How to get further IR range?

Hey, I have my receiver and transmitter circuits working (both off of 08M2's). I'm just wondering how I would get the most range out of them.
I have 3 IR led's and a flashlight with 3 led's that I can swap the IR led's for so it has a mirror behind it, but how would I connect the 3 LED's together?
I'm sure I read something somewhere but now Icant find it.
thanks
 

eclectic

Moderator
Hey, I have my receiver and transmitter circuits working (both off of 08M2's). I'm just wondering how I would get the most range out of them.
I have 3 IR led's and a flashlight with 3 led's that I can swap the IR led's for so it has a mirror behind it, but how would I connect the 3 LED's together?
I'm sure I read something somewhere but now Icant find it.
thanks
First, please tell us all exactly how
you have your circuits connected.
Schematics and Hi-res photo's.

Secondly, what do you want to do with the longer range?

e
 
sorry, I havent got a camera. I just want to be able to turn something on and off consistantly from about 20m away. I'm just wondering how I could make the three IR led's pulse together as one stronger unified IR signal.
I'm just using the irout c.4, 1, 1 command and connecting one IR led to pin 4 and ground right now, but the signal does not go very far.
 

westaust55

Moderator
From the datasheets on some domestic type IR controllers I have for audio equipment the indicative range is around 7 metres.
Certainly I ahve achieved ranges around double that.
For 20 metres, it begs the question where do you have this line of sight range?

eclectic asked for schematics and photos back in post 2.
We need to know more about your circuit before any specific recommendations can be given. IR LED details, series resistor values, switching transistor details/characteristics and transistor base resistor value so we can consider the transistor opewrating region, Vce and more.

Keep in mind that outdoors, sunlight includes an IR component which will have an impact upon your IR comms.
For some insights into IR and why carrier frequencies around 38 kHz are used, etc, have a read of my basic tutorial here: http://www.picaxeforum.co.uk/showthread.php?17303
 

Haku

Senior Member
For that kind of range I would look into using optics on the IR transmitter/receiver (simple lenses) or if the budget allows, RF wireless comms.

When I was testing a simple IR tripwire setup I put plastic lenses in front of the IR LED and IR receiver which was then pointed at a bike reflector at a 3 room distance, it worked ok and I'm guessing the distance the light travelled was over 20m. The use of a camcorder that can see IR light (nightvision mode) greatly helped aligning the setup.
 

Dippy

Moderator
So much depends on your requirements and application e.g. size, power consumption, budget, ambient conditions, fixing etc.

The bottom line is signal-to-noise.

In daylight or strong ambient light you will require focussing and shielding.
Even my own pathetic attempts with a sigle IRLED and photoD yielded 30m from a 100mm diam reflector.
But it required quality 1" lenses at each end and shielding at the receiver end to reduce ambient light interference.
The downside was the operating angle of dangle. The more you shield the more directional it can get.

My App was a people counter so both ends were fixed.
If yours is a wave-it-around hand-held then my design wouldn't be much good to you.

Yes, a remote control might do 7m but not outdoors in the mid-day sun.

You will have to provide more details about the project requirements , operational conditions and your own ability for people to help.

Is this a school/college project?
 

MikeGyver

Senior Member
You'd be immensely better off focusing the beam rather than wasting it in many directions. Just giving it more power isn't as practical to get the same results because of the inverse square law.

Here's an audio over light link I was tinkering with a while back. It used a 3 watt red led and would have easily worked over a distance of several thousand feet to a few miles. I only tested it to a couple hundred feet and the beam was absolutely blinding. A good reciever will pick up the audio even if the red light doesn't appear to be "illuminating" the receiver sensor by eye.
You just need to collimate your light source and use a large area (fresnel) lens to capture as much as that light as possible and focus it onto the receiving sensor.





How much power would it take to get a light this bright on that wall without any kind of lens? lol



See the little red light off in the distance? Thats a 3 watt luxeon LED thats over 107 miles away(!).
The modern record distance is 173 miles. There are few places on earth you can even do this due to it's curvature. http://modulatedlight.org/optical_comms/optical_qso_173mile.html


It's actually quite simple if you understand the basic principles behind it. Your 20m range doesn't seem so difficult now does it?
 
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srnet

Senior Member
For that kind of range I would look into using optics on the IR transmitter/receiver (simple lenses) or if the budget allows, RF wireless comms.
I have been seeing just how far, line of sight, you can go with a pair of RFM22 Wireless modules recently. To date I have got up to 8.2km line of sight on 12.5mW, but I believe that distance should be possible on 6.25mW. That would make the modules, which have a 100mW capability, having a theoretical range of 32kM LOS.
 
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