this is a minimalistic node for MySensors, consisting of an Arduino Pro Mini 3.3V/8Mhz with removed power regulator and power LED, a custom PCB which sits on the backside of the Arduino and accommodate a RFM95/6 transceiver module, a low quiescent PMIC (MCP1700-33 SOT-23), a voltage divider for battery voltage measurement via Arduino Pin A0 (two 1206 SMD resistors; 1M and 470K) and pads for an edge mounted Molex PicoBlade 2-pin connector for the battery. Also there is a footprint for I2C connection directly to a BME280 sensor on the widely used PCB breakouts. This board is in use now; I get the anticipated 6-9µA sleep current, together with a BME280 sensor approx. 12µA.
I also made a second PCB which incorporates two additional footprints for connecting two switches via A1 & A2 (to GND). This would make for a remote controlling node which could double as a climate sensor (same BME280 footprint on the board), but for this one unresolved software problems prohibit sleeping with regular wake up intervals for climate sensing and additional wakeup via the buttons. Hopefully discussion of the software problem takes place here.
Also to be seen on the pictures is a programming adapter for an Arduino Pro Mini with spring loaded pins, as I do not want to solder the serial pins on the Arduino (due to size requirements).
Lastly, I made up a case in FreeCad which houses the battery, in this case a 502035 type LiPo, the node hardware/PCB(s) and has two slots for inserting micro switches in the lid.
Regarding the photos: There are slight variants pictured; in the third photo an earlier prototype with the Molex connector upright is depicted (not practical; later versions have the edge/side mounted connector like the node pictured to its right). Also two versions of the BME280 are in testing right now: a smaller 4-pin breakout which includes a power regulator on the BME breakout (this regulator is unnecessary, as the whole node is 3.3V), and a slightly larger 6-pin breakout without the regulator (which should, in theory, use less power).
Happy to see any comments,