This project is about how display an audio signal from a computer/mp3 (or any other media player device's) audio jack by glowing the LED's. Normally voltage is measured and displayed on an LCD or a seven segment display but displaying a voltage in this form is very simple and attractive
A Volume Unit (VU) meter or Standard Volume Indicator (SVI) is a device displaying a representation of the signal level in audio equipment.
Now the aim was to make a vu meter that senses the volume and accordingly glow led's ... the more the amplitude the more number of led's glow. the IC i have picked for this purpose is lm3916 Dot/Bar Display Driver
ABOUT THE IC
The LM3916 is a monolithic integrated circuit that senses analog voltage levels and drives ten LEDs, LCDs or vacuum fluorescent displays, providing an electronic version of the popular VU meter. One pin changes the display from a bar graph to a moving dot display. LED current drive is regulated and programmable, eliminating the need for current limiting resistors. The whole display system can operate from a single supply as low as 3V or as high as 25V.
The IC contains an adjustable voltage reference and an accurate ten-step voltage divider. The high-impedance input buffer accepts signals down to ground and up to within 1.5V of the positive supply. Further, it needs no protection against
inputs of ±35V. The input buffer drives 10 individual comparators referenced to the precision divider. Accuracy is
typically better than 0.2 dB.
Audio applications include average or peak level indicators, and power meters. Replacing conventional meters with an LED bar graph results in a faster responding, more rugged display with high visibility that retains the ease of interpretation of an analog display.
The LM3916 is extremely easy to apply. A 1.2V full-scale meter requires only one resistor in addition to the ten LEDs. One more resistor programs the full-scale anywhere from 1.2V to 12V independent of supply voltage. LED brightness is easily controlled with a single pot.