Ladybug environmental data logger
Well, I was a little optimistic about the Ladybug environmental data logger. Reading the BME280 and VEML6040 sensors at 0.5 Hz and outputting pressure, temperature, humidity, altitude, RGB light intensity and RTC time and date to the Sharp memory display continued for just over five full days with a fully-charged 150 mA LiPo battery.
This is ~150 mAH/120 H = 1.25 mA average power, almost twice what I estimated based on my by-eye averaging of the current measured with the multimeter. The current jumps around a bit on the multimeter; better would be to plot the current versus time. I don't think my multimeter can do this though.
Updating every two seconds is nice but even every five seconds is good enough for sensor data that doesn't change too rapidly. So I am going to restart the experiment using a 5 second update time and let the STM32L4 rest in the STOP state in between updates. I am expecting to get 5/2 x 120 ~ 300 hours out of the same fully-charged 150 mAH battery. I'll update in about ten days with the results.