alan smith wrote:
>   I've sent an email to the end user asking to describe what isnt working exactly.  Of course I expect an answer...it doesnt activate when stepped on....hmmm...guess its broken.  I'd rather not make too many trips to site, waste of time and fuel (but I charge these guys mileage at least)
>
>   
That's kinda why I suggested looking at failure modes. If it's wet, and
muddy, there's lots of possibility for the pressure sensor not having
anything to press against underneath as mud softens, if I understand the
design right, and any design that depends on up/down motion will
probably fail. Mud will get in the gap, cavities can form under the
stone, grit can seize moving parts, etc. The design has to be able to
return to the start position under all mud conditions most likely, so
any motion has to be sealed. I would also guess the travel is small,
since stepping on stones that move a lot would be annoying, and this
makes the affect of grit or shifting worse.

How about a light beam across each stone? The foot breaks the beam.

Or embed a hall sensor or better, a reed switch, in the top of each
stone and embed some rare earth magnets in the soles of the stone
walker's shoes?

If the step can be made loud enough, as in hard shoes vs sneakers, an
embedded electret element might work too, but will have to be adjusted
so thunderstorms and lawnmowers don't set it off. Same idea as the piezo
one, but more easily waterproofed I'd think.

-Skip

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