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BBC Research and Development

Improved Cat cams for Cat Watch

For last year's The Secret Life of The Cat Alia Sheikh and colleague Tony Richardson successfully re-purposed miniature spy cameras - significantly increasing the battery life, making them capable of filming in the dark - to work as under-the-chin collar cameras for pet cats. In collaboration with the Royal Veterinary College's engineering team, they interfaced the cameras with the GPS trackers Prof Alan Wilson and his team were using to monitor the cats.

We had a larger team of interested BBC R&D engineers (many of them trainees) and lab technicians willing to spend some free time working on cameras for the Cat Watch 2014 production, so we took the opportunity to extend the filming capabilities we could offer the production crew.

Rather than hand-wiring the camera-GPS interface, Engineer Ranulph Poole and Chris Jenkins worked with the Royal Veterinary College team to design a circuit board that could be mass produced, allowing us to create a lot more cameras. Our trainees (Tom Howe, Sam Bason, Peter Taylour) got to work integrating cameras into a variety of different cat toys, allowing the production-team to potentially capture a preys-eye view of a cat attack.

We realised that we could split the camera lens away from the main body of the camera allowing us to film a view from between the cats ears - the wide angle lens allowed us to capture the movement of the ears themselves and this camera position resulted in very stable footage.

A few days before shooting began Alia Sheikh, Tom Nixon, Till Hackler, Karen Kingston-Lee, and Ranulph were still feverishly assembling and testing the 'chin' and 'head' cameras while R&D Engineer James Harrison was developing a 'cat flap camera' which triggered each time a cat used the flap. This system (based on the popular Raspberry Pi computer) not only took a photo each time the flap was used but also recorded time information allowing a graph of catflap activity to be created.

The Cat Flap Camera

GPS can provide a lot of information about where cats go outside, but is too noisy to give precise information about when cats are indoors or outdoors. The team also wanted a way to track who was coming and going at some of the houses, to see if any cats were paying their neighbours a visit. The solution was obvious - put a camera on the catflap.

However, off-the-shelf cameras are designed to run all the time, and even the highest capacity storage cards would only allow the camera to run for a day or two. The team wanted to get a longer term look at some catflaps. Motion-sensing cameras were an option, but they are expensive equipment and would pick up motion (not just that related to the cats), resulting in a lot of unwanted data that would have to be cleaned up and at worst obscure the cats' activity.

BBC Research & Development were tasked with building a camera for the task with off-the-shelf components that could be purchased and assembled by anyone at home. This comprised a small computer to handle taking a picture and keeping track of time, and a small reed switch - a magnetically operated switch, with the magnet mounted on the flap of the cat flap. This switch closed a circuit when the flap was moved, signalling to the computer that it should take a picture.

The popular Raspberry Pi single-board computer, about the size of a credit card and based heavily on the internal components found in modern smartphones, was chosen as the basis for the camera because of its accessibility. It's designed for schools, and as a result is low-cost and has a lot of documentation and resources for learning about programming and physical computing.