Portable Drum Kit

How to turn this stuff into a portable drum kit…

When I was at Maker Faire Bay Area this summer (already seems like a very long time ago!) I met the guys from Spikenzielabs when I purchased my Solder:Time watch. We also purchased a POVARD for my older son who was with me, and purchased the Drum Kit Kit AI (AI = All Inclusive) aka DKKAI for my younger son as a present. He has an electronic drum set and takes drum lessons, but wanted a drum kit that he could take for visits to his grandparents. The DKKAI is an ATMEGA168-based kit that comes with piezo sensors to make your own drum pads.

Once I got the set home, I realized it was a MIDI-out kit – you needed another device to make take the MIDI signals and make the drum sounds. I purchased a USB MIDI cable from Amazon for about $5 after realizing I couldn’t buy the cable ends for $5 🙂 I played around with MIDI and a laptop, but most of the MIDI sound programs were overly complicated for his age. When I went to Maker Faire New York, I spoke again to the Spikenzielabs team for ideas. The first improvement was adding the “DKKAI Roadie” – which is a small daughterboard that sits on the DKKAI. The roadie allows you to easily change the mapping of each drum head to a specific MIDI note, and then stores this mapping in the ATMEGA eeprom. This GREATLY simplifies configuration of the kit, since you don’t have to do all the mapping in code (or get out a computer, FTDI cable, etc.)  The Spikenzielabs guys didn’t bring any Roadies for sale with them to Maker Faire NY – but they GAVE me their display Roadie at the end of the Faire since I couldn’t buy one 🙂

Then, a few weeks ago, I started really exploring IOS5 on the iPad – I realized that since I’d last used IOS, they added USB MIDI support via the poorly named “Camera Connection Kit”. Turns out that USB MIDI with GarageBand is a snap, and many of the other apps like the iMS-20 synth from Korg support USB MIDI. I now had a target setup – the DKKAI, the DKKAI Roadie, a USB MIDI cable, the iPad Camera Connection Kit, and an iPad with GarageBand. While it seems complicated, it is all very plug & play, which I knew would work well for his age.

Now I needed to take all these parts and turn them into a drum kit! I had a ton of sketches drawn, and had some really cool thoughts on how to make the drum heads from laser-cut acrylic (we have a laser cutter at FamiLAB, our local hackerspace) – but before I spent a lot of time doing something very custom, I wanted to make sure the kit would work for “real” drumming.

I knew I needed 6 round enclosures to act as the drum heads, so I went to my favorite store for finding small things to repurpose – IKEA. While there, I grabbed 2 sets of the JAMKA 0.5L plastic bowls.


I laid out the 6 bowls into the approximate configuration, then started at them trying to decide how to mount them on something with adjustable height, adjustable angle, and I needed some way to run wiring into each drum head. I then realized that I’d done this type of thing before, and went to the living room to grab the box of PVC fittings that were by the Christmas tree. Turns out that the kids use this stuff like LEGO to build things (mostly marshmallow guns, swords, and tridents…) and so for a gift exchange gift, I’d purchased as much PVC pipe and fittings as I could with the $15 limit. I drilled holes in the bottom of each JAMKA container…


About this time, he walked in, saw it and became very excited. Next thing I know, he’d carried it to his brother’s room and was testing it out…


Once we knew the setup would work, we built the DKKAI kit, and tested it (on the kitchen table!)


I connected two of the piezos in order to test the full path from the DKKAI all the way to GarageBand.

I used a midi keyboard to map out some notes (more on that later…) and I also connected 6 MaceTech ShiftBrites – the Roadie has the ShiftBrite connector and lights up a specific ShiftBrite for each drum pad…

In this video, I’m using the iPad MIDI Monitor app to watch the USB MIDI commands – this lets me see the note, and the velocity for each drum pad hit.

We then ran the wiring using the PVC as conduit…


And I headed out to the garage to cut some metal discs to provide more mass for the piezo elements.

I used my Hypertherm PowerMax 30 plasma cutter to cut out 1/8th inch thick aluminum discs. My roll of blue tape made an excellent template 🙂


Each disc will be epoxied to the lid of the IKEA JAMKA container, and the piezo will be epoxied to the aluminum disc. Below is a disc right after plasma cutting. I DO NOT have a steady hand for this stuff. I wish I’d bought the circle-cutting guide for the plasma!

The angle grinder with a sanding disc allows me to take off the oxidation and smooth out the edges. Here you can see before and after…


Getting ready to epoxy the parts together…


He scuffed-up the lids with sandpaper to help with adhesion…


This is a lid with the disc and piezo epoxied, and the wires soldered and heat shrinked. The piezo leads are quite fragile (found that out the hard way), so I later added some duct-tape strain relief 🙂


We assembled it all in the (messy) garage and then mapped the pad hits to the right notes for GarageBand using the DKKAI Roadie.

This is MUCH easier if you:

1) Use a USB MIDI keyboard to find the right note in GarageBand for the drum / cymbal

2) Switch over to the MIDI Monitor app to see the note you are playing using the keyboard

3) Alter the pad hit note mapping using the Roadie WHILE watching the note change in the MIDI Monitor (Press the mode button on the roadie, hit the pad you want to change with a drumstick, then use the up / down buttons on the roadie and watch the MIDI command change until it hits the right note…it will send the note when you hit up / down, so you don’t have to keep hitting the pad…)

4) Switch back to GarageBand to verify the pad is playing the right drum / cymbal…

Once it was all configured, he gave it a good test…


I will design a laser-cut acrylic enclosure for the DKKAI sometime soon, but to let him start using it ASAP, I extended the blue kitchen container theme with a GLAD container and little more PVC…


We moved it into the living room, he pulled out his drum amp, and proceeded to show off the kit to Mom.

Note: the camera picks up the harshness of the sticks on the plastic much more than the amplified drum sounds. In person, you could hear the GarageBand drum sounds much more than the plastic hits, although we know we need to dampen the plastic hit sound ASAP.

I’ll let him use it for a few weeks to see how it works, but we already have some planned improvements:

1) Sound: We know we need to dampen the hits on the bare plastic – maybe using neoprene like the DKKAI kit instructions

2) Cosmetics: Take it back apart to paint it all and then glue it for more rigidity

3) Software: There appears to be a limit on how many hits can be transmitted in a row – on fast beats, it is missing a note. I need to look for possible delays, since MIDI should be able to handle it with no problem

4)  A real case for the DKKAI

5) An integrated iPad stand

6) An integrated USB hub, so a keyboard can easily be connected at the same time…

7) Pedals – need to add more inputs to the DKKAI and find something portable…

Build cost (Approx $100 not including the iPad):

DKKAI + Roadie = $45

USB Midi Cable = $5

Camera ConnectionKit = $29


Stuff we already had:

Gladware container

PVC Pipe & Fittings (I used MAYBE $10 in parts…)

iPad with GarageBand ($5) & Midi Monitor (Free)

Power supply

FTDI Cable for programming the DKKAI

18 gauge wire

About Ian Cole