Introduction: Led - VU Meter

About: I'm an amature engineer, love to build things that use lights, lasers, LED's.. you name it. Other from that, i run a Photography business, and i L0V3 taking pics :D
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.

Step 2: 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

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)

Step 4: Testing the Shizzle!

Hook it up to a few led's to see if it runs as it's supposed to do.

And connect the speakerwires to the base-pin and ground to make it show you how loud it is!
Adjust with the potentiometer if you are playing really loud.

Try the low-passfilter to see it bounce to the base-line and beat. Really eyecatching.

Step 5: Lunchtime.

Bring out your box, or in this case, the lunchbox.

Start punching holes in it, calculate where you want your switches to be and so on.

Step 6: Soldering and Soldering!

Okay, you made it this far.

So start adding on those LED's.
Remember to get them in the correct order.
The first transistor shines the most, the next one, a bit less, next one after that, more less, etc.

Solder the grounds to the pins of the transistors and the positive (to the positive of your power source, ofcourse)

Step 7: Add Some Glue and You Are Done!

There you go!

Hook it up to your stereo and watch it bounce.

I added some extra pictures to make it a bit easier with the electrical wiring.

If you are watching the third picture.

The bottom right 2 pins are the sound-input.
Top pin is positive, and bottom one is negative.

The top left 2 pins are for power supply (12V or depending on the LED's)
Left one is positive, right one is negative.
The left one is connected to all the LED's

IF you have any questions, be sure to comment or send me a pm!
It could be a bit confusing perhaps, since i messed up with some pictures :^)