The Cat Detector system was placed outside overnight and the following video illustrates the results obtained.
Sadly, no cats were actually detected but I feel very confident that should a cat pass by while the detector is in place, then it would be detected. Happily, the mobile robt sand smoothing part of the detector also seemed to survive being outside all night on a wet and relatively cold day and there was a great deal to be learnt. The use of tyres for an external mobile robot has problems due to slip caused by sand as well as wet surfaces so for future outdoors mobile robots I will have to have a think. Maybe four wheel driver and/or more knobbly or spikey tyres. For a fix moved such as for this Cat Detector then may even some sort of rack and pinion would be a good idea.
Still, fun was had by everyone involved (just me) and no cats were harmed in the making of this cat detector.
PS Somewhat disappointingly,, only 30 minutes after I dismantled the Cat Detector Using Sand, a cat strolled out from the alley way and wandered off into the garden. Cats! They never do what you want.