Ca I use a surface mount 0603 LED as a photodiode?

[kennyden]

Hello guys,

I understand from reading this great paper at "

http://www.merl.com/papers/docs/TR2003-35.pdf"

that an LED can basically be used as a light sensing device for communication (surprised don't you!?) Well perhaps some of U?

So my question is: has anyone tried this using a surface-mount LED (0603 more specifically) in this fashion?

I have very little time so If someone has ever done it and had success, please let me know so I don't waste my time trying it.

BTW, before you ask, NO, I have no room for an IR transceiver so if I could use my existing LEDs as a mean to communicate this would be great. Besides, I don't need much TX/RX speed.

Thanks.

 

[Skogsgurra]

Yes. Any LED works as a photodiode. Anytime.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[kennyden]

Thanks Skogsgurra.

You make it sound like something obvious. Have you ever used SMD LEDs as photodiodes in one of your projects?

I understand why it acts as a photodiode but I guess I'am more concerned about how well it works in a real world application. So if anyone has ever used surface mount LEDs to communicate, I'd be happy to know how reliable and succesfull it was.

Again, thanks for you time.

 

[IRstuff]

I don't think that you've given sufficient information about your application, nor is it possible to get sufficient about the LED to determine the efficacy of the reception. High performance or long distance requires receivers specifically designed and tailored for such applications. Going across a room probably does not. It will also depend on how much signal you can get onto the detector.

This is not something that can be trivially answered.

TTFN

FAQ731-376

 

[kennyden]

I understand your point IRstuff.

But again, I was hoping that someone would have had the experience of having two SMD LEDs successfully communicate with each other at any speed, any distances and by any means.

I’ve seen similar demonstrations on youtube but none of them were using SMD LEDs. So I wondered if there was anything I should know about using SMD as opposed to thru-hole LEDs.

So since there are no objections so far, it seems I’ll give it a try and see what happens. There is no better way to find out right...

As for my application, the source (one LED) and receiver (one 0603 green LED) are less than 2 centimetres apart. If I can achieve 9600 baud half-duplex, I’ll be more than happy. LEDs are driven (and reverse biased by a CMOS uCTRL).

Also, I can guarantee that no ambient light will create interference at the LED receiver. So there will be a direct optical link between the emitter and receiver. The only thing though is that light will need to go through a translucent rubber keypad and PMMA tube (Plexiglas). So this may attenuate the signal a bit. Nonetheless, I assume that operating the transmission in a dark environment and at such a small distance that it should not be an issue.

Of course, if the physical link works, I’ll need some higher level communication protocols, but this is another story.

Thank you again.

 

[MacGyverS2000]

It works, and it works well, so long as your circuit is designed appropriately. The fact you're using SMD LEDs is irrelevant, other than the viewing (and therefore, receiving) angle of SMDs are usually significantly wider than through-hole.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[GreenEE]

The lens will work the same coming in as going out - Wide angle out, wide angle in. Etc. Narrow angle high optical gain, wide angle low optical gain.