Infra-Red Detector For Alarm Systems

,E:ac 1,88 INFRA-RED DETECTOR FOR ALARM SYSTEMS As a follow-up to the design abstract on the Type PID-11 published last year (1), this article describes a versatile infra-red sensor which will find many applications in security and alarm systems. The Type PID-11 infra-red sensor from Siemens introduced in reference (I) is a versatile component that lends itself to building a simple, yet effective and sensi- tive, transducer that detects heat emanating from mammals. To be able to understand the basic operation of the circuit shown in Fig. 1, it is rec- ommended to read the sections Appli- cation tips and Some suggested circuits in reference (0. mono time of the MMV, i.e., the hold time of the circuit. Incident daylight on phototransistor Ti effectively raises the trigger threshold for the MMV, and hence ensures automatic disabling of the alarm by reducing its sensitivity. Pins 5 and 6 of the monostable are logic high in the non-activated state of the alarm. When the PID-11 senses t...