In the microcontroller era today, Arduino is more than just a tool to accomplish hobby tasks. There is actually a close relationship between microcontroller technology and home security, since you can ...

Figure 1 shows a way to control a light (or other 120-V ac appliance) with a passive-infrared (PIR) alarm sensor. The original concept was to turn a closet or shop light on whenever someone went into.

Unlike infrared optical sensors that use an LED transmitter and IR receiver, the PIR emits nothing. As its “passive” name suggests, it responds only to infrared energy radiated by the object being ...