by the detector amplifying circuit, and plots the voltage and the smoke concentration to obtain a voltage and smoke concentration curve, such as Figure 3 As shown, the voltage is directly proportional to the smoke concentration. It is worth noting that the detector in this experiment is equipped with an amplifier circuit. Its purpose is to amplify the electrical signal received by the optical signal receiving circuit and convert it into a signal, so that the controller can obtain the electrical signal. It does not affect the relationship between voltage and smoke concentration. It can be seen that for every increase in smoke concentration M, the output voltage of the detector amplifier circuit will increase by ΔV 放 , and when the detector is working, the final voltage V of the detector is equal to the voltage V output by the amplifier circuit. 放Vref is proportional to the difference in voltage. Therefore, to maintain the final voltage V between Vmin and Vmax, Vref must increase or decrease by ΔVref for every increase or decrease in smoke density M. Therefore, for each level change in Vref, the same amount of change in voltage corresponds to the same amount of change in smoke density.

[0031] The resolution K is , and the resolution is the same at each gear. Specifically, the resolution K is the ratio of the concentration difference that can be measured by the range at the current gear to the difference in the voltage value corresponding to the current range, that is, the concentration difference corresponding to a unit voltage value in the current range. At each gear, the detector's final voltage is within Vmin-Vmax, and the change in smoke concentration is M with each gear change. The minimum and maximum values in the range corresponding to each gear change by M, so the difference between the maximum and minimum values in the range corresponding to each gear remains unchanged, that is, T. Therefore, the resolution K is the same at each gear.

[0032] The value of M is less than or equal to the value of T. Specifically, the initial measuring range is 0-T. When the smoke concentration increases by M, the measured concentration range is M-T+M. The value of M is less than T to ensure the continuity of the measuring range when the detector detects smoke.

[0033] A smoke detector circuit is a circuit based on the detection method of the smoke detector, comprising a controller 1, a transmitting circuit, a receiving circuit, and a signal processing circuit. The transmitting circuit is used to emit infrared light, the receiving circuit is used to receive the infrared light and convert the optical signal into an electrical signal, the signal processing circuit is used to provide Vref and adjust and output a final electrical signal based on Vref. Specifically, the signal processing circuit is used to obtain a difference signal between the electrical signal converted by the receiving circuit and Vref and amplify the difference signal to obtain the final electrical signal of the detector. The controller 1 is used to control the transmitting circuit and the signal processing circuit.

[0034] It also includes an amplification circuit, which includes a first operational amplifier 8, a first feedback resistor 7 and a first matching resistor 6. The non-inverting input terminal of the first operational amplifier 8 is connected to the receiving circuit, the inverting input terminal of the first operational amplifier 8 is connected to one end of the first matching resistor 6, the other end of the first matching resistor 6 is grounded, the output terminal of the first operational amplifier 8 is connected to the signal processing circuit, one end of the first feedback resistor 7 is connected to the inverting input terminal of the first operational amplifier 8, and the other end of the first feedback resistor 7 is connected to the output terminal of the first operational amplifier 8.

[0035] The signal processing circuit includes a second operational amplifier 13, a second feedback resistor 14, a second matching resistor 10, a third matching resistor 11 and a fourth matching resistor 12. The non-inverting input terminal of the second operational amplifier 13 is connected to one end of the second matching resistor 10, and the other end of the second matching resistor 10 is connected to the receiving circuit. The non-inverting input terminal of the second operational amplifier 13 is also connected to one end of the fourth matching resistor 12, and the other end of the fourth matching resistor 12 is grounded. The inverting input terminal of the second operational amplifier 13 is connected to one end of the third matching resistor 11, and the other end of the third matching resistor 11 is connected to Vref. The output terminal of the second operational amplifier 13 is connected to the controller 1, one end of the second feedback resistor 14 is connected to the inverting input terminal of the second operational amplifier 13, and the other end of the second feedback resistor 14 is connected to the output terminal of the second operational amplifier 13. The second matching resistor 10 and the third matching resistor 11 have the same resistance value, and the second feedback resistor 14 and the fourth matching resistor 12 have the same resistance value. By setting the signal processing circuit and matching the resistance values of the second matching resistor 10, the third matching resistor 11, the second feedback resistor 14 and the fourth matching resistor 12, the final voltage of the detector is the product of the difference between the voltage value output by the receiving circuit (when an amplifier circuit is provided, the voltage value output by the amplifier circuit) and the voltage value of Vref and the amplification factor, and the amplification factor is the ratio of the resistance values of the second feedback resistor 14 to the third matching resistor 11.

[0036] The transmitting circuit includes an infrared emitting tube 2 and a transistor 3, one end of the infrared emitting tube 2 is connected to the power supply voltage, the other end of the infrared emitting tube 2 is connected to the first end of the transistor 3, the second end of the transistor 3 is grounded, and the control end of the transistor 3 is connected to the controller 1.

[0037] The receiving circuit includes an infrared receiving tube 4 and a sampling resistor 5. One end of the infrared receiving tube 4 is connected to a power supply voltage, the other end of the infrared receiving tube 4 is connected to one end of the sampling resistor 5, and the other end of the sampling resistor 5 is grounded.

[0038] Those skilled in the art will appreciate that the present invention is not limited to the foregoing embodiments. The foregoing embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A detection method for a smoke detector, characterized in that: The following steps are involved: Step 1: The controller pre-enters the detector's response voltage range (Vmin-Vmax), the initial smoke concentration range (0-T) corresponding to the response voltage range, the detector's resolution (K), and the unit smoke concentration change (M). The smoke detector's reference voltage is pre-divided into N levels, and the level corresponding to the initial range is set to level N0. Step 2: The detector detects the fire smoke concentration, converts the smoke concentration signal into a voltage value V, and outputs it to the controller. The controller also records the current level N of the reference voltage. The controller determines whether V falls within the range of Vmin-Vmax. If so, it establishes a smoke concentration calculation model, calculates and outputs the current smoke concentration value. Otherwise, it determines whether V≥Vmax or V≤Vmin. Step 3: If V≥Vmax, increase the reference voltage level by one, i.e., N=N+1. The detector re-detects the smoke concentration and outputs a voltage value V. The controller determines whether V falls within the range of Vmin-Vmax. If so, the controller calculates and outputs the current smoke concentration value according to the smoke concentration calculation model in step 2. Otherwise, repeat step 3. Step 4: If V≤Vmin, reduce the reference voltage by one level, i.e., N=N-1. The detector re-detects the smoke concentration and outputs a voltage value V. The controller determines whether V falls within the range of Vmin-Vmax. If so, it calculates and outputs the current smoke concentration value according to the smoke concentration calculation model in step 2. Otherwise, repeat step 4. The smoke concentration calculation model in step 2 is: , where Q is the maximum smoke concentration corresponding to the current gear position N, and its calculation model is .

2. The detection method of a smoke detector according to claim 1, characterized in that: The reference voltage increment or decrement corresponding to each increase or decrease of one gear of the reference voltage is the same.

3. The detection method of a smoke detector according to claim 1 or 2, characterized in that: The resolution K is , and the resolution is the same in each gear.

4. The detection method of a smoke detector according to claim 1, characterized in that: The value of M is less than or equal to the value of T.

5. The detection method of a smoke detector according to claim 1, characterized in that: The method is based on a smoke detector circuit, which includes a controller, a transmitting circuit, a receiving circuit, and a signal processing circuit. The transmitting circuit is used to emit infrared light, the receiving circuit is used to receive the infrared light and convert the optical signal into an electrical signal, the signal processing circuit is used to provide a reference voltage and adjust and output a final electrical signal according to the reference voltage, and the controller is used to control the transmitting circuit and the signal processing circuit.

6. The detection method of a smoke detector according to claim 5, characterized in that: It also includes an amplification circuit, which includes a first operational amplifier, a first feedback resistor and a first matching resistor, the non-inverting input terminal of the first operational amplifier is connected to the receiving circuit, the inverting input terminal of the first operational amplifier is connected to one end of the first matching resistor, the other end of the first matching resistor is grounded, the output terminal of the first operational amplifier is connected to the signal processing circuit, one end of the first feedback resistor is connected to the inverting input terminal of the first operational amplifier, and the other end of the first feedback resistor is connected to the output terminal of the first operational amplifier.

7. The detection method of a smoke detector according to claim 5, characterized in that: The signal processing circuit includes a second operational amplifier, a second feedback resistor, a second matching resistor, a third matching resistor and a fourth matching resistor. The non-inverting input terminal of the second operational amplifier is connected to one end of the second matching resistor, and the other end of the second matching resistor is connected to the receiving circuit. The non-inverting input terminal of the second operational amplifier is also connected to one end of the fourth matching resistor, and the other end of the fourth matching resistor is grounded. The inverting input terminal of the second operational amplifier is connected to one end of the third matching resistor, and the other end of the third matching resistor is connected to a reference voltage. The output terminal of the second operational amplifier is connected to the controller, one end of the second feedback resistor is connected to the inverting input terminal of the second operational amplifier, and the other end of the second feedback resistor is connected to the output terminal of the second operational amplifier. The second matching resistor and the third matching resistor have the same resistance value, and the second feedback resistor and the fourth matching resistor have the same resistance value.

8. The detection method of a smoke detector according to claim 5, characterized in that: The transmitting circuit includes an infrared emitting tube and a triode, one end of the infrared emitting tube is connected to the power supply voltage, the other end of the infrared emitting tube is connected to the first end of the triode, the second end of the triode is grounded, and the control end of the triode is connected to the controller.

9. The detection method of a smoke detector according to claim 5, characterized in that: The receiving circuit includes an infrared receiving tube and a sampling resistor, one end of the infrared receiving tube is connected to a power supply voltage, the other end of the infrared receiving tube is connected to one end of the sampling resistor, and the other end of the sampling resistor is grounded.

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