Chapter 6. Security/Automation Sensors

Security system sensors such as motion detectors, reed switches, pressure mats, glass-break detectors, infrared beams, and conductive film, can be very handy for all sorts of things including home automation systems, interactive art installations, and even security systems!. Almost all security system sensors provide a simple switched output that changes state based on whether the sensor has been tripped, which means that, when connected up in a circuit, they behave just like a switch that is activated automatically. That makes them extremely easy to connect to an Arduino to read their status.

However, things are not quite as simple as they may first appear.

Most security sensors provide a "normally closed" ...

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