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 dont 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.
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.