Arduino power up by RTC alarm
July 24, 2012
I’m trying to build a data logger that will only store data to an eeprom once an hour, and to conserve energy and have it log data for long periods I would like to turn the power off for everything except the Real Time Clock (DS1337).
So this is my setup.
I have a power source and a voltage regulator (3.3V) that will power the RTC all the time. When the alarm is tripped a digital line on the RTC goes low for 1 second (I think) then I need to power up everything else and keep the power on while I take my readings.
Here I think I need a MOSFET or a transistor or something to feed power to the rest of my circuit, until the ‘Arduino’ (clone) is done and pulls a digital pin low (or high) to go back to sleep.
Any ideas ?
Could this work? Or if not, what could be done to make it work?
My plan is still to turn everything off until the RTC alarm pin goes low. Then I hoped that I could use a MOSFET to switch the power on for everything else.
So this is a schematic of my idea. The net ‘Main 3.3V’ (circled in red) will always have power and it goes into the source of the MOSFET P-channel (AO3401). With the gate pulled high by the pullup resistor R6 the transistor should be off and no current is flowing through to the microcontroller or other devices.
When the RTC alarm pulls the line low, the transistor should be on and supply power from the ‘Main 3.3V’ net to the ‘3.3V’ net and power everything else up. The very first thing the microcontroller should do is pull the connected pin low to hold the switch in the on position until all logging is done and the microcontroller can ‘kill it self’ by pulling the pin high an losing power until the next logging sequence.
The header U10 (marked in green) is there for programming and testing purposes so we can lock the power to be always on.
I must admit that I really suck at this type of electronics and would appreciate any help to get this working.