low power relay

Thread Starter

nivlac

Joined Dec 5, 2019
1
I have a raspberry pi that I would like to turn off for 3 days then turn on for 3 hours then go back to an off state.
And if there was a way to adjust these times from site to site.
Thanks for any help
 

Marley

Joined Apr 4, 2016
344
Is this to save battery power?
One way to do this will be to use a low power relay driven by a simple micro-controller.
The 3-day time is done by counting clock cycles in a large (probably 32-bit) counter in software,
Similar method for the 3 hour time. Accuracy will be low, however.
Or, use a time switch driving a relay (or one that contains a relay). There are some low-powered time switches available
Like this.
 

dendad

Joined Feb 20, 2016
3,317
Whatever way you do it, make sure the RasPi controls the OFF time so it actually shuts down correctly. This will stop the SD card being corrupted.
So, a small low power micro, once every 3 days, turns on the power to the RasPi, say for 20 seconds, or enough time for the RasPi to boot and generate a square wave signal that drives a charge pump to hold the power on.
Then the RasPi holds the power on until it shuts down, stopping the square wave, releasing the power again.
 

Marley

Joined Apr 4, 2016
344
So, a small low power micro, once every 3 days, turns on the power to the RasPi, say for 20 seconds, or enough time for the RasPi to boot and generate a square wave signal that drives a charge pump to hold the power on.
This is the proper way to do it. Instead of a charge pump, the micro can monitor the square wave generated by the Pi and drop the power some short time after it stops.
 
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