Building an oven with ultimate control

[avidan]

Hey all,
I am a long time reader, and avid pizza maker. I started out with a simple self cleaning oven hack, moved to an LBE, and now a full blown wood fired oven. I love making pizza, but I am also a technology control geek at heart. As an engineer, I always am excited for pursuing perfection through computer based control. (I put a PID controller on everything that will take one, my espresso machine, smoker, sous vide, the works).
I know that pizza is an art, and many will take offense to the fact I am trying to build a highly controlled oven, but for those people, i simply ask, please look away.
So, here is what I am trying to do.

I have been working on a design of a wood burning oven with a supplement of either gas or electric with a highly controllable temperature system. The idea is to have the floor of the oven PID controlled so I can set it to 800 (or any other temperature). In addition, I am looking to control the oven air temperature with variable control. For example, I would like to start the pizza "cycle" with a 800 floor/ 1400 air temp. This will last about 10-15 seconds, then i will go 800/1200 degrees for the last 75 seconds (these numbers are just pulled out of the air, if anyone has specific numbers, please share).

In order to make the fire run at such high heat, we have been looking at running a forced air system connected to a centrifugal blower, run by an arduino controller. This forced air system should be able to make the wood fire burn within a much higher range of temperatures. I know that traditionalists are against this, but we are looking at implementing a gas powered or electric coil system (similar to a ceramic kiln) underneath the floor of the cooking base. This cooking floor heating element will be independently controlled by another arduino/pid.

We are looking to make all heating elements reside OUTSIDE of the main cooking chamber. The chamber should be pure heat. We have thought about keeping all the heating elements below the oven. The wood/air burners will be offset from center, and the gas or electric heaters in the center.

I have a friend of mine currently working up a 3d model of our rough plan design, so I will post this shortly.

That being said, I am looking at several designs, and have the resources to make this happen....but, before I begin, I wanted the insight of the pizzamaking.com community.

All insight is very much appreciated.

[david s]

Re: Building an oven with ultimate control

Good luck. Generally for most WFO nuts the attraction is the low tech nature of firing and cooking in them. Most owners find that high tech stuff rather redundant once they get to know their ovens. The three second semolina test for floor temp for example is not only simple and reliable, but is a connection to the way things have been done for centuries. Likewise a fist held in the centre of the oven for as long as is comfortable is another reliable method.

[OzOvenBuilder]

Re: Building an oven with ultimate control

The idea is to have the floor of the oven PID controlled so I can set it to 800 (or any other temperature

Hi avidan,

I can't wait to see what you come up with. We use 100s of PIDs at my day job in a large computer controlled plant, so I have a slight idea of what you can do with these little devices!

Cheers,
Russell.

[avidan]

Re: Building an oven with ultimate control

hey oz.
I'm quite excited about it as well.
i have used a fair number of PID controllers, while building and maintaining glass furnaces for my glassblowing studio....part of the inspiration for this project comes from all the lessons learned in the glass studio.
its pretty amazing to see what can be done with a small PID controller and some controlled environments.

david,
its funny that you mention the connection to history, as much of the glassblowing world is quite similar. its a connection to the way its been done for hundreds of years (if not thousands). however, even though much of the process of glassblowing hasn't changed, integration of technology has made the process more accessible (ironically). in a sense, it doesn't take years of training and apprenticeship to become a master. for example, in the glassblowing world, we no longer need to understand how to mix our own colored glass. the technology available allows factories to generate an amazing pallet of colors for us. as glassblowers, we can then focus on the task of making the artwork. that being said, i feel like we have an opportunity to control the machine, and allow the artisan to focus on making pizza
that being said, the art of making pizza will still continue, even with a controlled baking environment....

[texassourdough]

Re: Building an oven with ultimate control

With all due respect I think you are tilting at windmills. I would suggest you get some hands on experience with a conventional WFO before you potentially waste a tremendous amount of effort and likely money pursuing a control level that is beyond IMO meaningless. Note: we all have different things we focus on and you are welcome to this, but the most "perfect" oven in the world will need to vary with dough thickness and hydration, topping levels, etc. You seem to vastly overestimate the significance of precise temps. (And I am an engineer also.)

Your example of an 800 degree hearth and a 1400 or 1200 degree dome is an example of what I think is misguided. Heat from the hearth is clearly from contact (and don't underestimate the significance of heat conductivity and heat capacity of the hearth and subrefractory in maintaining the temperature PROFILE you want during the bake). The heat to the top is predominantly radiational and the dome and the flames are a significant factor in cooking/caramelizing the top and toppings.

Put simply methinks you are trying to microcontrol variables that are 1) not very critical and 2) ignoring other factors. The learning curve for what you propose would be very long and IMO not very illuminating because variation in other parameters would put too much noise in your outcomes. There is no truly "standard" pie.

OTOH, it can be a quest! Good luck!
Jay

[stoveup]

Re: Building an oven with ultimate control

What, pray tell, is a PID? Non-engineer but nonetheless inquiring minds want to know what this is all about!

[Faith In Virginia]

Re: Building an oven with ultimate control

PID= proportional–integral–derivative controller. Think of it as a fancy thermostat.

[stoveup]

Re: Building an oven with ultimate control

Yeah - I looked it up on the Wickedpedia and man do I feel stupid! Wish I hadn't asked. WAY too much information!

You engineer types need to go off to a corner by yourselves and leave the rest of us to our blissful ignorance. OK -not really. I thoroughly enjoy reading the posts from the obsessively tech savvy among us. There is such a wealth of knowledge out there and I constantly learn a lot of neat stuff from you guys and girls. I don't understand the desire to turn building a WFO into something approaching rocket science or cooking pizza into an industrial process, but as Jay so wisely said, that's your quest. So indulge yourself and keep the posts coming!

As for me, I'd much rather spend my time developing great pizza dough technique. And eating pizza!

[GianniFocaccia]

Re: Building an oven with ultimate control

This is a fascinating concept, one that I'm sure commercial oven-designers have considered: how to get a ceramic/brick vessel to efficiently respond to periods of slow/peak demand and still deliver the nuances that only wood can impart. Aside from the fact that discussing running gas in a home WFO is strictly forbidden on this site, I side with Jay's beliefs that this is not the best application for a micro-controlled environment. Bricks safely absorb heat only so fast, limiting the value of a dual-zone heating scheme. Also, the coasting curve of an oven is not easily manipulated, apart from dome-thickness and insulation. As sexy a concept as a hybrid oven is, even if you could build a system that is responsive, easy to build and cost-effective, the benefits, IMO would be incremental at best.

[robertjusher]

Re: Building an oven with ultimate control

I play with arduino and spend hours tweaking PID's for fun also, but in rc tricopter aircraft. I look forward to seeing what you come up with and would be keen to look over what code you come up with for this... However I for see many sensors required and kinda killing the old school art that a WFO has,.
I will be watching with interest but will keep the arduino's for flying and wood for pizza.
Good luck and keep us posted.
Rob

[avidan]

Re: Building an oven with ultimate control

hey all.
thanks for the feedback. i am quite excited about the project. its actually part of a larger pizza making project. i am also building proofing chambers with arduino controllers that will allow me to create a ramp/soak schedule for the proof process. essentially, i will be able to do a cold proof and slowly move the temperature up to optimal over a longer period of time. i use a wild sourdough for all my pizzas (almost 1,000 done in my current WFO), so this will be quite helpful.

in regards to using the forced air and wood burning, i do hear everyones point that stone is slow to absorb and adjust in temperature, but i believe the thermal mass will actually work to my benefit. in all PID environments i have worked with, the better the insulation, the more stable the temperature control can be. that being said, we will likely play with some electric coils and gas as well as the wood.
i am sure the argument has been made 100 times, but is there a good post/sticky about the merits of wood burning over electric/gas? I would like to make sure i am getting all the gains of wood, while adding the ability to have consistency from pie to pie.

lastly, i do appreciate that this is a huge departure from the truly romantic and timeless work of a traditional of a WFO, but my goal is to pay homage to the traditions and benefits of wood burning and brick ovens, while utilizing modern technology to "tinker" with the process.

looking forward to posting progress.

[texassourdough]

Re: Building an oven with ultimate control

Hi Avidan!

As it seems you have a WFO, you are, I assume, therefore aware of the subtle qualities you are tweaking...

WRT mass, I think hearth mass is pretty much necessary to get good results. I am not so sure of dome mass, especially if you go electric for wood flame temp should be in the 1950 deg F range so I suspect you would like to be in at least the 1700 range for the whole dome. Heating any significant mass to that temp electrically is beyond my experience. No doubt in the kiln range but??? Gas flame for the oven would be tidier and would provide the veil of flame to caramelize the toppings and would have faster response time...Not sure you really need mass in the dome. Seems like really good insulation might be the most important factor there.

Good luck!
Jay

[Dmendo]

Re: Building an oven with ultimate control

Hi Avidan.
It seems you have been busy avoiding boredom.
Well, I've been thinking the same stuff and reached some conclusions.
Make the heating element electric simplifies a lot the problem of PID control. But I think it's not interesting at all. You'll get a standard domestic appliance (ok, bigger) no matter if PID or ON-OFF controled.
The challenge is control the full thing with firewood (gas firing has the potential of convert the brick ballon into a bomb). As far as you are intending to control the whole system with Ardunios and use a fan i'd suggest to use a lambda sensor for get the optimal combustion. More air than necessary and you cold the oven, less and you get too smoke and less heat again. Not necessary to have a separate fire chamber, just a tight door and the air entry with the flux controled by the fan.
So we have a "constant" flow of high temperature gas. How can we switch on-off or more-less? The amount of heat we get in this point of optimum combustion depends only of the quantitie of burning wood mass. As we want to make the state of the art of the WFOs we want to stack a lot of wood and drink cold beers while the inferno-machine works . Well, for switch on-off we can use dampers (quite easy to electromecanically manage them). Of course, a separate firing chamber is now necessary. But if you switch off the fire to the oven you need to let the fire escape to the flue, or better into a laberinth of heat retaining bricks, and finally to the free atmosphere. This accumulated heat can be recovered whenever needed for heat the oven. As several temp sensors are used is quite ease to program a strategy for "where I take-deliver" heat from. Is like control a stream of water pumped from a well. In the start for fill a bath tube you turn on the pump, once it's full (imagine you can't stop the well pump) you can deviate the water flow to a swimming pool size tank.
I think that with this conditions the mass of the oven can be reduced a lot as we don't need to store the heat in the oven mass, only the necessary for the bulding self standing could offer enough termal inertia for the control.
Well, this are my thoughts about this interesting challenge.
Maybe someone is still awake
Regards