Instructables
INTRODUCTION AND DEFINITION
                         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
                           General Description
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.
                      
 
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mardikusumo4 months ago

What is the function of potentiometer? How to know the wire from 3.5mm audio jack is ground and other?

Thank you.

usbg3rd (author)  mardikusumo4 months ago

Hi mardikusmo, the function of potentiometer is to control the sensitivity of the Vu meter like for example if u are playing a song that is at a very low volume u can change the sensitivity so that it divides the voltage on all the LED's otherwise only 2-3 LE:D's might glow due to less voltage.
Secondly the sound is an alternating voltage signal i.e. it changes polarity every instance so u don't need to take care of ground.
and still if u need to find the common wire the one labeled orange in the pic is common the other two are for left and right indivisually :)
like and fav :)

earbud-stereo-jack-plug-wiring.jpg
jcalangi4 months ago
Can you use microphone for this project and how? Pls reply..
usbg3rd (author)  jcalangi4 months ago

Yes u can attach a microphone with the vu-meter. see this link Step:5

http://www.instructables.com/id/10W-RMS-Audio-ampl...

just connect the two wires with the input terminal in the picture
Rate and like :)

mehrin116 months ago

hi..its a nice project..however could u give in details,about the input signal..pls list the required components and the procedure to take the input... well thanks in advance :)

usbg3rd (author)  mehrin115 months ago

Thank u :)
u can take input from any media player /Mp3/mp4/Cell Phone/Computer device. all u have to do is buy a 3.5mm Audio Jack and solder 2 wires one one the ground terminal and the other connecting the other 2 terminals. now plug it in the computer and the other side in ur circuit.
Thanks again.

deeppu1 year ago
can i use 6v adapter?
it is very nice ..
where you live?
can we friend
my fb IS DAZZLER KUMAR
usbg3rd (author)  deeppu1 year ago
yes u can use 5V adapter as it is mentioned in the data sheet
i live in Pakistan (rawalpindi).
and sure.