I am currently working on a project which requires controlling two sensors (photodiodes) placed at 1 meter apart from a IR remote. The distance between the remote and sensors will be nearly 6-7 meters.
The problem I am facing is that I am unable to make the beam of my IR remote such narrow focused that it can be sensed by only one sensor at a time i.e whenever I am trying to trigger one sensor other is also getting triggered due to close spacing.
So please specify me any solutions to make my remote narrow focused as I cannot increase the spacing between sensors. Also use of RF or laser diodes are not allowed.

 

Optics.

Electronically, you could use a system that modulates the IR signals at two different frequencies, and set each receiver to discriminate only the appropriate frequency.

 

This is usually done by modulating the signals sent over the IR beam. One set of data is an ID which tells the devices which one it's talking to. Then that device starts listening and responds to the next set of data.

Trying to narrow your beam is really not the best option.

Matt

EDIT: Wayneh, you beat me to it! Slightly different method though.

 

I don't think this is an electronics challenge so much as a challenge in understanding how an IR LED creates a wide angle dispersion pattern and how it can be made narrow and focused on the sensor. Traditional optics may not be much help.

https://en.wikipedia.org/wiki/Beam_divergence
http://www.iiviinfrared.com/resources/choose_focus_lens.html

Most of the forum posts on this subject are long on wind and short on answers. Good Luck

 

Yeah, it is possible that way. But that was just an example in actual I have an series of sensors, so modulation will became a tough task. I am looking for any IR led with very narrow beam angle or any arrangement that will exactly focus the beam without much scattering.

 

Use laser instead of IR.

Use optics to focus IR.

Use a length of pipe to "focus" the receivers.

Use two separate and focused transmitters co-located.

Modulate the signals at different frequencies.

... let me see if I can think of anything else...

 

I think optics are not such a bad option at this distance. The main problems are that 1) it's hard to focus a beam you can't see and 2) it's easier to use a single LED, but that can limit the range. A TV remote often uses multiple IR LEDs. But I have some with just one and they work fine across the room.

Some of my visible light LEDs are already focused into a tight circle of maybe 5 feet in diameter across a distance of 30 feet. There is some stray light outside the beam, but it's pretty darn good for a cheap piece of plastic.

 

You can easily focus an IR LED by measuring at the receiver.

I would ask for a more descriptive title thread because I get notifications from threads and I have no idea what they are about until I open them again.

 

How about polarized filter pairs? One emitter and detector with polarizing film in a horizontal direction. And the other emitter and detector with their polarizing film rotated 90°.

Ken

 

Don't even play with a IR laser you'll put you eye out. I would try something a little simpler.
kind of like a gun you place the ir in a tube that can't let the light out from the side just straight down the barrow and make it close to the size as the led as you can get it.

 

And paint the inside of the tube flat black to stop reflections.
In the early days of video games there was a shooting game made that way. It could detect which part of the TV screen you were pointed at using a photo transistor in the gun barrel.

 

Two different frequencies for two IR LED transmitter and receiver.
Two sides of transmitter and receiver plus a Convex lens to focus the transmission light.

 

How about polarized filter pairs? One emitter and detector with polarizing film in a horizontal direction. And the other emitter and detector with their polarizing film rotated 90°.

Ken

I like this idea. I only have 2 worries. First, what happens if the user holds the transmitter at an angle? Second, the polarizing film may not pass IR as well as visible light.

 

The IR transmittance of polarizing film would have to be investigated. So, the transmitters are not in fixed positions? Maybe you could go into more detail of how these emitters and detectors are to be used.

Ken

 

I am currently working on a project which requires controlling two sensors (photodiodes) placed at 1 meter apart from a IR remote. The distance between the remote and sensors will be nearly 6-7 meters.
The problem I am facing is that I am unable to make the beam of my IR remote such narrow focused that it can be sensed by only one sensor at a time i.e whenever I am trying to trigger one sensor other is also getting triggered due to close spacing.
So please specify me any solutions to make my remote narrow focused as I cannot increase the spacing between sensors. Also use of RF or laser diodes are not allowed.

Modulate an IR laser diode - it has a narrow beam of coherent light.