Which sensor to detect rodent movment behind sheetrock or wallboard?

I have rodent issues and it is between a set of floor joist. The traffic is random and thee pest inpectors have not been able to find any evidence where they are comming into our residence from outside.

The last inspector wants to know, what times the run up and down the celing and I said anywhere from the morning to the evening. So, this got me thinking if there is a sensor that can detect the moment of mice and log the time they pass the sensor, I would have more definitive information.

I do not want to open up the celing so, the sensor would have to detect movement by vibrations or passing a beam. Please do not suggest sensors that you have not had experience with I do not want to waste my time or money ordering and using them.

I doubt that any type of vibration sensor would work well. Your wallboard already sees plenty of vibrations from other sources and detecting just rodents would be nearly impossible.

The simplest solution I can think of would be to use a small camera with motion detection software. A "borescope" USB camera starts around $20 and would only require a small hole in your wallboard. Rodent eyeballs reflect IR light and will show up very brightly in a dark environment so spotting them shouldn't be a problem.

Please do not suggest sensors that you have not had experience with I do not want to waste my time or money ordering and using them.

You could lay awake listening to them, as I do from time to time ;)

I would try an ultrasonic sensor. Mice communicate songs and chips at 30-110kHz which is largely outside our hearing range (I've seen the cat listening intently at the wall when I hear nothing at all). If you google "mice song" there's people who do research on such stuff. Here's a study of it: http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0030386

So with a ultrasonic mic with gain you ought to pick something up. The sensor from an ultrasonic distance sensors might work for the purpose (I have used them for other things, just not this application).

A cheap source of these ultrasonic sensors is eBay (not sure on the range/frequency so you'll want to check that). Here's one example: http://www.ebay.com/itm/HC-SR04-Ultrasonic-Module-Distance-Measuring-Transducer-Sensor-for-Arduino-3242-/181227585127

Good luck, this sounds like it'd be a really interesting project to share when you're done.

Alan

Just poison them. If you want to know what time they are there, listen carefully and look at your watch.

Just poison them.

Yep, that is why I said "from time to time" in the above post. Rodent bait does work, for a while.

As far as detecting via a "beam" - an IR distance/proximity sensor (basically monitors reflectance) should do the trick. I have used the sharp ones (generally for longer distances). But this one works between 3cm and 30cm which is probably what you'd want: https://www.sparkfun.com/products/8959

jremington:

Just poison them.

Yep, that is why I said "from time to time" in the above post. Rodent bait does work, for a while.

A bunch of dead rodents in your walls/ceilings doesn't seem that appealing to me, and given that OP is in Canada I find it unlikely they'll be heading outside to die. Learning their paths is the better course to understanding and stopping the problem.

Make holes with a drill, bit enough for small straws or possibly odd bits of shrink tubing you might have around. Fold over run a very fine enameled wire and pass it through (something very delicate like 40 gauge) so that one half is outside, the other inside. Using a syringe, squirt the straws/tubing full of peanut butter (overflowing a bit) and push the devices into the holes. I would think any respectable mouse is going to either chew the wire in two or pull it apart in an effort to get the peanut butter.

Connect the wires as a normally closed circuit and monitor them, by whatever means you wish, to become opens.

Small holes will patch easily when you are done hunting. The downside is, I suppose, that a mouse might try to 'burrow' into the living quarters to find the rest of the PB.

Put some traps out, put sensors on the traps, then the trap activation time will tell you when the mice were there.

Cat v1.0 works a treat. Other small predators (ferrets / martens) also work fine, but may be a little more difficult to keep. If you want to sense rodents electronically, use a contact microphone on the outside of the wall. That way you won't have to drill any holes. Anything you put inside the wall must be rodent-proof, which is a real challenge in itself. From my own experience, rodent-proof means steel (or at least metal), glass or ceramics. Everything else is just a challenge for the rodents, and they usually win.

A rodent ate the motor wire underneath the dishwasher.