I like the approach of suspending the batteries in cutouts to reduce the height of the board. Same with the magnetic reed switch - that's for detecting opening I'd guess?

Hi Dan,

Yes the reed switch basically is the main power switch for the entire design (The mechanical switch was used for development and is not populated).  Switching off the batteries when the card is closed was definitely one of the trickier parts of the design.  The reed switch is normally open when no magnetic fields are present.  

There are actually two magnets in the card, one of the left pamphlet, and one right under the reed switch in the right pamphlet.  When the card is closed, the two magnets actually negate each others magnetic fields out which allows the reed switch to relax and remain open.  When the card is opened, the magnet in the left pamphlet is taken away from the magnet in the right pamphlet, which applies a magnetic field to the reed switch and closes.

I plan on adding more details to this project, as well as upload updated design files as the project progresses.  Currently I have a prototype working, but there are still a few tweaks I wish to make.

Yeah, that is a tricky arrangement for the reed switch. I like the layout of the "candles" too - although it took me a minute to find the MEMS mics. I was looking for cans with tiny holes in them.

The microphone and LED's were also tricky.  I used LED's that get mounted on the opposite side of the board, and the LED goes through the board to show indication on the opposite side.  This was nice because it kept my card mounting side of the PCB very flat, and it allowed to be use a single stencil for all of my surface mount components.  The microphone had similar constraints.  Likely they have microphones where the port is actually on the bottom (soldered side), and you simply need to provide a drilled hole in the PCB to allow access.  Power management and form factor were definitely the more tricky parts of the project.