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[How-To] Digital VU Meter


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Mono VU Meter with BarGraph

Before you begin: I do not warrent this project to work 100%, it should not damage anything you hook it up to, but theres always the chance and I do not take responsibility for user error.

So, you got an MP3 player or iPod? Like seeing your music pulsate? This is tutorial is for you then.

With just a few dollars in parts, you can make your own mono digital VU meter that will fit inside a small project box. The only reason its mono, is the bar graph only reads one channel. The sound is still stereo when you listen to it through the box.

This project could get to be quite expensive depending on how good you are at soldering small joints. So, the minimum cost for this project would be around 20 bucks, depending on where you go and how many of each part you buy. Typically getting an IC by itself costs more than buying in bulk.


1 X LM3815 IC chip

1 X 10 segment LED (or 10 LEDS of the same/different color)

1 X 1 inch by 1 inch or larger protoboard

1 X 9v battery connector

2 X Stereo Headphone Jack (3.5mm, 1/4 inch)

1 X Red/Green/Yellow LED (any color will do, just which ever you like)

1 X Toggle switch, at least 10 vdc at 1Amp will work fine

1 X Project box (recommend you buy last, that way you know what you will need)

1 X Doubled ended 3.5mm stereo audio cable



First, your going to need some basic know-how on reading electronic diagrams. It really isn't that hard, you just gotta look at them and decipher the information. If you just follow it, chances are it'll work.

Now, the best thing to do, is familiarize yourself with the circuit. Build it a few times on a solderless breadboard to make sure its going to work for you.

After you have constructed the circuit on the breadboard, the next thing to do is move to a protoboard. Soldering all the joints is going to take a little while. It took me over 4 hours from start to finish to make this project. Soldering took an excrutiatingly long time. Especially when the solder won't stick to a wire lol.

Your going to want to have a passthrough so you can listen to and see your music. For this, your going to need 2 Headphone Jacks (3.5mm or 1/4 inch, however you get measurements). This is a very tricky soldering job as the poles on the bottom of the jacks are tiny. Using this, you can read the pinouts for the 2 jacks that you have. The jacks i used had 5 connectors on the bottom of them, the reason it had 5 instead of 3 was, these jacks can be used as a main or secondary plug. Meaning, that if you plug something in, itll will send the signal to the device plugged in and when nothing is plugged in, it will automatically go through the rest of the cirtuit to other devices, like an internal set of speakers. In a tv if you have a headphone jack and internal speakers, when you plug in a headset the speakers cut out, thats what this jack will do. The poles aren't numbered, so I can't help to much with that, that part was all trial and error for me.

To make the passthrough, you will have to have both of the connectors wired together that way you can plug in the 3.5mm audio cable into one jack, then the input cable from the audio device into the other jack (double ended 3.5mm audio cable) You only need 2 wires from one of the jacks, just a Ground and Left OR right channel wire. Either channel will work just fine, you can even make 2 of these circuits and make yourself a Stereo VU meter inside the one box. Hook these 2 wires up to the inputs on the IC (Pin 4 and 5) it doesn't matter the polarity because its just a speaker.

The passthrough will work something like this:


Now, for the case Design. I just cut a hole in the front of the project box with a soldering iron and the flat bit attatched. Makeing the opening a bit bigger than the actual 10 segment display, you can push it through and kind of lock it in place. At the top of the box I drilled 4 holes. 2 for the input/output jacks, one for the power LED and one for the toggle switch. Thats pretty much it. I would make a layout of the box before cutting anything, I

made that mistake lol, had to redo the box.


Heres what my box looks like:

Top (instrument panel)


Front (Readout, very hard to see in the pic, but the 10 segment display is on the left side in the middle)


After you have the circuit built, you can try and manipulate it inside of a project box. Once you have it in there, its best to secure it somehow that won't let it move around and even short out.

If you need more help, please post a question here and I will try to help you as much as I possibly can. If the tutorial is not very easy for you to read, post a question here, I'll be more than happy to help :)

PS Im sorry for the poor quality pictures, I will try to upload better ones later on.

Heres a movie of the VU playing along to Pearl Jam :P

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