Build a Simple Raspberry Pi Room Alarm System to Keep Intruders Away Lifehacker Alarm systems are pretty expensive, but if you want to whip up something on your own, Make shows off how to build a very simple alarm system with a Raspberry Pi . The system uses a Raspberry Pi , USB camera, keypad, revolving light, and a speaker.

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Build a Simple Raspberry Pi Room Alarm System to Keep Intruders Away – Lifehacker