[sdiy] Reed Switch and Magnet Keyboard

[Theo]

I have salvaged a old industrial computer keyboard that used reed switches
as the key contacts (the key switch assemblies come from TI).
These keys are/where closer together than the keys on a piano keyboard and
have no false trigger problems.
The trick seems to use tiny magnets so the switches trigger only when the
magnet is really close.
To do this the magnets run from the top (off) to the middle of the reed
contact (on).
Some organ brands use a similar system for pedal key contacts where the
magnets are in the "back-front side" of the keys.
Maybe this could work also work in our case?

Cheers,
Theo

----- Original Message -----
From: harrybissell <harrybissell at prodigy.net>
To: Tim Parkhurst <tparkhurst at siliconbandwidth.com>
Cc: 'Ray Wilson' <raywilson at comcast.net>; Scott Stites
<scottnoanh at peoplepc.com>; Synth-Diy <synth-diy at dropmix.xs4all.nl>
Sent: Thursday, December 11, 2003 5:23 AM
Subject: Re: [sdiy] Reed Switch and Magnet Keyboard


> (if I could find them I'd use) Tiny horseshoe magnets, with the reed
switch
> located across the gap.  As the magnet approaches the switch, the flux
will
> be concentrated through the switch vanes and tend NOT to leak to the
> adjacent switches.  Might be harder to install
>
> H^) harry
>
> Tim Parkhurst wrote:
>
> > You might get a little extra 'breathing room' between the adjacent
> > magnets/switches by offsetting every other magnet and switch assy. In
other
> > words, on one key the magnet and switch sits fairly close to the pivot
> > point; on the next key, the magnet and switch sit fairly far away from
the
> > pivot point. One problem I see with this approach is that the switches
> > sitting close to the pivot point will tend to close slightly earlier
than
> > the switches sitting further away. This might be such a minor timing
> > difference as to be unnoticeable, but (if needed) you might be able to
> > compensate by putting shims under the switches that sit further from the
> > pivot. This would raise them up slightly so that they would close
earlier.
> >
> > Tim Servo
> > "Imagination is more important than knowledge." - Albert Einstein
> >
> > > -----Original Message-----
> > > From: Ray Wilson [mailto:raywilson at comcast.net]
> > > Sent: Wednesday, December 10, 2003 5:11 AM
> > > To: Scott Stites
> > > Cc: Synth-Diy
> > > Subject: [sdiy] Reed Switch and Magnet Keyboard
> > >
> > > Hi Scott (and list)
> > >
> > > You mentioned that you had made a keyboard using reed switches and
> > magnets.
> > > I want to outfit a set of piano keys in this manner and am interested
to
> > > know how you kept adjacent key switches from being activated together.
I
> > > have a source for some nice inexpensive reed switches and magnets of
> > various
> > > sizes and would appreciate your suggestions (and anyone elses who
wants to
> > > chime in).
> > >
> > > Thanks
> >
> >
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