Wood heat offers unique advantages compared to more modern heating systems, especially in remote areas. But it also comes with its own challenges, namely, keeping the fire going at the optimum temperature. If it’s too cold you risk buildup in the chimney, but if you’ve got it stoked up more than necessary, you’ll end up burning through your wood faster.
To keep the fire in that sweet spot, [Jay] decided to put an ESP8266 and a thermocouple to work. Now, this might seem like an easy enough job at first, but things are complicated by the fact that the flue temperature above the stove lags considerably behind the temperature inside the stove. There’s also the fact that the top of the chimney will end up being much colder than the bottom.
In an effort to get a more complete view of what’s happening, [Jay] plans on putting at least two thermocouples in the chimney. But as getting on the roof in December isn’t his idea of fun, for now, he’s starting with the lower one that’s mounted right above the stove. He popped a hole in the pipe to screw in a standard K-type probe, and tapped it a few times with the welder to make sure it wasn’t going anywhere.
From there, the thermocople connects to a MAX6675 amplifier, and then to the WeMos D1 Mini development board that’s been flashed with ESPHome. [Jay] provides the configuration file that will get the flue temperature into Home Assistant, as well as set up notifications for various temperature events. The whole thing goes into a 3D printed box, and gets mounted behind the stove.
This project is a great example on how you can get some real-world data into Home Assistant quickly and easily. In the future, [Jay] not only wants to add that second thermocouple, but also look into manipulating the stove’s air controls with a linear actuator. Here’s hoping we get an update as his woodstove learns some new tricks.
The next obvious step is to get an actuator to control the influx of, and implement a PID to deal with the natural delay in the system – although it gets tricky as the control function will probably change a lot depending on how much fuel is on the chamber. Nice project!
I build Smoker controllers called a Heatermeter that have K-thermocouple and also a servo controller damper with a blower. I use on my Gravityfeed smoker, which uses Lump charcoal, a 35cfm blower. I can smoke 100+ pounds of chicken and keep the temperature at a very stable 220°.
I have an old 55 gal drum with a thrift store hot plate in the bottom. It holds temp and can smoke whatever I toss in there.
Maybe not everything needs servos and logic circuits to complicate something as simple as “make smoke go past food.”
Why do nerds always put wires and gadgets in places that don’t need them? Just keep an eye on your stove.
I see three main reasons:
– because it’s fun to do and learn new things
– because it can optimize your life
– because other people will take benefit of the work you shared on the Internet (given the fact that you publish it :).
I like to heat my house with wood, I have access to “free” wood, and thus every time I heat my house with it I save something like 3€, compared to what my heat pump will draw on electricity power.
To get that number I took benefit of things I have done earlier:
– an apparatus to measure the power usage of my home
– sensors to measure temperature from my chimney
– retrieve the heated air from my chimney to drive it to the input of my HVAC
– an apparatus to pilot my HVAC through modbus
– some python script that automatically detect chimney temperature, and force my HVAC in ventilation mode in order to spread the heat all other my house. Once the fire is off, the HVAC returns to “heat mode”.
I didn’t invent anything (maybe the python script), because for these jobs I’ve read many builds such as this one to make my system. Aside the (lot of) fun I had building this system, I know that I save some money every day I run my chimney because I have ways to measure and thus optimize my set up.
Of course, every part of my project gives me benefits to optimize my home, my budget, and my life:
– measuring the house power usage allows me to detect failures: for example: the water heater can draw more power if there’s a leak in the security system
– having my HVAC communicating with modbus allows me to set the temperature when I come back from holidays
– playing (prototyping) with all of these concept made my learn lots of things, some were “useless” for my work, other were priceless: learning modbus and industrial protocols, playing with my HVAC, and developping ways to measure power consumption gave me the opportunity to lead the project of making the supervision system of the datacenter I work in today.
It was definitely worth to do and learn these things :)
The function of having a dumb_me light system is my goal. Not for it to do the actual flu maintenance but to remind me it’s time to turn it at certain times I’m barely having knowledge (just got an uno and a couple boards to tinker with as practice). I thought about using some car sensors as indicators but ignorant on some of the coding and logistics. Having the fan system integration is fantastic idea though since most heat from stoves is wasted in the main room it’s set up in. Any advice or do and don’t you/y’all is welcome.
With any wood heat, air circulation is they key to being effective. Damper controls have been manual thermostatic for decades. Electronics are neither required or desirable since they are neither reliable or able to operate without an electrical system. The wood stove is simple and utterly reliable, why would anyone change that ?
Why do sourpusses always ha e to complain about things other people do that do not concern them at all
Why do sourpusses always ha e [sic] to complain about things other people do that do not concern them at all[?]
Why do sourpusses always ha e [sic] to complain about things other people do that do not concern them at all[?]
@Anonymous said: “Why do nerds always put wires and gadgets in places that don’t need them? Just keep an eye on your stove.”
The reason is because you have a whole bunch of old ESP8266 parts laying around that you MUST put to work! It’s an obsession…
Big box hardware stores sell sweep kits for under $60. Just do regular maintenance and inspection, because this isn’t going to replace the need to do regular maintenance and inspection.
Exactly … but that probe sticking sticking out into the stovepipe is going to make that sweep virtually impossible to do.
Highly doubt they will be sweeping that section of stove pipe that literally sits above the fire box.
Nice, I wonder if there would be useful warning conditions that could be added in HA. That might actually contribute some safety? I’d be tempted to whack on a BME680 for some room data.
Maybe blueooth monitoring for presence detection?
But definitely would not want to try and automate with it in case I started a fire.
Side note: those sterling engine (I think that’s how they work) fans on stoves have always held a spot in my heart since childhood.
It’s “Stirling engine” (not “sterling”) and, no, those stovetop fans don’t use that — they are thermoelectric (Peltier/Seebeck). The more clever ones also have a bimetalic strip that bends the bottom (hot mating surface) away from the stovetop when it gets too hot.
Some stove fans are actual Stirling engines and not peltier.
That would be cool to see. Got a link?
https://warpfivefans.com/?gad_source=1&gclid=CjwKCAiAmfq6BhAsEiwAX1jsZymFiQKWrNCPwR510hDC5sfSOcBooMpl_a2d9BJfbfZFFIZQGi7eOxoCKsMQAvD_BwE
DuckDuckGo-ing “stirling engine fan” found some for me.
Nifty. Good conversation pieces.
Why I love HaD that’s even cooler! I wouldn’t have believed that was possible, but must be more reliable than a stirling engine :)
I remember my Grandpa had a spring attached to the damper. As the room temperature(rt) rose, the damper closed. As the rt dropped, the damper opened. Motive force was a weight on one side of the damper control arm (bell crank config).
But, but, What if the engine is made out of a high grade silver?
It would be nice if those stove top fans actually moved some air. Mine won’t make tissue paper flutter in front of it. Useless but engaging to look at i guess.
When I was a kid we heated our house with a wood-fired cookstove and (later) a wood-fired furnace. The cookstove had standard singlewall flue pipe, in which was stuck a thermometer with a dial and a needle indicating tempeature. It was very useful to keep the flue the right temperature, but a PITA when it came time to sweep the flue: we had to pull the thermometer out so the brush wouldn’t damage the thermometer probe. Despite the monitoring and the cleaning, we still had chimney fires. They were dramatic, but never any damage.
The furnace had a double-wall heavily-insulated flue pipe that was a straight shot through the roof three stories up. No monitoring on that flue, and it was self-cleaning. Squeaky clean every time we checked, and we burnt about 3 full cords/year.
The furnace had bang-bang control on the air supply by a standard household bimetal/mercury tilt switch thermostat. Shortly after LEDs were invented I wired one across the switch: LED ‘ON’ meant the house was warm and we probably had enough wood in the firebox. LED ‘OFF’ for more than a while meant “go feed the furnace”. I thought about making a proportional control for it, but figured that the bang-bang control scheme with its intermittent hot fire probably did a lot to keep that flue clean.
By bang bang I assume digital as in on-off or 2 states. We had in the 50’s a coal fed gravity furnace. Slim vertical thermostat and a motor in the basement that made gear meshing sounds for about 3 seconds to open or close the flue through a chain and pulley. 3 second rise time for digital signal! The only thing was I’d have to go down and “shake the grate” move this lever back and forth once and come back upstairs.
I’m glad digital won over bang bang in technological words.
Exactly the same: a little geared-down synchronous AC motor rotated a crank arm to open the air damper, stalling against the endstop, also a few seconds of runtime. When the thermostat opened at the setpoint, removing the 24Vac motor power, a spring returned the motor and damper to the closed position.
“bang bang control” is pretty standard terminology for that kind of control loop. “digital” or not, there wasn’t a single semiconductor involved until I added the indicator LED.
I have his idea already fully realized https://github.com/lenne0815/hafireplaceautomation
I’ve had problems with the old MAX6675 TC amp/ADC.
Sensitive and it picks up RF on the TC leads; WiFi, cellphone etc. so you need some RF filtering on the input to stop the bogus readings. Very frustrating.
at the risk of the blind leading the blind.
i have only once made a proper long distance bus driver, for dallas one-wire temperature sensors. the exercise taught me a lot. you have to drive some current in your signal. voltage-level signalling with no current flow is super sensitive to noise. i don’t know how SPI is ‘supposed’ to do this but just looking at the MAX6675 datasheet input leakage current “I_LEAK” of 5uA…i think radio signals may be significant compared to 5uA.
One of the benefits of wood burning cast iron stoves like this (I have and use a similar one all winter long) is that they have lots of thermal mass so that you don’t need to do impractical stuff like this.
Pyro technologist here, pyrologist?
Any way, there is no way to automate the full wood stove process….. that would leave you in a domestic environment..,.perhaps some sort
of humanoid robot that was then provided with data streams could do
it, but it would never, ever, be cozy.
There are much more ellegant solutions. I do use the larger model
of stove pictured in the article, and it needs nothing beyond normal
cleaning and maintanence, and overheating it would be difficult as the
firebox, just isnt that big….unlike the cast iron “upland” I am sitting beside right now, which will happily launch into runnaway furnace from hell mode if encouraged.
The best wood burning appliances are the “finnish” thermal mass built in stoves. Those devices use very dry wood, that is weighed before bieng loaded. And are only fired intermitantly, as they capture all of the heat from the fire, and raidiate heat for many hours, untill the next fireing, which may be days apart in mild weather.
Also I have worked with an authentic and all original 1880’s “Rummford” fireplace, which is startling, in how well it works.
And all in all, I still prefer an open fire, and like to cook on an open fire, but that is benifit of living in a rural area, and sticking to the back roads
when traveling.,..,…….its an exceptionaly efficient way to unwind and relax
pellet stove :)
Exactly. Much smarter idea.