This is a locking SD card holder, compatible with both 3.3v and 5v systems. It uses a hex buffer to drop the 5v logic down to 3.3v, and includes a 3.3v regulator to power the SD card, which is only active when the 5v pin is powered. You can safely draw 400mA from the 3.3v line without endangering the SD operation if running in 5v mode.

This design started off when I was working on a sounding rocket payload. Our team used a standard push-push SD card holder (push in, click, push in again, card clicks out), this seemed good enough, and it survived initial testing quite nicely. We put our project together, and launched it into space. When it was recovered, we had some rough hours of panic, as our SD card had fallen out of the socket due to the g-forces on re-entry. Miraculously, our data was still there, but it could just as easily have fallen out on launch and ended our project in disaster. Determined that this should not happen again, I looked for a better breakout.

I noticed that there was not a locking SD card holder breakout available on the market, so I've designed and constructed a breakout board that will keep SD cards in place through rough movements and shocks. You may not be launching space payloads, but this holder will definitely keep your cards in place through whatever you subject your design to. I also included holes for zip ties or string if the SD card is planned to be semi-permanently mounted.

SD card is not included.