HI Rui and Sara,

Thank you for another great project just what I am looking for, but I need help with a small change.

I have remote ESP8266s monitoring room temperatures in a remote house, and reporting their readings to ThingSpeak. One thing that I have noticed is that the timing of the readings is drifting. I initially them set them up well spaced apart but some are now converging this can be because of delays in making the connection to ThingSpeak which in tern delays the next DeepSleep period. What I would like to do is to use a RTC to drive the latching power circuit so that I can be sure the the ESP8266 are awake at the correct time and enhance the battery life at the same time. This requires a change to the circuit, so that the negative signal from the RTC will start the latching process.

When I did my electronics education Thermionic Valves were King, and transistors were what we listened to Radio Luxembourg on!

What I think that needs to be done, is to change Q3 the 2N3904 NPN transistor to a PNP. What I would like help with is deciding which PNP transistor to use and what other circuit changes would be required. I would welcome any assistance that you can give me.

John