To continue from part 1: I want a wireless sensor that will last more than a month on 2x rechargeable AA or AAA batteries.
Some ideas I have for what I could do with such a sensor:
- indoor/outdoor temperature/humidity sensor
- garage door open sensor
- washing machine finished sensor
Collecting Power Usage Data
I setup influxdb and started logging the battery voltage measurements to it. I've updated https://github.com/ddrown/bluetoothadc with that code.
I also measured the battery voltage by hand with a multimeter and logged that to influxdb as well.
I setup Grafana to produce some nice graphs with that data:
These two data sources match pretty well, and adding +8mV to my ADC reading looks spot on:
From Energizer's AAA battery datasheet, the 100 mA curve is the lowest that they published.
At 2.518V, that's 1.259V per battery. On that graph, that's around 50% left. So maybe it'll last another week? It looks like the voltage should start dropping faster now.