The image above is referred from this SO link. My use case is the following:
A latching solenoid valve, which would be run using 4 AA batteries (6V)
Solenoid Valve (9 Ohm) operates at 6V under 40ms pulse. I'll be running a microcontroller (ESP 12E), which would go into deep sleep to save power. Since this is to be used in remote places, hence latching solenoid powered by AA was chosen.
I don't want a scenario where if battery dies after some weeks or months of operation, one day if the solenoid was turned on, and remained like that, will end up wasting water for a long time (since someone would inspect site only once in a day) before being noticed.
So I looked at the above circuit diagram, and I was thinking how to minimize the power wastage in the voltage divider (R1/R2) circuits. Of course I could increase the R1/R2 such that they are in 100K ranges.
Questions:
Is it possible that due to extremely low input current the GPIO IN would not be able to detect the falling pulse? Is there any minimum current for a GPIO (ESP 12E) to detect the falling voltage?
Also, I'm planning to use AMS1117 to step down 6V to 3.3V needed for ESP 12E. What kind of energy loss can I expect when the ESP is in "Normal" mode and when in "Deep-Sleep" mode?
The reason to use the voltage divider power off detector circuitry is because of its simplicity (I'm no electronics expert) and and cause its cheaper than other solutions.