For an upcoming project, I want to see how little power an arduino will require so I bread boarded an Arduino RBBB (really bare-bones board):
This simple project simply turns on an LED if you press the button lower left.
To reduce the power consumption, I put a switch on the power LED (upper right). I took a milliamp measurement of this simple circuit and it was drawing roughly 22mA. The 9V battery used would last at most 24 hours.
I then installed the Narcoleptic library on the arduino. Looking at the code of this library, it essentially sets a watchdog timer and puts the CPU to sleep. You tell it how long to sleep. When the interval completes, the CPU wakes backup and functions normally.
I configured it to sleep for 500ms. So it would check for the button to be pressed every 500ms. If pressed it would light the LED for 2sec. Either way, it would then go back to sleep for another 500ms.
I then measured the current drain with the new software: .7mA – that’s like 1/30 of the current. That extends the battery to roughly a month of use.
That is a MAJOR improvement. Unfortunately still not good enough for me because I really only want to replace the battery once a year at most.
Doing math on various batteries, I could use 4 D cells and that would last longer than a year though it would be kind of big. So that is a possibility.
The other possibility is using a rechargeable battery and solar cells. I’ve never done that before and I’m game to learn something new, so I think that will be my next step.