#musicubes

Originally I tried to solve this issue by taking some counter measures in the software:

Touches when no music was playing were ignored.

Touches shorter than 50ms were ignored.

And although this solved most of the false positives, it still wasn't perfect. Mainly the volume down button was triggered every once in a while, resulting in a mute state after a few hours of playing. Also the fact that I couldn't turn the volume all the way down before starting the music was a minor inconvenience as well. A modified touch system should solve this.

I originally added one plate of brass on each side of the the MusiCubes tray to handle the touches on the designated surface. The plates of brass were 40x30 mm, allowing me to touch the designates surface anywhere I wanted.

The Solution

The idea is to split up the touch surfaces in 4 sections each. Since I am using the MPR121 Proximity Capacitive Touch Sensor Controller which has 12 touch sensing inputs, connecting these four sections doesn't require any extra electronics.

Whenever the MPR121 reports a touch, I'll count the number of active touch surfaces. By setting a threshold of a minimum of 2 surfaces, false positives on one of the touch surfaces will be ignored.

Let's start cutting up the original brass plates!

I had used some hot glue to mount the brass plates to the MDF. A small screwdriver and a bit of force aloud me to pry of the glue and remove the plates. Removing the glue from the plates and cleaning them up was very a satisfying job.

Cutting the pieces of brass up into four sections was an easy job for my Dremel multitool, so soon enough I ended up with 8 small brass plates.

With an overdose of hot glue, I glued the four pieces back in place, making sure the four pieces didn't touch. The hot glue is a perfect isolator for this!

Next I connected four pieces on both sides to their respective MPR121 sensors. Note to self: next time solder the wires to the plates before glueing them in place, because the soldering heat melts the glue.

And with this modification done, it's time to modify the code.

To quickly count the number of active fields, I added a method to my TouchManager:

uint8_t TouchManager::activeFields(uint8_t sensorIndex) { uint16_t state = _sensors[sensorIndex].touched(); uint8_t count = 0; while (state) { count += state & 0x1; state >>= 1; } return count; }

If the number of active fields is above the threshold, I handle the touch like I did in the previous version. For the full modification of the code, check out this commit on GitHub.

The Big Discovery

To test if this works, I added some logging to report the false positives. Which brought me to my big discovery: the false positives of the sensors were completely gone! It turns out the false positives where caused by the fact that the original brass plates were to large. With four small plates, the MPR121 was much more reliable. As a matter of fact, I haven't had a single false positive in two weeks time! The issue was completely gone! Even though the touch surface is still as large. Awesome!

Because of this, I didn't need a threshold of 2 touched surfaces. In stead I can just respond to any touch detection. And because there aren't any false positives anymore, I can enable the tough controls even when there isn't any music playing.

Victory!

Turn Down The Heat

And with the touch changes, the hardware of the MusiCubes is almost perfect. Almost. Unfortunately there still was one minor issue. The system is powered with a Micro USB power supply, directly into the NodeMCU USB connection. This means that the Neopixels are powered over the same connection.

Unfortunately the USB power goes trough a diode on the NodeMCU board, to prevent any power going into the USB port. But this means the 1 amps that are necessary for the NeoPixels flow through that diode as well. It works, but the diode gets hot. Too hot.

To fix this, I added an external USB connector that directly feeds the 5V into the Neopixel power lines, as well as the the NodeMCU. The tiny diode no longer has to deal with the power hungry LEDs.

And with this change, all of the issues are solved!

The MusiCubes controller really turned out to be a perfect companion to my Sonos sound system. Starting and stopping the music is so simple that even my 3 year old son casually controls the music from time to time. It took a while to convince him to play something else then Disney's Moana music though ...

Read the full series of this project:

Part 1: Concept & Prototyping

Part 2: Assembling The Tray

Part 3: Touch Me!

Part 4: The Software

Part 5: The Finishing Touch

First off, lets give the MusiCubes tray a spray of paint! This MDF isn't too ugly, but a nice layer of white paint will blend it in to the rest of my furniture. Because it is MDF I sealed off the sides with some wood glue to prevent excessive absorption of the paint.

Next, I gave it a layer of primer ...

And before I put on the final layer of white spray paint, I gave it some light sanding. Of course I could pretend that after this whole paint process everything was perfect as I had it in mind, but unfortunately it took me a few days of sanding, painting and retrying to get the end result. Again: the last part of the project is never easy.

Now before I show you the end result, let's work on the cubes!

Using some design tools I designed the printouts that go into the 9 photo cubes. To make the MusiCubes more easy to use, I designed 9 cubes with each a different type of music:

Radio Staions

Male Artists

Female Artists

EDM

Playlists

Alternative Music

Moods

Special Occasions

Kids Music

All cubes have their own icon and color coding using a colored triangle in the bottom right of a cubes face. Filling up these 9 cubes was the most tedious part of the project.

To make the cubes easy to update without the need for a new RFID tag, I printed 9 black cubes that go inside the photo cubes, wrapped in the printouts. The added benefit to these cubes is that they add some weight to the cube, giving them a more high quality feel.

And there it is ... the end result!

The end result after the paint job and the 9 printouts is beyond my wildest expectation! I really Love the vibrant colors of the cubes against the clean white surface of the MusiCubes tray.

The pink LED glow whenever the music is playing makes it even cooler. But best of all ...

... are the magic touch surfaces that work surprisingly well!

And to give you a full impression on how well the end product works, check out the following video. Note that the laptop is only there to show you how quick the Sonos responds. (Watch the volume slider when I change the volume!)

Overall I think it really is a sexy looking project with a huge added benefit to my Sonos audio system. As a matter of fact, my 3 year old son can now start his own songs without my help. Although I'm not sure that's something I should be happy with. The wheels of the bus go round and round, round and round, round and round!

What I've learned ...

I really learned a lot from this project. I'm almost tempted to go for a new and improved version two. But for now let me state my learnings here. They might come handy if you decide to build one yourself.

Gluing multiple layers of MDF together is not a rush job. Take your time. Glue layer for layer and let those layers dry between two heavy flat surfaces.

Painting the tray isn't fun. At all. If you want to make it more easy to finish the project, do this at the start while you are still motivated. The paint can dray while you work on the electronics or software.

Experiment with multiple types and sizes of conductive surfaces for the capacitive touch sensors before you permanently glue them to your tray.

If you have the time, the knowledge and the funds: design a complete PCB in stead of using wires and perfboard. It would make the assembly much easier and would probably improve the reliability.

And last but not least: Think twice before you design a version with 9 cubes. Coming up with your 54 favorite artists, playlists or albums is much harder then you think. It also makes the MusiCubes tray pretty large.

And with that last one in mind: a version with just one cube would probably be just as effective: 5 of your favorite artists, playlists or albums and one stop-side. You can always swap it out for different cubes if you really need more artists, playlists or albums.

Who knows I might build one on the future. But for now, I'm going to focus on a complete different type of project. Keep an eye on my blog!

For now: Enjoy the music!

Read the full series of this project:

Part 1: Concept & Prototyping

Part 2: Assembling The Tray

Part 3: Touch Me!

Part 4: The Software

Part 5: The Finishing Touch

In my last blog post about the MusiCubes project I already showed that I experimented with a capacitive touch sensor behind 3mm MDF. And since that gave promising results, It's time to incorporate the sensors into the MusiCubes tray.

The sensor that I'll be using is the MPR121. A multichannel proximity capacitive touch sensor. It's a 3-in-1 module with the following features: Capacitance Sensing, Touch Sensing, and Proximity Sensing. Since it uses I2C it's pretty easy to connect to the ESP8266. And the breakout board on which I ordered them makes connecting them a breeze.

Because I want to make the two fairly large empty planes next to the play-bay touch sensitive, I need some sort of metal touch planes below the 3mm MDF to function as electrodes. I my case I just stole some pieces of brass my dad was using to built his NS 5500 model train. Not sure if he needs those pieces, but if that is the case, the model train will now need to be a cabriolet.

I glued the pieces of brass in place using an overdose of hot glue, and soldered a piece of wire to it.

The two plates where then connected to the MPR121 breakout board which is connected to the ESP8266 using a JST connector which allows me to easily disconnect or rewire it.

The first tests with the integrated touch sensor were very promising. But soon I noticed a lot of false positives on one of the two sensors. And since these sensors are controlling the volume of my Sonos system, false positives are very annoying. In this case the music was muted within a few minutes of idling.

It turns out that the long green wires to the brass plates pick up too much interference. Especially the wire that goes under the connection to the RFID reader. This interference generates most of the false positives.

The MPR121 gives you a lot of room to tweak the sensitivity of the sensors, but of course it's best to prevent as much interference as possible. And since the sensors are pretty cheap, connected via I2C and offer the option to change the I2C address, I opted for an extra MPR121 IC close to the brass plate. This eliminated a lot of false positives.

Unfortunately this didn't solve all the issues. So I've been playing with all the possible registers the are described in the documentation of the MP121. And while I did notice some improvement, I didn't manage to completely prevent all false positives. Because of this I added some code that checks the length of the registered touch. Anything shorter than 50ms is ignored. And since 99% of the false positives are around 17ms, this solves most of the issues. In addition to this, I added a few other countermeasures to prevent unwanted volume changes.

But let's save the software discussion for next blog. For now, let's enjoy this cool demo of me controlling the volume of my Sonos system using the two invisible capacitive touch sensors.

Read the full series of this project:

Part 1: Concept & Prototyping

Part 2: Assembling The Tray

Part 3: Touch Me!

Part 4: The Software

Part 5: The Finishing Touch

I ended last week's blog post with showing off the laser cut layers that make up the MusiCubes tray. These were ordered online and to keep things withing budget, I didn't order any spares.

And although I promised myself that I would carefully glue together these layer, my enthusiasm and curiosity got the best of me ... Just a few minutes after I opened the package of Snijlab.nl I started squirting wood glue like there was no tomorrow.

Of course these layers should be glued together two at a time, and pressed together on a flat surface while drying to prevent warping.

Of course, I got impatient and decided to glue all the layers at once.

More than enough clamps to keep everything the way I wanted ... right? Wrong! After drying, the tray was completely warped and the layers were terribly misaligned. I was so frustrated that I forgot to take a picture of the result.

Luckily my dad has more experience with woodworking (as well as with making embarrassing mistakes), so with some of his tips and suggestions, I could try to fix it.

First I sprayed the tray with hot water giving it a good soak. Next, I put it between two completely flat side tables and added a heavy barstool as additional weight. I left it like this over night, so the MDF layers could dry.

The next morning I had two successes:

The tray recovered almost perfectly. It's still a tiny bit warped, but my guess is that nobody will notice it as long as you don't tell anybody.

And more important: my wife didn't ask any questions on why I built an unstable tower of doom in our living room just before we went to bed. I'm finally convinced I married the right person.

The left over misaligned layers could be easily fixed by my disc sander.

Not only did the disc sander smooth out any misalignment, it also removed the burn marks caused by the laser cutter, making the spray paint in the future a bit easier.

Next I mounted the RFID reader and the ESP8266 microcontroller with the help of my hot glue gun.

Now we reached an important step in the process: I handed the MusicCubes over to Quality Assurance for a thorough inspection.

After confirming the RFID reader worked, I added four strips of WS2812 LEDs also known as Neopixels. To make sure I could see the light from below the tray, I also added some standoffs on the bottom of the tray.

And after soldering the four strips together with a few wires, and hooking it up to the ESP8266, it was time to give it a test.

This certainly looks promising! I do need to add a big capacitor to prevent power issues when the LEDs turn on. But other than that, they look beautiful!

Just before I wanted to write this update, I received the MPR121 breakout boards which will help me with the proximity capacitive touch sensors to control the volume of the music.

I didn't have time yet to incorporate it into the MusiCubes tray, but a quick test on a bread board does look promising. With a piece of aluminum foil as the sensor, the MPR121 is able to sense the touches trough the 3mm thick MDF.

Read the full series of this project:

Part 1: Concept & Prototyping

Part 2: Assembling The Tray

Part 3: Touch Me!

Part 4: The Software

Part 5: The Finishing Touch

The last few weeks, I haven't been spending a lot of time behind my desk or laptop, due to some back problems. I spent a lot of time wandering through my house doing every day tasks that didn't need any desk work. Because of this, I didn't have my Sonos Music controls at hand, and while Alexa occasionally offered me a good way to switch music without reaching for my computer or phone, the options to quickly start a different playlist was limited.

It turned out I somehow missed the old fasioned way to put on a record or CD. This gave me the idea to build a digital music controller in an analog form factor: The MusiCubes!

The first thing that came to mind was the RC522 RFID reader that I ordered over a year ago. After plugging it on to a breadboard to confirm I could use an ESP8266 to read out the RFID Unique Identifiers, I knew I was on the right track.

My initial idea was to add RFID tags to the original CD jewel cases. But after playing around in Fusion 360, I came up with a different concept which was a little more abstract. If I use cubes in stead of the jewel cases, it would allow me to have 6 RFID tags per cube. With a set of 9 cubes, this would allow me to play 54 playlists, streams, or artists. It also gives a more futuristic look and feel to the design, which is still an analog interface.

Fusion's render function really shows what I want: 9 acrylic cubes on a high-gloss white tray. The tray will 'float' in the air. LED illumination from below is used to confirm user interaction. One separate recess will contain the RFID reader and function as the play-bay. The empty planes next to the play-bay will get capacitive touch sensors to control the volume of my Sonos system.

Of course, the cubes won't be fully transparent. To show which cube plays what, I'll be using 50x50mm photo cubes. This allows me to print inlays showing album covers, icons, artist photos or station logo's. Finding these photo cubes took me a while, so if you are looking for them, check out this link.

I initially wanted to use the RFID tags extracted from the key chain tags. But since extracting these is a pretty tedious process with a high risk of damaging the RFID tags, I checked AliExpress to see if there was a better solution.

And luckily it turned out there is! For around 10 cents a piece you can buy RFID stickers. This makes the process way easier, and not unimportant: way cheaper.

There was one issue that I needed to check: since the 6 tags are contained within the 50x50mm cube, I was worried the RFID reader would pick up more than one tag a time. To make sure it would only pick up the bottom one, I built a small demo. And since I was coding anyway, I decided to hook it up to my Sonos to give me an impression of the result.

Awesome! This works perfectly. Time to start working on the real deal. Unfortunately I don't own a laser cutter (yet). But luckily the good folks of Snijlab.nl run a perfect service to quickly order the parts I need.

So only a few days later I received this exciting package ... the first parts of the MusiCubes controller!

These are the 5 layers that together will form the MusiCubes base tray. Next step: gluing them together and adding the electronics.

Make sure to keep an eye on my blog to follow the next steps of this projects, or follow me on Twitter and Instagram to be notified of the updates.