A system to truly control the power saving for any project that is created using development boards, which isn’t power saving in nature !
The Idea
Almost every modern microcontroller comes with power saving / sleep functions to reduce power consumption of a system. This is useful because it provides longer battery life, reduce carbon emission ( think about billions of microcontrollers ) and save cost.
But there is a problem, when you built a project using a development board rather than just using the bare microcontroller, sleep is not going to save power.
Most development boards have a power LED which is always on, there are debugging circuits and sensors on board which consumes power even though the primary mcu is sleeping. Another culprit is on board voltage regulator which draws quiescent current all the time. Development boards are USB powered which runs on 5 volts but the mcu on the board is usually runs on 1.8 Volts to 3.6 Volts. Lot’s of power is wasted even when the main mcu is sleeping.
Here is a nice article on this matter from Sparkfun.
The solution is simple, use another bare bone low power microcontroller to control the power for the entire development board. Here, my solution is to use a Attiny 84 to periodically on and off the development board as required . The timing can be user programmed. The system will power down both itself and the development board powered through it.”

Link