Determining polarity (with multimeter or otherwise?)
Recently put together a project, a 32u4 interface board to a RS232 device. For a first time out, a number of things went wrong (badly burnt my board, melted an LED, etc)
But at the end of the day, the damn thing basically worked (except it was undervolted; I think the Max3232 was a poor choice and I need the 10v off a 232a, but that's neither here nor there).
Here's the problem: I looked at my 10uf tantalum cap and convinced myself that the big stripe with what sure looked to me like a "-" on it must be the negative side...
so you can imagine my surprise when it let all its magic smoke out and remained a glowing cinder for some time. I tried replacing it, checking connections, checking voltages to be sure the + side was + and the GND side was GND, and the second cinder lasted even longer (the miracle is that the ATMega actually survived all this happily). I eventually patched over the smoking crater with a wire...
and just dropped both the 10uf cap and the power LED and the circuit seems to be working fine (aside from the undervolt from the 3232). I still don't know if the cap was marked strangely or if something was badly wrong with the circuit.
So, the point of all this:
Is there a standard marking for SMD polarized caps? A standard way they are loaded into the reel tape? Or a way to use my trusty EX330 multimeter to figure out which end is which? Same with diodes; I can't find any useful marking on the LEDs at all:
(incidentally... if you do any SMD work, I LOVE my USB microscope, basically the same one sold here. Highly, highly recommended)