long range IRDA (your opinions please)

[Phil]

Hi,


hypothetically, do you think that I could extend the range of an IRDA unit
like this one
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=3375028267&category=14
417


I'm thinking I can greatly extend the range of communications by using a
telescope.

Picture this: The IR receiver is carefully mounted on the eyepiece of the
telescope, which is positioned to look at an IRDA device quite far away. To
further extend the range, one could probably easily separate the IR
transmitter diode from the emitter diode, and set up a target of multiple IR
emitters, which could easily be viewed through the telescope up to a km
away. With the same setup at the remote location.

Do you think this will work? Would the distance achieved be only limited by
the power of the telescope? I doubt there would be timing issues, as the IR
is traveling at the speed of light.

Regards, Phil

 

[Rob]

"Phil" <haxby@removethisbitandjustleave dodo.com.au> wrote in message
news:3ff038a6$2@news.comindico.com.au...

Hi,


hypothetically, do you think that I could extend the range of an IRDA unit
like this one

http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=3375028267&category=14
417


I'm thinking I can greatly extend the range of communications by using a
telescope.

Picture this: The IR receiver is carefully mounted on the eyepiece of the
telescope, which is positioned to look at an IRDA device quite far away.
To
further extend the range, one could probably easily separate the IR
transmitter diode from the emitter diode, and set up a target of multiple
IR
emitters, which could easily be viewed through the telescope up to a km
away. With the same setup at the remote location.

Do you think this will work? Would the distance achieved be only limited
by
the power of the telescope? I doubt there would be timing issues, as the
IR
is traveling at the speed of light.

Regards, Phil

I did not check out you link, however something worth checking (which you
may already be aware of) is that the lenses used are transparent to IR.

rob

 

[Mark Harriss]

You'll need IR transparent plastic lenses as glass is
opaque to IR, a parabolic reflector (torch reflector) with an IR
filter across may do the trick nicely.

Mark Harriss

 

[Bill]

so why do remote controls work on DVD's & VCR's in glass TV cabinets?

"Mark Harriss" <ningauble@removethis.bigpond.com> wrote in message
news:e%dIb.70354$aT.69092@news-server.bigpond.net.au...

You'll need IR transparent plastic lenses as glass is
opaque to IR, a parabolic reflector (torch reflector) with an IR
filter across may do the trick nicely.

Mark Harriss

 

[Phil]

"Mark Harriss" <ningauble@removethis.bigpond.com> wrote in message
news:e%dIb.70354$aT.69092@news-server.bigpond.net.au...

You'll need IR transparent plastic lenses as glass is
opaque to IR, a parabolic reflector (torch reflector) with an IR
filter across may do the trick nicely.

Mark Harriss

I didn't know that glass stopped IR. Are you sure you are not talking about
UV? I have an IR security camera outside which is enclosed around glass.
Works OK. I dont think it is any sort of special glass.

Cheers, Phil

 

[Rod Speed]

Phil <haxby@removethisbitandjustleave dodo.com.au>
wrote in message news:3ff246f1@news.comindico.com.au...

Mark Harriss <ningauble@removethis.bigpond.com> wrote

You'll need IR transparent plastic lenses as glass is
opaque to IR, a parabolic reflector (torch reflector)
with an IR filter across may do the trick nicely.

I didn't know that glass stopped IR.

Only far IR which isnt what's used by remotes.

Are you sure you are not talking about UV?

Nope, its true of IR too.

I have an IR security camera outside which is enclosed around glass.
Works OK. I dont think it is any sort of special glass.

Because thats near IR.

 

[Mark Harriss]

Bill wrote:

so why do remote controls work on DVD's & VCR's in glass TV cabinets?

See Rod Speed's answer which is the correct one, I was thinking in
terms of far IR such as that from CO2 lasers (10600 nM) which is unable to
pass through silica glass to the point where a beam of a couple of watts
will shatter glass immediately through thermal heating effects. At those
wavelengths optics are made from crystal materials including table salt.

Mark Harriss