Hello =),
I'd like to make a "probe" using an arduino waterproofed by a box and fed power through a solar battery (charging through the simple power rectifier diode concept) - but the solar panel will not feed enough power for a 24/7 uptime nor will the battery have enough capacity to hold the entire night with a UNO pumping those mAh.
So the question is: is it in any way possible to power on an arduino for a defined period of time and then make it turn off completely the rest of the time?
I've read on the forums people talking about getting the arduino to sleep but the power consumption was still around 20mAh.
It depends what you are trying to do. If all you need is to check a simple switch once a second then the Arduino can spend 99,999999 % of its time in deep sleep with fantastic power savings. But if you need to check the same switch every 10 micros then your not going to get any power saving and you need to provide a bigger solar array.
pixelsafoison:
nor will the battery have enough capacity to hold the entire night with a UNO pumping those mAh.
If you're looking for low power consumption then the very first step is to not use a UNO. You need a standalone Arduino or a clone designed for low power consumption.
you could always do something like have a supercapacitor which is also charged all day from the sun, and once the voltage drops below some level you begin discharging the supercap.
would take some design to boost it to the correct voltage (if you need 3 or 5V) and make sure the discharge was slow enough to last during the dark hours,
but there should be some value of supercap that would work for you if the sleep mode isn't an option. (or a smaller one if sleep is an option).