Curve Fitting

A bunch of random resources from the web found by Tom Mitchell regarding finding how close curves are together and stuff... TO BE UPDATED

http://en.wikipedia.org/wiki/Taylor_series

http://mathworld.wolfram.com/Polynomial.html

http://en.wikipedia.org/wiki/Newton's_method

http://www.google.co.uk/search?hl=en&client=safari&rls=en&q=bezier+curve+fitting+applet&aq=f&aqi=&aql=&oq=&gs_rfai=

http://www.serc.iisc.ernet.in/~amohanty/SE288/lagrange/curves.html

http://www.cs.princeton.edu/~min/cs426/jar/bezier.html

http://www.theparticle.com/applets/nyu/BezierApplet/

http://www.cse.unsw.edu.au/~lambert/splines/Bspline.html

http://www.cs.uwaterloo.ca/~r3fraser/splines/bspline.html

http://saltire.com/applets/advanced_geometry/spline/spline.htm

SOS Korg Wavedrum Entry

http://www.soundonsound.com/sos/apr10/articles/korgwavedrum.htm

FYP Order Form

1 - Arduino Uno - RS - 715-4081

1 - Texas Instruments OPA350UA op amp - Farnell - 1106197

1 - 1m USB 2.0 A to B Lead - Maplin - NO8JA

4 - piezo xducer 27/1.8 - Maplin - YU87U

Arduino And Max

http://www.arduino.cc/playground/Interfacing/MaxMSP

See Arduino2Max

http://cycling74.com/docs/max5/tutorials/max-tut/communicationschapter02.html

Serial communication tutorial from Arduino to Max

MIDI Equipment

Here are some sources for MIDI equipment in case I decide to stick with the Arduino and communicate via MIDI:

Female MIDI socket component with breadboard compatible pins - SparkFun Electronics

Various breadboard components from CuriousInventor.com. MIDI IN/OUT modules towards the bottom. Also available is a breadboard minijack socket which might be useful. *Both currently out of stock*

MIDI IN/OUT to USB converter from Amazon. Also see Maplins

Arduino and Audio

This post is dedicated to research into how best to set up an Arduino environment for audio.

http://interface.khm.de/index.php/lab/experiments/arduino-realtime-audio-processing/

http://www.ladyada.net/make/waveshield/libraryhc.html

As far as I understand it audio can be processed using the Arduino. When I say processed here I just mean ADC and pass to the computer and DAC from the computer and pass to a power amp. The first link above seems to be the way to do this but it seems rather problematic and tedious and the results have a very limited sample rate and depth (for audio) and so are unlikely to provide adequate quality in the long term.

I'm not looking into the possibility of having a dedicated device to perform the conversions and simply using the Arduino as it is designed to be used, to control data. Thinking about it now however even using a dedicated ADCDAC device the Arduino would still need to sample the output from the device and so would impose its crappy sampling rate and depth. Or would it if the audio input to it was in digital form?? The only analogue input would then be the FSR and the arduino is fine for that...questions!!!

Hardware Choices

For the Arduino I think I good place to go is Arduino starter packs. They contain the board itself as well as loads of other stuff that I'd probably end up having to buy or root around for at uni. These include basic things like wires, USBA/B cable, bread boards etc to more specific bits of kit which nevertheless would be useful for experiments such as transistors, resistors, LEDS, motors, photodiodes, etc. One UK based company that provides a good choice is Oomlout, offering a range of Arduino products here. They offer an all inclusive kit here and a slightly toned down version here. I'd probably opt for the latter since its cheaper but includes all the main components.

UPDATE

After borrowing an Arduino Diecimila I think the Uno would be better. Its very similar but one new feature is that it automatically selects where to draw power from (USB or Jack) based on what its plugged into. This would therefore be one less thing a user would need to know about when playing the instrument.

This piezo seems to be a good choice, though it is more expensive than others. This may be indicative of a better quality and since I hope to use the raw audio signal to not only trigger sounds but to influence them based on its characteristics, quality seems important. The piezo presents a reasonable frequency response (as reasonable as a piezo mic could be I guess) in the required range for knocks (100Hz to 5kHz).

This is a nicely sized square FSR from UK based Cool Components. I think a bigger size for the FSR, rather than the much smaller circular models, is a good idea since i think it would be easier to use ergonomically if the player didn't have to aim too much to use it could just lunge in its general direction without too many problems. It is important to note however that the FSR will need to form one resistor in a voltage divider in order to convert the resistance change of the FSR to a voltage change for input the arduino analogues.

I keep coming back to this loudspeaker driver so I suppose its appropriate. It certainly seems that way.

Arduino

I have pretty much made up my mind that I will use Arduino to input sensor data to the computer. There are several reasons. Its reasonably priced. It has a good reputation. There seems to be a good community and lots of tutorials. It comes with its own coding language and environment with plenty of help and examples. People have created similar projects. It uses a simple USB interface which also powers the board.

The Arduino Uno seems like a good choice. It is their newest product and is being billed as setting the standard for Arduino. Here is the Arduino Uno available from RS. The Duemilanove is also a popular modal so may be worth comparing. Here it is from RS.

Here is an application of a (frustratingly) basic drum machine using two piezo elements a speaker and an arduino. Not a lot of tech details but just for interest.

Here is an arduino forum entry by a guy building some thing that looks horribly similar to some of my very first ideas (very similar to the nukulele). They have a conversation regarding preamps for his piezo pickups which may prove useful later.

Preamp

Here I will consider the preamp that I (think) I will need to increase the output of the piezos. I reckon I should only need one preamp for two (for example) piezos since its IC has multiple input and outputs.

Preamps seem relatively inexpensive. Here are some available from Farnell. Here is one from Digikey.

Power Amplifiers

Here I will consider my choice of power amplifiers for the loudspeaker drive unit.

This seems to be a more problematic decision to make since a lot of power amplifiers are big bulky and heavy. I could of course use an off the shelf model external to my instrument, but this would mean running extra cables from the instrument and would also go against the sense of "self containedness" that I would like to aim for. Marshall created custom amplifier circuits for his viblotar so perhaps this is some thing I could look into. It may transpire though that this could be a project in itself and that I will be forced to choose a commercial model. In this case I could cite the development of an internal custom circuit as potential for future work.

For the time being, here are some power amplifiers available on RS. Obviously, power amplifiers are readily available from many sources (though not necessarily for cheap!). Number of speakers is also a consideration here since I reckon if I only have one speaker I will only need a mono amp!

Piezo Electronic Transducers

Here I will consider my choice of piezos for the detection of strikes on the Cajon.

A range of Piezos are available from RS here. I'm not sure what are the most important features of a good piezo but according to the literature* the full bandwidth for various knocks amd taps os 100Hz-5kHz so a piezo with a good response in this range would be a good start. This piezo may be an option. Here is its spec. A piezo element is available from Farnell but it does not seem to have a spec. Piezos seem to be dirt cheap!

Here is an entry in sensorwiki for piezos with some technical and practical details. Here is a youtube video of an engineer attaching piezo pickups to his acoustic guitar which provides a few practical hints, for example the use of a hot glue gun to attach the piezos.

Loudspeaker

In this post I will consider potential choices for the loudspeaker to be included in the design of my DMI. It is important to note that technical it is the loudspeaker drive unit that I will be including, this is useful to know when searching google etc.

I figure I need a loudspeaker which focuses on frequency response, but which also has a reasonable amount of power ie for playing in the studio. External speakers would naturally be used for filling live performance spaces. Size is also an issue since recent designs of my Cajon have been small enough to be played between the knees or on the lap. The speaker therefore needs to be of a reasonable weight and size to allow this.

The main contender so far is this speaker from Visatron, available through RS. The technical spec. is available here. Its 6.4cm/2.5inches and is described as a full range speaker driver. It has a typical impedance of 8ohms (the literature suggests this is the norm) and a power of 8W. Is this a good power level?