After getting @
Gordon Gecko's excellent LAPD badge, I'm slowly getting the rest of the ID wallet together. I've got a wallet in transit from the US, so in the meantime I'm working on a backlight system for the ID. I got a few parts together and knocked this together for a test in the lab during lunch:
The backlight needs to be as thin and compact as possible to fit in the wallet, so my idea is based on a very cheap replacement backlight panel from an older-model iPhone (the one in the picture is from a 5S i think). As standard, they contain 6 tiny right-angle LEDs that shine into a diffuser panel. The panel runs at 18V (6 white LEDs x 3V), which is really too high to get from the size of battery I had in mind. However, you can get very tiny 3V to 12V boost converters which would allow me to run the panel with 4 LEDs at 12V. Here's a closer look:
Notice the silver appearance when it's off, just like the pictures of the real prop.
The tiny PB on the left is the boost converter (from Pololu). I carefully split the backlight panel open and peeled off the flexible PCB that the LEDs are mounted on. I then unsoldered 4 of the LEDs, mounted them in series on the edge of the piece of stripboard, and then cut the end off the base of the backlight panel so I could get them in contact with the edge of the diffuser. The final version will have the backlight panel mounted on the stripboard, with recesses cut into it for the battery, boost converter and a reed switch (so it will be turned off by the presence of a magnet in the badge side of the wallet).
The bench PSU I tested it with only went down to 4V, but I tested it with a 3V CR2032 coin cell and still got 11V out of it, which was still enough to light the LEDs at reasonable brightness. I plan on using a 2mm thick Lithium-Manganese 'pouch' cell which can deliver a bit more current than the coin cell though, which will hopefully get the voltage up nearer 12V.
Although I have a wallet on the way, it would help a lot if someone could measure the dimensions of the ID window from a police wallet (and a standard US police ID card), as that will tell me which backlight panel I should use as a base.