A few weeks ago my heating system broke. I noticed this - well because it got pretty cold at home. So I thought it would be really nice to get an early notification e.g. via mail, if the temperature of the heating boiler drops below the normal temperature. So I would have some buffer time to call the heating technician or check the heating myself, before the whole house is cold. I´m sure I could have bought something proprietary from the heating system manufacturer, but building an TTN sensor would be a lot cheaper - and it´s fun! :D
I wanted to use hardware I already had lying around, this was:
- Adafruit Feather 32u4 LoRa board
- 100k ntc resistor
- 2000 mAh LiPo
I couldn´t find a fitting formula to convert the analog read input values of the ntc to temperature, so I did A LOT of measuring the analog inputs, while attaching the ntc to hot and cold things. XD And with some help of Excel I got a formula which is actually pretty good.
Putting together the hardware and printing an enclosure was the easier part. Adafruit published some variations for printable feather cases. I just modified it a bit for my needs and made a custom wall mount.
For visualizing the temperature, I´m using NodeRED.
Next step for me was battery testing. With measuring and sending the LoRa packet every 20 minutes, the device only lasts for 8 days. This was not very surprising because I did not use any sleep library so far. So I installed the Adafruit Sleepydog library. Now it is running for 10 days and the battery voltage is still very good. I think it could last about 6 to 8 weeks now, until I have to recharge it. (which is pretty simple with feather boards, just plug a powerbank in the USB port)
What´s still left to do, is to program the email notification, but that’s also very easy in NodeRed. 😊 You can see the process of the designing in full detail (in german) in this Mastodon thread: https://social.tchncs.de/@LittleJoeMuc/105304013699179714