Its crude but a 6mm hole with a 3 mm rod inside it a small weight
beneath the hole and suspend the rod from a piece of fishing twine. Make
the hole conductive and there you have it a bump sensor (same as used in
pinball machines) to change sensitivity make hole larger / smaller and
decrease / increase the distance to the pivot point or change the
weight.

        Works in 360 degrees (all axis) to restrict to two access make
only part of the hole conductive you can then choose the axis of
response.

Option 2 (contact less)
        Same as above but you can use two slotted opto switches and
organize them so that the rod intersects the beams on both switches
hence the thickness of the rod should be only a little more that net
response area of the photo transistor same principle as above but with
less contact bounce


Steve....

-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Denny Esterline
Sent: 02 March 2004 23:13
To: PICLIST@MITVMA.MIT.EDU
Subject: [EE:] Vibration sensor?

Hey guys and gals,
I need some sensors to pick up vibration. Needs to be sensitive in two
axis, and capable of detecting being bumped with less than 1/8 inch
movement. It'll feed a PIC so I can work with most any output, but I
only
need a single pulse when it's bumped.

Right now I need about a dozen, but eventually I might need several
hundred. And yes I could do it with an accelerometer from analog, but I
was
hoping for something simpler/cheaper.

Ideas?

-Denny

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