Finally have the Arduino, capacitors, and the SOMO 14-D.  Still need to figure out what micro-SD memory card to get for the SOMO as not all are compatible.

Computer Controlled Amplifier

• To reduce number of problems, the oscillator circuit will be used to produce the sound.  Later this will be replaced with the SOMO 14-D.
• Fried first amplifier because I had the pin numbering wrong.  Pin numbering on ICs is numbered down on the left side then up on the right side.  For some reason I thought it was down on both sides and got the VCC and GND pins reversed causing smoke.
• The capacitor used to filter the audio signal is not supposed to be polar but a polar capacitor will work as long as, the positive side is on the pin and the negative side goes to the audio source.  This seems strange considering the direction of the current but when I had it the other way no sound came out.  Luckily the audio signal isn’t strong enough to blow the capacitor.
• Switched piezoelectric speaker with regular speaker to make sure it wasn’t causing problems due t it having a higher resistance
• Realized that when the amplifier was changing volume the sound light sound would cut off.  I figured this was due to lack of power.  Took the whole circuit off the i2c-usb controller’s power and onto the power supply.
• Was not able to change the resistance on the the rheostat chip.  Realized that all i2c controlled chips must be grounded to the i2c controller gnd.
• Test class worked for controlling volume!
• The amp has to be muted digitally in order to get absolute silence.  The piezoelectric speaker, due to having a higher internal resistance, can be adjusted down to being “muted” without having to control the mode of the amplifier.
• The piezoelectric speaker seems to work well.  Not sure how good it will be for playing sounds, instead of tones.  Need to find out if I can get samples of those tiny speakers I mentioned in a previous post.

Arduino

• Considering part of the goal is to reduce the number of usb devices(not a very important goal but still), the mega would have probably been better then the Uno.  That said, the uno should be useful to see if it will work for our application, and should have enough outputs for a two finger prototype.  Another advantage of the mega is it can speak i2c which would eliminate the need for the usb-i2c adapter.  However, if I find its better to control the mute function on the amplifier with the second rheostat on the variable resistor chip, we will need two i2c channels in order to communicate with 5 amplifiers.
• Before I attempt to get the Arduino to communicate with the SOMO 14-D, I am going to try some basic tutorials to make sure I understand how to program it.

Speakers

• Spoke to a representative at Murata to see if we could get samples of the VSLBP2115E1200-T0.  He directed me to a local distributor Glen White Associates(434-385-6110).  He also said that the Speakers should be used with a audio amplifier for ceramic speakers.  There is no problem with using a regular amplifier but it may not be loud enough due to the higher impedance.

Arduino research:

• Found many links regarding the Arduino electronics platform:

1. Explanation of different version:    http://www.ladyada.net/library/arduino/unofaq.html
2. Tutorials: http://arduino.cc/en/Tutorial/HomePage
3. 414 Arduino projects and counting: http://hackaday.com/category/arduino-hacks/
4. Search engine for chips: http://www.findchips.com/
5. Ada’s Store: http://www.adafruit.com/
6. Sparkfun Store:  http://www.sparkfun.com/

• I determined that the version we want is the Arduino Uno.  I believe that all latest versions have similar specs, but this one is probably the best for our stage of prototyping.  A smaller one, which mounts onto a board may be better once the electronics are finalized.
• Due to the recession, DIP chips are getting hard to find because many producers are cutting costs by only make SMTs, which have higher demand.  This is making it so the arduino’s main chip is becoming increasingly rare.  There is a SMT version now to help keep up with demand.  I figured we should stick with the DIP chip while we still can.
• The Arduino cannot directly control our amplifiers.  This can possibly be done using a gate to route the current through a volatage spliter maintaining a Float, open or close the gate with a second pin to bypass the voltage splitter to make a High and turn off the main pin to make a Low.  This may be easier to program then the current method because you just have to control 2 pins.  That said the Arduino can communicate with i2c devices like the rheostats
• The Arduino is very easy to program.  Basically you just initialize and loop.  Communication to the device works very similarly to communication with the usb-i2c master chip.  Just set the arduino loop to listen to the com port and do various things depending on what it is sent.  On the PC side its identical to the i2c program, since the Arduino has more memory, I believe the commands can be in the form of char arrays as opposed to hex only.
• When we were looking at ladyada.net you asked where do people get the time to do all this stuff?  The answer is MIT.  All the students are required to have a website.

Other Electronics

• I’m going to call the murata company and see if we can get some samples of http://www.murata.com/products/catalog/pdf/p82e.pdf.   They are finger tip sized full-ranged peizoelectric speakers.  Currently I can only find them in quantities of 2000….  They really look perfect for our application but don’t think we will need 2000 til we start production.  (not to mention its still $5 each at this quantity)
• There are some other options for speakers but I haven’ sen any that look as good as those.  Most speakers this size have a far more limited range of sound.

Amplifier Circuit:

• Waiting on a few capacitors that were not at the electronics store.
• Found a small portable break-out board to play audio with. http://www.sparkfun.com/products/9534.  Its has somewhat of an amplifier but only 7 volume settings so our amp chips will still be needed.
• Needed a bigger breadboard to prototype this circuit.  Not nearly enough room on the one I have
• Audio will be driven by the aurdino.