DIY Private-Knock-Knock-Knock Cipher

The secret hideout - a thing of the past, a childhood luxury, an adult-less adventure. Those were the days. And remember the secret knock? The only way in. You either knew it or you didn't. The only way to keep the kids in and the grown-ups out.

Well, Steve Hoefer has come up with a way for adults to be kids again - The Secret Knock Detecting Lock.

The secret knock lock is made from a piezo speaker, LEDs, Arduino microcontroller, gear motor, along with a few odds and ends. Perfect for an afternoon DIY project, which you can accomplish yourself with Steve's detailed instructions.

Great way to keep the wives out that late night poker game. See it in action below.