Keyboard Encoder

[Dave Halliday]

How about using a linear hall effect encoder - more $$$ up front but a lot
less time involved in making them.

Got the idea from:
http://www.seanet.com/~tpaddock/mag2cv.html

Here is the manufacturers page:
http://www.allegromicro.com/selguide/hed1.htm

they are listed as costing from $1.50 to about $3.00 depending on linearity,
temperature range and sensitivity.  They are generous with samples - when I
requested some, I get a bag of six units plus lots of data sheets.

As I said, there would be more $$$ up front but a significant drop in
construction hassles and time.

Dave



-----Original Message-----
From: patchell [mailto:patchell at silcom.com]
Sent: Monday, October 02, 2000 3:08 PM
To: synth-diy at node12b53.a2000.nl
Subject: Keyboard Encoder


    I am working on a keyboard encoder I had an idea for a long time
ago, but never tried. (this will go into the Paia 8700 keyboard I am
rebuilding).

    It consists of a 5/16 in OD styrene tube, about 1.5 inches long.
The I.D. is 1/4".  On this tube, I wrapped two coils, about .75" long on
each have of the tube.  Inside the tube, I run a 1/4" Dia ferrite rod
that can move back and forth.

    I apply a fairly high frequency signal to one coil, and look at the
output from the other coil.  As you move the ferrite rod into the tube,
the signal on the output increases as some function of the position.
(Not exactly linear, but that is not really important, I think).

    Anyway, now that the idea at least shows promise, I will have to see
what I can do to make it come to life.  There are a few mechanical
problems that need to be solved (I am not much of a mechanical
engineer).  Plus, I am not sure exactly how to apply this to a keyboard,
but, I am sure I will come up with something.

    **This was the perversion of the 8700 I was refering to in a
previous post.**

--
 -Jim
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