PIR sensor output doesn't respond to the expectation

Question

When uploading the PIR sensor to arduino mega board , it gives a output which is opposite to the expectation in the code! Instead of turning the light on when a motion is detected, its turns it off. And it's comes on again when there is no motion detected! What could be the problem? Need help

Answer 1

Check if the pinMode is set to INPUT or INPUT_PULLUP. In INPUT_PULLUP mode you will receive opposite states. It will return LOW when input is HIGH.
For more help post your code.