[sdiy] Keyboard Encoder Experiments...

[Jim Patchell]

Each LVDT will need an amplifier and a synchronous detector (ok...real 
simple...just an analog switch that toggles an amplifer from a gain of 
+1 to -1 synchronized with the signal).  Should be able to do that with 
a quad opamp (per key) and an analog switch.  Probably about $3 worth of 
parts for each key.

The AD converter I plan to use is a tlc2551 which only costs $9 in ones 
(12 bits) and converts at 400KHz.  I will mux that between all the keys 
for an overall sample rate of about 5KHz per key.  The digital 
electronics will be an FPGA...(about $10), and an AVR ($12).

-Jim

Ben Stuyts wrote:
> Hi Jim,
> 
> On 11 Feb 2008, at 20:50, Jim Patchell wrote:
> 
>> http://www.noniandjim.com/Jim/KeyboardEncoder/KeyboardEncoder.html
> 
> Looks great! And if you go away from 'conventional' keys, you could even 
> build something lake the Haken Continuum keyboard 
> <http://www.hakenaudio.com/Continuum/>. I think this 
> <http://www.google.com/patents?vid=USPAT6703552> is the patent.
> 
> I've looked a bit at (commercial) LVDT's for the company I work for, but 
> cost was, as you said, always prohibitive. But wouldn't this need a lot 
> of electronics? AD has some LVDT amplifiers, but these are expensive (> 
> $15) too.
> 
> How about hall-effect sensors?
> 
> With kind regards,
> Ben
> 
> 
>