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!

Step 1: 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.

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WilliamS166 months ago
I guess I see that you said a leg of the resistor connects to the diode.. and in the schematic it then shows the other end of the resistor connecting to a leg of the transistor.. In the schematic I think it shows the other end of the resistor connecting to the center pin of the transistor but from the bottom side of your pcb board the soldering u did doesn't look like the resistor connects to the center pin?? Sorry I am electronic illiterate.
Dufva (author)  WilliamS166 months ago

The audiosignal which goes up and down in voltage when the music plays, is the line the furthest to the left with the AC-symbol. If you follow that line, you will se intersections of the other lines (cables)
However, the lines that cross over and have a dot at the crossing, means that they are soldered together.
If there aren't any dot at the intersection, the lines go over or under eachother.
If that's what you meant.

And the schematic is always a simplified version to make it easier for people to view and understand it on paper. when you have it in your hands, the pins could be swapped, and you have to check which one is the base, the emitter and source.

WilliamS166 months ago
Can you please help me with the basics of this circuit?? How does the resistor and diode connect to the transistor?? How is that circuit built. ?? And what specific diode do I need to by?? Is it used as a switching diode?? I'm not the smartest about this at all.. But any help would be appreciated! !! Thank you

Schematics don't necessarily show the pins in order. You have to look up the datasheet for the part to find out which pin is which. B connects to the resistor/C to the LEDs/ E to ground. I would guess that he is using something like a 1n914 diode. When a diode conducts it has a voltage loss across it (for the 914 it is .7v). Here that is used to "chop up" the audio signal level & use it to turn on the transistors in order. Hope this helps!! Cheers!

Dufva (author)  Lectric Wizard6 months ago

1n4148 - Diode actually, but you weren't too far off!

And yes, the diodes is used to create a voltagedrop the further "up" the chart it goes.

The schematic is correct, but when you come to real-life soldering you might have to do some adjustments because the pins could be in another order as "Lectric Wizard" wrote. :)

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

Community Manager
Dufva (author)  audreyobscura1 year ago
Updated (found it!) :^)
WilliamS16 Dufva6 months ago

I am wanting to build this thing but don't know much about electronics at all.. Can you help me out with this?? It seems like you ran the center pin of the transistors to run to the negative pin of your led strip... however the schematic seems to show the center pin going to that resistor and then to the diode string?? I don't understand?

llinneman1 year ago

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

Dufva (author)  llinneman1 year 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: http://www.instructables.com/id/Build-a-huge-7-segments-8-digits-red-LED-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
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