What kind of switch is this?

[Primus]

I'm looking for a cross between a footswitch and a pot. I want to be able to step on the switch and have it work like a compact expression pedal. That is, isntead of on/off it would have a resistance proportional to the distance i pressed it down.

[phaeton]

Not sure what they're called, but IIRC there is a sort of switch like that (comprised of carbon sheets) used in scales.  Resistance goes down with increased force, i believe.  Same principle of carbon microphones, but designed for "less gain".....

Not exactly inexpensive, but http://www.sciplus.com/singleItem.cfm?terms=8118&cartLogFrom=Search can probably be scavenged for the pressure switch.  Otherwise, you can probably mod the element from a cheapo K-mart microphone to act as the 'switch', with some other (physical) mechanism providing the opposition to force.  Leaves of 1/4" plywood or plexiglass, or even steel...

[Paul Perry (Frostwave)]

Your search is over.
http://www.phidgetsusa.com/cat/viewsubcategory.asp?category=5000&subcategory=5210

keyword is "force sensing resistor".
I remember one kind (not sure if it is these) is mde from microscopic pyramids on a conductive polymer, as you press the tips flatten out & mke better contact with a surface sheet.

[SonicVI]

Or maybe you could rig something to do it optically. Small Bear has an actuator for pressing tactile switches. Attach something to it where the spring sticks out to block light from an LED from reaching an LDR.

[dr]

....I
was reading this and wondered where my post was; it seems to have vanished.anyway, if you want to build a force-sensing resistor, do what I have done for years: take a piece of that conductive foam that comes with IC's; take a couple of pieces of self adhesive copper tape, stick a piece on two opposite sides, sloder a piece of wire to each, and connect up and press-it works ok for a lot of things. I have stacked several small sheets together to get more resistance......one was a speed control for a leslie simulator!......