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Room Noise Detector Circuit: Build Your dB Threshold!
Description
This circuit is designed to indicate, through a blinking LED, the surpassing of a predetermined level of ambient sound, selectable from three distinct configurations: 50, 70 & 85 dB. Two operational amplifiers furnish the necessary amplification for signals captured by a small electret microphone, enabling driving of the LED. When SW1 is positioned in the initial location, the circuit remains inactive. Subsequent placement in the third, fourth, or fifth positions activates the circuit and sets the input sensitivity threshold to 85, 70 & 50 dB, respectively. Power consumption is 1mA with the LED off, scaling to 12-15mA when the LED is consistently illuminated.
LM358 Operational Amplifier
The LM358 is a versatile, low-power dual operational amplifier. This integrated circuit offers high gain and excellent precision, making it suitable for a broad range of analog circuit applications. Its low power consumption makes it ideal for battery-powered devices. Commonly used in audio circuits, instrumentation, and control systems, the LM358 is known for its stability and ease of use. It operates over a wide supply voltage range and features complementary inputs, allowing for a variety of circuit designs.
Circuit diagram:
Parts:
- R1 = 10K
- R2 = 22K
- R3 = 22K
- R4 = 100K
- R5 = 56K
- R6 = 5.6K
- R7 = 560R
- R8 = 2.2K
- R9 = 56K
- R10 = 56K
- R11 = 1K
- R12 = 33K
- R13 = 330R
- C1 = 100nF-63V
- C2 = 10µF-25V
- C3 = 470µF-25V
- C4 = 47µF-25V
- D1 = 5mm. Red LED
- Q1 = BC327
- B1 = 9V PP3 Battery
- SW1 = 2 poles 4 ways rotary switch
- IC1 = LM358 Low Power Dual Op-amp
- MIC1 = Miniature electret microphone
Use:
- Place the compact enclosure containing the circuit within the room where ambient sound levels are to be monitored.
- The 50 dB setting is provided to track noise levels in bedrooms during nighttime hours. If the LED remains consistently lit or flashes frequently, it indicates that the bedroom environment is unsuitable and too noisy for restful sleep.
- The 70 dB setting is intended for living rooms. If this level is regularly exceeded during the daytime, the apartment's comfort level is compromised.
- If the sound level persistently exceeds 85 dB for a duration of 8 hours daily, it signifies an exposure to a potentially hazardous environment.