Here it the task. If you find a solution that works (in a prototype)
and we can implement you will get a $100 tip.

So here is the challenge. We have a small high end flashlight which is
using rotary knob in the back. The knob can be rotated, the rotation
(uses a thread) results in the knob making contact with the battery -
in which case the flashlight turns on. Now we noticed that when I just
slightly turn the knob, that there seems to be a mechanical current
limitation - where the light turns on but isnt very bright - this is
because the current is limited physically we assume.
However this is way too sensitive. We are basically looking for sort
of a pressure-sensor we can put onto the tip (of the knob) which
contacts the battery - which will limit the current that can flow from
the battery to the knob - depending on how much pressure the knob
applies to this sensor.

The battery has a voltage between 2.5V and 4.5V. The maximum current
is 1000mA (which is regulated by a circuit). The pressure sensor
should either allow full current with max. pressure or very little to
no current with no pressure.

Size constraints. The solution should fit onto the tip (or other end
of the knob) which is a circle with a 7mm diameter. The height of the
solution can be up to 10mm (however smaller is preferred). However the
distance travel of the knob from max pressure to no pressure should
only be a couple of mm.

I hope that makes sense. If not ask.

Here is the closest thing I was able to find myself:
http://www.cui.com/adtemplate.asp?invky=933192&catky=560054&subcatky1=895884&subcatky2=&subcatky3=

The problem it can only take 5mA. Ideally we have a sandwich the more
the sandwich is squeezed together the more current can flow from the
top to the bottom of the sandwich. Max Current 1000mA, max diameter
7mm (if your solution is a bit larger let us know maybe we can
accomodate something larger).

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Request for Question Clarification by sublime1-ga on 05 Dec 2005 20:07 PST

mobile1...

I'm not sure why you're insistent on using a pressure sensor
to vary the voltage/current. Why not simply use a variable
resistor to vary the voltage/current in the circuitry you
already have in place?

sublime1-ga