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Topic: Arduino Sleep for hours ? (Read 2227 times) previous topic - next topic


Guys i am developing a system for measurement but it only needs to measure like 1 time per day....

The problem is it needs to be the lowest power consumption i can make it....

But the watchdog only can sleep for 8sec and then wake up, is there a really low power external alarm system like a chip you can program.
I saw that the 555 chip isnt that great for high intervals of time but does anyone recommends me anything ?

Will it take too much power if it sleeps - wakes up adds a counter and sleeps again do that maybe 1000 times... Maybe it will use to much energy on the wakeups....?

Nick Gammon

Check this out:


Any sort of external chip is itself going to use power, so I'm not sure if you totally save much. I think I would go with the 8 seconds watchdog, coupled with some of the other suggestions on that page. For one, running at 3.3V rather than 5V saves about 10x the power, so in the milliseconds it is awake it uses less.

You might also look at the fuse settings - at some settings it takes 65 mS to wake up, at others under 1 mS. So the less time it takes to wake up and add 1 to a counter the better.
Please post technical questions on the forum, not by personal message. Thanks!

More info:


That is a really good post!!!

I will be using arduino pro mini 5v with a 16Mhz crystal.

It will only need to measure some ultrasonic sensors data and send info with a gsm/gprs shield once a day.
I will look into those fuse settings

I will be using  a 6v battery and the regulator that comes with the pro min wich i think doesn't use much power.


Look at post http://arduino.cc/forum/index.php/topic,99588.0.html

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