Category: Main page » Guard and Security

Room Noise Detector

 

One LED monitors three levels: 50, 70 & 85 dB

Useful to detect too noisy environments


Noise Detector circuit diagram



Parts:

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

Device purpose:

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.

Use:


dB

Example of sound sources

20

Quiet garden, electric-clock ticking, drizzling rain

30

Blast of wind, whisper @ 1 m.

40

Countryside areas, quiet apartment, wrinkling paper @ 1 m.

50

Residential areas, quiet streets, fridges, conversation @ 1 m.

55

Offices, air-conditioners

60

Alarm-clocks, radio & TV sets at normal volume

64

Washing machines, quiet typewriters

67

Hair-dryers, crowded restaurants

69

Dish-washers, floor-polishers

70

Loud conversation, noisy street, radio & TV sets at high volume

72

Vacuum cleaners

78

Telephone ring, mechanical workshop

80

Passing trucks, noisy hall or plant, shuffling @ 1 m.

90

Passing train, pneumatic hammer, car hooter @ 1 m.

95

Mega "disco", circular saw

100

Motorcycle without silencer


This page no comment. You can be the first.

Your name:
Your Email:

Comment:
Type the characters: *
captcha
Refresh

CHC40213 Cert 4 Education Support