I'm not going to lie, i don't have a lot of experience with electronics. However, I have an Arduino lying around and i thought it wouldn't take much work to turn it into an ad hoc data capture device for an optics project i'm running.
A laser goes through a bunch of optic dealies and hits a detector with an intensity, the detector then outputs a voltage which corresponds to that intensity. Until now i've just been reading it with a multimeter, however, it would be a lot less tedious if i could log the data directly into my computer.
The problem is that the detector will output anywhere from nothing to 0.7v when the experiment is running, but will spike to 12v when the main light is turned on between sets. I talked to some friends and they suggested using an op amp as i could tune it so that the voltage wouldn't exceed 5v for the arduino, yet i could also amplify small signals.
After some reading, I thought i'd give the circuit below a try with a TL081 Op Amp.
The pot is so the amplification could be tuned as the maximum input varied.
Running it for the first time, the arduino just returns a slew of values in the ~830-833 range when i would have expected anything from 0 to ~1000. The software side seems alright, so i'm assuming it's the hardware that's letting me down. Is the circuit i picked just plain ridiculous or is there something else i might be doing wrong?
Thanks for any help you might be able to give!