Here's the thread that started this project going.Here's the build document.PCBs are here.
I have received some emails with questions about the project so I thought it would be a good idea to start this thread to have these questions and answers available to all who might be wondering.
I wasn't sure about the orientation of the NSL32 - can you help me understand how to orient that?
The optocoupler orientation goes like this: the LED side is the one with the short legs, the resistor side has the long legs. The resistor orientation doesn't matter, just like a regular resistor. The LED does matter. The negative side is the one indicated by a little white dot. The PCB has a + sign next to one of the pads, obviously put the positive (non-dotted) side here and the dotted side next to it. Then feed in the resistor-side legs.
I don't know about the dot you're talking about. Mine doesn't have one at least. One end, I think it was the short lead side, has writing on it. The other is glossy smooth. I have the writing side on the + side of the PCB. Is there a way to measure with my DMM?
I believe you have it in wrong. The end with writing on it is the resistor side. The glossy side is the LED, and the dot marks the negative LED lead.
Are you sure you've got an NSL-32? They should all have the white dot. As with all things, the datasheet reveals much:http://www.alliedelec.com/Images/Products/Datasheets/BM/SILONEX_INC/Silonex-Inc_Actives-and-Passives_6995014.pdf
There is a way to check with a DMM, but it's convoluted. Connect 9v to a 10k pot's center lug, and connect one of the short NSL-32 leads to one of the outer lugs of the pot. Connect the other NSL-32 lead to ground. Put your DMM in resistance mode, in the 200k setting, and put a DMM lead on each of the long leads. You should have some resistance. If the resistance you measure varies by turning the pot, then the short lead connected to the pot is the positive one. If there's no resistance, or it doesn't change, then flip the short leads around and try again until you can make the resistance change by moving the pot.
Now, that's a pain, so I'd recommend first verifying that you have the right optocoupler, and trying to figure out why there's no polarity mark on it.