Room Noise Detector Schematic Circuit

This circuit is intended to signal, through a flashing LED, the exceeding of a fixed threshold in room noise, chosen from three fixed levels, namely 50, 70 & 85 dB. Two Op-amps provide the necessary circuit gain for sounds picked-up by a miniature electret microphone to drive a LED. With SW1 in the first position the circuit is off. Second, third and fourth positions power the circuit and set the input sensitivity threshold to 85, 70 & 50 dB respectively. Current drawing is 1mA with LED off and 12-15mA when the LED is steady on.

Circuit diagram :

Room Noise Detector Circuit diagram

Parts List :

R1____________10K 1/4W Resistor
R2,R3_________22K 1/4W Resistors
R4___________100K 1/4W Resistor
R5,R9,R10_____56K 1/4W Resistors
R6_____________5K6 1/4W Resistor
R7___________560R 1/4W Resistor
R8_____________2K2 1/4W Resistor
R11____________1K 1/4W Resistor
R12___________33K 1/4W Resistor
R13__________330R 1/4W Resistor

C1___________100nF 63V Polyester Capacitor
C2____________10µF 25V Electrolytic Capacitor
C3___________470µF 25V Electrolytic Capacitor
C4____________47µF 25V Electrolytic Capacitor

D1_____________5mm. Red LED

IC1__________LM358 Low Power Dual Op-amp

Q1___________BC327 45V 800mA PNP Transistor

MIC1_________Miniature electret microphone

SW1__________2 poles 4 ways rotary switch

B1___________9V PP3 Battery

Clip for PP3 Battery

Use :

• Place the small box containing the circuit in the room where you intend to measure ambient noise.
• The 50 dB setting is provided to monitor the noise in the bedroom at night. If the LED is steady on, or flashes bright often, then your bedroom is inadequate and too noisy for sleep.
• The 70 dB setting is for living-rooms. If this level is often exceeded during the day, your apartment is rather uncomfortable.
• If noise level is constantly over 85 dB, 8 hours a day, then you are living in a dangerous environment.

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Low Noise operational amplifier

Low noise balanced input is can also call for the circuit schematic above , because it has a very small noise output and balanced on each input. The noise output is only  117.0 dBu, its very small maybe even not at all out noise. The schematic based on IC5532 , to maintain ic remain good and avoid damage, you should install heatsink in every IC. If the circuit is finished and ready to use, then connect circuit in final befor going out to other components . Because this circuit is also suitable as a buffer amplifier.

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Environmental Noise Ratio Detector Wiring diagram Schematic

This schema is called the detector noise environment, and also indicates by means of a flashing LED when exceeding the limit specified in the environmental noise, chosen from three fixed levels. This schema uses two operational amplifiers, in the first position SW1 schema is not connected, positions 2, 3 and 4 define the input sensitivity threshold to 85, 70 and 50 dB, respectively.

Environmental Noise Ratio Detector Circuit Diagram

Parts List

R1 = 10K
R3 R2 = 22K
R4 = 100K
R5, R9, R10 = 56K
R6 = 5K6
R7 = 560R
R8 = 2K2
R11 = 1K
R12 = 33K
R13 = 330R
C1 = 100nF
C2 = 10μF 25V
CAP 470UF 25V C3 =
C4 = 47μF 25V
D1 = LED red
IC1 = LM358
Q1 = BC327
MIC1 = Miniature electret microphone
B1 = 9V

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