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1  Forum 2005-2010 (read only) / Interfacing / Re: DIY IR proximity detector on: September 28, 2007, 03:02:19 pm
I was looking at IR emitter/detectors for use in ranging while researching balancing robots. This is the type of sensing that was used the LegWay robot. What they seem to be doing is to try to use two detectors and only trust their relative differences (rather than trying to use them to get an exact range). Of course, the problem still exists that if the two sensors are over two different materials (like transitioning across floor types or whatever), the readings would be way off.
2  Forum 2005-2010 (read only) / Interfacing / Re: Impact Sensor Ideas on: May 27, 2008, 10:48:12 am
Wow, thanks for all of the ideas.

My son and I have been brainstorming on different kinds of games to play with foam swords and mounted sensors, not all of them really related to "sword fighting" (although several of them are), so these are all really good ideas. While we were messing around in the garage this weekend, we built two "swords" out of PVC pipe and Fun Noodles with plywood handguards and rubber taped handles. In addition to "dueling" around the yard, we also used them to investigate the form factors for different game ideas.

I think the first sensors I am going to build are going to be rigid, foam covered uprights (maybe steel pipe cores) with modulated IR LEDs and sensors on both sides. With the emitters on the ground facing up and the shielded sensors on the top looking down, it should be almost trivial to recognize a "hit" on either side of the upright by looking for occlusion of the light beam. My initial idea is just for a game that's somewhere between Simon, Dance Dance Revolution, or Guitar Hero, where you have to strike the targets in a certain order with a certain timing to succeed. I think this will work well with two "swords". There are many different game themes that would work with this type of setup with four or six (or more) sensors.

My son wants to do more of a virtual combat type game, so we've also been thinking about body mounted sensors, shields, etc. Should be a fun summer...
3  Forum 2005-2010 (read only) / Interfacing / Re: Impact Sensor Ideas on: May 23, 2008, 04:51:31 pm
Good ideas (plus I've got a few air pressure sensors lying around).
4  Forum 2005-2010 (read only) / Interfacing / Impact Sensor Ideas on: May 23, 2008, 03:29:51 pm
I've had an idea floating around my head for quite a while to build a physical game interface using a "sword", where the sword will be a wooden handle and shaft with thick foam covering (like a Fun Noodle over a medium thickness dowel). The sensors for the game would be a set of targets arranged around the player, perhaps 4 or 6 padded posts rising from a platform or even suspended from above (or maybe both for more sensors).

I haven't done any experimentation on the sensors yet, but I've had a few ideas (they are very similar to drum sensors) and I wanted to know if anyone had any ideas or experience in building these kinds of things.

The requirements would be:

Very sturdy, rigid supports than can stand a pretty hard whack with the "sword"

Sensors that would reliably trigger on a hit over a large area of the target, but not so sensitive that it would trigger on false hits from nearby sensors (or ambient noise/vibration).

Proportional (analog) response would be nice, but not essential (most of the time, if the sensor input was analog, it would just be compared to a threshold value for a hit/no hit determination).

I've mulled over microphones, piezo elements, conductive foam with foil or mylar surfaces for variable resistance or capacitance, flex sensors (either on the surface or mounting the targets on stiff springs), and accelerometers (probably a good choice, but more expensive than I would like). They all have their pros and cons (some more than others). Any ideas?
5  Forum 2005-2010 (read only) / Interfacing / Re: Reading Volume Through the Analog Pins on: February 29, 2008, 03:16:37 pm
Those pads look cool - let us know how well they work. The laser harp is very cool, BTW.

I've been too busy at work to start on my wind controller, but I'm still thinking and collecting parts. I found some really nice switches the other day at a surplus store for $0.25 each. They have a great feel and a very low activation force, but they are a bit "clickier" than I wanted. I may use them for the octave keys. I'm also thinking about putting a 2-axis accelerometer on the instrument to play around with using the horn angle to control overall volume (straight down would be pianissimo, raised up high would be forte) and maybe using the other axis for pitch bend or vibrato (I'll have to really average out or dampen the response, but that's the cool thing about having a mostly software instrument).

I'm going to try to dump the sensor data to the computer as compactly and as quickly as I can to give me more opportunity to process it without lag and to get as much responsiveness as possible.

I have one of those really old "toy" Casio MIDI saxophones (the ones with an onboard synthesizer as well as MIDI out) and it was always pretty fun to play around with, but it had some really annoying characteristics, like an auto vibrato in the onboard synth. The breath control and aftertouch was pretty good and you could transpose it and switch MIDI channels, but it was a far cry from a pro wind controller (or a real instrument, for that matter). I know that you really need a good MIDI synth/sampler to get the best sound (with the sampled breath sounds and stuff), but I'm using the Casio as my target to beat - if I can build a wind controller that good or better, I'll be happy.

There are also some other cool things to experiment with in a mostly software instrument. One of my first thoughts was just to use four finger controls and binary fingering since you can cover one octave chromatically that way. Then you could combine that with two closely spaced octave keys to get a four octave range. Of course, I know the saxophone fingerings (and derivative/similar ones like recorder or Xaphoon) best, so I decided to go with eight keys, but I'm still going to do the two octave key arrangement for extended range. Of course, since I can re-map the keys in software and generate multiple MIDI messages, I can configure it to saxophone style fingerings and still experiment with the binary fingerings on the left or right hand. Theoretically, you could play two notes at once. You would only have breath control over one, but you could play root chord notes like a bagpipe drone. You could also use the binary fingerings and octave keys to select chords, so you could play it like an old chord organ - selecting chords with one hand and fingering the melody with the other.

Maybe I'll get a chance to start actually building something on it this weekend...
6  Forum 2005-2010 (read only) / Interfacing / Re: Reading Volume Through the Analog Pins on: January 31, 2008, 11:09:20 am
Maverick, it sounds like we're on the same sheet of music (no pun intended).

I was thinking of keeping the Arduino sketch as simple as possible and just dumping out the button inputs, breath sensor, and whatever else I can think of through the serial port as fast as possible. I found a C# library for sending and processing MIDI, so I think I'll write a PC based app to read the serial data and convert to MIDI.

I've thought about doing something like this for a long time (pretty much ever since I found out how much a really good MIDI wind controller costs), but I would usually get hung up on the hardware design, fingering plans, etc. Then when I got my first Arduino, I started looking at sending MIDI from it, but I was still stuck on fingerings, the complexity of the sketch, and so on. The other day I decided that I would just use a saxophone/recorder type arrangement of eight switches, a rocker switch or a couple of buttons for the left hand thumb/octave key position, and a button near the right hand thumb - they would use the digital input lines on the Arduino. The sketch would stay simple because I would just read the switch matrix and dump it up the PC to translate to MIDI. That way I can easily experiment with mapping fingerings to notes without sending new sketches.

The breath control is the trickiest part. A simple on/off/volume/aftertouch wouldn't be hard with a microphone or a pressure transducer, but, like you, I am more interested in making it as expressive as possible. Another idea I may play with is to "split" the microphone output and use the ADC to just do the note start, volume, and limited aftertouch. Then I would send the analog signal out either to the PC's mic input to do signal processing to shape the ADSR envelope, or maybe to an analog mixer/amp where the shape of the "noise" would shape the synth audio.

Either way, I think that keeping the instrument hardware and Arduino portion as simple as possible would give me the most flexibility in designing a personalized and responsive instrument.

Keep us informed of your progress and I will do the same.
7  Forum 2005-2010 (read only) / Interfacing / Re: Reading Volume Through the Analog Pins on: January 30, 2008, 03:32:37 pm
Cool! That is very encouraging. I was thinking of drilling out a small diameter bore in the mouthpiece to provide a realistic amount of resistance.
8  Forum 2005-2010 (read only) / Interfacing / Re: Reading Volume Through the Analog Pins on: January 30, 2008, 11:16:02 am
Actually, I do have a pressure sensor that I bought for that purpose, but I haven't got around to playing with it yet either. I got interested in the microphone type circuit as an alternative because I think that ultimately it would have a better response. In fact, I've also thought about not digitizing the volume curve but using it as an analog gain to modulate the audio output. I would like to be able to expressively control the musical output with breath, tonguing, humming or growling. The transducer may or may not work for that.

I saw an electronic wind instrument that used a pressure transducer in a sealed cavity where you didn't blow air through a mouthpiece, you just compressed the air in the mouthpiece cavity using your lungs and cheeks.
9  Forum 2005-2010 (read only) / Interfacing / Reading Volume Through the Analog Pins on: January 29, 2008, 03:04:57 pm
I'm toying around with the idea of an Arduino based musical instrument and I have an odd idea for a breath controller...

I would like to take a microphone (any type that would be easiest) and read the intensity/volume through one of the analog inputs. The idea is to create a responsive "solid state" breath controller that could be easily protected from the moisture in your breath (those of you who play wind instruments know what I'm talking about) by isolating the microphone behind a sounding membrane that your breath would be funneled to. What the microphone should pick up behind that sounding membrane would be more or less white noise. I think the steps would look something like this:

Microphone picks up white noise
Scale to 0-5V range
Read through the analog pin and convert to 10bit digital value.

The "filter/smooth" step is the one I'm not sure about. I do have an oscilloscope, so I can experiment around with filters, but I want to know if I am basically on the right track before I get started and my analog electronics skills are lacking. Am I making this too complicated?
10  Forum 2005-2010 (read only) / Interfacing / Re: AC (guitar) signal to Analog Input on: February 11, 2008, 04:41:31 pm
You might also want to check out these threads - they are all doing something very similar (trying to read volume/sound intensity via the analog pins):

It sounds like once we get some solid solutions, this should go in a FAQ or in the Playground...
11  Forum 2005-2010 (read only) / Interfacing / Re: Arduino and Wiimote - what's the state of the on: January 24, 2008, 06:06:04 pm
I just ran across some awesome information on the wiki pages today. This wiki is primarily about using Wiimotes and Nunchuks with Linux, with a little info about PC and Mac OSes as well, but I followed a link there from one of the electronics blogs to this article about motion analysis of the Wiimote accelerometer and sensor bar data which had a lot of insight into how to integrate all of the data to get a full state of the controller and its position. If you combine this with the info on reading the raw data via the Arduino (linked above), you should be able to interpret almost anything you would want.

Motion Analysis:
12  Forum 2005-2010 (read only) / Interfacing / Re: Reading/Writing SD/MMC Cards Via SDI on: September 21, 2007, 10:54:01 pm
I was thinking of writing the raw data with the Arduino as well. If you used it for data an Arduino program could read the card back and write the data serially, right?

Of course, supporting a file system would be even better, but I was thinking of keeping it simple.
13  Forum 2005-2010 (read only) / Interfacing / Reading/Writing SD/MMC Cards Via SDI on: September 21, 2007, 09:50:40 pm
I'm stuck at work, but I keep running across these cool things to try with my Arduino, but don't have the time yet...

These two links describe how to use an old floppy drive connector as an SD card slot and tell how you can use one in MMC mode using SPI and five pins (3.3V, GND, clock, data in, and data out). As it happens, I had been thinking about how to store some configuration data for an Arduino program and update it without connected back to the computer or adding an interactive input device.

Does anyone of any reason why this technique wouldn't work with an Arduino program? If I'm reading all of this right, it appears that you could write a bunch raw data to a card (maybe using a tethered Arduino), then read the card from another program running standalone. This would also be great for long-term data logging, wouldn't it?
14  Forum 2005-2010 (read only) / Interfacing / Re: Need primer on Xbee communications on: October 10, 2007, 04:29:15 pm
I can't help you directly, but I just picked up a copy of Tom Igoe's book, Making Things Talk, and it has a rather extensive section on XBee communications. I just haven't read and digested it all yet.
15  Forum 2005-2010 (read only) / Interfacing / Re: Making an eternal pendulum on: October 10, 2007, 10:57:15 am
I think you want the 26 gauge (.45mm) or 30 gauge (.31mm). If I recall, the rules of thumb are:

1) More loops in the coil -> more magnetic strength
2) You need thicker coil wires if you are handling high currents (which this won't be)
3) The thinner the better to get maximum coil density, but when you get really small, the wire can kink, break, or stretch too easily making it hard to hand wire a coil.
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