Velocity sensitive key for keyboards; hall effect or optical

D

Dylan Horvath

Guest
I am looking for an off-the-shelf key switch that is suitable for sensing
the velocity or force with which a key is hit. I am designing a keyboard
with over 200 keys arranged in a honey-comb grid. If there were a suitable
keyboard key that has a replaceable keycap and that I could embed a magnet
in, that would also be suitable as I have already determined a suitable
surface-mount hall-effect sensor that could be mounted underneath a moving
magnet (Honeywell's SS19 surface-mount hall effect).

I might also be able to retrofit a keycap to someone else's sensor, like a
retrofit kit for turning an acoustic piano into a MIDI-capable keyboard. I
would prefer not to use the SPDT type switches available as I would like to
be able to play a key hit that does not necessarily travel all the way down.
I am finding the cost of custom-molding a key a bit inhibitive at this point
though.

Has anyone completed a similar project, or encountered switches that might
be suitable for a magnet retrofit?

Thanks very much! Could you please also email your replies to dhorvath at
thegateway dot net.

- Dylan
 
In article <2n2Ka.3228$iM4.409290@news20.bellglobal.com>, "Dylan
Horvath" <dylan.horvath@sympatico.ca> wrote:

I am looking for an off-the-shelf key switch that is suitable for sensing
the velocity or force with which a key is hit. I am designing a keyboard
with over 200 keys arranged in a honey-comb grid.

There is a Canadian company that makes a module for use on pipe organ
Click to expand...
keyboards. There are pictures on this web site:
http://207.236.55.58/users/opustwo/Opus-two_I.htm
--
Dave Schutt <schutt@netgate.net> San Jose, California
 
"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:vfi5f0mfu3l70b@corp.supernews.com...
"Dylan Horvath" wrote ...
I am looking for an off-the-shelf key switch that is suitable for
sensing
the velocity or force with which a key is hit. I am designing a keyboard
with over 200 keys arranged in a honey-comb grid. If there were a
suitable
keyboard key that has a replaceable keycap and that I could embed a
magnet
in, that would also be suitable as I have already determined a suitable
surface-mount hall-effect sensor that could be mounted underneath a
moving
magnet (Honeywell's SS19 surface-mount hall effect).

"Velocity sensitive" keyboards actually use SPDT contacts and measure
the time it takes between opening the NC connection and closing the NO
connection.

Unfortunately, most (all?) conventional SPDT switches tend to be
"snap-action" type which minimize the "transit" time between NC and NO
and are not suitable for "velocity" detection.

If you use a sensor with an analog output (like the Honeywell you are
considering), you will have to sense 200 analog signals which is
considerably more complex (and expensive) than scanning simple digital
SPST
switches.
Click to expand...
True -- the electronics are much more complex, but not inhibitively so; and
you can get a far more versatile switch with Hall-effect as opposed to SPDT.
However if there were a suitable SPDT switch that had a nice travel and
operating pressure, I would consider using it. Anyone have any
recommendations on switches? I know most people that build custom keyboards
also build custom keys, but the large number of keys in this design make
that a bit cost-inhibitive.

- Dylan
 
In article <vfi5f0mfu3l70b@corp.supernews.com>, rcrowley7@xprt.net
says...
"Dylan Horvath" wrote ...
I am looking for an off-the-shelf key switch that is suitable for sensing
the velocity or force with which a key is hit. I am designing a keyboard
with over 200 keys arranged in a honey-comb grid. If there were a suitable
keyboard key that has a replaceable keycap and that I could embed a magnet
in, that would also be suitable as I have already determined a suitable
surface-mount hall-effect sensor that could be mounted underneath a moving
magnet (Honeywell's SS19 surface-mount hall effect).

"Velocity sensitive" keyboards actually use SPDT contacts and measure
the time it takes between opening the NC connection and closing the NO
connection.

Unfortunately, most (all?) conventional SPDT switches tend to be
"snap-action" type which minimize the "transit" time between NC and NO
and are not suitable for "velocity" detection.

If you use a sensor with an analog output (like the Honeywell you are
considering), you will have to sense 200 analog signals which is
considerably more complex (and expensive) than scanning simple digital SPST
switches.
Click to expand...
No wonder I think most of those keyboards sound like cr@p.

Gary (I knew there was a reason) Rimar
 
Hey Gary,

Are you a musician? I am designing this keyboard for musicians (obviously),
but I am not a keyboard player myself. Can you give me some feedback on what
the difference between what you consider a good-sounding vs. bad sounding
keyboard are like?

- Dylan

"Gary Rimar" <pianoguy@garyrimar.com> wrote in message
news:MPG.1963f295a508438e989713@news.mi.comcast.giganews.com...
In article <vfi5f0mfu3l70b@corp.supernews.com>, rcrowley7@xprt.net
says...
"Dylan Horvath" wrote ...
I am looking for an off-the-shelf key switch that is suitable for
sensing
the velocity or force with which a key is hit. I am designing a
keyboard
with over 200 keys arranged in a honey-comb grid. If there were a
suitable
keyboard key that has a replaceable keycap and that I could embed a
magnet
in, that would also be suitable as I have already determined a
suitable
surface-mount hall-effect sensor that could be mounted underneath a
moving
magnet (Honeywell's SS19 surface-mount hall effect).

"Velocity sensitive" keyboards actually use SPDT contacts and measure
the time it takes between opening the NC connection and closing the NO
connection.

Unfortunately, most (all?) conventional SPDT switches tend to be
"snap-action" type which minimize the "transit" time between NC and NO
and are not suitable for "velocity" detection.

If you use a sensor with an analog output (like the Honeywell you are
considering), you will have to sense 200 analog signals which is
considerably more complex (and expensive) than scanning simple digital
SPST
switches.


No wonder I think most of those keyboards sound like cr@p.

Gary (I knew there was a reason) Rimar
Click to expand...
 
On Thu, 26 Jun 2003 13:07:05 -0400, in
<2MFKa.4445$iM4.705516@news20.bellglobal.com>, "Dylan Horvath"
<dylan.horvath@sympatico.ca> wrote:

"Gary Rimar" <pianoguy@garyrimar.com> wrote in message
news:MPG.1963f295a508438e989713@news.mi.comcast.giganews.com...
In article <vfi5f0mfu3l70b@corp.supernews.com>, rcrowley7@xprt.net
says...
"Dylan Horvath" wrote ...
I am looking for an off-the-shelf key switch that is suitable for sensing
the velocity or force with which a key is hit. I am designing a keyboard
with over 200 keys arranged in a honey-comb grid. If there were a
suitable keyboard key that has a replaceable keycap and that I could
embed a magnet in, that would also be suitable as I have already
determined a suitable surface-mount hall-effect sensor that could
be mounted underneath a moving magnet (Honeywell's SS19
surface-mount hall effect).

"Velocity sensitive" keyboards actually use SPDT contacts and
measure the time it takes between opening the NC connection
and closing the NO connection.

Unfortunately, most (all?) conventional SPDT switches tend to
be "snap-action" type which minimize the "transit" time between
NC and NO and are not suitable for "velocity" detection.

If you use a sensor with an analog output (like the Honeywell
you are considering), you will have to sense 200 analog signals
which is considerably more complex (and expensive) than
scanning simple digital SPST switches.

No wonder I think most of those keyboards sound like cr@p.

Gary (I knew there was a reason) Rimar

Hey Gary,

Are you a musician? I am designing this keyboard for musicians (obviously),
but I am not a keyboard player myself. Can you give me some feedback on what
the difference between what you consider a good-sounding vs. bad sounding
keyboard are like?
Click to expand...
And *exactly* how good vs bad sound corresponds to the method
used for sensing velocity... whether it be Hall effect, optical,
SPDT contacts, you name it...


--
Jim Higgins, quasimodo AT yahoo DOT com

alt.music.midi FAQ - http://home.sc.rr.com/cosmogony/ammfaq.html
 
In article <2MFKa.4445$iM4.705516@news20.bellglobal.com>,
dylan.horvath@sympatico.ca says...
Hey Gary,

Are you a musician?
Click to expand...
Very much so.

I am designing this keyboard for musicians (obviously),
Click to expand...
Smooth move.

but I am not a keyboard player myself.
Click to expand...
Not a requirement.

Can you give me some feedback on what
the difference between what you consider a good-sounding vs. bad sounding
keyboard are like?

- Dylan
Click to expand...

Well, sound and playability are intertwined but also two different
qualities. A keyboard that sounds good is one that has good samples, but
you can have a Steinway grand as your piano sample and with velocity
switching it can sound really bad and be hard to play. My gripe with
velocity switching is that it is the amount of pressure, and not the
speed, which should determine how loud the note is.

As an example, one of the music styles which I play is Klezmer music. If
I'm playing a rather loud passage and I want to do a very soft glissando
(think of running a hand down the keyboard with a sweeping motion), I may
be moving very fast. On a pressure-sensitive keyboard, so long as I
don't push down hard when I'm doing this sweeping motion, the notes will
be soft--just like on a regular piano. Because I'm moving fast, however,
if the velocity-sensitive keyboards will play the notes at all, it will
play them loud. That doesn't work.

If you want to design something that is pressure sensitive, have you
considered piezoelectric crystals? Measure the voltage to determine the
pressure. I don't know what they use in regular weighted keyboards, but
you could also consider that.

I would love a light keyboard that responds to pressure rather than
velocity.

Gary (if anyone knows of one, let me know) Rimar
 
"Gary Rimar" <pianoguy@garyrimar.com> wrote in message
news:MPG.1966f70c342d4fe9989714@news.mi.comcast.giganews.com...
In article <2MFKa.4445$iM4.705516@news20.bellglobal.com>,
dylan.horvath@sympatico.ca says...

If you want to design something that is pressure sensitive, have you
considered piezoelectric crystals? Measure the voltage to determine the
pressure. I don't know what they use in regular weighted keyboards, but
you could also consider that.

I would love a light keyboard that responds to pressure rather than
velocity.
Click to expand...
Art Whitfield modified a windsynth with pressure sensitive aftertouch. I
imagine the pressure sensitive resistors would work for a piano, too.

http://members.aol.com/whitfiel/aftouch.htm

dtk
 
"dt king" <usenet@leztoys.com> wrote ...
Art Whitfield modified a windsynth with pressure sensitive aftertouch. I
imagine the pressure sensitive resistors would work for a piano, too.

http://members.aol.com/whitfiel/aftouch.htm
Click to expand...
A very interesting web page. Thanks for the citation.

Be careful about confusing "aftertouch", "velocity sensitive" and
"pressure sensitive". They are very different things...

"Aftertouch" = a second set of (digital) contacts activated by additional
pressure on the key. Commonly used on (and devised for, AFAIK)
theatre pipe organs from >70 years ago. Frequently connected to
percussive instrument "ranks" (piano, marimba, tubular bells, etc.)

"Velocity sensitive" means detecting the speed (roughly equivalent to the
force) with which a key is struck. Usually implemented (in modern digital
equipment) by using a "form-C" switch (SPDT) and measuring the TIME
between opening the top contact and closing the bottom one.

"Pressure sensitive" means detecting (continuously) the pressure
applied to a control (such as a key). The major difference between
"pressure sensitive" and "velocity sensitive" is that PS continues to
measure pressure continuously AFTER a key is activated. Very important
to many instrument controlers such as for wind synths (such as
the web page describes).
 
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