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Directing IR Beam

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SeaRR85

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I'm trying to use an IR LED for a project but I want to direct the IR LED so that it's a straight line of light. I've been trying to find a lens to place in fron of the LED but I don't know if that will work. The project has an transmitter and a receiver where the trans and receive are at least 32 inches away from eachother. The transmitter needs to emitt a straight line of IR and the receiver needs to receive it (obviously) Please help! Thanks.
 
How narrow do you need the beam to be? If you need it to be really narrow, have you considered using a low power IR laser like that used in garage door safety interruption systems?
 
Depending on your sensor you might even be able to get away with a cheap red laser pointer, too. That is, assuming visible light is acceptable for your application.
 
SeaRR85 said:
I'm trying to use an IR LED for a project but I want to direct the IR LED so that it's a straight line of light. I've been trying to find a lens to place in fron of the LED but I don't know if that will work. The project has an transmitter and a receiver where the trans and receive are at least 32 inches away from eachother. The transmitter needs to emitt a straight line of IR and the receiver needs to receive it (obviously) Please help! Thanks.

You can certainly use a lens - but you need to be aware that a lens has a different focal length at IR - so it's difficult to set up!.

Presumably this is just for a 'broken beam' detector?, in which case there's no need to focus the beam - a simple IR LED is all that's required.
 
hi,
I used the lenses from old hand torches [ flash lights] for pulsed IR, works over 5 metres, for a security beam, no problem.

Do forget to use a collimator tube in front of the receiver if its subject to ambient light.
A 150mm length of 25mm dia plastic plumbing pipe works OK, if need be, paint the inside black.
 
Two beam system

Thank you to all who have replied. The system is a two IR beam system for an occupancy counter. I need the beams to be as small and straight as possible. I think the garage door minder system would be the closest system to what I'm trying to accomplish. Does anyone know where I could get the lens from that type of system?
 
How narrow do you need the beam to be? If you need it to be really narrow, have you considered using a low power IR laser like that used in garage door safety interruption systems?
What kind of IR circuits do they use in gaarage door safety systems? I'm trying to fix mine & can't identify components to replace. Tried Radio Shack & found a 940 nm emitter
but think it might be too low a frequiency for the reciever. I'd love to get some specifics
but can't find any!
oj3
 
Wouldn't placing the IR emitters each in say a straw of an inch or two long give you the same results as a lens for each? As I see it you wish to limit the dispersal of the IR emitter so as not to interfere with the second emitter, not nessesarly focus for increased sensitivity. You can always increase the emitter current to get more range.

Lefty
 
If it's a door or hallway (32 inches), wouldn't somebody passing through, pretty much block both the emitter and receiver? The tube idea would probably be all you need, and much easier, since it'll tough to focus something you can't see...
 
Wouldn't placing the IR emitters each in say a straw of an inch or two long give you the same results as a lens for each?
Lefty

I don't think a tube as described around the emitter will increase the intensity of the light hitting the detector (i.e., collimate a divergent beam). John
 
I don't think a tube as described around the emitter will increase the intensity of the light hitting the detector (i.e., collimate a divergent beam). John

hi John,
You are correct is dosnt increase the intensity, just makes it more difficult to align.

Using a simple lens from a torch etc will focus the beam, alignment is not difficult if you monitor the receivers output.
A lens can also be used at the receiving end.

If its in well lit area, a collimator at the receiving end is essential.

The OP should buy the IR receiver photodiodes with built in daylight filter.
 
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