This project is a 160 LED stereo VU-meter, with 80 LED per audio channel. It is based around an AVR microcontroller ATmega328p, the same inside an Arduino UNO or nano.
This VU-meter reacts to sound fed-in the RCA jacks at the back of the unit and can be plugged on any audio amp. I tested it on the preamp output of my amp and the levels are fine, and can be adjusted with the help of a potentiometer.

This project is not hard to make but I don't recommend it for a beginner in electronics, as you need to know how to solder SMD components. But you will have a lot of fun building it, soldering it, and putting it together as I did !

This guide has the goal of teaching how to build this VU-meter out of my project files. All the files relating hardware or software are on my Github as this project is open source. Feel free to modify it ! Code is documented (doxygen way) as well !

Let's start the build !

Step 1: The Electronics

We will start by building the core of the VU-meter: the electronics.

I made a PCB using EAGLE. Files are on my Github.

You will need for that two PCB and a few components. In fact, the bill of material refers to one PCB, and as there is two audio channels, you will need two PCB and each component twice.

You can access the BOM (Bill Of Materials) here: BOM.

You can access to the PCB Gerber files here: Gerber.

For the PCB you will need to made it manufactured, there is a lot of companies out there that will do it for cheap like JLCPCB or PCBWAYS. I used PCBWAYS personally and they offered me the boards in exchange to some shout-out/review on my Github.

If you never ordered a PCB before, it is very easy, you just need to zip the Gerber files linked above in a .zip archive and drop it on the website of your favorite manufacturer. And that is it !

If you choose to use PCBWAYS, you can easily order the PCB without messing with Gerbers by following this link : EASY_ORDER_LINK

Once you have all the required components you can solder everything by following the components name on the BOM and on the PCB.

Step 2: Microcontroller Programming

Once your two boards are all soldered, you will need to program the ATmega328p microcontroller on them.

To burn the firmware on the atmega32, you first need to download the sofware folder on GitHub.

For that you will need an AVR programmer like this one USBASP (you can find it on Aliexpress, bangood, ebay by searching for usbasp...) or simply an Arduino.

If you use the Arduino just follow this tutorial: Arduino tuto

If you use the AVR programmer just follow this one:

I'm just going to give you the headlines on how to do it with the isp programmer listed before (make sure that the drivers are installed correctly, you can fin useful infos on that by searching on Google.)

Install WinAVR (for windows) (to allow the computer communicate with the ATmega trough the programmer) : Link

Then connect the programmer to the computer and to the PCB (6 pin
connector). Take attention when doing it, if you plug it the wrong way, it obviously wont work.

Open a terminal (CMD on Windows) and type :

avrdude -c usbasp -p m328p -B 5 -U flash:w:firmware.hex -U lfuse:w:0xBF:m -U hfuse:w:0xD9:m

Done ! Firmware flashed on the microcontroler ! (If it fail, make sure that you have the correct drivers installed, the correct isp programmer name, good connection on your circuit.)

Step 3: Making the Enclosure

I used MDF and plywood as the base material to make the enclosure. You can find all the blueprints for cutting the wood and assembling it HERE.

Enclosure Mechanical Drawing.pdf
Download

Step 4: Populating the Enclosure

You will need to add the USB connector, the RCA jacks and the pots. One pot is used to set the input gain of the VU-meter, the other is unused and can be used for anything you want just by modifying the software.

Once that is done, add the PCBs and connect them to the connectors and pots.

I added a clear acrylic bottom part to the enclosure so that you can still look inside the VU-meter.

Step 5: Engraving the Aluminum Front Panel

I used Aluminum for the front panel and I decided to add in my logo. I engraved it by using a electro-chemical method called electrolysis. It is very easy to do and you can learn a bit more on it HERE.

I used electrical masking tape to protect the part I did not want to engrave.