Background
My Dad had many problems with cats damaging plants and using his garden as a toilet. Over the years he fought back with a dog who loved nothing better than chasing cats down the path, strategically placed piles of stones and soil to fire at the cats and cans of water placed around the garden that could be launched at a cat if it was spotted.
When i took over the garden i quickly got sick of the smell and sight of the stinking mess that the cats left behind. The better tended the garden the more likely cats were to use it as a toilet. I despair of the attitude of cat owners who think it is perfectly reasonable to allow their cats to wander around fouling their neighbour's gardens but object if a dog owner allows their dog to foul a public street.
I decided to fight back and make the garden a very uncomfortable toilet indeed for any cats that decided to try.
When i took over the garden i quickly got sick of the smell and sight of the stinking mess that the cats left behind. The better tended the garden the more likely cats were to use it as a toilet. I despair of the attitude of cat owners who think it is perfectly reasonable to allow their cats to wander around fouling their neighbour's gardens but object if a dog owner allows their dog to foul a public street.
I decided to fight back and make the garden a very uncomfortable toilet indeed for any cats that decided to try.
I found an outdoor ultrasonic unit from Kemo Electronics(of Germany) intended to scare off cats, foxes, rodents, birds etc. The frequency is adjustable to the range required to discourage a particular type of animal.
I also happened to have some burglar alarm components left over from a project. A blue strobe light, and passive infra-red(PIR) sensor. I also had a central heating controller box and a general purpose project box to hand.
Over a day i put these together to create the unit shown. The central heating wiring box contains some circuitry to handle the signal levels from the PIR and convert them to a level to drive the strobe light and ultrasonic generator unit.
Switches were installed to allow the unit to be switched on/off, to enable/disable the strobe light and ultra-sonic unit and a push button was provided to allow the unit to be tested. The system was driven by a 12V sealed lead acid battery.
The unit works very well and when powered on keeps the cats away. When the unit is triggered the cats get a 30 second blast of ultrasound which distracts them from what they originally intended doing when they entered!
The system did have a surprising unintended consequence soon after it was installed. The local paper girl approached the garden wearing earphones of an iPOD. Unfortunately the PIR field extended slightly beyond the hedge onto the street and she triggered the unit. She received a sharp painful whistle in her ears, her knees gave way and she immediately pulled the earphones from her ears thinking there was something wrong with her iPOD. I had happened to see this from the window and dashed out to explain the problem to the paper girl. She was somewhat skeptical but when she walked back along the street she removed her earphones and walked past gingerly until she felt safe again. Over the next few days i adjusted the angle of the unit to ensure the PIR range was not extending into the street. Sadly, the system does not have quite the same effect on the cats but it certainly distracts and spooks them and they tend to leave fairly quickly.
I also happened to have some burglar alarm components left over from a project. A blue strobe light, and passive infra-red(PIR) sensor. I also had a central heating controller box and a general purpose project box to hand.
Over a day i put these together to create the unit shown. The central heating wiring box contains some circuitry to handle the signal levels from the PIR and convert them to a level to drive the strobe light and ultrasonic generator unit.
Switches were installed to allow the unit to be switched on/off, to enable/disable the strobe light and ultra-sonic unit and a push button was provided to allow the unit to be tested. The system was driven by a 12V sealed lead acid battery.
The unit works very well and when powered on keeps the cats away. When the unit is triggered the cats get a 30 second blast of ultrasound which distracts them from what they originally intended doing when they entered!
The system did have a surprising unintended consequence soon after it was installed. The local paper girl approached the garden wearing earphones of an iPOD. Unfortunately the PIR field extended slightly beyond the hedge onto the street and she triggered the unit. She received a sharp painful whistle in her ears, her knees gave way and she immediately pulled the earphones from her ears thinking there was something wrong with her iPOD. I had happened to see this from the window and dashed out to explain the problem to the paper girl. She was somewhat skeptical but when she walked back along the street she removed her earphones and walked past gingerly until she felt safe again. Over the next few days i adjusted the angle of the unit to ensure the PIR range was not extending into the street. Sadly, the system does not have quite the same effect on the cats but it certainly distracts and spooks them and they tend to leave fairly quickly.