A smoke detection circuit and a smoke alarm

Abstract

The application provides a smoke detection circuit and a smoke alarm, and relates to the field of electronic detection.The smoke detection circuit comprises a photoelectric detection branch, a smoke detection branch and a signal output branch.The photoelectric detection branch is used for detecting a light abnormal signal.The smoke detection branch is used for detecting a smoke concentration signal.The signal output branch is used for outputting a smoke alarm signal after processing the light abnormal signal and the smoke concentration signal.The smoke detection circuit of the application can break through the functional limitation of the existing single sensor, synchronously realize the detection of the light abnormal signal and the smoke concentration signal, accurately amplify the weak signal of the sensor and filter out the environmental noise, and significantly improve the detection precision and the anti-interference ability.

Description

Technical Field

[0001] This application relates to the field of electronic detection, and more specifically, to a smoke detection circuit and a smoke alarm. Background Technology

[0002] In fields such as security monitoring and environmental monitoring, the demand for combined detection of optical anomalies (such as flames) and smoke is increasing. Existing technologies for combined detection devices mostly employ a single sensor for detection or a modular physical stacking design, which has significant drawbacks: First, they are functionally limited, only capable of detecting smoke or a single optical signal, unable to simultaneously achieve coordinated early warning of optical anomalies and smoke, making it difficult to meet the security monitoring needs of complex scenarios; second, signal processing is crude, with weak output signals from photodiodes and smoke sensors, and existing solutions lack targeted multi-stage amplification and filtering designs, resulting in low detection accuracy, poor anti-interference capabilities, and susceptibility to environmental noise leading to false alarms or missed alarms; third, they lack flexibility, with fixed sensor parameters that cannot adjust detection sensitivity or range according to the needs of different scenarios such as industrial and civilian applications, limiting adaptability. Utility Model Content

[0003] The purpose of this application is to provide a smoke detection circuit and a smoke alarm, which solves the above-mentioned problems existing in the prior art. It can improve the smoke detection accuracy and anti-interference ability through two-stage amplification and multi-stage filtering, and adapt to the needs of multiple scenarios.

[0004] In a first aspect, this application provides a smoke detection circuit, which includes: a photoelectric detection branch, a smoke detection branch, and a signal output branch; The photoelectric detection branch is used to detect optical anomaly signals; the photoelectric output terminal of the photoelectric detection branch is connected to the first input terminal of the signal output branch; the photoelectric detection branch includes a photodiode and a first photoelectric amplification and filtering circuit. The smoke detection branch is used to detect smoke concentration signals; the smoke output terminal of the smoke detection branch is connected to the second input terminal of the signal output branch; the smoke detection branch includes a smoke sensor and a first smoke amplification and filtering circuit. The signal output branch is used to process the light anomaly signal and the smoke concentration signal and output a smoke alarm signal.

[0005] In one possible implementation, the first optoelectronic amplifier and filter circuit includes: a first operational amplifier, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, and a first resistor, a second resistor, and a third resistor; In this configuration, one end of the first capacitor, the second capacitor, and the photodiode are all connected to the first positive power supply, the other end of the photodiode is connected to one end of the third capacitor and the first resistor, and the other ends of the first capacitor, the second capacitor, the third capacitor, and the first resistor are all grounded. The other end of the photodiode is also connected to the non-inverting input of the first operational amplifier. One end of the second resistor and the third resistor are respectively connected to the inverting input of the first operational amplifier. The other end of the third resistor is connected to the output of the first operational amplifier. The other end of the second resistor is grounded. One end of the fourth capacitor is connected to the output of the first operational amplifier. The other end of the fourth capacitor is grounded. The output of the first operational amplifier serves as the photoelectric output terminal.

[0006] In one possible implementation, the first smoke amplification and filtering circuit includes: a fifth capacitor, a sixth capacitor, a seventh capacitor, a fourth resistor, a fifth resistor, and a second operational amplifier; Among them, the fifth capacitor, the sixth capacitor, and the first, second, and third terminals of the smoke sensor are all connected to the first positive power supply; one end of the fourth resistor is connected to the fifth terminal of the smoke sensor, one end of the fifth resistor and one end of the seventh capacitor are respectively connected to the fourth and sixth terminals of the smoke sensor, and one end of the seventh capacitor is also connected to the non-inverting input terminal of the second operational amplifier; the other ends of the fifth capacitor, the sixth capacitor, the seventh capacitor, the fourth resistor, and the fifth resistor are all grounded; the inverting input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier serves as the smoke output terminal.

[0007] In one possible implementation, the signal output branch includes a second photoelectric amplification and filtering circuit, a second smoke amplification and filtering circuit, and an amplification and filtering circuit.

[0008] In one possible implementation, the second photoelectric amplifier and filter circuit includes a sixth resistor, a seventh resistor, an eighth resistor, an eighth capacitor, a third operational amplifier, and a first diode; Among them, one end of the sixth and seventh resistors is connected to the inverting input terminal of the third operational amplifier, one end of the eighth resistor is connected to the non-inverting input terminal of the third operational amplifier, and the other end of the eighth resistor is connected to the output terminal of the third operational amplifier; the non-inverting input terminal of the third operational amplifier is connected to the photoelectric output terminal, and the output terminal of the third operational amplifier is connected to one end of the first diode; the other ends of the sixth and seventh resistors are grounded.

[0009] In one possible implementation, the second smoke amplification and filtering circuit includes a ninth resistor, a tenth resistor, an eleventh resistor, a fourth operational amplifier, and a second diode; Specifically, one end of the ninth and tenth resistors is connected to the inverting input of the fourth operational amplifier, one end of the eleventh resistor is connected to the non-inverting input of the fourth operational amplifier, and the other end of the eleventh resistor is connected to the output of the fourth operational amplifier; the non-inverting input of the fourth operational amplifier is connected to the smoke output, and the output of the fourth operational amplifier is connected to one end of the second diode; the other ends of the ninth and tenth resistors are grounded.

[0010] In one possible implementation, the amplification and filtering circuit includes a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a ninth capacitor, a tenth capacitor, and a transistor; Among them, one end of the twelfth resistor is connected to the other end of the first diode and the second diode respectively, the other end of the twelfth resistor is connected to one end of the ninth capacitor and the thirteenth resistor, the other end of the thirteenth resistor and one end of the fourteenth resistor are connected to the base of the transistor, one end of the fifteenth resistor is connected to the second positive power supply, the other end of the fifteenth resistor and one end of the tenth capacitor are both connected to the collector of the transistor, the other ends of the ninth capacitor, the tenth capacitor and the fourteenth resistor are all grounded, and the emitter of the transistor is grounded.

[0011] Secondly, this application provides a smoke alarm, which includes the smoke detection circuit described in any one of the first aspects.

[0012] This application provides a smoke detection circuit and a smoke alarm. The smoke detection circuit includes a photoelectric detection branch, a smoke detection branch, and a signal output branch. The photoelectric detection branch is used to detect abnormal light signals. The photoelectric output terminal of the photoelectric detection branch is connected to the first input terminal of the signal output branch. The photoelectric detection branch includes a photodiode and a first photoelectric amplification and filtering circuit. The smoke detection branch is used to detect smoke concentration signals. The smoke output terminal of the smoke detection branch is connected to the second input terminal of the signal output branch. The smoke detection branch includes a smoke sensor and a first smoke amplification and filtering circuit. The signal output branch is used to process the abnormal light signals and the smoke concentration signals and output a smoke alarm signal. The smoke detection circuit of this application has multiple technical advantages: First, it breaks through the limitations of existing single-sensor functions, simultaneously detecting optical anomaly signals (such as flame light) and smoke concentration signals. It can superimpose optical anomaly judgment on the basis of smoke warning, reducing the false alarm rate of single detection and adapting to the composite early warning needs of multiple scenarios such as security and environmental monitoring. Second, both the photoelectric and smoke branches are equipped with independent first-stage amplification and filtering circuits. Combined with the second-stage amplification and multi-stage filtering design of the signal output branch, it can accurately amplify the weak sensor signal and filter out environmental noise, significantly improving detection accuracy and anti-interference ability. Third, the sensitivity of the smoke detection branch can be flexibly adjusted by adjusting the resistance parameters. The alarm signal output by the signal output branch can be directly connected to an external processor, taking into account both scenario adaptability and equipment compatibility. The overall circuit structure is simple, the cost is controllable, and it is easy to promote and apply in practice. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram of a smoke detection circuit provided in an embodiment of this application. Detailed Implementation

[0015] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0016] In fields such as security monitoring and environmental monitoring, the demand for combined detection of optical anomalies (such as arc light) and smoke is increasing. Existing technologies for combined detection devices mostly employ a single sensor for detection or a modular physical stacking design, which has significant drawbacks: First, they are functionally limited, only capable of detecting smoke or a single light signal, unable to simultaneously achieve coordinated early warning of optical anomalies and smoke, making it difficult to meet the security monitoring needs of complex scenarios; second, signal processing is crude, with weak output signals from photodiodes and smoke sensors, and existing solutions lack targeted multi-stage amplification and filtering designs, resulting in low detection accuracy, poor anti-interference capabilities, and susceptibility to environmental noise leading to false alarms or missed alarms; third, they lack flexibility, with fixed sensor parameters that cannot adjust detection sensitivity or range according to the needs of different scenarios such as industrial and civilian applications, limiting adaptability.

[0017] Therefore, the present application provides a smoke detection circuit that solves the above-mentioned problems in the prior art. It can improve the smoke detection accuracy and anti-interference ability through two-stage amplification and multi-stage filtering, and adapt to the needs of multiple scenarios.

[0018] The preferred embodiments of this application are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit this application. Furthermore, the embodiments and features in the embodiments of this application can be combined with each other without conflict.

[0019] like Figure 1 As shown, this application provides a smoke detection circuit, which may include: Photoelectric detection branch, smoke detection branch, and signal output branch; A. The photoelectric detection branch is used to detect abnormal light signals; the photoelectric output terminal of the photoelectric detection branch is connected to the first input terminal of the signal output branch; the photoelectric detection branch includes a photodiode D7 and a first photoelectric amplification and filtering circuit. The first optoelectronic amplifier and filter circuit includes: a first operational amplifier IC1B, a first capacitor C15, a second capacitor C13, a third capacitor C2, a fourth capacitor C16, a first resistor R16, a second resistor R17, and a third resistor R20. One end of the first capacitor C15, the second capacitor C13, and the photodiode D7 are all connected to the first positive power supply (+5V). The other end of the photodiode D7 is connected to one end of the third capacitor C23 and the first resistor R16, respectively. The other ends of the first capacitor C15, the second capacitor C13, the third capacitor C23, and the first resistor R16 are all grounded. In other words, one end of the first capacitor C15, one end of the second capacitor C13, and the anode of the photodiode D7 are all connected to the first positive power supply (voltage value of +5V). The other ends of the first capacitor C15 and the second capacitor C13 are both connected to ground. The second capacitor C13 and the first capacitor C15 form a parallel power supply filter network. This filter network can filter out high-frequency interference signals and voltage fluctuations in the first positive power supply (+5V) line, preventing power supply noise from affecting the stability of the output current of the photodiode D7 and ensuring that the photodiode D7 can operate in a stable power supply environment.

[0020] The other end of photodiode D7 is also connected to the non-inverting input of the first operational amplifier IC1B. One end of the second resistor R17 and the third resistor R20 are respectively connected to the inverting input of the first operational amplifier IC1B. The other end of the third resistor R20 is connected to the output of the first operational amplifier IC1B (forming feedback). The other end of the second resistor R17 is grounded. One end of the fourth capacitor C16 is connected to the output of the first operational amplifier IC1B. The other end of the fourth capacitor C16 is grounded. The positive power supply terminal of the first operational amplifier IC1B is connected to +5V, and the negative power supply terminal is grounded. Its output terminal serves as the photoelectric output terminal. In other words, the cathode of photodiode D7 serves as the signal output terminal, connected to one end of the third capacitor C23 and one end of the first resistor R16; the other ends of the third capacitor C23 and the other ends of the first resistor R16 are both connected to the ground terminal. The third capacitor C23 can perform preliminary filtering on the weak current signal output by the photodiode D7, filtering out high-frequency environmental noise in the current signal; the first resistor R16 plays the role of current limiting protection, which can prevent excessive current from flowing into the subsequent circuit and avoid damaging the subsequent operational amplifier components.

[0021] The non-inverting input of the first operational amplifier IC1B is directly connected to the cathode of photodiode D7 to receive the current signal after preliminary filtering by the third capacitor C23. The inverting input of the first operational amplifier IC1B is connected to one end of the second resistor R17 and one end of the third resistor R20. The other end of the second resistor R17 is connected to ground. The other end of the third resistor R20 is connected to the output of the first operational amplifier IC1B. Through the above connection, the second resistor R17 and the third resistor R20 together constitute the non-inverting proportional amplification feedback network of the first operational amplifier IC1B. By adjusting the resistance ratio of the second resistor R17 and the third resistor R20, the first-stage amplification factor of the first operational amplifier IC1B can be set (the amplification factor is calculated by adding 1 to the resistance value of the third resistor R20 and dividing by the resistance value of the second resistor R17). Based on the parameters of the second resistor R17 and the third resistor R20, the first-stage amplification factor is approximately 8 times, which can convert the microampere-level current signal output by photodiode D7 into a millivolt-level voltage signal that can be further processed.

[0022] Simultaneously, the positive power supply terminal of the first operational amplifier IC1B is connected to the first positive power supply (+5V), and the negative power supply terminal of the first operational amplifier IC1B is connected to the ground terminal. This connection provides the power required for the normal operation of the first operational amplifier IC1B. The output terminal of the first operational amplifier IC1B is also connected to one end of the fourth capacitor C16, and the other end of the fourth capacitor C16 is connected to the ground terminal. The fourth capacitor C16 acts as an output filter capacitor, filtering out residual high-frequency noise in the signal amplified by the first operational amplifier IC1B, further improving the purity of the output signal. Finally, the output terminal of the first operational amplifier IC1B serves as the photoelectric output terminal of the photoelectric detection branch, connected to the first input terminal of the signal output branch, completing the preliminary processing and transmission of the optical anomaly signal.

[0023] B. The smoke detection branch is used to detect the smoke concentration signal. The smoke output terminal of the smoke detection branch is connected to the second input terminal of the signal output branch. The smoke detection branch includes a smoke sensor and a first smoke amplification and filtering circuit. Specifically, the smoke detection branch converts the smoke concentration in the environment into a processable electrical signal, and uses a first smoke amplification and filtering circuit to achieve preliminary signal amplification and noise filtering, providing a clean and stable input signal for subsequent signal processing. The specific structure and connection relationships of the first smoke amplification and filtering circuit are as follows: The first smoke amplification and filtering circuit includes: a fifth capacitor C18, a sixth capacitor C19, a seventh capacitor C20, a fourth resistor R26, a fifth resistor R27, and a second operational amplifier IC1C. Furthermore, one end of the fifth capacitor C18 and the sixth capacitor C19, as well as the first, second, and third ends of the smoke sensor U5, are connected to the first positive power supply (+5V), and the other ends of the aforementioned capacitors and resistors are grounded. The fifth capacitor C18 and the sixth capacitor C19 constitute a power supply filtering network, which can filter out high-frequency interference in the +5V power supply line, preventing power supply noise from affecting the signal acquisition accuracy of the smoke sensor U5 and ensuring the stability of the sensor's operation.

[0024] Among them, the fifth capacitor C18, the sixth capacitor C19, and the first, second, and third terminals of the smoke sensor U5 are all connected to the first positive power supply; one end of the fourth resistor R26 is connected to the fifth terminal of the smoke sensor U5, one end of the fifth resistor R27 and one end of the seventh capacitor C20 are connected to the fourth and sixth terminals of the smoke sensor U5, respectively, and one end of the seventh capacitor C20 is also connected to the non-inverting input terminal of the second operational amplifier IC1C; the other ends of the fifth capacitor C18, the sixth capacitor C19, the seventh capacitor C20, the fourth resistor R26, and the fifth resistor R27 are all grounded; the inverting input terminal of the second operational amplifier IC1C is connected to the output terminal of the second operational amplifier IC1C, and the output terminal of the second operational amplifier IC1C serves as the smoke output terminal. Furthermore, the fifth terminal of the smoke sensor U5 is connected to one end of the fourth resistor R26. The fourth resistor R26 is used to limit the current of the sensor output signal to prevent excessive current from damaging subsequent circuit components. The fourth and sixth terminals of the smoke sensor U5 are connected to one end of the fifth resistor R27 and one end of the seventh capacitor C20, respectively. The fifth resistor R27 and the seventh capacitor C20 form an RC filter circuit, which can perform preliminary filtering on the original electrical signal output by the smoke sensor U5, filtering out environmental electromagnetic interference and sensor noise, and improving signal purity. At the same time, one end of the seventh capacitor C20 is also directly connected to the non-inverting input terminal of the second operational amplifier IC1C, so that the filtered smoke signal is input to the operational amplifier for amplification. The inverting input of the second operational amplifier IC1C is directly connected to its own output, forming a voltage follower (a special form of the non-inverting proportional amplifier circuit, with an amplification factor approximately 1). This design can significantly increase the input impedance and reduce the output impedance of the circuit while achieving initial signal amplification, avoiding the load influence of subsequent circuits on the smoke sensor output signal and ensuring amplitude stability during signal transmission. Finally, the output of the second operational amplifier IC1C serves as the smoke output terminal of the smoke detection branch, transmitting the initially amplified and filtered smoke signal to the second input terminal of the signal output branch, laying the foundation for the subsequent second-stage amplification.

[0025] C. The signal output branch is used to process the light anomaly signal and the smoke concentration signal and output a smoke alarm signal.

[0026] The signal output branch includes a second photoelectric amplifier and filter circuit, a second smoke amplifier and filter circuit, and an amplifier and filter circuit.

[0027] C1. The second photoelectric amplification and filtering circuit includes a sixth resistor R18, a seventh resistor R19, an eighth resistor R15, an eighth capacitor C14, a third operational amplifier, and a first diode D8. The second photoelectric amplification and filtering circuit performs a second-stage precise amplification and filtering on the initially amplified optical signal transmitted from the photoelectric output terminal of the photoelectric detection branch to ensure that the amplitude of the optical abnormal signal meets the requirements of subsequent composite processing.

[0028] Among them, one end of the sixth resistor R18 and the seventh resistor R19 is connected to the inverting input terminal of the third operational amplifier, one end of the eighth resistor R15 is connected to the non-inverting input terminal of the third operational amplifier, and the other end of the eighth resistor R15 is connected to the output terminal of the third operational amplifier; the non-inverting input terminal of the third operational amplifier is connected to the photoelectric output terminal, and the output terminal of the third operational amplifier is connected to one end of the first diode; the other ends of the sixth resistor and the seventh resistor are grounded.

[0029] In summary, the non-inverting input of the third operational amplifier is directly connected to the photoelectric output (output of the first operational amplifier IC1B) of the photoelectric detection branch to receive the initially amplified optical anomaly signal. The inverting input of the third operational amplifier is connected to one end of the sixth resistor R18 and one end of the seventh resistor R19. The other ends of the sixth resistor R18 and the seventh resistor R19 are both grounded. One end of the eighth resistor R15 is connected to the non-inverting input of the third operational amplifier, and the other end is connected to the output of the third operational amplifier, forming a non-inverting proportional amplification feedback network. By adjusting the resistance ratio of the eighth resistor R15 and the seventh resistor R19, the second-stage amplification factor can be set (the amplification factor formula is 1 + R15 / R19). Combining the parameters of R15 and R19, a second-stage amplification of approximately 17 times can be achieved, meeting the signal composite requirements.

[0030] One end of the eighth capacitor C14 is connected to the output of the third operational amplifier, and the other end is grounded. It is used to filter out residual high-frequency noise in the optical signal after the second stage amplification. The output of the third operational amplifier is also connected to one end of the first diode D8. The other end of the first diode D8 is connected to the subsequent amplification and filtering circuit. Its function is to conduct the optical signal unidirectionally, prevent the reverse interference of the two signals when they are combined, and ensure that the optical abnormal signal is transmitted to the composite processing unit only in one direction.

[0031] C2. The second smoke amplification and filtering circuit includes the ninth resistor R24, the tenth resistor R25, the eleventh resistor R23, the fourth operational amplifier IC1D, and the second diode. The second smoke amplification and filtering circuit performs a second-stage amplification and filtering on the initially amplified smoke signal transmitted from the smoke output terminal of the smoke detection branch, while retaining the adjustable sensitivity characteristics. Specifically, one end of the ninth resistor R24 ​​and the tenth resistor R25 is connected to the inverting input of the fourth operational amplifier, one end of the eleventh resistor R23 is connected to the non-inverting input of the fourth operational amplifier, and the other end of the eleventh resistor R23 is connected to the output of the fourth operational amplifier; the non-inverting input of the fourth operational amplifier is connected to the smoke output, and the output of the fourth operational amplifier is connected to one end of the second diode; the other end of the ninth resistor R24 ​​and the tenth resistor R25 is grounded.

[0032] In summary, the non-inverting input of the fourth operational amplifier IC1D is directly connected to the smoke output (output of the second operational amplifier IC1C) of the smoke detection branch, receiving the initially amplified smoke concentration signal. The inverting input of the fourth operational amplifier IC1D is connected to one end of the ninth resistor R24 ​​and one end of the tenth resistor R25. The other ends of the ninth resistor R24 ​​and the tenth resistor R25 are both grounded. One end of the eleventh resistor R23 is connected to the non-inverting input of the fourth operational amplifier IC1D, and the other end is connected to the output of the fourth operational amplifier IC1D, forming a non-inverting proportional amplification feedback network. The core advantage of this circuit is that it retains the adjustable smoke detection sensitivity. By adjusting the resistance value of the tenth resistor R25 (e.g., reducing the resistance value of R25 can reduce the grounding resistance of the inverting input and increase the amplification factor), the second-stage amplification factor of the fourth operational amplifier IC1D can be changed to adapt to the smoke detection sensitivity requirements of different scenarios (e.g., low sensitivity is required in industrial scenarios to prevent false alarms, while high sensitivity is required in civilian scenarios for early warning).

[0033] The output of the fourth operational amplifier IC1D is connected to one end of the second diode, and the other end of the second diode is connected to the amplification and filtering circuit. Together with the first diode D8, they form a signal isolation barrier to prevent crosstalk between the light signal and the smoke signal before they are combined, thus ensuring the independence and purity of the two signals.

[0034] C3, the amplification and filtering circuit includes the twelfth resistor R5, the thirteenth resistor R21, the fourteenth resistor R22, the fifteenth resistor R1, the ninth capacitor C17, the tenth capacitor C3, and the transistor Q3; the amplification and filtering circuit combines, shapes, and amplifies the two signals output from the second photoelectric amplification and filtering circuit and the second smoke amplification and filtering circuit, and finally outputs a stable smoke alarm signal.

[0035] Among them, one end of the twelfth resistor R5 is connected to the other end of the first diode D8 and the second diode respectively. The other end of the twelfth resistor R5 is connected to one end of the ninth capacitor C17 and the thirteenth resistor R21. The other end of the thirteenth resistor R21 and one end of the fourteenth resistor R22 are connected to the base of the transistor. One end of the fifteenth resistor R1 is connected to the second positive power supply (3.3V). The other end of the fifteenth resistor R1 and one end of the tenth capacitor C3 are both connected to the collector of the transistor. The other ends of the ninth capacitor C17, the tenth capacitor C3 and the fourteenth resistor R22 are all grounded. The emitter of the transistor is grounded.

[0036] In summary, one end of the twelfth resistor R5 is connected to both the other ends of the first diode D8 and the second diode, serving as a composite node for the two signals, receiving the light anomaly signal and smoke concentration signal after secondary processing; the other end of the twelfth resistor R5 is connected to one end of the ninth capacitor C17 and one end of the thirteenth resistor R21, with the other end of the ninth capacitor C17 grounded, forming an RC filter circuit to filter out high-frequency noise in the composite signal; the other end of the thirteenth resistor R21 is connected to the base of transistor Q3, and one end of the fourteenth resistor R22 is connected to the base of transistor Q3, with the other end grounded. Together, they limit the current flowing into the base of the transistor, preventing excessive current from damaging the transistor.

[0037] One end of the fifteenth resistor R1 is connected to the second positive power supply (3.3V), and the other end is connected to the collector of transistor Q3; one end of the tenth capacitor C3 is connected to the collector of transistor Q3, and the other end is grounded to filter out noise from the collector power supply; the emitter of transistor Q3 is grounded, forming a common-emitter amplifier circuit. When a composite signal (light anomaly and smoke signal) is input to the base of the transistor, the transistor conducts and amplifies the signal, ultimately outputting a standard smoke alarm signal (TXEX0 terminal) from the collector of transistor Q3. This output signal can be directly connected to the input pins of an external microcontroller or processor to realize the digital processing of the alarm signal and subsequent early warning control.

[0038] It should be noted that, Figure 1 In the photoelectric detection branch, smoke detection branch, and signal output branch, the pin numbers 1-4 for the third operational amplifier, 5-7 for the first operational amplifier, 8-10 for the second operational amplifier, and 12-14 for the fourth operational amplifier are all pin numbers of the OPA4322AIPWR chip. Similarly, the pin numbers 1-2 for the first and second diodes are pin numbers of the BAV70 chip; and the pin numbers 1-3 for the transistors are pin numbers of the MMBT3904 chip.

[0039] The working principle of the smoke detection circuit provided in this application is explained as follows: When an abnormal light signal appears in the environment, photodiode D7 receives the light radiation and converts the light signal into a weak reverse current signal (microampere level). This current signal is the original carrier of the abnormal light signal. The anode of photodiode D7 is connected to the first positive power supply. The weak current signal output from the cathode first passes through the parallel power supply filter network composed of the first capacitor C13 and the first capacitor C15. This network can filter out high-frequency interference in the +5V power supply line and prevent power supply noise from mixing into the current signal. At the same time, the third capacitor C23 and the first resistor R16 further perform preliminary filtering and current limiting on the current signal to ensure the purity of the signal input to the operational amplifier. The preprocessed current signal is input to the non-inverting input terminal (corresponding to chip pin 5) of the first operational amplifier IC1B. The first operational amplifier IC1B amplifies the signal in the first stage (amplification factor of about 8 times) through the non-inverting proportional feedback network composed of the first resistor R16, the second resistor R17, and the third resistor R20, converting the microampere-level current signal into a millivolt-level voltage signal. The amplified signal is then filtered by the fourth capacitor C16 to remove residual high-frequency noise introduced during the amplification process. The voltage signal, after being amplified and filtered in the first stage, is transmitted to the non-inverting input of the third operational amplifier IC1A (corresponding to chip pin 3). The third operational amplifier IC1A amplifies the signal in the second stage (amplification factor of about 17 times) through the feedback network composed of the eighth resistor R15, the sixth resistor R18, and the seventh resistor R19, ensuring that the amplitude of the optical anomaly signal meets the requirements of subsequent composite processing.

[0040] Meanwhile, after sensing the smoke concentration in the environment, the smoke sensor U5 outputs a weak electrical signal (voltage or current signal) of corresponding amplitude according to the concentration level. The higher the concentration, the greater the amplitude of the output signal. The electrical signal output by the smoke sensor U5 first passes through a multi-stage RC filter network consisting of the fifth capacitor C18, the sixth capacitor C19, and the seventh capacitor C20. C18 and C19 filter out power supply line noise, while C20 filters out high-frequency interference from the sensor's own output, ensuring that the signal input to the operational amplifier is free from noise interference. The filtered smoke signal is input to the non-inverting input of the second operational amplifier IC1C (corresponding to chip pin 10). The second operational amplifier IC1C performs preliminary amplification and impedance matching on the signal through a voltage follower feedback network (amplification factor approximately 1) formed by the fourth resistor R26 and the fifth resistor R27, so as to avoid the load influence of subsequent circuits on the sensor signal. The smoke signal, amplified in the first stage, is transmitted to the non-inverting input of the fourth operational amplifier IC1D (corresponding to chip pin 12). The fourth operational amplifier IC1D amplifies the signal in the second stage through a non-inverting proportional feedback network composed of the eleventh resistor R23, the ninth resistor R24, and the tenth resistor R25. Adjusting the value of the tenth resistor R25 changes the proportional relationship of the feedback network. Decreasing the value of R25 increases the amplification factor and enhances the smoke detection sensitivity (suitable for low-concentration smoke scenarios), while increasing the value of R25 decreases the amplification factor and reduces the sensitivity (suitable for high-concentration smoke scenarios), thus achieving scenario-specific adaptation for smoke detection.

[0041] Finally, the second-stage optical signal output from the third operational amplifier IC1A of the photoelectric detection branch and the second-stage smoke signal output from the fourth operational amplifier IC1D of the smoke detection branch are input to the signal composite node of the amplification and filtering circuit. The two signals are first shaped by the unidirectional conduction of the first diode D8 and the second diode to prevent signal back crosstalk and ensure that only the positive valid signal enters the subsequent processing. After the shaped composite signal is current-limited by the twelfth resistor R5, it is input to the RC filter circuit composed of the ninth capacitor C17 and the thirteenth resistor R21 to filter out high-frequency noise in the composite signal; at the same time, the fourteenth resistor R22 and the thirteenth resistor R21 work together to divide the voltage and adjust the signal amplitude to the range of the base input of the transistor. The conditioned signal is input to the base of transistor Q3. With the support of the second positive power supply (3.3V) and the fifteenth resistor R1, transistor Q3 amplifies the signal (converting the millivolt-level signal into a current signal with driving capability). Finally, the amplified smoke alarm signal is output from the TXEX0 terminal of the collector of transistor Q3. This output terminal can be directly connected to the input pin of an external processor (such as a microcontroller). After receiving the signal, the external device can perform digital processing to achieve accurate triggering and subsequent control of the smoke alarm.

[0042] In some embodiments, other types of photodiodes can be selected, such as BPW34 (high sensitivity to visible light) and S1133 (good response to infrared light). The appropriate model is chosen based on the wavelength of the target detection light signal (e.g., flame light is mostly infrared or visible light) to meet the light detection requirements of different scenarios. If enhanced versatility in light detection is needed, a phototransistor (such as PN2003) can be used instead, which has higher photocurrent gain. However, it is necessary to adjust the parameters of the subsequent amplifier circuit to match its output characteristics.

[0043] Smoke sensors can also be either ionization smoke sensors (such as the MQ-2, which has both smoke and combustible gas detection functions) or laser scattering smoke sensors. The former has a lower cost, while the latter has higher detection accuracy. The choice can be made based on the cost and performance requirements of the application scenario.

[0044] Other low-power, high-gain operational amplifiers, such as the AD8605 (precision op-amp with lower noise) or LMV321 (single-supply operation, suitable for low-power scenarios), can be used to replace the OPA4322AIPWR in the existing solution. Note that after replacement, the resistor and capacitor parameters of the amplifier circuit need to be readjusted to ensure amplification and bandwidth matching.

[0045] The existing two-stage in-phase amplifier can be replaced with an instrumentation amplifier topology (such as using the INA2134 instrumentation operational amplifier) ​​to further improve the common-mode rejection ratio and enhance anti-interference capabilities, making it particularly suitable for industrial scenarios with complex electromagnetic environments.

[0046] If direct digital signal output is required, a comparator (such as LM393) can be added before the transistor output to convert the analog signal into a digital level signal, which can be directly connected to digital circuits (such as FPGA), eliminating the need for the external processor's AD conversion stage.

[0047] The manual adjustment of resistor R25 can be replaced with a digital potentiometer (such as X9C103S), which enables automatic adjustment of smoke detection sensitivity through a microcontroller, improving the intelligence of the circuit and making it suitable for scenarios that require dynamic adjustment of the detection threshold.

[0048] This application provides a smoke detection circuit, which includes a photoelectric detection branch, a smoke detection branch, and a signal output branch. The photoelectric detection branch is used to detect abnormal light signals. The photoelectric output terminal of the photoelectric detection branch is connected to the first input terminal of the signal output branch. The photoelectric detection branch includes a photodiode and a first photoelectric amplification and filtering circuit. The smoke detection branch is used to detect smoke concentration signals. The smoke output terminal of the smoke detection branch is connected to the second input terminal of the signal output branch. The smoke detection branch includes a smoke sensor and a first smoke amplification and filtering circuit. The signal output branch is used to process the abnormal light signals and the smoke concentration signals and output a smoke alarm signal. The smoke detection circuit of this application has multiple technical advantages: First, it breaks through the limitations of existing single-sensor functions, simultaneously detecting optical anomaly signals (such as flame light) and smoke concentration signals. It can superimpose optical anomaly judgment on the basis of smoke warning, reducing the false alarm rate of single detection and adapting to the composite early warning needs of multiple scenarios such as security and environmental monitoring. Second, both the photoelectric and smoke branches are equipped with independent first-stage amplification and filtering circuits. Combined with the second-stage amplification and multi-stage filtering design of the signal output branch, it can accurately amplify the weak sensor signal and filter out environmental noise, significantly improving detection accuracy and anti-interference ability. Third, the sensitivity of the smoke detection branch can be flexibly adjusted by adjusting the resistance parameters. The alarm signal output by the signal output branch can be directly connected to an external processor, taking into account both scenario adaptability and equipment compatibility. The overall circuit structure is simple, the cost is controllable, and it is easy to promote and apply in practice.

[0049] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0050] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the utility model is in use. They are used only for the convenience of describing this utility model and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0051] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0052] Although preferred embodiments of the present application have been described, those skilled in the art, once they have learned the basic inventive concept, can make other changes and modifications to these embodiments.

[0053] Obviously, those skilled in the art can make various modifications and variations to the embodiments of this application without departing from the spirit and scope of the embodiments of this application. Therefore, if these modifications and variations in the embodiments of this application fall within the scope of equivalent technology in the embodiments of this application, then the embodiments of this application are also intended to include these modifications and variations.

Claims

1. A smoke detection circuit, characterized in that, The smoke detection circuit includes a photoelectric detection branch, a smoke detection branch, and a signal output branch; The photoelectric detection branch is used to detect optical anomaly signals; the photoelectric output terminal of the photoelectric detection branch is connected to the first input terminal of the signal output branch; the photoelectric detection branch includes a photodiode and a first photoelectric amplification and filtering circuit. The smoke detection branch is used to detect smoke concentration signals; The smoke output terminal of the smoke detection branch is connected to the second input terminal of the signal output branch; the smoke detection branch includes a smoke sensor and a first smoke amplification and filtering circuit. The signal output branch is used to process the light anomaly signal and the smoke concentration signal and output a smoke alarm signal.

2. The smoke detection circuit as described in claim 1, characterized in that, The first optoelectronic amplifier and filter circuit includes: a first operational amplifier, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, and a first resistor, a second resistor, and a third resistor; In this configuration, one end of the first capacitor, the second capacitor, and the photodiode are all connected to the first positive power supply, the other end of the photodiode is connected to one end of the third capacitor and the first resistor, and the other ends of the first capacitor, the second capacitor, the third capacitor, and the first resistor are all grounded. The other end of the photodiode is also connected to the non-inverting input of the first operational amplifier. One end of the second resistor and the third resistor are respectively connected to the inverting input of the first operational amplifier. The other end of the third resistor is connected to the output of the first operational amplifier. The other end of the second resistor is grounded. One end of the fourth capacitor is connected to the output of the first operational amplifier. The other end of the fourth capacitor is grounded. The output of the first operational amplifier serves as the photoelectric output terminal.

3. The smoke detection circuit as described in claim 1, characterized in that, The first smoke amplification and filtering circuit includes: a fifth capacitor, a sixth capacitor, a seventh capacitor, a fourth resistor, a fifth resistor, and a second operational amplifier; Among them, the fifth capacitor, the sixth capacitor, and the first, second, and third terminals of the smoke sensor are all connected to the first positive power supply; one end of the fourth resistor is connected to the fifth terminal of the smoke sensor, one end of the fifth resistor and one end of the seventh capacitor are respectively connected to the fourth and sixth terminals of the smoke sensor, and one end of the seventh capacitor is also connected to the non-inverting input terminal of the second operational amplifier; the other ends of the fifth capacitor, the sixth capacitor, the seventh capacitor, the fourth resistor, and the fifth resistor are all grounded; the inverting input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier, and the output terminal of the second operational amplifier serves as the smoke output terminal.

4. The smoke detection circuit as described in claim 1, characterized in that, The signal output branch includes a second photoelectric amplification and filtering circuit, a second smoke amplification and filtering circuit, and an amplification and filtering circuit.

5. The smoke detection circuit as described in claim 4, characterized in that, The second photoelectric amplifier and filter circuit includes a sixth resistor, a seventh resistor, an eighth resistor, an eighth capacitor, a third operational amplifier, and a first diode; Among them, one end of the sixth and seventh resistors is connected to the inverting input terminal of the third operational amplifier, one end of the eighth resistor is connected to the non-inverting input terminal of the third operational amplifier, and the other end of the eighth resistor is connected to the output terminal of the third operational amplifier; the non-inverting input terminal of the third operational amplifier is connected to the photoelectric output terminal, and the output terminal of the third operational amplifier is connected to one end of the first diode; the other ends of the sixth and seventh resistors are grounded.

6. The smoke detection circuit as described in claim 5, characterized in that, The second smoke amplification and filtering circuit includes a ninth resistor, a tenth resistor, an eleventh resistor, a fourth operational amplifier, and a second diode; Specifically, one end of the ninth and tenth resistors is connected to the inverting input of the fourth operational amplifier, one end of the eleventh resistor is connected to the non-inverting input of the fourth operational amplifier, and the other end of the eleventh resistor is connected to the output of the fourth operational amplifier; the non-inverting input of the fourth operational amplifier is connected to the smoke output, and the output of the fourth operational amplifier is connected to one end of the second diode; the other ends of the ninth and tenth resistors are grounded.

7. The smoke detection circuit as described in claim 6, characterized in that, The amplification and filtering circuit includes a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, a ninth capacitor, a tenth capacitor, and a transistor; Among them, one end of the twelfth resistor is connected to the other end of the first diode and the second diode respectively, the other end of the twelfth resistor is connected to one end of the ninth capacitor and the thirteenth resistor, the other end of the thirteenth resistor and one end of the fourteenth resistor are connected to the base of the transistor, one end of the fifteenth resistor is connected to the second positive power supply, the other end of the fifteenth resistor and one end of the tenth capacitor are both connected to the collector of the transistor, the other ends of the ninth capacitor, the tenth capacitor and the fourteenth resistor are all grounded, and the emitter of the transistor is grounded.

8. A smoke detector, characterized in that, The smoke alarm includes the smoke detection circuit according to any one of claims 1-7.

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