A sensor to detect ground disturbance

[swingfire]

ground disturbance detection

Hi it's my first post so forgive me if straight away I'm looking for help.

I'm attempting to design and build a small circuit that will detect when an area of ground is disturbed by being dug into. Ideally it would be able to screen out animals and activity on top of the surface. and only detect if the the ground itself is disturbed ie by something digging into it. I had intially intended to use an accelerometer, but I really need it to be able to screen out just general movement. Also I'd ideally like it to have as long a range as possible.

I intend to output to an analague to digital converter, and then to a PC so if neccessary I imagine the PC can do some of the screening. I'm hoping to keep the costs well below $100.

I'm starting to suspect this project is at the edge of my ability but I would appreciate any and all help.

 

[aryajur]

ground disturbance sensor

Hello swingfire,
this is an interesting problem. Would really like to know how you end up solving it. A few questions that come to my mind are:

1. Is there a possibility to monitor the ground from above? Then maybe we can make a depth profile of the surface using ultrasonic ranging and find out if any hole starts appearing.

2. Since you were thinking of using MEMS do you always expect the digging to cause significant disturbance? If that is the case MEMS may be a good idea.

 

[flatulent]

detect what is in the ground

How large is the area you are monitoring? If it is small enough, you can economically string a matrix of wires under the surface and look for a break in the wire (open circuit).

With the accelerometer you can use DSP to detect the different types of "sounds."

 

[swingfire]

How large is the area you are monitoring? If it is small enough, you can economically string a matrix of wires under the surface and look for a break in the wire (open circuit).

With the accelerometer you can use DSP to detect the different types of "sounds."

I'm hoping to cover a radius of at least 5 metres from the sensor.

Am I perhaps looking at this the wrong way?. Should I be looking at something that would instead detect the metal in the shovel. Would I be able to lay a magnetised cable that would detect another metalic object in proximity?.

As for your suggestion aryajur I think ultrasonic ranging would be well beyond my capabilities. I'd ideally like a simple probe type sensor that can just be buried in the ground.

 

[aryajur]

The idea to place a wire mesh can be good but there maybe a problem if some animal digs up and causes it to trigger. The idea to detect metallic objects might be good too. I think you can place the detection coils at some strategic places below the ground to cover the whole area and then use that. The circuitry would be same as a metal detector but this may need multiple sensors to cover the whole area. But maybe the ultrasonic might be cheaper and less complicated. It's not as difficult to make a ultrasonic radar.

 

[Externet]

Very nice subject.

I would use piezoelectric film or transducer discs as microphones buried in the area of interest.
The ideal "as long a range as possible." would be matter of a larger array of multiplexed or mixed microphones, or more sensitive/larger/amplified ones.

https://www.sparkfun.com/commerce/product_info.php?products_id=9196

**broken link removed**

Miguel