Well the title says it all, and I am here out of desperation! I have tried every commercial product (ultrasonic, water sprayer, pellets, smells, plants etc) to no avail. So as an electronics and software design engineer of 30 years I have decided to attempt to build my own system. Whilst I appreciate it will require a fair amount of effort and probably cost if it means my family can use our garden without getting cat mess on them it will be worth it.

So I am here really for any suggestions about how best to achieve this. From my own experience I have discovered that water based systems have been the most effective. Therefore, I think a system that sprays water is likely to be the most successful.

The issues with the commercial PIR based water systems are multiple false triggers, and failure to trigger at all if an object moves into sensor area slowly enough. But when it does work, it works well. So I think I need to improve on this type of concept.

In order to get maximum coverage of my garden I plan to use a series of water sprays, all linked together and controlled by an MCU. I will archive this by using irrigation hose buried in the ground Tee’d off to each ‘nozzle’. The nozzle will have a solenoid valve to control water on / off. That’s the easy bit.

In my day job we use thousands of PIC processors (8 to 32 bit) so will use one of those to control everything – probably an 8 bit, not sure it will need the might of a 32 but I see what is going spare!

Now the difficult bit, I need to be able to reliably sense the presence of a cat (or fox) when it moves into a hot zone. I do not want to use a PIR as these do not seem reliable. In an ideal world I would have an IR emitter one side of garden and IR receiver the other and when broken the relevant solenoid is triggered. But I am not sure this would work over a 15 to 20 foot range and even if it did it would need careful physical alignment. Is there a sensor I could use that is single sided (a bit like an IR reflective sensor)? May be some kind of IR heat sensor? I know Omron do some but they are quite expensive (so yes cost is an issue I guess) I would need about 10 to cover my garden.

My other thought is to mount a USB IR surveillance camera on the wall of the house such that it has a good view of the garden. Then connect this to a PC. Then I could process the image looking for changes across a series of frames, mapped against the various zones. Then send message to my PIC to fire relevant sensors. This seems to be a good solution as I could visually see things whilst developing the code and tweak accordingly. But would require a PC running 24/7 – may be a Raspberry PI could do this.

I am aware I sound quite mad, but this is really a very frustrating and disgusting problem.


I would appreciate any input or thoughts about how I could humanely solve this issue – I can’t be alone!

My background is in microelectronic design of medical equipment and computer software. I have access to full PCB prototyping and assembly facilities as well as hardware prototyping and machining.

Thank you!

 

hi Quad,
I have the same problem, cats and foxes [4].
The night IR camera system will not be reliable, trust me I have it installed.
Every flying bug , close to the camera causes a false trigger, heavy windy rain also a pain.

I have tried low power laser beams, again flying bugs, you will be amazed how many of those critters fly around at night.

E

BTW: detection of small animals is not a problem, its the false alarms.


EDIT:
One method I did some tests with was two PIR's mounted about 18 inches apart,horizontally, with their main sense patterns over lapping , on known animal pathways.
So both PIR's had to be activated to set the alarm, this cut out most of the critters problems.

 

There may be be some ideas on how to do this using the IR camera module for the Raspberry Pi in one of the raspberry Pi magazines which can be downloaded (Free) from https://www.raspberrypi.org/magpi/issues/
You could also try Googling something like "Raspberry Pi motion detector"
There are also motion detectors that use radio frequencies (About 10 Ghz) to detect motion. I think they use the doppler effect. I think they mix the reflected signal with a sample of the transmitted signal which results in a low frequency difference signal.

Les.

 

Hi, Thanks for your reply - I had completely not factored in bugs! I guess two cameras from different angles could be used to provide two outputs that must agree before there is a trigger.

Or some other method of detecting body presence. If there was a wire loop running across the lawn (just under the service) oscillating at some frequency, would there be a shift in the oscillator as an intruder crossed it? I'm thinking probably not.

 

If a cat can trigger your system then presumably birds will also get sprayed. That doesn't seem desirable to me.

An alternative possible solution would be to provide a place that the cats can easily dig in. A patch of nice loose earth or a sand pit might well deflect the cats from the rest of your garden.

 

hi Quad,
I have the same problem, cats and foxes [4].
The night IR camera system will not be reliable, trust me I have it installed.
Every flying bug , close to the camera causes a false trigger, heavy windy rain also a pain.

I have tried low power laser beams, again flying bugs, you will be amazed how many of those critters fly around at night.

E

BTW: detection of small animals is not a problem, its the false alarms.


EDIT:
One method I did some tests with was two PIR's mounted about 18 inches apart,horizontally, with their main sense patterns over lapping , on known animal pathways.
So both PIR's had to be activated to set the alarm, this cut out most of the critters problems.

If a cat can trigger your system then presumably birds will also get sprayed. That doesn't seem desirable to me.

An alternative possible solution would be to provide a place that the cats can easily dig in. A patch of nice loose earth or a sand pit might well deflect the cats from the rest of your garden.

That's called my sons vegetable patch! Not desirable! Also the cats scare most of the birds off....

 

hi Albert,
My system is not proactive against the animals, it just alerts me and I decide what action to take to scare them off.
Most times just turning on an outside floodlight is enough, sometimes a 'shooo'.

It not foxes I have an issue with , its the damned awful smell they leave behind when they pee on the garden, lingers for days!

E

EDIT:
With PIR's and IR camera's , if you have street lighting falling on your garden area and trees close by and shielding the street light, it is a problem.
In a light wind there is enough change in the ambient light falling on the detectors to cause a false alarm.

 

hi Albert,
My system is not proactive against the animals, it just alerts me and I decide what action to take to scare them off.
Most times just turning on an outside floodlight is enough, sometimes a 'shooo'.

It not foxes I have an issue with , its the damned awful smell they leave behind when they pee on the garden, lingers for days!

E

Or when your 5 year son goes to play in the garden and comes back covered in cat **** and then wonders why he isn't allowed to go and play in his own garden or pick the vegetables he has grown. If I had a dog, and I let it do it's business in someones garden I would fined - sorry for the rant! But I have just cleared 15 piles of the stuff from my garden! cat mess can be extremely harmful!

 

Have just discovered something called Radio Frequency Intruder Detection (RAFID). I can see from the blurb the gist of how this works I wonder if I could devise something similar. Or a thermal imaging camera!

 

An electric field disturbance sensor would respond to things like large conductors (cats) moving in the field and could probably be adjusted to ignore smaller animals and insects.

 

An electric field disturbance sensor would respond to things like large conductors (cats) moving in the field and could probably be adjusted to ignore smaller animals and insects.

interesting. will investigate further

 

The night IR camera system will not be reliable, trust me I have it installed.
Every flying bug , close to the camera causes a false trigger, heavy windy rain also a pain.

Turn off the Led's in the cameras and mount others in locations away from the cameras.
It works for Me for the bugs and rain can't say about snow I live in the dessert.

 

Turn off the Led's in the cameras and mount others in locations away from the cameras.

hi N,
I do have stand alone IR Emitters.
I get very clear images, but too many flying critters, tried many schemes.
Thanks for the suggestion.
E

 

put separate LED light someplace away to attract bugs (and keep them away from camera)

 

I do have stand alone IR Emitters.

You have to turn the ones off in the cameras.

 

hi,
Done that too.
I do not do any image processing to detect intruders, only PIR's, so the bugs do not cause too many problems.
I wanted to warn the TS who was considering image processing, that close up bugs would cause an alarm.

He may be interested in the external IR illumination idea.

E

 

But I have just cleared 15 piles of the stuff from my garden! cat mess can be extremely harmful!

Have you considered putting a fence around your garden?

I live on 5 acres and we put a fence around our garden to keep the deer out. None of our neighbors' cats ever used our garden as a litter box; even when 8 from one neighbor discovered a food source on our deck and moved in. We had an outdoor cat for 17 years and she never used our garden as a litter box.