MOTION click will let you know whether someone has entered the room, or left it. If that someone has a physical body the click will detect it, so ghosts are excluded from the detection range.
How PIR sensors work
All objects emit radiation, and human bodies emit radiation of a certain wavelength. The hotter an object is, the more radiation it emits. The radiation emitted by a human is for the most part in the infrared wavelength.
A pyroelectric sensor, like the one on MOTION click, generates a voltage when exposed to infrared radiation, emitted by live bodies.
MOTION click range
MOTION click has the range of up to 4 m. So, if you place it in a room, you can use the onboard potentiometer to the range you desire. Once someone steps within the range the sensor will register thermal energy of their body, and send an interrupt to the target MCU.
You could know if your dog went into the kitchen when you are not there. Maybe you want the light in your front yard to turn on every time someone steps near it. You could set up a burglar alarm. Anything that incorporates detection of live bodies.
Other motion sensor click boards
Of course, we have other motion sensor click boards available. Here is a selection, and you can check the rest in our shop.
You can detect vibration with Vibra Sense click, the name itself says it all. Tilt click is a 4-directional optical tilt sensor that you can use to get positional feedback for left, right, backward or forward movement.
If you want accurate positioning and orientation information, look no further than 3D MOTION click.
For more information about the MOTION click, see the product page.