I've measured 2 LDRs of the same size from the same package. One gets up to about 40k at perfect dark, one over 2megohms. I'm almost 100% confident I"m not measuring anything wrong. I measured one of the smaller ones and got no resistance at all. One of the larger ones was pretty close to the higher-resistance one of the two, but there's still a bit of a different-but an OK difference. Anyone else experience such problems?
-Colinc
Might depend. I bought a assortment of several there, and they (surprise!) turned out to be a assortment. Several appeared the same, but were not.
Yeah. I measured 6 more, some smaller types and some larger types. One smaller type had a ton of resistance, one had very little, the other two were about "medium". Really, I've yet to find 2 that are reasonably close to the same, even if they are the same size. Are the LDR's available from smallbear reasonably consistant?
-Colin
I wouldn't be surprised if some of those "assortments" contain manufacturing rejects that didn't meet specs.
I've bought a couple of those assortment packs because they had a nice sealed unit in them. The "raw" cells are all over the place in my experience too.
Take care,
-Peter
Seems like it's hard to find ones that go to a low enough resistance is the 'trick?'.
I don't need 2 meg much, if I could get one that works like a 100k pot resistance range wise...I don't know that they even exist like that...
Smallbear got the opto-couplers you need...
To me, it only makes sense that they're all over the place, resistance-wise. I can appreciate that. Usually, if the specs aren't listed, assume the worst. :)
FWIW, I bought a $5 clairex for a specific application, but instead one of the RS cells turned out to have the goods.
radio shack used to have the specs for their LDR assortments (the blister pack of 5) on their website. i don't know if it's still there, but you could look around, and it may help. all of mine were pretty close to the specs, if i remember right. none of them were the same values though. even the ldrs that looked the same were apparently different models, and spec'ed as such on the data sheet.
"Welcome to Radio Shack. Would you like to try Sprint? Can I have your phone number?"
Get them from Steve- he will have what you need.
Doug
i woudl take your defective ratshack ldrs to them and explain that they are problematic i got mine because i didint' have time to wait for them and all of mine are from 500k-2.5M in theyre dark mode and a flat 0 on most of the light mode from an led two were at 4k.. thats perfectly acceptable for me.
also if they ask you for you phone no. ask them why cause my brother works there and they have been instructed to no longer ask for a phone no. unless you are using a check.
If you want cheap LDRs, you can try getting cheap/dead mouses, the ones with the ball. There's two inside each one of those, and the ones i've measured go from 5k to 500k-1M (i tested quite informally ;) ).
I'll use them in some build and report how they work.
they work good actually there gringo. yours only have two.. most of mine have at least four.. ???
but yeah they are reall cheap. and easy..
Sometimes those photo sensors in mice are not LDRs but photo diodes. Becareful.
If your building a common project then Small Bear will set you up. If your building something with a very specific range needed you can order from some good part suppliers like Digikey and Mouser.
RadioHack stuff is intented for people to experiment with and not for serious building.
Andrew
yea, I liked those cased ones, but I couldn't get anything out of the exposed ones...they read 0 with light, and about 10k (? my AMM needs batteries and im lazy) dark. the other one is about 10k light, 1M dark. Much better....but i guess i could work with either...
and I agree with Andrew, this stuff is not made for production...not only unstable, but too damn expsensive...
Buy opto-couplers from Small Bear. The cells in them are designed for low distortion of audio signals, not turning on lamps at dusk and other stuff where linearity doesn't matter (and is often HORRIBLE). Bargain packs of LDRs - aren't.
AND BTW,
The correct name of the merchant is RADIO SLACK :lol:
ok, surprised it didn't come up earlier...
Colin, please define "bunk"
thanks you :-D :lol: :D
Quote from: Halok, surprised it didn't come up earlier...
Colin, please define "bunk"
thanks you :-D :lol: :D
It's a favorite word of mine-meaning "a failure". Sort of like, the whole project was bunk-the whole project was a failure.
-Colin