Maker Pro
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why infrared??

A

Ahmed Samir

Jan 1, 1970
0
Hi there
Sorry if this question seems repeated or something but i have dont a quick
web search and couldnt come up with a good answer.

the question is : why for remote controls the infrared band of light
frequencies is used and not visible light for example?

shouldnt the infrared band be very noise since all hot objects emit infrared
light??

Best regards
ahmed samir
 
W

Watson A.Name - Watt Sun, Dark Remover

Jan 1, 1970
0
Hi there
Sorry if this question seems repeated or something but i have dont a quick
web search and couldnt come up with a good answer.

the question is : why for remote controls the infrared band of light
frequencies is used and not visible light for example?

shouldnt the infrared band be very noise since all hot objects emit infrared
light??

It's a matter of wavelength. Hot objects emit IR at much, much longer
wavelengths than the shorter IR wavelengths - 880 nm - from the IR
LEDs.

Best regards
ahmed samir

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W

Wade Hassler

Jan 1, 1970
0
Ahmed Samir said:
Hi there
Sorry if this question seems repeated or something but i have dont a quick
web search and couldnt come up with a good answer.

the question is : why for remote controls the infrared band of light
frequencies is used and not visible light for example?

shouldnt the infrared band be very noise since all hot objects emit infrared
light??

Best regards
ahmed samir

Remote controls use _very_bright_ IR light, cutting through the noise.
(one I looked at pulsed the transmit LED at .4 amps.) In addition, the
signals are encoded, using a precise carrier frequency.
As for why visible light isn't used: dunno.
Wade Hassler
 
B

Bob Myers

Jan 1, 1970
0
As for why visible light isn't used: dunno.

Maybe because a visible light beam at comparable brightness (i.e.,
enough to provide sufficient range w/o interference from other
visible-light sources) would be REALLY annoying? Who would
want to illuminate their TV screen with visible light every time they
used the remote?

Bob M.
 
J

JeffM

Jan 1, 1970
0
why is infrared used and not visible light for remote controls?
ahmed samir

Think about all the hokey TV shows where the guy shines a flashlight
into the photoelectric beam of the burglar alarm.

The answer is false triggering by ambient light.
 
J

John Larkin

Jan 1, 1970
0
why is infrared used and not visible light for remote controls?

Think about all the hokey TV shows where the guy shines a flashlight
into the photoelectric beam of the burglar alarm.

The answer is false triggering by ambient light.

But there's plenty of ambient infrared... incandescents and sunlight,
to name a couple of sources. Remotes use optical bandpass filters,
coding, modulation, and tuned receivers to supress ambient light
response. Those tricks would work just as well in the visible.

John
 
L

Lord Garth

Jan 1, 1970
0
John Larkin said:
But there's plenty of ambient infrared... incandescents and sunlight,
to name a couple of sources. Remotes use optical bandpass filters,
coding, modulation, and tuned receivers to supress ambient light
response. Those tricks would work just as well in the visible.

John

Ir LEDs are more efficient emitters than visible light emitters. They
consume less battery for a given output intensity and nobody would
use it as a flashlight. :)
 
J

John Larkin

Jan 1, 1970
0
Ir LEDs are more efficient emitters than visible light emitters. They
consume less battery for a given output intensity and nobody would
use it as a flashlight. :)

Not unless they customarily wear night-vision goggles around the
house. Kinda kinky.

John
 
L

Lord Garth

Jan 1, 1970
0
John Larkin said:
Not unless they customarily wear night-vision goggles around the
house. Kinda kinky.

Ala 'Silence of the Lambs' ...
 
L

Luhan Monat

Jan 1, 1970
0
John said:
But there's plenty of ambient infrared... incandescents and sunlight,
to name a couple of sources. Remotes use optical bandpass filters,
coding, modulation, and tuned receivers to supress ambient light
response. Those tricks would work just as well in the visible.

John


Visible light is often modulated - especially from the TV screen, or
florescent lights. I think this gives an edge to infared.
 
N

norm d.

Jan 1, 1970
0
Visible light would radomly trigger the remote receiver every time you turn
on the room lights, or walk past the receiver. IR receivers of the type you
are asking about are not sensitive enough to trigger on body heat, but work
well with IR light sources.
 
J

John Larkin

Jan 1, 1970
0
Visible light would radomly trigger the remote receiver every time you turn
on the room lights, or walk past the receiver.

Would not. The IR signals are coded and modulated, generally about 40
KHz. A *huge* amount of ambient light could block the receiver, but it
wouldn't "randomly trigger the remote".

Note that you can use multiple IR remotes, for different devices, in a
room; the coding keeps them from interfering.
IR receivers of the type you
are asking about are not sensitive enough to trigger on body heat,

because the wavelength is off a couple orders of magnitude.

John
 
K

Keith R. Williams

Jan 1, 1970
0
@newsread1.news.atl.earthlink.net>, [email protected]
says...
Visible light would radomly trigger the remote receiver every time you turn
on the room lights, or walk past the receiver. IR receivers of the type you
are asking about are not sensitive enough to trigger on body heat, but work
well with IR light sources.

I don't buy that argument. There is *lotsa* IR in incandescent
lighting. Rejecting false triggers is simply a matter of coding
and filtering.
 
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