Direct sunlight sensor

Sylvia Else · 2015-10-29T06:41:59+00:00

I want to make something to detect whether there's direct sunlight shining on particular place. I thought the obvious approach would be to use a pair of light dependent resistors (LDR) - one located where it will definitely be in direct sunlight (when the sun is shining) and another that is at the location to be tested. Compare the resistances, and the result should be clear enough. But this means that at least one LDR will be in direct sunlight for extended periods, and I can find nothing in the datasheets to indicate whether the devices will survive that. My concern is UV degradation of the encapsulation material. I can put them behind glass, which will provide some protection, but even then, they'll have to survive some UV. Anyone have experience of this? Sylvia.

Oct 29, 2015 40 Replies

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Joe Hey 10 years ago

I think you don't need to worry too much about saturation. In 'really bright sunlight' the shaded photo diodes will be far from saturated and all your equations will still hold.

In case

1: I1 >> I2, I1 >> I3 2: I1 >> I2, I1 ~ I3 3: I1 ~ I2, I1 ~ I3

I like it.

joe

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