Electronics > Beginners

The energy cost of powering down vs deep sleep

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ledtester:

--- Quote from: Peabody on September 28, 2019, 02:24:40 pm ---Even if the sleep current is only 1µA, power shutoff still looks good.

--- End quote ---

To properly compare the two you should take into account the amount of energy required to get your software up and running from power on -- i.e. initialize its state. This is work that won't have to be done if you just wake the microcontroller from deep sleep.

james_s:
Just to put things in perspective, a 1uA draw would take 200,000 hours (~22 years) to drain a tiny little 200mAh CR2032 coin cell. Just about any battery you would conceivably use will die from self discharge or leakage before a 1uA draw would become noticeable.

Peabody:

--- Quote from: ledtester on September 29, 2019, 03:01:49 am ---
--- Quote from: Peabody on September 28, 2019, 02:24:40 pm ---Even if the sleep current is only 1µA, power shutoff still looks good.

--- End quote ---

To properly compare the two you should take into account the amount of energy required to get your software up and running from power on -- i.e. initialize its state. This is work that won't have to be done if you just wake the microcontroller from deep sleep.

--- End quote ---

As I said, I'm new to ESP8266, but my understanding is that waking one up requires a reset.  There is no pin change wakeup from deep sleep.  It that's the case, then the same initialization would be required either way.

Peabody:

--- Quote from: james_s on September 29, 2019, 03:30:45 am ---Just to put things in perspective, a 1uA draw would take 200,000 hours (~22 years) to drain a tiny little 200mAh CR2032 coin cell. Just about any battery you would conceivably use will die from self discharge or leakage before a 1uA draw would become noticeable.

--- End quote ---

Yes, I just wanted to be sure that powering down wasn't somehow worse than that.

But I do need to look at the deep sleep option and see how the mailbox door reed switch could reset the 8266.  I'm thinking maybe an inline capacitor like DTR has on AVRs.

james_s:
The proper way to do this is have a timer interrupt that wakes up the mcu periodically and polls the pin, or use a hardware interrupt pin.

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