Picture of Led - VU Meter
In this instructable, I will show you how to put together an analog VU-meter.
You can plug any light in (with the right voltage ofc) and it will work.

A Vu-Meter is simply measuring the volume of the sound, the bigger the voltages, the higher the light will go on the bar. :)
Though, getting it accurate takes calibrating and such, and I will not go over that.

This is as simple as it gets, and it's pretty awesome!

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Step 1: Gather your parts!

Picture of Gather your parts!
The main component we are using this time is the "Tip 31C"
Standard transistor, cheap and easy to find.
How many?
Use as many as you want!

Then you need just as many diodes + a few spares. (take note of the Vf drop they have, too high, and you can't use many leds with low voltage)

A pcb board.

a pin-breakable thing :^) -- The same thing you use to build shields with.

A potentiometer (100k for this one) To adjust sensitivity on the bar.


A simple switch.

Some Led's 

And last but most important, a lunchbox.

Step 2: Step 1, or step by step, or step, or ..

Picture of Step 1, or step by step, or step, or ..
First of all, you want to put the transistors in a nice line to work with, not to close, and not too far away. (I calculated the holes exactly)

Then you solder a Diode (shown on the picture) as a starting rectifier for the BASE-pins.
Connecting another diode onto the end, with another diode, and so on. so you "split the voltages, the further away you go.

Since there is a Forward-voltage, you drop, in this case 0,6V per diode. Making the LED's shine less the further away it is in the bar.

Continue adding a diode, then connecting the end to a base with a resistor (10k ohm)
(view the picture)

Trying to view from below just makes my eyes hurt.

Step 3: Connectors

Picture of Connectors
Moving on with adding some metal pins so we can easily connect our LED's to the board.

And not necessary, but done here, a simple passive low-pass filter done with a 1k ohm resistor and a 1µf capacitator.
(sorry for poor documentation here)
llinneman10 months ago

Awesome project!! Quick question, what kind of LED strip is that and where can I find them? Thanks so much!

Dufva (author)  llinneman10 months ago

That is a 5050-Ledstrip which i bought on ebay.

Like this one, exactly the same :)

cikaceka1 year ago
it will be nice if I could now the right position of potentiometer in wiring shema...I bought the whole PDF, so....
Dufva (author)  cikaceka1 year ago
The potentiometer is positioned on the line in.
The sound input that is :-)
cikaceka Dufva1 year ago
That means after the line-in input and before input diode?
Dufva (author)  cikaceka1 year ago
Correct :-)
smuggly1 year ago
Would you be able to have the sound be determined by a 1/4" input for a musical instrument with a 1/4"output as well? Basically I want my guitar to control the LEDs but still output to my amplifier for live shows. Could you build this? I'd pay ya for it! :-)
kschmidt21 year ago
Just looking, your strip LED's that you're using are multi coloured, so you could set it up so that the bottom few are green then yellow, then red. Would look more like a VU meter then. :)
No yellow, but Blue green red, or green blue red would be awesome
Dufva (author)  kschmidt21 year ago
That's correct :)
But i didn't have any coloured led's when i built it, and fully red made it look sweet aswell.
The strips you're using are multi coloured, you have Red, green and blue. See how the the end of the strip has four terminals, there's red positive, green positive and blue positive, then negative. You could just switch some of the wires and it'll work
Dufva (author)  kschmidt21 year ago
Ah you mean those, the strip is actually only red.
The 3 diodes inside are just red :-) .. And the three terminals are connected.
maraz11 year ago
Could you tell me the values ​​of the materials used in this circuit, and voltage input, audio input, potentiometer ports.
  Thank you. Greetings from Turkey
Dufva (author)  maraz11 year ago
The Values are all typed out on the instructable.
Voltage input is 12V.
Audio input is audio input, it ranges from 0V - 12+V
Krifus1 year ago
Where is sound input?
Dufva (author)  Krifus1 year ago
Sound input is the Sinus-wave icon you see on the left on the schematics.
Positive cable as the input.
Hmm interesting but am I wrong there is a mistake between transistor bases of pink and blue in your diagram
Dufva (author)  KROKKENOSTER1 year ago
Wow, I did mot see that error, you are absolutely right, and that connection is not supposed to be there. It's only supposed to be connected with the diodes! :-)
Dufva (author)  Dufva1 year ago
And now it's fixed.
Edgar1 year ago
Nice. Went a description and Link of this, to my Blog:
Dufva (author)  Edgar1 year ago
Thank you very much! :D
nstancil1 year ago
do you think you could use this idea and make a big panel to hang on your wall?
You can make an entire wall with these LEDs :) I made once a 7 segments display: Just drive them accordingly
If you wanted to switch larger lights on and off instead of small LED strips, all you would need to do is have the transistors switch on relays (or larger transistors) instead of the LED strips. Then have the relays switch your lights on and off.
Dufva (author)  NitroRustlerDriver1 year ago
You can make a big panel with this yea.
And if you want it as simple as possible, switch the transistors in the circuit to some more powerful ones :).

Or as Nitro said, use the transistor to turn on another transistor :-)
rejsps1 year ago
Nice, simple circuit with lots of flexibility. My only pet peeve is that this is not a VU meter, since volume units are in decibels (logarithmically spaced) to correspond more closely to the ear's response. So it simply measures the half-wave rectified voltage level of the audio signal in 0.6 V steps. Still a good display if you don't care about being technically correct and just want to flash lights to the music.
Dufva (author)  rejsps1 year ago
Thanks! Yeah, thats true, but if you alter the resistors to the corresponding values, you get one that's more of a vu-meter than this :)
Dylon1241 year ago
You should using an lm3915. It's a much better way to go.
Dufva (author)  Dylon1241 year ago
I decided not to use it to show people how easy it is to create something so powerful in visuals, but yet so easy :)
With easy-to-get parts.
grimka1 year ago
could you post a video of it working please. would love to see it in action
Dufva (author)  grimka1 year ago
Clip is up!
Dufva (author)  grimka1 year ago
Let me get home from work, and I'll upload it later tonight :-)
(Don't know why I haven't done it already)
You should correct your schematic to show where the diodes go. Technically what you have created is a "color organ" not a Vu meter. A Vu meter is a logarithmic meter used to measure audio levels, it will react very differently that this. None the less great job building it & on the instructable !!
Dufva (author)  Lectric Wizard1 year ago
Well, I did my research and I wouldn't call it a color organ completely, since the higher the volume the further up the LEDs it shines.
And yes I need to update that schematic,, missing original file though :(
Let me know when you update your schematic, and I will feature your project :D

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Dufva (author)  audreyobscura1 year ago
Updated (found it!) :^)