This is a decibel meter electronic circuit, For an audio engineer,
this circuit seems to be very helpful, especially for checking of
sound pressure levels from about 60 to 70 Decibel (dB). EACH light
represents about a 3dB change in sound level so That Pls all three lights are on, the sound level
is about 4 times Greater than the level needed to light one lamp. The
sensitivity cans be adjusted with the 500K pot so That one lamp comes on with a reference sound level. The other two lamps will from then indicate about a 2X and 4X increase is in volume.
Download Skema :
Sound Level (Decibel) Meter Circuit
Password : asinan
Download Skema :
Sound Level (Decibel) Meter Circuit
Password : asinan
In operation, with no input, the DC voltage at pins 1,2 and 3 of the op-amp will be about 4 volts, and the voltage on the (+) inputs to the 3 comparators (pins 5,10,12) will be about a half volt less due to the 1N914 diode drop. The voltage on the (-) comparator inputs will be around 5.1 and 6.5 which is set by the 560 and 750 ohm resistors.
When an audio signal is present, the 10uF capasitor connected to the diode will charge toward the peak audio level at the op-amp output at pin 1. As the volume increases, the DC voltage on the capacitor and also (+) comparator inputs will increase and the lamp will turn on when the (+) input goes above the (-) input. As the volume decreases, the capacitor discharges through the parallel 100K resistor and the lamps go out. You can change the response time with a larger or smaller capacitor.