keyboard contact rubber fun

Hairy Harry paia2720 at hotmail.com
Thu Aug 24 20:35:03 CEST 2000


Hi Barry (et al)

Measurement Specialties has a pizeo/polymer sensors which would be
suitable for individual key sensing.

Piezo's can only be used for dynamic sensing, so velocity would be
easy, and pressure almost impossible.

Each piezo will probably need its own preamp, a single opamp stage might be 
sufficient.

Highest voltage could be > 80- 100 VDC, they will light a neon lamp
on a really severe impact (your keyboard off a second story roof ???)

Digi-Key distributes in the USA, $0.52 each /10
Measurement Specialties #LTD0-028K   DigiKey MSP1006-ND

I'm trying them for impact (drum) triggers.  They need a preamp
in my application :^(

H^) harry


>From: Barry L Klein <Barry.L.Klein at wdc.com>
>To: synth-diy at node12b53.a2000.nl
>Subject: RE: Re: keyboard contact rubber fun
>Date: Thu, 24 Aug 2000 10:13:39 -0700 (Pacific Daylight Time)
>
>One might be successful with piezo film strips for key sensors.
>You should be able to get a voltage proportional to velocity, depression,
>and pressure with one sensor along with the right interface circuitry.
>The stuff isn't exactly cheap to play with though but maybe the
>strips can be really thin?
>
>
>Barry
>
>----------
>From: 	Hairy Harry[SMTP:paia2720 at hotmail.com]
>Sent: 	Thursday, August 24, 2000 9:09 AM
>To: 	czech at Micronas.Com; dragonser at clara.net
>Cc: 	synth-diy at node12b53.a2000.nl
>Subject: 	Re: keyboard contact rubber fun
>
>Most keyboards have a scanning matrix... usually bytewide
>(8 bits). A clever design would use this to power only those
>hall devices that are being scanned at the time... so power
>could be a lot lower.
>
>Would this work... depends on the hall device...?
>
>The same would definatly work with led / phototransistor
>
>H^) harry
>
>
> >From: Martin Czech <czech at Micronas.Com>
> >Reply-To: Martin Czech <czech at Micronas.Com>
> >To: dragonser at clara.net
> >CC: synth-diy at node12b53.a2000.nl
> >Subject: Re: keyboard contact rubber fun
> >Date: Thu, 24 Aug 2000 17:30:19 +0200 (MET DST)
> >
> >
> >:::Dear Martin
> >:::know I know why the contacts sometimes need changing .
> >:::I think it would be possible to use reed contacts and magnets to
>replace
> >:::the rubber contacts ....might it also be possible to use hall effect
> >:::devices ?
> >
> >No, it must be passive, 76 keys gives 76 times the power consumption
> >of an otherwise nice hall sensor, much too much for the often
> >cheap power supplies.
> >
> >Yes, velocity means two reeds, one magnet.
> >
> >m.c.
> >
>
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