Sensor to detect LED on/off

Looking for a sensor that can be put over an LED and open/close depending on whether the LED is on or off. Example use cases would be detecting whether dryer is on or off, a cooking surface is hot or not, etc. These would be cases where wiring directly into the LED circuitry isn’t practical. In my case, I want to detect when a Robovac is docked or not (there is a rather bright LED on top that shines when the vac is not docked).

There was mention in a thread about “LED identification sensor” but have found nothing like that. Something like that could be built using a photocell (light-dependent resistor), I guess, but like the idea of something in a package. A lux sensor for dawn to dusk detection would be overkill and a bit larger.

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Is this what you are looking for?


Well, yes, I have to say that pretty much is exactly what I was looking for, though the $48 price tag might be a bit much. Guess I was thinking about just the sensor that opens/closes so I could just wire it into an existing Konnected zone.

I'm in the middle of a project where I am wiring a Tasmotized node mcu with a BH1750 light sensor to send HTTP requests to HE to change a virtual lux sensor. I am doing it to detect the LED on the front of an Echo Flex so I know when she is activated/speaking


True, Black Friday and cyber Monday will be here soon.

I've been using 3 of these sensors for a couple of years for exactly that - the photoresistors are mounted next to LEDs on my HVAC zone controller, with the relay outputs going to a Konnected board.


I use these on washer and dryer to detect the "done" light. They work very well. Warning: direct sunlight will trigger them, so I cover the sensor and about 2cm beyond with electrical tape.
If you plug them into AC, they become repeaters as well.