measure amount of movement

I am failing to figure out how to measure the amount of movement in a room. for example I would like to be able to make an LED light brighter the more movement there is in a room. So if people stand still it would dim and if they start to dans it shines brighter and brighter the more they dance.

Anyone having any suggestions how this can be done, with what kind of sensor?

many thanks jan

some ideas,

  1. many IR beams through the room, (like a bad police film where they try to break a bank or so) .
    If there is no movement the nr of broken beams is contant, when there is movement the amount of switch off/on will increase

  2. cheap webcam
    make image - compare with previous
    count the nr of pixels changed
    Note - As you play with light intensity you must compensate for that …not trivial…

  3. sensors in the floor

  4. measure the sound(levels) → FFT
    (assumption) danceing people have another freq spectrum than talking people

thanks robtillaart,

maybe "sensors in the floor" is worth a try.

Cheap Doppler radar module?

I have never heard of "Doppler radar module". Can you point me in a direction where I can learn more about this module and where to find it?

many thanks! /jan

Have you tried Google?