If you've ever been awakened at 3 a.m. by a fidgeting Fido who needs to go out, you'll appreciate the bark-activated doggie door invented by David Hunt, a software engineer, photographer and new owner of a yapping dog.

Using cheap electronic components such as a noise detector, a 12-volt motor and a Raspberry Pi (a simple, programmable computer), Hunt wired up a device that opens an exterior door when it detects a dog's bark. His solution, dubbed a "Pi-Rex," is outlined in detail on Hunt's blog.

Hunt's setup isn't the most secure solution to the problem — it won't unlock a deadbolt, for example — but it might be an improvement over what's typically available now: The flapping plastic dog escape hatch that requires users to saw a big hole into an existing exterior door.

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