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Monitor my heating system

Written by LittleJoeMuc — January 22, 2021

Ein sensor im Heizungsraum und eine Grafik des Temperaturverlaufs 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

Sensornode ohne Batterie und Gehäuse

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.

temperaturkurve excel

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.

Sensor fertig und montiert

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)

Grafik Temperaturverlauf

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

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Comments

sharase sharase

April 6, 2023 03:54

Once you have determined the Steinhart-Hart coefficients for your NTC subway surfers thermistor, you can use the above equation to convert the analog readings to temperature values in Kelvin. To convert from Kelvin to Celsius, simply subtract 273.15 from the temperature value.

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