Have you ever needed to log some data over a long time period, say months or years? This low power data-logging Arduino shield designed by Dead_Bug_Prototypes can last on one battery. Taking samples once per hour it will last about 1.75 years from an alkaline 9v or up to 3.5 years on a 7.2V 900mAh LiPo battery. Tindie buyers have left reviews for the shield with uses ranging from logging battery voltage in a remote antarctic camp for 3 months to logging the temperature in a vegetable garden.
So why use this shield in the first place? It turns out that using a normal Arduino board to log data long term is not possible due to the relatively large standby current drawn by these boards. Things like voltage regulators and pullup resistors on the board draw a constant 5-15mA which may not sound like much but will seriously restrict battery life. Dead_Bug_Prototypes measured his Arduino’s standby current at 25mA and got only 36 hours of run time when taking measurements every 30 seconds. After adding his shield and repeating this experiment, the data logger increased that time to 14 days.
The shield works by bypassing the Arduino’s stock voltage regulator. It then uses an on-board Real Time Clock (RTC) to wake up the Arduino every few minutes, take a reading before cutting all power to the Arduino. This means the Arduino is hardly ever powered, which gives huge energy savings compared to it just being in sleep mode. Data is stored on a micro SD card, making simple to pop out and copy over to your computer.
