Physical Prototype Complete!

After a couple of weeks of liasing with an expert carpenter, the physical prototype is complete, alomost exactly to spec!

The box measures 1000mm (length) x 300mm (width) x 100mm (depth).
The top and bottom of the box, and the instrument board is 100mm wide plywood.
The sides are 200mm white deal.
It is coated with a matt black finish.

Open, the instrument looks like this.

The instrument board that sits inside measures 800mm x 280mm.
Underneath the board lies 4 arduino boards and their cables.
Placed on the board are 24 sensors.
A 5mm holes was drilled through the board for each sensor's wires.
Each hole was placed 65mm apart, and the side holes were placed 57mm from the edge.
They then had to be countersunk with a 10mm drill bit to accommodate the solder underneath each sensor.
A white sticker is placed over each sensor.

Finally a 16mm hole was placed at the back of the box to accommodate the usb cables.

Having fun - Marimba Solo

This is what happens when the first 6 notes are left open in max/msp.
Sounds like someone is actually playing a marimba solo. Pretty cool!

Meeting with Mikael 7th August

On Aug 7th we met with Mikael to discuss the progress of our prototype. We gave him a quick demo and identified difficulties and further work.

The main points of the meeting were as follows:
- On subject of Threshold and its inconsistency, Mikael suggested that we try and retrigger the condition in Arduino code rather than Max/Msp.
Or possibly try to induce "Temporal Hysteresis" (needed when there is wide signal variations, such as smacking a marimba mallet at various velocities)

-Mikael suggested we try to improve bouncing of sound on the Arduino code side.

-In addition to this, Mikael suggested affixing a 10 nK (nanoFarads) CAPACITOR to the resistor and Piezo wire in order to take out the high frequencies. this effectively acts as a low pass filter for the signal.

-finally, as opposed to using static wav/aif files as sounds, the other future option is to develop sound models, Putting an ADSR envelope (ATTACK DECAY SUSTAIN RELEASE) is a useful approximation of the volume of REAL instrument (but not always a substitute)

-We were also encouraged to use pd rather than max/msp, as it is open source.
ls dev in a mac terminal tell what serial port is being occupied. This will hopefully fix connectivity problem with PD

September Examination and Exhibition

August 27-31
Build and prepare for examination and exhibition.

September 3, Monday
Examination of MusicTech students
In the evening, Official opening of Digital Arts Week Now 2007
Music Tech concert.

September 4, Tuesday
Examination of MusicTech students
DAWN exhibition open to the public

September 5, Wednesday
Examination of Imedia students
DAWN exhibition open to the public

September 6, Thursday
Examination of Imedia students
DAWN exhibition open to the public

September 7, Friday
DAWN exhibition open to the public
Closing of exhibition and take-down.

Building the Prototype

This week we hope to have the instrument built.

We decided that the most practical and accessible design would be to incorporate the instrument into a hinged box.
The below figure demonstrates this idea.


The main piece of timber that will contain the piezos needs to be solid and firmly attached to the box without any rattling (so as not to trigger the wrong sensor).

I've arranged for a carpenter to build box.
Below are dimensions I'll be providing him.


Stay tuned for more...

First draft report Fri July 27th

Here's a link to our first draft report.
http://richie.idc.ul.ie/%7EHackettc/Thesis/DraftReport.pdf

Technical Advice - David Merrill MIT MediaLab

Last week we contacted David Merill, an MIT PhD student who Dave met on a visit to the MediaLab Boston in March. We asked him for technical advice on implementing our prototype.

He advised that for interfacing percussive sensors to a computer, we could probably get by with multiple Arduinos if we sample quickly enough, or build a little pulse-stretching circuitry for our sensors. There is a growing community of Arduino users out there, so we'd likely be able to find someone who's already done something like what we're after. He advised that there are commercial interfaces that are designed specifically to detect impacts, such as the DM5 from Alesis ,but those would probably be more expensive.

He advised also that we'd be better off using Piezos rather than FSRs to detect impact, since they are more sensitive to percussive gesture. FSR might be better suited to aftertouch, or more long time-scale actions.

He also recommended we only use one sensor per bar because if we have a rigid bar, we're likely to get a similar signal from each sensor if we place multiple piezos on it, so a single one may be enough. this is worth testing to see what works best.

In terms of sound, he advised that mapping gesture to sound is where the real "art" of making a musical interfaces comes in - it's simultaneously the most important element of the design, and the one that is the most difficult to offer good advice about.

His final piece of advice was try lots of different possibilities, work with other people to get feedback along the way (especially musicians), and make sure the instrument remains nimble. ( i.e. able to start and stop sounds quickly, and able to expressively shape sounds in some way)

Thanks to David Merill!

Chris H