Alarm and Sensor Technologies
Overview of Alarm Technologies
Alarm circuits and sensors are the "detection" portion of this cycle. The typical alarm system includes overlapping sensors to check for door/open closed status, glass breakage, motion, and more. These sensors are electrically "supervised" by a microcontroller and monitored constantly for changes in state.
A basic alarm circuit
Commercial alarm systems are typically wired up as follows:
- One or more sensors are placed in series to form a "loop." Each loop forms a sensor zone.
- Sensor zones are always wired up as "normally closed"
- Each zone includes a resistor in the middle of each loop, a resistor at the end of each sensor loop, and the ability to check voltage or resistance at the alarm panel. circuits.
- Passive Infrared (PIR)
This type of sensor is used to protect inside and outside spaces by watching for changes in radiated IR.