Hey everyone,

after getting so many valuable informations in this forum, I think it's my time to give something back.
Don't know if anyone needs it, but here are the facts:

• Sensor is powered by 2xAA batteries
• using a SI7021 Temp-/Humidity sensor
• using a DS18b20 Temp sensor
• battery monitored
• status LED
• drawing about 4,5µA (0,0045mA) while sleeping, about 1-3mA while sending, 17mA during boot up
• using really cheap parts like a usual Atmega328p-pu microcontroller and the mentioned SI7021

First of all, some photos:

The used batteries are "N" or "LR1" so you can guess the size of the pcb

Top side of the pcb

Bottom side of the pcb

Current draw in sleep mode, where the blue "30" on the right side is 30µA. (The device used for measuring might be old, 1960, but double checked and calibrated with a 600€ Fluke 289 Multimeter which, unfortunately, is not mine :-P )

I integrated a push button for current saving, so it needs to be pushed before connecting the pcb to the batteries and released about 3 seconds after boot up.
The LED indicates the begin and the end of the main loop in my code.

If anyone is interested, I can provide my PCB files (although it's not that hard to make your own from the photos ;-) ) and the sketch I use.

Have a good day everyone and so long
DonHorsto