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I am trying to add an on and off power switch to my arduino project. My project is running off a 9v battery and I would like to save as much power as I can. There might be a better why that I don’t know. I added SLEEP_MODE_PWR_DOWN to my project and from what I can tell, the arduino enters sleep mode. I am having a hard time getting the arduino to wake from sleep mode. Am I able to do this from a full power down? I have been reading this link. http://www.gammon.com.au/forum/?id=11497 and others.

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  • Yes, I am using a Uno.
    – user1277281
    Feb 27 '15 at 5:01
  • It would also be helpful to know what else are you powering in your project (sensors, modules etc.), their part numbers and their typical and maximum current consumption.
    – Ricardo
    Feb 27 '15 at 5:12
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    Is there a problem with an actual switch? You could store state in NVRAM... Feb 27 '15 at 8:40
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Since you are using an Arduino Uno board, putting the MCU (the ATmega328P-PU) to sleep won't save you much battery juice. Putting the MCU to sleep won't make a difference because the voltage regulator on the Uno will waste a lot more power than anything else on the board. The ON LED will also draw significant amount of current on that board.

To really save power you should look into getting an Arduino board that has a more efficient voltage regulator, or use no regulator at all by changing your 9V battery by, say, 4 NiMH AA cells.

Here's some more information about the issue for you to look at: What are (or how do I use) the power saving options of the Arduino to extend battery life?

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    And the usb-to-serial chip on the Uno will also consume power.
    – Gerben
    Feb 27 '15 at 14:29
  • I will end up moving off the arduino board and just use what is needed down the line. I have read about this being an issue. Feb 27 '15 at 16:55
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There is a very good write-up on how to save power, use sleep mode etc, at: http://www.gammon.com.au/power

This includes step-by-step examples of what was done to save power, and how much power was saved, including examples on how to go to sleep and wake back up.

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