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'[EE]: Lasers and IR'
2001\06\21@134653 by Shawn Yates

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I have some general question about making a line of site communication
device.

I want it to be able to go about 200 feet.  Can an IR diode go be detected
from that distance?  If not I assume I will have to go to a laser.  Are
there any off the shelf laser communication modules, or is it easy enough
that I can just make one myself?  What do the classes of laser mean?

Any ideas or just general input is appreciated.

Shawn

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2001\06\21@170948 by Shawn Yates

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> I have some general question about making a line of site communication
> device.
>
> I want it to be able to go about 200 feet.  Can an IR diode go be detected
> from that distance?  If not I assume I will have to go to a laser.  Are
> there any off the shelf laser communication modules, or is it easy enough
> that I can just make one myself?  What do the classes of laser mean?
>
> Any ideas or just general input is appreciated.
>
> Shawn

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2001\06\21@173535 by Douglas Butler

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       You can go a long way with just IR diodes and some lenses if you can
maintain aiming accuracy.  Also with IR focusing lenses is non-trivial.
I friend of mine sent video a few hundred yards using a pair of 3"
Newtonian reflector telescopes.  A Newtonian reflector focuses the same
at all wavelengths so he could set it up with visible light, then just
pull out the eyepieces and put in his IR devices.  His biggest problem
was wind and day/night temperature cycles throwing his telescopes out of
alignment.
       For 200 feet you will need some kind of lens but nothing that
sophisticated.  Alignment would then be less of a problem.
       The big danger with lasers is hitting someone in the eye.  If you
expand the beam with a lens you lower the power density which makes it
safer, or allows you to use more power.  You can get the particulars on
laser classes from most laser manufacturer's web sites.

Sherpa Doug

> {Original Message removed}

2001\06\22@035455 by Anand Dhuru

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You can use the inexpensive pocket laser pointers; just modulate the unit's
battery inputs. Of course, your alignment between the transmitter / reciver
will have to be accurate.

Regards,

Anand

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2001\06\22@040403 by Peter L. Peres

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> going 200ft

You can go 300+ft with a modulated IR beam and some optics. The mirror
from a large pocket torch (flashlight or whatever you call it) is required
on the Tx side and simple telescope optics on the receiver (one lens is
enough). There is a website with a collection of electro-optical circuits
that you may want to see. Use Google.

There are pre-made modules but good results can be obtained using IR
modules for remote control use. These can be made to pass RS232 with a
simple (even 555) modulator on the Tx side. Jan Axelsson wrote some
articles on this I think (http://www.lvr.com)

FYI by simply replacing the LED in a remote control with a laser diode
from a defunct CD player head (but make sure the laser still works - NOT
by looking into it - use a video camera or CCTV camera, or digital camera)
ranges of 40 feet can be attained. Aiming becomes a problem but 40-50 feet
? ;-)

hope this helps,

Peter

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2001\06\22@054131 by Vasile Surducan

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On Fri, 22 Jun 2001, Peter L. Peres wrote:

> FYI by simply replacing the LED in a remote control with a laser diode
> from a defunct CD player head (but make sure the laser still works - NOT
> by looking into it - use a video camera or CCTV camera, or digital camera)
> ranges of 40 feet can be attained. Aiming becomes a problem but 40-50 feet

Peter, have you really test this ?
Vasile

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2001\06\22@081920 by mike

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On Thu, 21 Jun 2001 13:35:46 -0400, you wrote:

>I have some general question about making a line of site communication
>device.
>
>I want it to be able to go about 200 feet.  Can an IR diode go be detected
>from that distance?  If not I assume I will have to go to a laser.  Are
>there any off the shelf laser communication modules, or is it easy enough
>that I can just make one myself?  What do the classes of laser mean?
>
>Any ideas or just general input is appreciated.
>
>Shawn
For that distance, you might just do it with a well-focussed IR diode
(or several), but a laser would probably be easier. You don't say what
data rate you want - for up to a few KHz, you can get modulateable
laser modules off the shelf. For everything you ever wanted to know about lasers, go to
http://www.laserfaq.com

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2001\06\22@084756 by Roman Black

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Shawn Yates wrote:
>
> I have some general question about making a line of site communication
> device.
>
> I want it to be able to go about 200 feet.  Can an IR diode go be detected
> from that distance?  If not I assume I will have to go to a laser.  Are
> there any off the shelf laser communication modules, or is it easy enough
> that I can just make one myself?  What do the classes of laser mean?
>
> Any ideas or just general input is appreciated.


We have remote testers at our shop, I have seen normal
TV remotes with one IR led at 30mA good for about 50 feet,
I assume if you use more power and a few IR leds and a
parabolic reflector (torch?) you can get a few times
this distance.

Remember sunlight will have a VERY bad effect on your
IR remote distance.
-Roman

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2001\06\22@095226 by Graeme Zimmer

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> We have remote testers at our shop, I have seen normal
> TV remotes with one IR led at 30mA good for about 50 feet,
> I assume if you use more power and a few IR leds and a
> parabolic reflector (torch?) you can get a few times
> this distance.

How about Cloud Bounce Broadcasting?

There are a number of guys getting city-wide coverage using a panel of
infrared LEDs...

for example see  http://www.qsl.net/w1vlf/techinfo/optical_transmitters.html

................ Zim

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2001\06\22@100308 by Roman Black

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Graeme Zimmer wrote:
>
> > We have remote testers at our shop, I have seen normal
> > TV remotes with one IR led at 30mA good for about 50 feet,
> > I assume if you use more power and a few IR leds and a
> > parabolic reflector (torch?) you can get a few times
> > this distance.
>
> How about Cloud Bounce Broadcasting?
>
> There are a number of guys getting city-wide coverage using a panel of
> infrared LEDs...
>
> for example see  http://www.qsl.net/w1vlf/techinfo/optical_transmitters.html



Now that is cool! An IR remote with over 4 miles
range...
-Roman

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2001\06\22@140246 by Shawn Yates

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Thanks everyone.

I have found an IR beam for monitoring a boundry in a security system.  One
of those things that when you break the beam it closes a realy.  Its good
for 200' outdoor (300 indoor).  There is nothing special about the parts,
but there is a nice convel lens setup at each end.  I can buy and use these
because that are$100 each pair and they only go one way, so for one duplex
link it would be $200.  Not good.  I have found some IR LED's and Photo
Transistors that a a couple of buckes each.  now I just need to get them to
reach one another from 200 feet.

       Any comments on lens sources?

Shawn


{Original Message removed}

2001\06\23@032104 by Peter L. Peres

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>> about 40-50 feet range using IR laser diode in remote controller

> Peter, have you really test this ?
> Vasile

Certainly. Using a Sony remote controller if I am not wrong. 40 feet is
less than 15 meters. Of course you knew that ;-) You better have a steady
hand and check the laser spot on a wall using a CCTV camera. Misalignments
of a few (one, two) degrees are significant at 40 feet. The target is only
2 inches across fyi. You can compute the amount of coffee you can consume
in your previous life (before using this) from the required
hand-steadiness. <g>.

Notice that the way in which the remote operates the diode means certain
death to it (no feedback, full current drive = mirror blown to bits after
a few milliseconds). This does not seem to bother the remote link. A
proper modulator would limit the current somehow. Although pulsed lasers
can work at higher levels than the 1.5A pulses in this remote.

Peter

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2001\06\23@052103 by Jinx

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> I have found an IR beam for monitoring a boundry in a security

I bought some brass-sleeved IR laser diodes + collimating lenses
from Oatley Electronics in Oz (http://www.oatleyelectronics.com/ )
for only $10 each. To drive them you only need a constant current
source, which can be modulated for voice or data. If a 38kHz
carrier is used then there are a variety of cheap IR receivers that
can be used

> Remember sunlight will have a VERY bad effect on your
> IR remote distance.
> -Roman

The only way I ever got a decent range (40ft) outdoors with
LEDs was to have 4 in a parabolic reflector, and the receiver
at the bottom of a tube with a violet filter to block as much
stray sunlight as possible. This makes the transmission angle
very narrow though

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2001\06\24@173249 by Michael Noel

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Vasile Surducan wrote:

> On Fri, 22 Jun 2001, Peter L. Peres wrote:
>
> > FYI by simply replacing the LED in a remote control with a laser diode
> > from a defunct CD player head (but make sure the laser still works - NOT
> > by looking into it - use a video camera or CCTV camera, or digital camera)
> > ranges of 40 feet can be attained. Aiming becomes a problem but 40-50 feet
>
> Peter, have you really test this ?
> Vasile

I think not Vasile! I designed a small laser therapy device for a private clinic
specialized
in laser therapy, Lasermed,and this device have a 50mW power, and we don't need
special
protection, for eyes. For a pick-up CD player, diode need few uW(micro) !
To a burn the skin you need at least 2-3W and the penetration is max. 0.5mm!
For laser link, I think the best solution is 2 cheap laser pointers, with ASK or
FSK modulation.
Theoretical maximum frequency is around 13 THz for a laser, but for laser
pointers a few KHz
is enough to sustain a typical RS232 (max.115.4K).
Regards
Miki

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'[EE]: Lasers and IR'
2001\07\11@170916 by Sten Dahlgren
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"Peter L. Peres" wrote:
>
> > going 200ft
>
> You can go 300+ft with a modulated IR beam and some optics. The mirror
> from a large pocket torch (flashlight or whatever you call it) is required
> on the Tx side and simple telescope optics on the receiver (one lens is
> enough). There is a website with a collection of electro-optical circuits
> that you may want to see. Use Google.

I think i found it here:

<http://www.cix.co.uk/~lasertag/lasertag.htm>



{Quote hidden}

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