In the below link the PIR sensor was used to detect the motion..from that i have doubt ...I have PIR sensor in my outdoor …to detect the motion …but it gives an alarm even if birds crossed or any other light movement …..it was exceeding even I reduced the sensitivity value….why I don’t know?????
http://www.ingenstech.com/6-digital-io-pir-sensor-arduino-beginners/
http://www.ingenstech.com/6-digital-io-pir-sensor-arduino-beginners/