i have a diode running from the positive side of a capacitor to the vcc of a light strip.. it has markings that read "SB120 1222", i'm trying to identify this diode and it's purpose. does anyone recognize this specifically or have an idea of it's usage here?
That picture is a bit on the useless side - you are focused on the background and not the diode in question.
Searching Digikey.com, it could be a SB120 20v 1A Schottkey diode. Here is the page for it at Digikey - note the link for a datasheet for it on the page:
Fairchild SB120 Diode
My first guess at the 1222 part could be a date code, but I'm not sure on that (if it was it would be the 22nd week of 2012)
so if it's a 3.7v battery -> atmega328p -> capacitor vcc -> sb120 rectifier diode -> 5v vcc led light strip.
what would a rectifier be used for in this setup?
No idea what the intent is. A diode can be used for 2 things basically - preventing reverse polarity (which doesn't sound like the case here - I would have expected that between the battery connection and anything else) or to get a voltage drop which does not seem reasonable here either. Perhaps the LED strip has some sort of switching regulator on it and they are trying to prevent that from getting back into the Arduino supply? Your description of the connections doesn't make sense to me with what I see, so I can't provide any additional information.
It might allow the other end of the strip to be powered separately without risk of back-powering.
MarkT:
It might allow the other end of the strip to be powered separately without risk of back-powering.
Good point (which was sort of what I mentioned but had not thought about the possibility of feeding power in the other end of the strip (and those strips often have connections on both ends)).
A "5 V" light strip and a 3.7 V battery were mentioned.
I interpret the photo as having the diode feed away from the light strip.
I call "XY problem".