Re: MIDI key transducers (physical)
Re: MIDI key transducers (physical)
- Subject: Re: MIDI key transducers (physical)
- From: "James Chandler Jr" <email@hidden>
- Date: Tue, 25 Sep 2007 10:44:27 -0400
Roland, its off-topic to the list a bit (not chiding, but some folks take 'on
topic' pretty seriously (grin)).
You probably know this already, but the majority of music keyboards detect
velocity by measuring the time delay between closure of two slightly-offset
switches. One switch closes, then a microprocessor measures the time before the
second switch closes.
In most modern keyboards, this is 'ingeniously done' with little silicone rubber
nipples mounted ontop of a sensing circuit board. Inside each rubber nipple are
little bits of conductive plastic that perform the function of the two-switch
closure against contact areas on the circuit board.
The little switch pads on the circuit board, to be long-term-durable, are
usually coated with something more durable / more corrosion-resistant than
tin/solder. Sometimes gold, often what appears to be conductive plastic. It is
black anyway (grin).
Long ago, Panasonic made those parts, and probably still makes em. An italian
company Fatar makes many of the keyboards used by other manufacturers.
You could probably get the rubber nipples out of a junk keyboard, or buy em as
replacement parts from one of many keyboard manufacturers, Roland, Korg,
whatever. The trickiest part would be making your switch circuit board pads good
enough to work reliably, both right-out-of-the-box and long-term. When the
factory coating on the circuit board pads starts wearing out, the keyboards get
very difficult to keep em working correctly. Simple cleaning no longer does the
trick.
jcjr
----- Original Message -----
From: "Roland Silver" <email@hidden>
To: <email@hidden>
Sent: Tuesday, September 25, 2007 10:26 AM
Subject: MIDI key transducers (physical)
I want to build a MIDI-like keyboard for playing scales based on
quarter-tones, i.e. for a 24-tone equal-tempered octave, rather than a 12-tone
octave.
Where can I buy the basic transducer that sits under each key? Not an on/off
switch, but one that transduces position (or velocity).
-- Roland Silver <email@hidden>
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