A sound alarm circuit

Abstract

This utility model relates to the field of alarm circuits, and more particularly to a sound alarm circuit, comprising a status detection unit, a signal isolation unit, a drive unit, and an alarm execution unit; the output terminal of the status detection unit is electrically connected to the input terminal of the signal isolation unit; the output terminal of the signal isolation unit is electrically connected to the control terminal of the drive unit; the output terminal of the drive unit is connected in series with the power supply circuit of the alarm execution unit; the status detection unit generates a level signal according to an external trigger state, which, after impedance isolation by the signal isolation unit, drives the on / off state of the drive unit, ultimately controlling the working state of the alarm execution unit. This utility model adopts a pure hardware architecture to realize a complete functional chain of signal detection, isolation, drive, and execution, eliminating software processing delays and meeting the application scenarios with extremely high real-time requirements.

Description

Technical Field

[0001] This utility model relates to the field of alarm circuits, and more particularly to a sound alarm circuit. Background Technology

[0002] In the fields of security alarms and equipment status monitoring, audible alarm circuits are widely used in various electronic devices and systems as an important means of status indication and hazard warning. Currently, common audible alarm solutions are mainly divided into software control solutions based on microcontrollers (MCUs).

[0003] MCU-based control schemes detect input signals and drive alarms through software programs. While they can achieve complex logic judgments and functional customization, they have significant shortcomings: First, the circuit structure is complex, requiring crystal oscillators, reset circuits, and peripheral interfaces, resulting in high costs. Second, the software program is susceptible to electromagnetic interference or voltage fluctuations, leading to system crashes or freezes, which reduces system reliability. Third, the MCU's response speed is limited by the program scan cycle, resulting in a certain processing delay, making it difficult to meet the real-time requirements of applications.

[0004] Therefore, there is an urgent need for a sound alarm circuit that can balance fast response, high reliability and anti-interference capability, in order to solve the problems of circuit complexity, high cost, susceptibility to interference and response delay in the existing technology. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a sound alarm circuit that combines rapid response, high reliability, and anti-interference capabilities.

[0006] To achieve the above objectives, the technical solution adopted by this utility model is: a sound alarm circuit, comprising: a status detection unit, a signal isolation unit, a driving unit, and an alarm execution unit; the output terminal of the status detection unit is electrically connected to the input terminal of the signal isolation unit; the output terminal of the signal isolation unit is electrically connected to the control terminal of the driving unit; the output terminal of the driving unit is connected in series with the power supply circuit of the alarm execution unit; the status detection unit generates a level signal according to the external trigger state, which drives the on / off state of the driving unit after impedance isolation by the signal isolation unit, and finally controls the working state of the alarm execution unit.

[0007] Furthermore, the signal isolation unit is a voltage follower circuit, including an operational amplifier U6-A. The non-inverting input of the operational amplifier U6-A receives the signal from the state detection unit, and the inverting input is directly connected to the output to form a closed-loop feedback. The voltage follower circuit also includes a resistor R156, and the inverting input of the operational amplifier U6-A is directly connected to the output through the resistor R156 to form a closed-loop feedback.

[0008] Furthermore, the state detection unit includes: a trigger switch SW4 with normally open and normally closed contacts; a pull-down resistor R78, one end of which triggers the switch SW4, and the other end of which is connected to the non-inverting input terminal of the operational amplifier U6-A; and a filter capacitor C57, one end of which is grounded, and the other end of which is connected to the non-inverting input terminal of the operational amplifier U6-A.

[0009] Furthermore, the driving unit includes an NPN transistor Q7-A, whose base is connected to the output of operational amplifier U6-A via a current-limiting resistor R102; the emitter of transistor Q7-A is grounded, and its collector is connected to the power supply terminal of the alarm execution unit. The driving unit also includes resistors R123 and R124, one end of resistor R123 is connected to the base of NPN transistor Q7-A, and the other end is grounded via resistor R124.

[0010] The beneficial effects of this utility model are as follows: 1. This invention achieves high impedance isolation between the preceding and following stages through a signal isolation unit (voltage follower circuit), effectively blocking disturbances from the preceding stage and power supply fluctuations. Combined with the pull-down resistor and filter capacitor design in the status detection unit, it completely eliminates the risk of level drift caused by floating input terminals, significantly reducing the false alarm rate. Compared to traditional hardware solutions, stability is significantly improved in complex electromagnetic environments.

[0011] 2. This utility model adopts a pure hardware architecture to realize a complete functional chain of signal detection, isolation, driving and execution, eliminating software processing delay and meeting the application scenarios with extremely high real-time requirements.

[0012] 3. This invention uses only conventional operational amplifiers, transistors, and basic passive components to construct a complete alarm function, requiring no programming or dedicated chips, and the material cost is less than 1 / 3 of that of traditional MCU solutions. It also eliminates peripheral components such as crystal oscillators and reset circuits, greatly simplifying circuit design and manufacturing processes. Attached Figure Description

[0013] Figure 1 This is a specific circuit diagram for an audible alarm. Detailed Implementation

[0014] Please see Figure 1As shown, this utility model provides a sound alarm circuit, including: a status detection unit, a signal isolation unit, a driving unit, and an alarm execution unit; the output terminal of the status detection unit is electrically connected to the input terminal of the signal isolation unit; the output terminal of the signal isolation unit is electrically connected to the control terminal of the driving unit; the output terminal of the driving unit is connected in series with the power supply circuit of the alarm execution unit; the status detection unit generates a level signal according to the external trigger state, which drives the on / off state of the driving unit after impedance isolation by the signal isolation unit, and finally controls the working state of the alarm execution unit.

[0015] This utility model's audible alarm circuit employs a four-level hardware architecture to achieve efficient status response. The status detection unit senses changes in external trigger states in real time, generates corresponding level signals, and transmits them to the signal isolation unit. The signal isolation unit isolates upstream interference through its high input impedance characteristics, while simultaneously sending the processed, clean level signal to the control terminal of the drive unit. The drive unit switches between on and off states based on the input signal, directly controlling the current path connected in series in the power supply circuit of the alarm execution unit. When the external trigger state reaches a preset threshold, the status detection unit outputs a high-level signal, turning on the drive unit and energizing the alarm execution unit; conversely, it outputs a low-level signal to turn off the drive unit, and the alarm execution unit enters a silent state.

[0016] Its advantages are: the all-hardware architecture eliminates software processing latency, with signal transmission latency from status detection to alarm execution being less than 5ms. The drive unit adopts a transistor switch design, compressing the on / off switching time to the 1μs level, which is more than 20 times faster than traditional relay solutions.

[0017] Furthermore, the signal isolation unit is a voltage follower circuit, including an operational amplifier U6-A. The non-inverting input of the operational amplifier U6-A receives the signal from the state detection unit, and the inverting input is directly connected to the output to form a closed-loop feedback. The voltage follower circuit also includes a resistor R156, and the inverting input of the operational amplifier U6-A is directly connected to the output through the resistor R156 to form a closed-loop feedback.

[0018] The signal isolation unit uses operational amplifier U6-A to construct a voltage follower circuit. The non-inverting input of operational amplifier U6-A directly receives the level signal generated by the state detection unit, while its inverting input forms a closed-loop feedback loop with the output through resistor R156. This structure forms a deep negative feedback mechanism, and its technical advantages are reflected in three aspects: First, it significantly improves the input impedance, effectively blocking disturbances in the preceding circuit and ensuring the accuracy of level signal transmission; second, it greatly reduces the output impedance, providing sufficient current drive capability for the subsequent drive unit; and finally, through the introduction of feedback resistor R156, it effectively suppresses the risk of high-frequency oscillation and ensures stable output of the circuit under temperature fluctuations.

[0019] In practical applications, when the state detection unit outputs a high-level signal, the voltage follower output synchronously generates a stable high-level drive signal; when the input is low, the output quickly switches to a low-level state. This strict voltage following characteristic eliminates distortion during signal transmission and avoids the risk of false triggering of the drive unit in the critical voltage region. Compared with traditional open-loop transmission architectures, this design significantly reduces the malfunction rate under electromagnetic interference environments.

[0020] This circuit is compatible with general-purpose operational amplifier chips (such as the LM358 series) and requires no special custom components. The value of the feedback resistor R156 can be adapted over a wide range, making it easy to adjust the response characteristics according to actual operating conditions.

[0021] The further optimized status detection unit includes a trigger switch SW4, a pull-down resistor R78, and a filter capacitor C57. The trigger switch SW4 employs a dual-contact mechanical structure; its common terminal is connected to the power supply VCC, the normally closed contact is floating, and the normally open contact is connected to the non-inverting input of operational amplifier U6-A through a current-limiting resistor. One end of the pull-down resistor R78 connects the common terminal of SW4 to the signal node of the non-inverting input of U6-A. The filter capacitor C57 is connected in parallel between the non-inverting input of U6-A and ground, forming a high-frequency interference absorption circuit.

[0022] This combined structure achieves three technical effects: First, the mechanical contact design of SW4 provides a reliable physical triggering mechanism, which realizes two triggering logics by switching between normally open and normally closed states; Secondly, the pull-down resistor R78 eliminates the risk of level drift caused by floating input terminals and avoids false triggering; finally, the filter capacitor C57 effectively absorbs environmental electromagnetic interference (such as mobile phone signals and power ripple) to ensure the purity of signal detection.

[0023] When there is no intrusion, SW4 remains in the normally open position. At this time, the switch contacts are open, the pull-down resistor R78 anchors the potential of the non-inverting input of U6-A to the ground reference, the voltage follower outputs a low-level signal, transistor Q7-A is reliably cut off, and buzzer B2 remains silent. In this state, filter capacitor C57 continuously absorbs environmental electromagnetic interference, ensuring a stable standby state even in the event of sudden pulse disturbances (such as lightning strikes). When an intruder is detected, SW4 is forced to the normally closed position, forming a closed circuit. The power supply VCC is applied to the non-inverting input of operational amplifier U6-A through the current-limiting resistor, generating a high-level signal. The voltage follower transmits this signal to the output, driving transistor Q7-A to conduct, energizing buzzer B2 to emit a continuous alarm sound. This process fully realizes the signal chain of "intrusion occurrence → mechanical action → circuit triggering → audible and visual alarm".

[0024] Furthermore, the driving unit includes an NPN transistor Q7-A, whose base is connected to the output of operational amplifier U6-A via a current-limiting resistor R102; the emitter of transistor Q7-A is grounded, and its collector is connected to the power supply terminal of the alarm execution unit. The driving unit also includes resistors R123 and R124, one end of resistor R123 is connected to the base of NPN transistor Q7-A, and the other end is grounded via resistor R124.

[0025] The driving unit of this invention uses an NPN transistor Q7-A as the core switching device. The base of transistor Q7-A is connected to the output of operational amplifier U6-A through a current-limiting resistor R102, its emitter is directly grounded to form a reference potential, and its collector is connected in series in the negative power supply circuit of buzzer B2. When the signal isolation unit outputs a high level, current is injected into the base of Q7-A through R102, driving it into a saturated conduction state, so that buzzer B2 forms a complete current path to issue an alarm; when the output is low, the base of Q7-A loses voltage and is reliably cut off, and the buzzer B2 circuit is open, remaining silent.

[0026] The further optimized drive unit includes a base voltage divider network composed of resistors R123 and R124. One end of resistor R123 is connected to the base of Q7-A, and the other end is grounded through resistor R124. This structure achieves triple technical benefits: the voltage divider network absorbs high-frequency noise and prevents the transistor from being falsely triggered by electromagnetic interference.

[0027] Furthermore, SW4 can employ the following specific solutions for different intrusion detection scenarios: Door and window intrusion detection (most commonly used) Micro switch (with trigger arm) Working principle: Select a micro switch with a long trigger arm and install it on the door or window frame. When the door or window is closed, the trigger arm is pressed down, and the switch is in one state (normally open or normally closed). When the door or window is opened, the trigger arm is released, the switch automatically switches states, and the circuit is triggered.

[0028] 2. Detection of Moving Objects in Space Passive Infrared Sensor (PIR) Module Working principle: The PIR module can detect the infrared thermal radiation emitted by a human body when it moves. The module itself integrates signal processing circuitry and typically outputs a digital level signal directly (e.g., outputting a 3.3V / 5V high level when movement is detected, which returns to a low level after a few seconds).

[0029] microwave sensor module Working principle: It detects moving objects by transmitting and receiving microwave signals based on the Doppler effect. It also outputs a voltage level signal.

[0030] The above embodiments are merely preferred embodiments of the present utility model and are not intended to limit the scope of the present utility model. Various modifications and improvements made to the technical solutions of the present utility model by those skilled in the art without departing from the spirit of the present utility model should fall within the protection scope defined by the claims of the present utility model.

Claims

1. A sound alarm circuit, characterized in that, include: The system includes a status detection unit, a signal isolation unit, a drive unit, and an alarm execution unit; the output terminal of the status detection unit is electrically connected to the input terminal of the signal isolation unit. The output terminal of the signal isolation unit is electrically connected to the control terminal of the drive unit; the output terminal of the drive unit is connected in series with the power supply circuit of the alarm execution unit; the status detection unit generates a level signal according to the external trigger status, which drives the on / off state of the drive unit after impedance isolation by the signal isolation unit, and finally controls the working state of the alarm execution unit.

2. The sound alarm circuit according to claim 1, characterized in that: The signal isolation unit is a voltage follower circuit, which includes an operational amplifier (U6-A). The non-inverting input of the operational amplifier (U6-A) receives the signal from the state detection unit, and the inverting input is directly connected to the output to form a closed-loop feedback.

3. The sound alarm circuit according to claim 2, characterized in that: The voltage follower circuit also includes a resistor (R156). The inverting input of the operational amplifier (U6-A) is directly connected to the output through the resistor (R156) to form a closed-loop feedback.

4. The sound alarm circuit according to claim 3, characterized in that: The status detection unit includes: a trigger switch (SW4), one end of which is connected to the power supply VCC; a pull-down resistor (R78), one end of which is connected to the other end of the trigger switch (SW4), and the other end is connected to the non-inverting input terminal of the operational amplifier (U6-A); and a filter capacitor (C57), one end of which is grounded, and the other end of which is connected to the non-inverting input terminal of the operational amplifier (U6-A).

5. The sound alarm circuit according to claim 1, characterized in that: The driving unit includes: a transistor (Q7-A), the base of which is connected to the output of an operational amplifier (U6-A) through a current-limiting resistor (R102); the emitter of the transistor (Q7-A) is grounded, and the collector is connected to the alarm execution unit.

6. The audible alarm circuit according to claim 5, characterized in that: The drive unit also includes resistors (R123) and (R124). One end of resistor (R123) is connected to the base of transistor (Q7-A), and the other end is grounded through resistor (R124).

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