Reducing Arduino Power Consumption
Contributors:
Alex the Giant
Alex the Giant 
Resources and Going Further
More information on low-power modes and options can be found in the datasheet for the 328P.
For more power-related fun, check out the following SparkFun tutorials.
FemtoBuck Constant Current LED Driver Hookup Guide v13
The FemtoBuck board is a high-efficiency, single-channel constant-current LED driver.
Measuring Internal Resistance of Batteries
Classroom STEM activity that has students build a battery from a lemon, measure the open and closed circuit voltages, and determine the battery's internal resistance.
ESP32 Thing Power Control Shield Hookup Guide
This tutorial shows you how to get started with the ESP32 Thing Power Control Shield.
MicroMod Ethernet Function Board - W5500 Hookup Guide
Add Ethernet and PoE capabilities to your MicroMod project using the Ethernet Function Board - W5500.