Do you have an motion sensor example?

[janey]

I have read an articles about the working principle of sensors. However, I have a question after I read the article. I need an example to understand the motion sensors. Could you help me? This is the articles link: Spam removed

[PlainName]

What do you want to understand, or what kind of example do you think would be useful? There are several types of motion sensors and they work in different ways. You might use the same sensor for different purposes.

[RJSV]

   The interesting motion sensor I've encountered used a simple resistive light sensor, old school cadmium that is a little flat white disk.  Obviously does not do the whole job but (the toy) had code that checked a couple times each second, and responded when your hand came near.
So, the code had to know what ambient conditions were, in terms of the cds resistive output, and do some action, when that simple reading had a large enough change.  Likely one channel in the processor, for doing A to D conversion.
   The range of that was for if you waved your hand near the cds sensor, so perhaps not for self-driving systems, but rather a simple TOY.
   I hadn't tested for what kind of room light had to be present, or if it worked outdoors...I think the cds sensor was invented, maybe 1930's ( ? ).

[RJSV]

...oh and I believe the older film projectors used cds sensor for producing audio, off of a track on side of moving picture film.  Also though, many movie projectors used a vacume tube light sensor, to make the audio for the film viewing audience.