This is mini sound level monitor project. It will display fluctuating light bars as response of audio signal from Electret Microphone. The louder sound that come into this device, the brighter the light bar. This project use alkaline battery as power source.
The ‘brains’ of this project is a LM358 general-purpose op-amp. The front part of the circuit is an audio amplifier which boosts the 500-micro-volts from an electret mic to about 1-volt. It can be used to drive LEDs or the input pins of an Arduino processor. The second part of the circuit is a voltage-to-current converter, which limits the brightness of the LEDs to 10mA or less.
Since it size small enough, it will fit in your shirt pocket or placed on a flat surface. This project designed by quantastuff.
Sound Light Display
Schematic and Documentation Project