why infrared??

A

Ahmed Samir

Guest
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
 
In article <bocv0k$1db7kv$1@ID-36824.news.uni-berlin.de>,
ahmdsamir@link.net mentioned...
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??
Click to expand...
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
Click to expand...
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"Ahmed Samir" <ahmdsamir@link.net> wrote in message news:<bocv0k$1db7kv$1@ID-36824.news.uni-berlin.de>...
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
Click to expand...
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
 
"Wade Hassler" <wadeh@neti.saber.net> wrote in message
news:d44d2251.0311060855.3d67cee2@posting.google.com...

As for why visible light isn't used: dunno.
Click to expand...
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.
 
why is infrared used and not visible light for remote controls?
ahmed samir
Click to expand...
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.
 
On 6 Nov 2003 13:37:22 -0800, jeffm_@email.com (JeffM) wrote:

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.
Click to expand...
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
 
"John Larkin" <jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote in
message news:2uolqvc93uch8agd3djg2rsgqp2qoht6kv@4ax.com...
On 6 Nov 2003 13:37:22 -0800, jeffm_@email.com (JeffM) wrote:

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.

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
Click to expand...
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. :)
 
On Fri, 07 Nov 2003 01:23:46 GMT, "Lord Garth" <LGarth@Tantalus.net>
wrote:

"John Larkin" <jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote in
message news:2uolqvc93uch8agd3djg2rsgqp2qoht6kv@4ax.com...
On 6 Nov 2003 13:37:22 -0800, jeffm_@email.com (JeffM) wrote:

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.

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. :)
Click to expand...
Not unless they customarily wear night-vision goggles around the
house. Kinda kinky.

John
 
"John Larkin" <jjlarkin@highlandSNIPtechTHISnologyPLEASE.com> wrote in
message news:eek:84mqv4ldno9e60r3dlqbvf9fu0f9841bb@4ax.com...
On Fri, 07 Nov 2003 01:23:46 GMT, "Lord Garth" <LGarth@Tantalus.net
wrote:



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.
Click to expand...
Ala 'Silence of the Lambs' ...
 
John Larkin wrote:

On 6 Nov 2003 13:37:22 -0800, jeffm_@email.com (JeffM) wrote:


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.


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
Click to expand...

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

--
Luhan Monat, "LuhanKnows" At 'Yahoo' dot 'Com'
http://members.cox.net/berniekm
"The future is not what it used to be."
 
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.

"Ahmed Samir" <ahmdsamir@link.net> wrote in message
news:bocv0k$1db7kv$1@ID-36824.news.uni-berlin.de...
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
Click to expand...
 
On Sun, 09 Nov 2003 16:13:03 GMT, "norm d." <wrkdiver@ix.netcom.com>
wrote:

Visible light would radomly trigger the remote receiver every time you turn
on the room lights, or walk past the receiver.
Click to expand...
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,
Click to expand...
because the wavelength is off a couple orders of magnitude.

John
 
In article <jItrb.18284$Oo4.14018
@newsread1.news.atl.earthlink.net>, wrkdiver@ix.netcom.com
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.
Click to expand...
I don't buy that argument. There is *lotsa* IR in incandescent
lighting. Rejecting false triggers is simply a matter of coding
and filtering.

--
Keith

"Ahmed Samir" <ahmdsamir@link.net> wrote in message
news:bocv0k$1db7kv$1@ID-36824.news.uni-berlin.de...
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
Click to expand...
 
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