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Hannover, Germany
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Hi *,

for a (perhaps silly  smiley) project I need some advice for the selection of distance sensors. I'll try to explain:

This should be a sort of a head (my first idea was a skull of a dinosaur, but this is difficult to find), which is mounted onto a server to follow people (colleagues  smiley-evil) - and perhaps light some LEDs in the eyes, if they approach. So I thought of three distance sensors: one in the viewing direction, the two left and right with an angle of (perhaps) 30° or 45°. So if one of the outer sensors receives a smaller distance, the servo turns the head until the middle sensor has this distance (or nearly this distance). All this stuff shall sit on my desk. The possible distances are between 50 cm and 2 m (or 150 cm - I'm not quite sure). So, what is the better choice: IR distance sensors (e.g. Sharp GP2-0215) or ultra sonic (e.g. SRF 05)?

And for another project: how can I detect motion throw a window? I think ultra sonic sensors will not work. Does IR work?

best regards
Andreas
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Phoenix, Arizona USA
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This should be a sort of a head (my first idea was a skull of a dinosaur, but this is difficult to find)

They are?

http://www.dinostoreus.com/skull.html

...is this your first day on the internet? smiley-grin
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the land of sun+snow
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Sonars tend to have wider beams, on the order of 30-40 degrees, while GP2 devices
tend to have much narrower beams, 5-degrees or so. You probably want a wider
beam device to make the initial detection, and possibly a narrow beam device to
localize.

OTOH, I keep thinking I could do it all with 2 wide-beam sonars [40-deg each], and mount
them so as to have a small degree of overlap on the center edge of the beams. That way, 
only one sonar would pick up an object moving in from the periphery, and would trigger
the servo to move them until both picked up the moving object simultaneously. Then, as
the object moved around, it would move out of one of the beams, and cause the servo
to move to track it.

I keep thinking this might work, one day I'll try it. :-).

You might also checkout Rod Brooks' old robot Genghis. It used multiple PIR sensors to
track and follow after moving persons.

http://www.ai.mit.edu/projects/genghis/genghis.html
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Hannover, Germany
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...is this your first day on the internet? smiley-grin

Less than a day for me, but in the measure of you earthlings this is more than a century  smiley smiley

Seriously: I looked at amazon and in local toy stores. I'm not sure, if a server can move the load; and I have to convince my "secretary of finances" - these are quite expensive (especially for a first project).

...
OTOH, I keep thinking I could do it all with 2 wide-beam sonars [40-deg each], and mount
them so as to have a small degree of overlap on the center edge of the beams. That way, 
only one sonar would pick up an object moving in from the periphery, and would trigger
the servo to move them until both picked up the moving object simultaneously. Then, as
the object moved around, it would move out of one of the beams, and cause the servo
to move to track it.
...

I think this could be easier and more exact. Thanks!

And thanks for the two links.

best regards
Andreas

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