Don't know if anyone here cares, but I think it's neat so I'll keep updating. I've been working on these sensor devices when I have time, so here's where I am so far.

quote:
I realized it was never going into a low power sleep mode, so after adding a popular low power library to the code, the difference so far is pretty drastic

So that "drastic" improvement amounted to about 12 days vs. the original 4 days. Again this is using a 1,000 mah lipo pack, which measures about 1"x1.5"x.25".

Turns out I still wasn't using sleep mode properly, and I also had my sensor wired so that it was drawing power all the time (a small amount but enough to matter here). After fixing those errors I've started a new longevity test, and so far it's looking like it'll last about 3 months on 5 minute transmission intervals. It should last nearly twice as long with 10 minute intervals, and if I switch to an 18650 cell that should triple the life again. Also there are probably more things I should be doing to lower the power consumption during sleep, so more work to do here.

I also configured the helium console with a custom MQTT integration pointed at my Home Assistant server, so I'm getting my readings in HA so I can set up some automations. Here are the temp readings from inside my freezer, which is where this sensor has been living for the last few hours:

Looks like the compressor kicks on about every 30 minutes. I'll probably set up a notification if the temp ever gets above 5 degrees, and another for if those compressor cycles ever start stretching out.

Next up I will probably do a mailbox notifier because I've always wanted one. There are a few commercial options, with Ring being one of the cheapest at $30, but frick Amazon. I'll power mine with a couple of CR2032 coin cells which I hope will last a few years doing only a couple transmissions per day. If I can package it up nicely, I might sell kits or pre-assembled units if anyone is interested. Should have coverage most anywhere judging by the Helium map. I'll build a simple companion app for notifications, and of course an API for integration with HA or whatever else you want to use.

This post was edited on 2/6/22 at 11:46 am