[sdiy] Force Sensing Resistor

Sat Sep 15 11:40:22 CEST 2007

JH,

Yes, Ive built my own keyboard (actually several now) from scratch the hard 
way (wooden keys, partly machined and then hand finished + keytops etc).
I dont recommend it.
I dont regret doing it, but I actually lost hair during the course of the 
development and would only do it again for a "special" / "different" type of 
keyboard. Some ideas I had included using replica fingerbones for a true 
"frankenstein" / Goonies type thing or hand carved keys for a "rustic" look. 
The concept of combining organic look and feel with modern technology lights 
my little candle.
Im also still very taken with building a keyboard or two from composite 
materials or even glass.

As to the sensing, monitoring and other control stuff, I really could write 
a book. the conclusions I came to were as a result of years of testing 
different methods. At one point I even tried a sealed conductive liquid 
position sensor that my other half was kind enough to help develop with me. 
It was not good.

Eventually, I got stuck into the idea of optical measurement and initially 
went with the slotted optical transistor output sensors with vane attached 
to the lower part of the key (as per work done by Graham Hinton for a breath 
controller in the eighties and the work done more recently by Adrian Freed 
at berkeley).

The vane design was a royal posterior ache and hand-manufacturing tolerances 
were laffable. I was eventually left with two choices: 1) have vanes 
lasercut or moulded specifically (quotes I got were ridiculous for the size 
of the things) 2) go with optical distance measuring technology. I went with 
the latter.

I also decided to go with the Fatar TPM10 (hammer action weighted keyboard) 
available through Doepfer for my prototype because I had the opportunity to 
test one out a while back and liked it very much.
Although I had difficulty dealing with Doepfer initially (confusion over 
where Im located because I have a uk email address, but dont live in the 
uk), they turned out to be very helpful, very professional and pleasant to 
deal with.

The PCBs for my senso arrangements will be done by the time the keyboards 
arrive and as long as the spec hasnt changed, they should slot right in.

Im happy to share my photos with you of the keyboard mechanisms I designed. 
I dont have many (Im not much of a photographer) but I'll send them over.

Either way, my advice to you is to either buy a midi keyboard and adapt it 
(cost anything from 30 bucks to 300 bucks) or go with the fatars from 
doepfer (800 bucks or thereabouts) because building your own is very costly 
in terms of man hours lost sleep and wood splinters.

Regards

EK

----- Original Message ----- 
From: "JH." <jhaible at debitel.net>
To: "Edward King" <edwardcking2001 at yahoo.co.uk>; <xyzzy at sysabend.org>
Cc: "Synth DIY List" <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, September 15, 2007 10:31 AM
Subject: Re: [sdiy] Force Sensing Resistor

>I came late into this thread. Edward, have you built your own keboard with
> polyphonic aftertouch ?!
> What keyboard action did you use to retrofit with QTC pills?
> Do you have any pictures of what you've built?
>
> I thought the Pills respond in en exponential rathe than linear way. 
> Thought
> I read this somewhere.
> I've ordered some of these from Maplin yesterday. Curious to try them
> myself!
>
> JH.
>
>
> ----- Original Message ----- 
> From: "Edward King" <edwardcking2001 at yahoo.co.uk>
> To: <xyzzy at sysabend.org>
> Cc: "Synth DIY List" <synth-diy at dropmix.xs4all.nl>
> Sent: Saturday, September 15, 2007 5:42 AM
> Subject: Re: [sdiy] Force Sensing Resistor
>
>
> Hi Tom!
>
> Actually, although they make some products in the uk, they also have a
> manufacturing unit in the far east (or at least in that direction).
>
> I went a bit overboard with them when I came acrross them and have given
> proportional control to various objects that really shouldnt have
> it....however....
> Let me know if you want me to send you over a couple of samples as I've 
> got
> to order some more in anyway.
>
> A nice quickie experiment (proof of concept) is find someone with a 
> slightly
> earlier model car, pop off the electric window switch, shove a QTC pill in
> between the contacts and hey presto! You have (or should have depending on
> the car and switching arrangement) proportional electric window control 
> :o)
>
> for more relevant uses, the forum on peratechs website will be helpful in
> getting the best out of the materials and if you want more hints and
> practical advice, just gimme a shout. Remember, the output is 
> _very_nearly_
> linear but not quite so for finer control, you need to tweak things a bit.
>
> EK
>
>
> ----- Original Message ----- 
> From: "Tom Arnold" <xyzzy at sysabend.org>
> To: "Edward King" <edwardcking2001 at yahoo.co.uk>
> Sent: Friday, September 14, 2007 5:32 AM
> Subject: Re: [sdiy] Force Sensing Resistor
>
>
>> On Fri, Sep 14, 2007 at 05:26:45AM +0300, Edward King wrote:
>>> QTC cable is what Im using for keyboards that only need aftertouch for
>>> the
>>> whole board. For individual aftertouch (I can never remember whether its
>>> called poly or mono) QTC pills.
>>
>> Oh.  Nifty, How did I miss this product??   Looks like its made in the 
>> UK?
>>
>>> Both QTC cable and QTC pills are very cheap and pretty linear.
>>
>> For Poly I'm back to playing with Hall Effect sensors since they have
>> dropped in price.  I hope to have something to report soon...
>>
>> -- 
>> --------------------------------------------------------------------
>> - Tom Arnold           -  "...is it a virus, a drug, or a religion?"
>> - Sysabend Caretaker   -    Juanita Shrugs. "What's the difference?"
>> ------------------------       -- Neal Stephenson,  Snow Crash
>>
>>
>
>
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