Finally finishing it up with a ton of help from Nick. It's ugly as hell on the inside but works just fine. Probably order up some new supplies to make a nicer, more durable one as my soldering (lack of) skills made a mess.
Looks great for a first attempt.
What parts / schematic did you end up going with?
I used the same exact components as Nick listed at the top of the discussion. The 3.5mm jack from Mouser is a pain but I did like he did and clipped the unused tabs off the back, filed them down and put some superglue over the remaining exposed metal to ensure I didn't get any solder on them. Those are the only jacks I've found with the longer "neck" that would reach outside of the fob. I found some easier to solder ones on Amazon but they will take some extra work to get the jack up to or even with the fob wall.
Understanding the whole Tip/Ring/Sheath and where they go was the hardest part but Nick's helpful instructions are:
Assuming you used the SJ-3541A-TR-67 connectors from mouser and you're using a standard TRS (tip, ring, sheath) plug, the sheath is the ground and spots 1 and 4 serve the sheath. They're the outermost posts on the back.
The grounds for both 3.5mm jacks will connect to one another as well as the negative terminal on the battery.
For the jack serving the microphones, spot 3 (the middle post, for the ring of the TRS plug) will get the capacitor(+ side)/resistor, with the negative side of the capacitor going to spot 3 on the jack going back to the recorder.
Spots 2 and 5 serve the tip of the TRS plug. Pick one of those (either works, so I went for the one that helped space everything out as far as possible) for the second capacitor(+ side)/resistor, with the negative side of the capacitor going to either spot 2 or 5 on the jack going back to the recorder.
The positive lead from the battery goes to the other end of both resistors.
Topic: DIY key fob battery box (Read 36125 times)