Britton Kerin has launched an Arduino add-on designed to dramatically improve your projects' battery life: the Battery-Saving Arduino Power Supervisor Shield.
"This shield lets an Arduino turn itself entirely off, and get powered up again after some time passes or other conditions are met," Kerin explains of the board's design. "This makes long-term battery power viable with a standard [Arduino] Uno Rev3 or the like. There’s also a connector to switch an additional external load from the Arduino."
"The underlying problem is that voltage regulators capable of driving loads like those found on many Arduino shields waste some power at no-load. For example, the NCP1117 regulator on the Uno Rev3 has a quiescent current of up to 10mA at 15V input (5V output). Smaller regulators waste less power but can’t handle much load. Better regulators are available but none of them are good enough. A staged power system wouldn’t be appropriate for the Arduino itself, because it emphasizes simplicity and modular design. This shield effectively adds a low power supervisor stage."
According to Kerin, the shield - which uses the popular Arduino Uno form factor — drops the idle power draw of a project to 30uA in sleep mode, while allowing the system to wake based on a timer set using on-board jumpers from one second to nine hours. For more advanced users, an optional mode allows the Arduino to request a longer sleep period than is configured on the jumpers — and the shield can also wake the Arduino when the connected battery's voltage reaches a minimum threshold.
"Usually all that’s really necessary," Kerin says of the board's use, "is to program a sleep time using jumpers, connect the sleep request line to an output of your choice on the controlled Arduino, and connect a battery."