The scenario
Design a simple alarm system using a PIR motion sensor that activates a buzzer upon detecting movement. The circuit is battery-operated for portable use.
What is in this drawing
Read the decisions behind it.
01
Used an NPN BJT as a switch to drive the buzzer
02
Included a base resistor to limit current from the PIR output
03
Added a bypass capacitor for noise filtering from the battery
Suitable for DIY home security projects, low-power motion detection alerts, and educational prototyping.
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