Pet Door 2.0 Programmer Builds Twitter-Enabled Cat Flap

Ioan Ghip had a problem. When the neighbors' cats kept coming through his cat door and stealing his kitties' food, he devised a solution: a high-tech cat flap that monitors the door and sends the images to Twitter.

Since March 20, Gus and Penny have left their home exactly 673 times. The two cats live in the garage next to the suburban home of Ioan Ghip, a programmer at a telecommunications company who is originally from Romania but now lives in Salem, Oregon. They can go outside whenever they feel like it by going through a cat flap in the door leading out to the home's concrete driveway. On average, each of them leaves the garage 5.71 times a day.

Ioan Ghip actually knows even more about where his kitties wander. Gus, the fluffy, black cat with the yellow eyes, likes to stay out longer, and he's often out and about for a few hours. Penny, Gus' gray-striped garage mate, often only strays outside for brief periods ranging from five to 20 minutes.

Ghip happens to know such precise details about his cats' behavior because he has figured out how to make the world's first photo-tweeting cat door . Penny and Gus both wear collars outfitted with thumb-nail-sized radio-frequency identification (RFID) chips. The chips are passively sensed, which means they don't require a battery and don't weigh down the collar. Whenever a cat goes near the door, a small RFID reader scans the tag and determines whether the cat is authorized to go in or out.

If the chip tells the reader that the cat is authorized, it not only activates the door opener; it simultaneously also activates a camera and a program on an attached laptop that sends the captured image to a separate Twitter account, where it is automatically posted on the cats' microblog  with a simple, cute caption that is automatically generated, such as "Gus is out to get rid of a hairball" or "Penny is in to shred the chair."

Cost: 10 Hours and $100

As Ghip told SPIEGEL ONLINE, it all started when he was confronted with a few small, practical problems. First, when his daughter, Madeline, was born last December the house cats had to move to the garage. So Ghip put a cat door on the people door and solved his first problem.

The second problem arose when Ghip figured out that the neighbors' cats were sliding in and out of the cat door for free meals because, as he says on his Web site, they "learned that the food my wife buys is better than what they get from (their own) owners)."

Ghip's solution to this problem was exactly the type you'd expect from a programmer: From an online merchant, Ghip was able to get: passive RFID chips for a little over a dollar a piece; an RFID reader ($60 or €46) that reads passive chips from a certain limited distance; and a servo motor and matching controller ($40 or €30), which opens and closes the cat flap. A servo is a small mechanical devise that accepts signals and is commonly found in radio-controlled airplanes, puppets and robots. The RFID reader sends a message to the laptop and the software on the laptop then sends a message to the servo controller, which then tells the servo whether or not to open the door using power from the USB connection to the computer.

Putting the set-up together is not the hard part. "Anyone with some tools and time on their hands can do it," Ghip told SPIEGEL ONLINE. "The hard part that requires some programming skills is to write the software to handle the cat door." Ghip says he did it all in about 8-10 hours after work and adds: "If there is a demand for them, I will sell kits and the software."

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