How does an LDR work?

Hi.

I am about to start my AS Level physics coursework, and as preparation have to find detailed info about how an LDR works. Much googling has lead me to negative coefficients, and the like. However, I can't actually find any info on what causes the resistance to chance.

Can any one help? Or at least give me some phrases to search for so I have somewhere to start?

Cheers,

Tim

My first shot a Google (second item down with "light dependent resistor" for the search string) gave me https://encyclopedia.thefreedictionary.com/Light-dependent resistor

It looks like there's an explanation there along with some cross-references. Vactec and Clairex were the biggies in the LDR business and both have been bought out by other companies. Perkin-Elmer of Hubble mirror fame owns one of them and an outfit in St. Louis has the other as I recall. A search under those name should get you contacts for some good information. I have databooks from Clairex, but they're in deep storage right now or I'd scan the theory pages for you. Clairex made some really neat optoisolators that used LDR inside rather than photodiodes or phototransistors and they had a variable output that you could work in with a voltage divider circuit to do some really neat things.

Dean

damnit! I hate it when that happens. You just manage to miss things like that...

ah well, thanks for the info. I will look up the manfs.

cheers,

Tim