Datasheet

The SD Activity LED is connected to the clock pin, it will blink when data goes over SPI,

which can help you detect when its ok to remove or insert the SD card or power down the

Arduino.

The Level Shifter moves all signals from 3.3 or 5V down to 3.3V so you can use this shield

with any Arduino safely and not damage cards. Cheaper shields use resistors to level shift,

but this doesn't work well at high speed or at all voltage levels!

Real Time Clock

This is the time-keeping device. It includes the 8-pin chip, the rectangular 32KHz crystal

and a battery holder

The battery holder must contain a battery in order for the RTC to keep track of time when

power is removed from the Arduino! Use any CR1220 compatible coin cell

CR1220 12mm Diameter - 3V Lithium Coin Cell Battery

PRODUCT ID: 380

These are the highest quality & capacity batteries, the same as shipped with the

iCufflinks, iNecklace, Datalogging and GPS Shields, GPS HAT, etc. One battery per order...

http://adafru.it/em8

$0.95

IN STOCK

3.3V Power Supply

An on-board 3.3V LDO (low drop-out type) regulator keeps the shield's 3V parts running