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FOLLOWING HIGH INFRA RED EMITTING BODIES???

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waltr:
Consider using a flashlight (torch in UK talk) reflector as the 'telescope' optical element for the IR sensor. This works just like the diagrams in Soeren's link.

HAPPY BOY:
it was really useful to read that..

however i did  use an alluminium foil present at base of a pringles cylinder, i cut out a piece of 4.5cm *4.5cm , and placed my sensor at its focus that is 0.222cm using the formula ( y = ax^2  ; y being the folding plane),  but did not get any reading (voltage)..

however without the aluminium plate , sensor was giving output. i wanted to ask may be the aluminium foil acts opaque to  the radiations ??? or  have i used the correct material for parabola reflector??
or  have i placed the the sensor at the  wrong focal length??

thanks

Soeren:
Hi,


--- Quote from: HAPPY BOY on November 18, 2012, 03:49:56 AM ---however i did  use an alluminium foil present at base of a pringles cylinder, i cut out a piece of 4.5cm *4.5cm , and placed my sensor at its focus that is 0.222cm using the formula ( y = ax^2  ; y being the folding plane),  but did not get any reading (voltage)..

--- End quote ---
I don't know if Pringles cans vary between countries (I'd guess not), as all the Pringles cans I've seen have a flat steel bottom and a waffel-patterned matte alu-foil as top seal - neither would work as a parabolic mirror.
What do you mean by 4.5x4.5cm? A square?
What do you mean with "folding plane?
Where did you find the formula and what does a and x stand for?
A focal length of 2.2mm sounds very wrong.



--- Quote from: HAPPY BOY on November 18, 2012, 03:49:56 AM ---however without the aluminium plate , sensor was giving output. i wanted to ask may be the aluminium foil acts opaque to  the radiations ??? or  have i used the correct material for parabola reflector??
or  have i placed the the sensor at the  wrong focal length??

--- End quote ---
My guess is that it's either the form or the (wrong) focal point. The material may not be optimum, but it should still help somewhat.

Best way to quick-test a parabolic mirror is by looking into it (keep it perpendicular in bot x and y, to an imagined line between your face and the mirror) at arms length and holding a lit cigarette at the imagined line, slowly moving it back and forth until you feel the intense heat in your face (with eg. a 20cm mirror, this can be quite a lot).
In case you're a non-smoker, point a lit LED into the mirror until you see it filling the entire diameter - that will be relatively close to the true focal point.

If you can't find a real parabolic mirror, you could cut around a third of a sphere (ball shape), which means you get two (or 3 if you cut them slightly smaller) and cover the inside with aluminum foil ("polish" the wrinkles out after gluing). This time of year is ripe with cheap hard plastic spheres (depending on your country of course).

Focal distance of such an off-cut will be half the diameter of the sphere, no matter how large or small sections of the discs you cut.

Larger diameter mirror will give more signal and larger dimeter spheres will have a longer focal distance.

Most of all... Experiment, experiment and experiment - that's the fun way of learning :)

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