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Topic: Sensing for someone in the room (Read 1 time) previous topic - next topic

stoopkid

I'm wondering how much work it would be to see if someone is in the room. Not just moving, but even sitting or lying still. and having a pretty wide angle of view. As close to 180 as possible. It doesn't need to sense location, just presence. What would be the best way to do this, and how much work would it involve?

thanks

Magician

Piece of cake, any IR sensor sensitive up to 10 um wavelength, like they use for remote temperature meters, will spot presence of object.
There are two potential problem:
- if a person wearing a balaclava, sunglasses, gloves, winter coat;
- if temperature in the the room above 36.6 C degree.


stoopkid

#2
Mar 26, 2011, 04:15 am Last Edit: Mar 26, 2011, 04:18 am by stoopkid Reason: 1
Could I get a very wide angle out of that?

Also, would lights or anything else interfere?

Magician


For MLX90614xBA field of view up to 90 degree, probably you have to install it in the corner.
Interference will be from hot object, like incandescent bulb or heaters.

Second option, ultrasonic sensor. Draw back, it likely to be triggered from any moving box in the area. 

The most advance one, is remote brain activity scanner -): :D

u0421793

Compare the acoustic resonance of the room without lifeforms with the current resonance.

stoopkid

The thing is, its going in a clock. So it needs to be able to be placed in the middle of a wall, not just the corner. And acoustic resonance would change from a simple repositioning of the clock, and would be difficult to calibrate.

I'm wondering if this less expensive one would do. It doesnt say its angle though... Could I put a cheap lens on it for wider angle?

Magician

The lens wouldn't give 180 field of view anyway, plus I think, good IR lens cost a lot.
Easier to put 2-4 sensors, pointing it in different directions.

stoopkid

Well I wouldn't need quite 180 degrees. But more than 90 would be good. I suppose 90 could suffice. I just figured IR light could be refracted just like any other light so if properly set up something as simple as a disposable camera lens would do.

Magician

Don't confuse between IR that your TV remote works in (0.8 um)
and long wave termo- IR (10-15 um).
Chip glass lens doesn't works in second range, only made from some "special" cristalls.

stoopkid

Hmm I see. What about a convex mirror!? Surely that would work.... Hmm okay I just go with 90 degrees.

AWOL

Quote
What about a convex mirror!? Surely that would work

Only if surface-coated.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

Magician

Just came across:
http://arduino.cc/forum/index.php/topic,54655.0/topicseen.html

Making scanning mechanics has a big advantage in sensitivity level over mirroring, that will work
on big area/distance.
I remember 've been watching a movie, something about a war in Iraq.
They use similar temp-cam on a helicopter to hunt bad boys in complete darkness of the night.
One pilot or even unmanned dron could control a small city or few sq. km of the desert....

The same time its not something advisable nowadays, reliability of moving part issue.

AWOL

Quote
The same time its not something advisable nowadays, reliability of moving part issue.

Well into the 1990s, state of the art FLIR on combat aircraft was an eight or sixteen element thermal sensor mechanically scanned with a spinning multi-faceted mirror to build upa video image.
These devices were absolutely mission-critical, because they allowed NOE missions to be carried out in complete darkness.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

Terry King

The hard part is detecting MotionLess humans. Otherwise the usual motion detectors work.

Maybe hack a cheap Infrared Thermometer like http://www.harborfreight.com/infrared-thermometer-93984.html ??

Or a pressure sensitive switch on whatever they lie on  ;)
Regards, Terry King  ..On the Red Sea at KAUST.edu.sa
terry@yourduino.com  LEARN! DO! (Arduino Boards, Sensors, Parts @ http://yourduino.com

pluggy

Standard passive IR detectors aren't so hot if the warm bit isn't moving. I was locked in a building and the alarm system armed around me a couple of years ago (They didn't know I was still there). The alarm went off about an hour later when I stood up and the PIR a couple of metres behind me caught on I was in the room :)
http://pluggy.is-a-geek.com/index.html

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