[sdiy] organ pedals, was:Synth Keybards and Number of Keys

[Edward King]

Ingo, I forgot to mention...

If you do decide to go the optical slotted switch route, you need to reduce 
the power to the LED part of the switch until the receiver is _Just about_ 
saturated, otherwise it wont output analogue linearly. It needs a fine 
control and the type of switch you buy will pretty much dictate the type of 
vane you will have to build.
Some manufacturers are familiar with this type of implementation and 
therefore already have documentation. Others simply say "our product isnt 
designed to be used this way".

Regards

EK

----- Original Message ----- 
From: "Ingo Debus" <debus at cityweb.de>
To: "Synth-DIY DIY" <synth-diy at dropmix.xs4all.nl>
Sent: Friday, March 02, 2007 3:25 PM
Subject: [sdiy] organ pedals, was:Synth Keybards and Number of Keys


>
> Am 02.03.2007 um 02:30 schrieb John Luciani:
>
>> I am building a couple of two octave pedal boards that use slotted
>> optical switches
>> (PCBs arrive tomorrow!). I am thinking of doing some keyboards that  use 
>> slotted
>> optos in an analog mode.
>
> Are you using the slotted optical switches just for switching or also  for 
> displacement sensing?
> I was thinking about adding a displacement sensor to one of my 
> pedalboards, so the thing could double as an expression pedal. This 
> pedalboard (a very old one) already has a common switch for all keys, 
> probably used to trigger an envelope. That switch moves nicely when  any 
> key is pressed down, so I thought I could just attach a small  magnet 
> there and measure the field with an analog hall sensor. Of  course this 
> would only sense the displacement of one key at a time,  but I don't think 
> that this is a drawback. The individual key  switches are still there.
>
> One option I'd like to have when a synth parameter is controlled with  key 
> displacement: the setting should keep its value even after the  foot is 
> removed from the key. I was thinking about two modes: when  the key is 
> pressed first (mode 1) only values greater than the  current value are 
> output. Once the key is pressed all the way down it  switches to mode 2: 
> then only values smaller than the current value  are output. If it's 
> completely released it switches back to mode 1.  This way a value could be 
> held as long as the key isn't pressed all  the way down. Pressing it all 
> the way down then releasing it would  set the value back to 0. A LED for 
> each key indicating which mode it  is in is probably a good thing.
> Any better ideas?
>
> Ingo 


	
	
		
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