[sdiy] Ensoniq patent, was: distance meter for keyboard, was: Where to get special white keys?

[cheater cheater]

What is QTC, Amos?

Also, as far as shutter schemes are concerned: those can skip. This
would be very detrimental to the key's performance, as it would
pretend the key is depressed less than it really is. This means that
the key actually being fully depressed would never register.
Intermittent fault.

D.

On Mon, Mar 2, 2009 at 5:39 PM, Amos <controlvoltage at gmail.com> wrote:
> there's the option of an infrared emitter and phototransistor pair, with a
> moving vane or shutter between them & attached to the key.  Something like
> this ought to be reasonably fog-resistant I would expect, and if it's hidden
> beneath the keybed should be resistant to ambient/sunlight issues.  I don't
> know if there are any typical temperature-related changes to linearity or
> operating point with IR phototransistors, but none of the circuits I've seen
> which use these devices seem to have any temperature compensation so I
> suspect it's not a significant factor.
>
> Somebody (or multiple persons) on this list was/were working on a QTC-based
> poly-AT scheme last year or so...
> any progress on that front?
>
> Cheers,
>
> Amos
>
> On Mon, Mar 2, 2009 at 11:53 AM, cheater cheater <cheater00 at gmail.com>
> wrote:
>>
>> You don't really need an additional contact.
>> Just tell the user not to touch the keyboard when calibrating... like
>> the SQ-80 does!
>> DON'T TOUCH KEYBOARD << SQ80 does it like this. I love it.
>> but it could be useful, indeed.
>> now the question is whether temperature can change the *linearity*.
>> That's more important, I think. That's also a reason why I had
>> thoughts about an optical sensor.
>> Optical mice use cheap optical sensors... you can have a mouse like
>> that for 5 dollars, can't you? And that's including all the other crap
>> they put in em :) You'd also need a focused laser beam... no idea how
>> much those could be.
>>
>> Optical sensors don't work that well in smoky rooms though... so no
>> jarre fog i guess? This definitely disqualifies optical technology for
>> some people ;)
>>
>> On Mon, Mar 2, 2009 at 2:42 PM, ChristianH <chris at chrismusic.de> wrote:
>> > On Mon, 02 Mar 2009 07:31:06 -0700 Ian Fritz <ijfritz at comcast.net>
>> > wrote:
>> >
>> >> At 11:52 PM 3/1/2009, Simon Brouwer wrote:
>> >>
>> >> >Have you looked at the spec sheet on that page? Although not
>> >> > particularly
>> >> >linear, these appear to be analog sensors.
>> >>
>> >> Ooops!  Right you are.  I got confused by the Futurlec description.
>> >>  These
>> >> might be worth looking into further.  One thing to be careful about is
>> >> whether they have temperature compensation.
>> >>
>> >> Ian
>> >
>> >
>> > I don't know about temperature characteristics in this case, but a
>> > simple offset could be compensated by measuring the all-notes-off
>> > values.
>> >
>> > If there *is* an additional key contact, that is.
>> >
>> > Christian
>> >
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