Movement/Vibration Detection

I am looking for a way to detect movement/vibration around a specific area, using some type of sensor(s) that are buried under the ground. I would like this sensor to activate an alarm when there is vibration around it - such as digging, or vehicles driving, etc.

I have heard of sensors for house alarms that are buried in the ground surrounding the house - could that be applicable? I thought about seismographic equipment, but that might used for too big of a scale.

If anyone has information regarding this, or could point me in the right direction, it would be appreciated.

Thanks.

Reply to
ceebee
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bury a multimode optic fibre. shine a laser in one end, put a video camera, (or wiimote light-source sensor) at the output end look for changes.

Reply to
Jasen Betts

Geophones aren't very expensive, and will do what you want.

Leon

Reply to
Leon

Since the OP is gmail and therefore blocked...

Is it important to reject false positives from sources outside the perimeter you are protecting? Do you need to detect non-metallic as well as metallic 'signals'.

If only metallic then there are lot's of wire loop detectors available.

If non-metallic perimeter detection is necessary, then a double fluid tube system would work, however such systems are more complex and frequently require maintenance.

If you are only interested in area detection, and not perimeter protection, then a geophone system would work just fine.

Reply to
PeterD

Yes. I would suggest more than one geophone. A micro controller with a multichannel ADC can digitize the signal from, lets say, three geophones. The software can then do some simple processing to reduce the response to things like earthquakes and increase the response to activity within the area of interest.

The easiest system to think about is one with horizontal motion sensing geophones in a row. These won't see much motion from a source directly below. The speed of sound through the ground is close enough to constant that you can exclude shock-waves that appear to be going past the line of geophones. Sources within the area of interest will get to the middle geophone before the ones on either end.

Reply to
MooseFET

Hmm; Maybe I should put some in my backyard! With a bit of tweaking, you could design a circuit to triangulate the location of the intruder and direct a mini-gun equipped robot to dispatch him!

Simple detector circuit here:

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Geophones are available surplus at a relatively low cost.

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©
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Reply to
RFI-EMI-GUY

I have solved this problem with an ultrasonic receiver from a transmitter receiver pair. With a simple amplifier I was able to detect a dog walking on the lawn from 40 feet. This was developed to follow a flow of water to a blockage in a sewer line.

Reply to
Herman

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Others have used humans armed with side arms to do this sort of thing. You need more geophones so that you get the location information. The software involved uses an FFT of several thousand points. A modest DSP is needed.

geophone3.htm

Reply to
MooseFET

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