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Hello Orlando

I am constructing a visual light communication system for indoor communication. My transmitter is an RGB LED panel (50 LEDs for now am planning to make a bigger panel) mounted on the ceiling and serial data is modulated onto the LED light. The three colors in the LED are for creating three communication channels that can be separated by the use of color filters at the receiver. The receiver is placed at the table top about 2 m from the ceiling. I had been using a photo transistor that is part of a photo interruptor at the receiver side and displaying the data onto a computer. It is working fine upto 28800 bps but only after the light is focused by the use of a convex lens onto the detector so difficult when the receiver is mobile.

I need a detector (photo diode or photo transistor whichever is better) that can give me some freedom in movement, the data rate of at least 14400 bps is enough for me. Could you suggest me a better option ?

Your help is appreciated..

Natasha

P.S. The area of movement is round about a square of side 200 cm.

Hello Natasha,

I think, if I understood your issue correctly, this is due to not having enough light hitting the detector. There are number of factors that can paly a role here, starting from beam angle of the LEDs. The gain setting on the detector can also paly a role. As a check, you can take the detector closer to the light source and see if that helps. If it is the amount of light that is not sufficient for the detector, this test will help. If it helps, you can find a detector that has the feature to set the gain of the internal trans imp. amp (amplify the light before processing) externally and have the issue solved. Avago Tech or TAOS will have RGB sensors that you can use. I hope this helps.

Hello Muhinthan

I have attached the system block diagram and the experimental setup in this the post just before. If it is the issue of less light hitting the detector, will increasing the number of LEDs and using a detector with larger surface area solve the problem in some extent ?

Thanks

Natasha

Hallo Orlando,

i'm a FSE at Farnell.

So many times customers coming up with a question about a component they are currently investigating for.

I still don't know a good portal to search ( and find ) components by specs. 

I.E.   a customer is lookig for an   Infrared LED with high output  

              -  roundabout   740nm

              -  fast    <= 12-15ns

              -  100mA

any idea or suggestions ? 

thx in andvance

Cheers

Goetz