In the microcontroller era today, Arduino is more than just a tool ... is used to measure the light level. The alarm system is triggered when a “Logic High (H)” level signal is detected at its sensor ...

Using motion detectors and an Arduino you can trigger lights ... A simple way to think of the sensor is a switch; the diagram below explains the difference between the two approaches.

Here is a simple general-purpose security alarm circuit built on the Arduino platform. It brings up an obtrusive alert signal when an intrusion/theft attempt is observed by its front-end sensor. In ...