palmerc@infonode.ingr.com (Chris Palmer) (12/04/90)
I am thinking about building an electronic instrument. Actually, it will be an input device for a computer music program that uses saxophone fingerings. I know that Casio makes a little MIDI sax and that there are several very high end machines, but I thought this could be a fun (and inexpensive) project, especially if I let the computer do the sound generation and maybe even MIDI encoding. The keys are going to be simple switches that will be encoded via TTL or CMOS logic and send in throught the parallel port of the computer (to leave the serial for MIDI (on an Amiga if you're interested)). My problem is the mouthpiece. What should I use? What I need is some kind of device that outputs a digital or analog signal proportional to the pressure of an airstream applied to it. The sensor should be cheap and immune to moisture and should respond to changes quickly. Does anyone have any suggestions? -- | Christopher M. Palmer # | / Intergraph Corporation # \ \ Internet: b14!abulafia!palmerc # / | UUCP : ...uunet!ingr!b14!abulafia!palmerc # |
ron@vicorp.com (Ron Peterson) (12/06/90)
In article <1990Dec3.185404.7641@infonode.ingr.com> palmerc@infonode.UUCP (Chris Palmer) writes: >I am thinking about building an electronic instrument. >My problem is the mouthpiece. What should I use? What I need is some >kind of device that outputs a digital or analog signal proportional to >the pressure of an airstream applied to it. The sensor should be cheap >and immune to moisture and should respond to changes quickly. Does anyone >have any suggestions? > A breath controller option is available for DX-11 (and probably other) synthesizers. It is a headset like device with a small tube that extends out to a small whistle-like mouthpiece. The tube has a wire running through it so that it can be bent to accomadate different head sizes. The air you blow into the mouthpiece presses against a resistive strain gauge which can be read electronically. The breath controller sells for about $70-$80 US. Electronic Musician had an article a year or two ago on how to adapt this device to produce a control voltage for controlling other synths. Between the two you should be able to cobble up a breath sensor for under $100. If I remember correctly, playing a sax involves using the tongue or teeth to damp the reed also. Maybe a waterproof microswitch or another strain gauge could be used for that. ron@vicorp.com
larry@kitty.UUCP (Larry Lippman) (12/07/90)
In article <1990Dec6.002534.18546@vicorp.com>, ron@vicorp.com (Ron Peterson) writes: > >I am thinking about building an electronic instrument. > >My problem is the mouthpiece. What should I use? What I need is some > >kind of device that outputs a digital or analog signal proportional to > >the pressure of an airstream applied to it. The sensor should be cheap > >and immune to moisture and should respond to changes quickly. > >have any suggestions? > > A breath controller option is available for DX-11 (and probably other) > synthesizers. It is a headset like device with a small tube that extends > out to a small whistle-like mouthpiece. The tube has a wire running through > it so that it can be bent to accomadate different head sizes. The air > you blow into the mouthpiece presses against a resistive strain gauge > which can be read electronically. I'll offer a few off-the-wall suggestions for the design of an electronic mouthpiece. Readers should bear in mind that I don't claim any particular expertise in the design of electronic musical instruments, with my last project being a theramin about 25 years ago. Also, my personal musical ability is limited to piano, organ and Polymoog. I could not play a wind instrument to save my life. :-) It would seem to me that one wants to sense more than a simple gage pressure change. I suspect that air *velocity* with a directional vector is more desireable. Velocity can be sensed using a differential pressure transducer connected across both sides of an orifice plate, thereby providing a signal which varies in both magnitude and polarity. Low-cost differential pressure transducers employing silicon strain gage technology providing say, 100 in-H2O FS range are readily available. Frequency response to several hundred Hz is possible. Such transducers are often intended for the HVAC market, and are available from such vendors as Honeywell, SenSym, etc. It is possible to purchase suitable transducers in single quantity for $ 75.00 or less. One should be careful in selecting a transducer which will withstand moisture without damage. Some differential pressure transducers have only "dry" ports, while others have one "wet" port and one "dry" port. In this application, *both* ports should be rated as "wet". In addition, the pressure transducer should be connected to the pressure ports across the orifice plate using tubing that is as short and large in diameter as possible to assure maximum frequency response. > If I remember correctly, playing a sax involves using the tongue or > teeth to damp the reed also. Maybe a waterproof microswitch or another > strain gauge could be used for that. A possibililty here is to mold an outer mouthpiece covering using silicone rubber or polyurethane, such that a *hollow* chamber is formed between the covering and the body of the mouthpiece. This hollow chamber would be filled with silicone fluid and connected to a gage pressure transducer such that increased mouth or teeth pressure against the mouthpiece results in an increased amplitude from this pressure transducer. For initial experimentation, a low-cost disposable pressure transducer intended for arterial and venous blood pressure measurements would be quite suitable. H-P, Spacelabs, Mennen Medical and Graphic Controls all offer such products which typically sell to hospitals for between $ 25.00 and $ 35.00. While it might be difficult to purchase just one device, a "friend" working in a hospital might be able to procure one. While such a medical transducer only has a single pressure port and is not truly differential, most of such products will sense a negative pressure. Electrically, this type of device will look like a four-arm bridge. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 {utzoo, uunet}!/ \aerion!larry
rbrink@hubcap.clemson.edu (Rick Brink) (12/11/90)
From article <4224@kitty.UUCP>, by larry@kitty.UUCP (Larry Lippman): > In article <1990Dec6.002534.18546@vicorp.com>, ron@vicorp.com (Ron Peterson) writes: >> >I am thinking about building an electronic instrument. >> >My problem is the mouthpiece. What should I use? What I need is some >> >kind of device that outputs a digital or analog signal proportional to >> >the pressure of an airstream applied to it. The sensor should be cheap >> >and immune to moisture and should respond to changes quickly. >> >have any suggestions? I just bought a CASIO electronic SAX from my local BIG Lots store for $33.00. It beats hell out of building one yourself. I don't have much experience playing a SAX, but for the money, it's pretty good. It also has a MIDI interface. Anyone interested should look in their local remarketers. I'm sure there are equivelent stores all over this country. I will not start a drop/ ship on these with-out significent profit. All my cash is tied up in christmas gifts! Good Luck!