1. Technical Field
The present disclosure relates to alarm systems, and particularly to a noise level alarm system.
2. Description of Related Art
Noise level is limited in many fields, such as boot noise of computers and working noise of appliances. The noise levels should be tested before the computers and the appliances are shipped. Generally, the noise levels are tested under artificial conditions. However, there is a large margin of error between a tested result and the actual noise. Therefore, there is room for improvement in the art.
Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean “at least one.”
The power supply 10 includes a positive pole and a negative pole. The positive pole outputs a +5V voltage to supply a working voltage for the sound gathering circuit 20, the amplifying circuit 30, the wave filtering circuit 50, and the alarm circuit 70.
The sound gathering circuit 20 includes a sound collector 21. The sound collector 21 includes an audio output terminal 211. The sound collector 21 is used for gathering a sound signal and outputting the sound signal from the audio output terminal 211. The sound signal is an analog signal and includes a noise signal and other sound signals. In one embodiment, the sound collector 21 is a microphone.
The amplifying circuit 30 includes a first amplifier 31, a first resistor R1, a first capacitor C1, and an adjustable resistor R2. The first amplifier 31 includes a first negative terminal 311 and a first output terminal 312. The audio output terminal 211, the first resistor R1, the first capacitor C1, and the first negative terminal 311 are connected in series. The first output terminal 312 is connected to a first end of the adjustable resistor R2. A second end of the adjustable resistor R2 is connected to the first negative terminal 311. The amplifying circuit 30 is used for amplifying the sound signal. An amplifying multiple of the first amplifier 31 is equal to the ratio of a resistance of the adjustable resistor R2 to a resistance of the first resistor R1. The amplifying multiple of the first amplifier 31 can be adjusted by adjusting the resistance of the adjustable resistor R2. In one embodiment, the first amplifier 31 is a chip OP07.
The wave filtering circuit 50 includes a second amplifier 51. The second amplifier 51 includes a first positive terminal 511 and a second output terminal 512. The first output terminal 312 is connected to the first positive terminal 511. The wave filtering circuit 50 is an active band-pass filter circuit. The wave filtering circuit 50 is used for filtering other sound signal in the sound signal and outputting the noise signal from the second output terminal 512 amplified by the amplifying circuit 30. In one embodiment, the second amplifier 51 is a chip AD620.
The comparing circuit 60 includes a comparer 61 and a potentiometer R3. The comparer 61 includes a second positive terminal 611, a second negative terminal 612, and a third output terminal 613. A first end of the potentiometer R3 is connected to the positive pole of the power supply 10. A second end of the potentiometer R3 is grounded. The potentiometer R3 includes a node A. The voltage of the node A is a reference voltage of the comparer 61. The reference voltage can be adjusted by adjusting a position of the node A. When a voltage of the second negative terminal 612 is greater than the reference voltage, the third output terminal 613 outputs a low level, such as logic 0. When the voltage of the second negative terminal 612 is smaller than the reference voltage, the third output terminal 613 outputs a high level, such as logic 1. Thus, when the noise level signal is greater than a reference noise level signal, the third output terminal 613 outputs a low level, while when the noise level signal is smaller than the reference noise level signal, the third output terminal 613 outputs a high level.
The alarm circuit 70 includes a photocoupler 71 and a buzzer 72. The photocoupler 71 includes a light diode 711 and a triode 712. A first end of the buzzer 72 is grounded, and a second end of the buzzer 72 is connected to an emitter of the triode 712. A positive end of the light diode 711 is connected to the positive pole of the power supply 10 via a pull-up resistor R4. A negative end of the light diode 711 is grounded. When the third output terminal 613 outputs the high level, the light diode 711 is off, and the alarm circuit 70 is off. When the third output terminal 613 outputs the low level, the light diode 711 is switched on and drives the triode 712 to switch on. Then the triode 712 drives the buzzer 72 to sound to point out that the noise signal is greater than the reference value.
It is to be understood, however, that even though numerous characteristics and advantages have been set forth in the foregoing description of embodiments, together with details of the structures and functions of the embodiments, the disclosure is illustrative only and changes may be made in detail, especially in the matters of shape, size, and the arrangement of parts within the principles of the disclosure, to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Number | Date | Country | Kind |
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201210149651.8 | May 2012 | CN | national |