LED as detector for high speed link

klaus.kragelund · 2019-05-20T21:48:08+00:00

Hi For a test setup I am toying with an isolated interface where I need 1 Mbit speed if possible The receiver is a dirt cheap red LED: (which is also used as an indicator w hen the link is not active) 4.pdf If I use the same dirt cheap LED as transmitter I can get about 10kBit with small amplitude. However, I need a large amplitude, to be able to detect b it level with logic 3V. (so over 2.4V) The price of the emitter is not relevant. So I was thinking to use a white LED (to cover the entire spectrum of the RED LED detector), a big one, and driving it with a lot of current, to get sufficient photon level at the red LED to have both high speed and logic IO level An LED often have a different emission wavelength than the responsivity wav elength, so that is why I use a white LED to be sure wavelenghts overlap I will drive the emitter LED with high current, and then have a sufficient low load resistor for the red detector LED to have high bandwidth (1MHz) But, is this a good idea? Will I be overdriving the detector LED, is there some kind of saturation effect? For the setup, I could use Win Hills 200A pulser: Cheers Klaus

May 20, 2019 42 Replies

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Joerg 7 years ago

Ah, a serious retina burner :-)

Regards, Joerg http://www.analogconsultants.com/

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Klaus Kragelund 7 years ago

Yes. I was more careful with my setup than when I do high voltage. Voltage zaps, retina burn is not recoverable

Cheers

Klaus

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Joerg 7 years ago

Yep, got to watch for that in the field. All it takes is accidentally hitting a shiny surface that reflects it into an eye. I knew a guy who slowly turned blind because he got hit with a high power radar beam that way.

Regards, Joerg http://www.analogconsultants.com/

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