Glass VU-meter

Did you know that you can use only the microcontroller for your Arduino projects? You don't need that big blue board that can be difficult to include! And more than that: it's extra simple!

I will show you how to build a PCB around your Arduino, but on glass!

There are several ways to make a glass PCB:

• You can glue copper on glass and then use conventional PCB etching
• You can cut a sheet of sticky copper with a specialized machine (or even a 3D printer) and then stick it to the glass
• Or... you can do it by hand and place one by one each trace with copper tape.

Let's begin!

For this project you will need:

• a piece of glass (pre-cut or not)
• wood for the stand
• copper tape
• basic SMD part (LEDs, resistors, capacitors)
• a standalone Arduino (µC + quartz) and the programmer (FTDI)
• an opamp
• an electret microphone

And also some tools to cut the glass (if needed) and build the wood stand.

For this particular project, you will need a long strip of glass, but you can use any shape!

Use a rotary tool and a glass cutting disk, that's pretty easy, but you need to go slowly.

Then with sandpaper, or a sanding tool, smooth the edges of the piece of glass.

It will take some trials and errors to get a good result (or even have a result at all), so take your time and make sure you have enough glass! Personally, I scavenge the glass pane of old scanners, it's thick and cheap.

The hole drilling is the most difficult part of this project!

What I learned:

• Use a proper glass drill bit
• Start with a sheet of wood, this way, you will not slip
• Use plenty of water when drilling
• Drill slowly
• When halfway through, turn around the glass piece and drill from here, this way, you will have a nice hole

If you failed, you have two options: start with a new piece, or enlarge the hole with a stone sander, and then glue back the two pieces.

When you're finally done with the glass, you can start the layout of the components.

Place only the big ones, to have a rough idea of where things should be.

Also, cut some small copper strips (approx. 1 to 2mm wide).

One more step before truly begins!

If one of your edges is not straight enough, you can add copper to hide it.

It's time for serious business! We will put in place the first component.

Start by placing the mains things (like the microcontroller), and draw a line with a non-permanent pen where you should put copper.

Then, cut small pieces of your copper strip, and place it, but remember to erase your line before! Because it can be seen from behind.

Now you can place your component and solder it, do not use a too hot iron, and be slow, or the glass can crack.

Be sure to test your circuit often!

If you put a too hot tip too rapidly on the glass, the temperature gradient will be too high and the glass has strong chances to crack. And it's even worse if you're near an already weakened area (like an edge that you have cut, a hole, or event another crack).

To best avoid cracks, try to heat the glass evenly and slowly, by hovering the tip of your iron on it.

If one layer is not enough, you can always go behind the glass, by warping around the edge.

If you want to add an angle to your traces (and you'll probably need it), you can

• Stick a trace on top of another, and solder it: simple, but not really nice IMO
• Bend the trace, it adds volume, and I find it prettier, but it's harder to do so, and it can be weaker
• Use a component to join two traces

As said before, here the Arduino is only two things: the microcontroller (ATmega328P with the Arduino UNO bootloader), and it's quartz or resonator.

You will also need a programming connector, with: RX, TX, Reset, GND, 5V.

Before soldering it, make sure that there is no short circuits and that you have not forgotten anything!

If you want to cross two copper traces, you can leave a piece of paper on the sticky side of the top trace, it will insulate the two strips!

It's time to test the LEDs!

You can find the code I used here: https://github.com/telec16/VUmeter

Check if everything lights up and that you can control it well.

Well, you know the process now: rough layout using the components, place the copper traces, and solder everything in place!

If you see some erratics behaviors or other weird stuff, do not hesitate to add some filtering capacitors here and there, or even add a filter before the analog supply (that's what I did).

Finally! It's beautiful and ready to program.

The code is here: https://github.com/telec16/VUmeter

Try things, tweak it until you have some good results, and then, go to the next step!

Ok, now, we will need something to hold the glass.

Find a piece of wood slightly larger than the glass, and also long enough to fit a 9V battery.

With a drill press and an angled wise, make some holes to start the slot where the glass will fit.

Then, use a rotary tool to shape the slot, and make sure that the glass can fit, but not too loose.

We have to find a way to transmit power from the base to the circuit.

For that, I used two pieces of metal (found in an old 9V battery), that I bent. I also made two holes to put them in the slot.

It's time to make some dust! You will need to carve a hole for the 9V battery and the 5V regulator.

Start by drawing the rectangle that you will carve, make sure that the battery will fit, and add some margins.

Then, with a router, mark the shape of the rectangle, and start carving!

Make sure to set the end-stop correctly, as you don't want to go through the other side!

You can add smalls holes on the side for a switch or a power-on LED. I used a small round bit for that.

Sand the wood, it will be nicer and have a better touch feeling. I have waxed it too, as the wood was too clear for me.

Now you have to connect everything up.

Make sure that there are no short-circuits, and double-check the polarity! You don't want to fry the board that you've just made!

Add some hot glue where necessary (on the switch, for example).

Check again that you have the good polarity on the springs!

Finally, it's finished!

Give it a try!

And if you have any problems, do not hesitate to contact me!