Hi all,

For some fun hide&seek related project I'm trying to have an IR LED visible on a mobile phone from a distance of at least 10m (preferably 15m or more) in the dark (at night; under trees; no light sources around other than the moon and the stars).

I've done some experimenting with remote controls, and found that my phone camera can see the flashes fine but only up to about 2m distance. And that's too close for my purpose.

The idea is that I want to lead people to a certain place, and from there they have to scan the surroundings using a digital camera, to see these IR flashes, which will be at a rate of 1-2 per second.

Now my main question here at this moment: is this even possible? Can we get IR LEDs that are so bright that they can be seen by an unmodified digital camera from 10-15m distance? And if so, how?

Obvious ways to increase brightness are to get a super-bright LED, have a narrower beam (I've seen 5°, normal RC LEDs have something like 20-25° beams), or pushing them with a very short, but high current pulse - other posts claim RCs may use 500 mA pulses.

Important is that it works for unmodified cameras, without special night mode. Cheap cameras will likely work better (poorer IR filter), though expensive ones may have a night vision mode which would make this a no-brainer but can't count on that.

Any experiences? Thank you in advance for any replies!

Wouter.

 

I think you already fell on the answer by yourself. High current pulses are allowable at low duty cycles. It depends on the exact part you are using to find the ratio.

 

The question is not as much "how do I boost an LED", but "will this be possible to begin with". Can one boost an LED (starting with a high efficiency one with narrow beam) to make it visible on a normal digital camera at 10-15m distance?

I hope anyone tried this out, so I don't have to waste time and money on what may be a doomed experiment.

 

Doubt that anyone else has done that, but I guess anything's possible.

You can get more output IR by using several LEDs close together. By increasing the number of LEDs experimentally you will eventually find how many will do the job.

They also sell IR illuminators and high power IR LEDs for night vision cameras that will likely be bright enough for you.

 

5W IR LEDs from a China supplier on ebay.

A guy in my class did a project to project IR light onto a movie screen to prevent camera piracy in theaters.

The IR LEDs were pretty "bright" but required a decent power source and a heatsink.

 

... I'm trying to have an IR LED visible on a mobile phone from a distance of at least 10m (preferably 15m or more) in the dark (at night; under trees; no light sources around other than the moon and the stars).

I've done some experimenting with remote controls, and found that my phone camera can see the flashes fine but only up to about 2m distance. And that's too close for my purpose.
...

Your phone camera should crank up the gain when it is outside in the dark, something like a IR LED from your remote control should be visible at a lot more distance than 2 metres. Most cameras will see a remote control LED fine even with indoor lighting from a few metres.