Arduino Forum

Using Arduino => Sensors => Topic started by: Smajdalf on Jan 28, 2019, 12:47 pm

Title: Stove pipe temperature measurement
Post by: Smajdalf on Jan 28, 2019, 12:47 pm
Hi,
we are using a mechanical thermometer for measuring temperature of the stove pipe. It is similar to this (https://www.ebay.com/itm/Wood-Log-Burning-Magnetic-Stove-Pipe-Thermometer-Fire-Flue-Heater-Temp-Gauge/401629892746?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3D7384a675e69842a282f9b3af87b7e22b%26pid%3D100005%26rk%3D3%26rkt%3D8%26sd%3D332926849750%26itm%3D401629892746&_trksid=p2047675.c100005.m1851):
(https://forum.arduino.cc/index.php?action=dlattach;topic=593906.0;attach=292149)

I would like to make similar measuring but wireless and battery powered. The mechanical one measures 0-500°C with precision +/-10°C and is likely to survive (much) higher temperature. Normal semiconductors cannot survive such high temperature. Obvious choice may be using a thermocouple. But maybe thermocouple is too complicated and too precise for such. Maybe there is something easier and cheaper? I thought measuring of the emitted IR light with a photodiode or phototransistor. But when I tried a phototransistor it was much more sensitive to the ambient light than to the IR from the pipe (I have only one with visible light filter - it is a "flame sensor" from my starter kit - maybe the filter is poor). I have also considered using a thermistor but they are rated only for "low" temperatures. But maybe a wire from a light bulb may be used instead? It survive much high temperature - but only in a protective atmosphere of the bulb?
Do you have some experience with something like that?
Title: Re: Stove pipe temperature measurement
Post by: MarkT on Jan 28, 2019, 01:00 pm
Thermocouples and platinum resistance thermometers are the obvious choices for high temperature.

You might be able to find a IR thermometer sensor too on a breakout.  Standard photodiodes can't see
far IR at all and are no use for temperature until red/orange heat kinds of temperatures!

You could make a differential radiation meter by using two DS18B20's or LM30's, one in view of the
stove pipe and one shielded from it, but that's also sensitive to local air flow/ventilation, not just
radiant heat.  Black epoxy packaged thermsensors are surprizingly sensitive to radiant heat sources
and pick up body heat quite noticably, for instance.
Title: Re: Stove pipe temperature measurement
Post by: terryking228 on Jan 28, 2019, 01:35 pm
Hi,

Here's example of using thermocouples with Arduino. I use 2 on my woodstove, on the pipe and on the firebox.

https://arduinoinfo.mywikis.net/wiki/Brick-Temperature-Thermocouple#Brick-Temperature-Thermocouple (https://arduinoinfo.mywikis.net/wiki/Brick-Temperature-Thermocouple#Brick-Temperature-Thermocouple)

(https://arduinoinfo.mywikis.net/w/images/e/e5/YD-Thermocouple1-1024.jpg)

See Amazon etc. and search on "arduino thermocouple"

Like:
(https://images-na.ssl-images-amazon.com/images/I/5195o1V8m8L._AC_US327_FMwebp_QL65_.jpg)
for $6

Or make your own:

https://arduinoinfo.mywikis.net/wiki/Thermocouple-MakeYourOwn (https://arduinoinfo.mywikis.net/wiki/Thermocouple-MakeYourOwn)

I use one of those on a kiln.
Title: Re: Stove pipe temperature measurement
Post by: MorganS on Jan 28, 2019, 11:34 pm
Thermocouple would be my first suggestion.

Search for "thermopile" to find sensors sensitive to IR radiation.

A temperature-sensitive resistor such as RTD or NTC would also be useful for those temperatures. Soldering to it is the biggest problem as you don't want the solder to melt in use. You end up crimping to the wires instead of soldering.
Title: Re: Stove pipe temperature measurement
Post by: Smajdalf on Jan 29, 2019, 05:50 pm
Thanks for help, I think the RTD is the best option. App notes say it should be driven from a precision current source but since I don't need any high precision and want minimal power consumption I think simple resistor divider turned on only for a millisecond until ADC conversion finishes should work well.
Title: Re: Stove pipe temperature measurement
Post by: terryking228 on Jan 29, 2019, 06:42 pm
Hi Everyone,

Slight OT but here's the ideas I'm working on (https://arduinoinfo.mywikis.net/wiki/Project-WoodStoveMonitor#Project-WoodStoveMonitor) for my woodstove monitor:
Title: Re: Stove pipe temperature measurement
Post by: larryd on Jan 29, 2019, 08:10 pm
Hi Everyone,

Slight OT but here's the ideas I'm working on (https://arduinoinfo.mywikis.net/wiki/Project-WoodStoveMonitor#Project-WoodStoveMonitor) for my woodstove monitor:
Need to do these things:
. . .
Check batteries in smoke/CO2 detectors   ;)


Title: Re: Stove pipe temperature measurement
Post by: terryking228 on Jan 31, 2019, 06:01 pm
Quote
Check batteries in smoke/CO2 detectors   ;)
You Betcha!  I have two, near the woodstove and near the propane furnace.

My wife and I are both very conscious of CO dangers. Several years ago we were working at a school in Africa and the assistant principal and his wife both died one night.  Blockage in a natural gas heater. :-(  !
Title: Re: Stove pipe temperature measurement
Post by: AmphenolSensors on Feb 08, 2019, 01:50 pm
Also make sure your CO sensors are in date, most only last 7 years, tops.

On flue temp, issue is amking sure the outgoing cable can also withstand temperature, and any connector. Exhaust gas NC types go to 600°C, but have cooling fins on the body, and PTFE based cable to cope with the heat. All normal cable will just melt, or in extremis, catch fire.