EDWARD.STAUFF@OFFICE.WANG.COM (Edward L. Stauff) (01/25/91)
After my posting about implementing a sustain "pedal" by attaching a mercury
tilt switch to the back of my hand, I've had a couple of inquiries on how to
do it, so I thought I'd post the details to the net.
Sustain Pedals in General
A sustain pedal is about the easiest synth control to hack together. The
vast majority of (all?) sustain pedals consist of a momentary single-pole
switch - i.e. a pushbutton. So all you have to do is wire a plain old
ordinary 1/4" phone plug to some sort of switch, and there you have it. Now,
there's one more detail: is sustain engaged when the switch is open or when
it is closed? Of course there's a standard for that, right? Wrong.
Different manufacturers do it different ways. (I seem to remember somebody
saying that Yamaha does it backwards from everyone else, but I'm not sure.)
The quickest and most conclusive way to find out is to just experiment. On
my Yamaha PF-85, sustain is on when the switch is open (off).
Mercury Tilt Switches
These little wonders can be obtained at your friendly (?) neighborhood
Radio Shack - at least, that's where I got mine. And they're cheap - a few
bucks or less. In my application, the tricky part was finding just the right
position and angle at which to mount it. I've been thinking that I need a
more precise unit - something with less hysteresis and less bounce.
From Z-bar to H-bar
Another idea I've been thinking about is to mount a metal rod the whole
length of the keyboard, just in front of and above the keyboard. I could then
drop one of my hands down to contact the metal rod, turning on (or off) the
sustain (or anything else). A well-polished rod would, theoretically, enable
my hands to slide along it while playing, without losing much dexterity.
(-: All right, I didn't INTEND for that to sentence to sound obscene. :-)
Unlike the Zee-Bar, I wouldn't lose a finger, and it would run the whole
length of the keyboard.
The problem to be solved here is to find one of these capacitance-touch-
plate circuits, so that I can sense when the metal rod has been touched. Can
anyone tell me how to build one, or point me at any references? Analog
circuits mystify me.
-- Ed Stauff Edward.Stauff@OFFICE.Wang.com
"the ones that call the shots won't be among the dead and lame"
-- John McCutcheon: Christmas in the Trenches