Experimenting With Using an LED as a Light Sensor

RE: Experimenting With Using an LED as a Light Sensor

DAB — Fri, 03 Apr 2020 18:12:29 GMT

Very good experiment.

It is one of those projects where you know intuitively that it will work, but it is always fun to verify theory with testing.

DAB

RE: Experimenting With Using an LED as a Light Sensor

Fred27 — Fri, 03 Apr 2020 10:04:17 GMT

Great stuff, Jon. I knew this was possible and mentioned it recently on Dubbie's recent Laser Activated Display. I've never tried it myself though.

RE: Experimenting With Using an LED as a Light Sensor

dubbie — Fri, 03 Apr 2020 09:53:21 GMT

A good solution. I had a go at getting this to work and failed but I think that was because I wasn't using a large enough resistor (I used only a 10kOhm resistor) and a 5V power supply. Maybe I'll have another go now, although I'm not sure I have a 10 MOhm resistor.

Dubbie

RE: Experimenting With Using an LED as a Light Sensor

jw0752 — Thu, 02 Apr 2020 22:26:05 GMT

Hi Jon,

Actually I think that this was quite an important experiment. Finding out and experimenting with the fringe properties of components can lead to a better understanding and who knows there may even be an application under certain circumstances.Perhaps you can use it as an isolated bidirectional communication between two Arduinos.

John

RE: Experimenting With Using an LED as a Light Sensor

Andrew J — Thu, 02 Apr 2020 22:17:22 GMT

I Did not know that! Don’t pack it away just yet, turn it around. Attach a momentary switch on what is currently the output side and have the Arduino detect it. See if you can create an opto-coupler morse code receiver. If you can measure high and a short/long duration you have a dot and a dash. Might be fun.

RE: Experimenting With Using an LED as a Light Sensor

dougw — Thu, 02 Apr 2020 21:31:57 GMT

Cool experiment.

I have had problems with normal silicon rectifier diodes (1N4001) in opaque packages causing 60 Hz noise due to sensitivity to fluorescent lights. It seems most diodes respond to light. I have never tried to see if normal transistors are also sensitive to light, but it makes sense that they should be. I know phototransistors obviously are, so maybe it has a lot to do with the packaging. Is that why transistors packages are black?

RE: Experimenting With Using an LED as a Light Sensor

genebren — Thu, 02 Apr 2020 21:14:49 GMT

Fairly cool experiment! I too have heard of this feature of an LED, but I guess I never found a need to use this in this way. Thanks for sharing!