Velocity sensitive key for keyboards; hall effect or optical

Discussion in 'comp.music.midi' started by Dylan Horvath, Jun 24, 2003.

  1. 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
  2. Dave Schutt

    Dave Schutt Guest

    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
    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
  3. "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.
  4. "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.


    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
  5. Gary Rimar

    Gary Rimar Guest

    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
  6. 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
  7. Jim Higgins

    Jim Higgins Guest

    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?


    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
  8. "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).


    That's funny, I've just finished designing a velocity sensitive, honeycomb
    grid MIDI Master keyboard for C-Thru Music (who btw own the patent).

    Velocity is not detected with Hall effect switches which give more of a
    positional information, it has to be derived from it. Most velocity
    keyboards work by timing the contacts of a c/o switch. You either have to
    develop a key to suit a switch or vice versa, the chances of finding both
    'off the shelf' are virtually nil.

    There is a velocity keyboard scanning chip capable of handling up to 192
    keys available to keyboard developers on my website:

    http://www.hinton.demon.co.uk/components.html#kv64
  9. Gary Rimar

    Gary Rimar Guest

    In article <2MFKa.4445$iM4.705516@news20.bellglobal.com>,
    dylan.horvath@sympatico.ca says...
    > Hey Gary,
    >
    > Are you a musician?


    Very much so.

    > I am designing this keyboard for musicians (obviously),


    Smooth move.

    > but I am not a keyboard player myself.


    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
    >



    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
  10. "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


    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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