Automated home brewing
The office conversation this lunchtime went a bit like this:
Me: “Two beer posts in a week is too much, isn’t it.”
Me: “OK. Damn shame: I’ve been sent a great automated brewing project; it’s way more complicated than the ones I’ve seen before. I’ll maybe put it up next week, after the new website goes live.”
James: “Can you send it to me now please? I’d love to read that. I want to update my system at home.”
Gordon: “Me too, please.”
Laura: “Can I see it?”
Clive: “That sounds brilliant.”
Eben: “Mmm. Beer.”
Lance: “Did someone say beer?”
Emma: “Do you have a link I can see?”
Me: “OK. I’ll POST ABOUT IT TODAY.”
So I apologise for inflicting two posts about beer on you in three days: I promise not to mention fermentation at all next week.
Ted Hale blogs at Raspberry Pi Hobbyist, where he concentrates on physical computing with the Raspberry Pi. His most recent project brings in another of his hobbies: home brewing.
We like this not only because we like beer, but because think more Pi projects should employ propane.
We’ve seen brewing projects where a Pi controls simple heating and cooling, but here, Ted uses a Pi here to control all the parts of the brewing method called partial mash: for this he needs to be able to:
- Open and close a valve to a tank of propane
- Start a grill igniter to light the burner
- Detect if the burner actually did light
- Sense the temperature for the wort (the brew of water, malt extract, and hops)
- Operate a pump for circulating water through the wort chiller.
I used shielded audio cables commonly used for microphones. I am also a musician so I had some of this already. If you have to buy a small reel you may find that it is rather expensive. Cat-5 cable may also work well. That is what I use for my hot tub controller, but it is not subjected to the massive EMI of this system.
There’s a writeup over at Raspberry Pi Hobbyist about how the whole setup comes together, and James, I expect you to have overhauled your entire home system over the weekend.
Detecting a flame is easy: it’s plasma so it conducts, whereas cold gas doesn’t. That’s how domestic boilers work.
For safety you really need a crashproof controller. It should have an uninterruptable timer. A boiler control-board has a particular startup sequence. If anything goes wrong it shuts down and nothing will persuade it (not even power cycling) to retry for another 3 minutes. The gas valve has a big solenoid pulling against a big spring; any sign of trouble and it shuts off.
The startup is to ensure then pump and fan are running, then open the gas and try sparking. If it lights then stop sparking. If, after preset period, it doesn’t light shutdown for 3 minutes.
If the flame detect wire falls off then it goes open-circuit, much like when there’s no flame, so it shuts off.
Yes, there needs to be several additional safety devices built in to this design and I need to discourage people from attempting to duplicate this until I have everything worked out well. In my post about the hot tub controller I described the fail-safe circuit used. It is basically a clock fail detector. To keep the relay powered on, the GPIO pin must pulse it at least once a second. If it hangs high or low then the relay will turn off. I will incorporate that into this design.
I was not especially concerned about safety on this project since I will be monitoring the system constantly anyway. However, I will ramp up the safety mechanisms in the follow up version.
Far safer to abandon gas heating and use electric.
With electricity if you are incompetent and/or unlucky just electrocute yourself and maybe burn your house down; but you will have to try quite hard.
I believe flame sensors based on UV emission, or conductivity (plasma – flame is conductive) are available as modules. A thermocouple in the flame may not be reliable long-term (soot build up, or corrosion etc).
“I disabled the flame detection logic. This is a critical safety feature…” I can’t imagine what my homeowner’s insurer would say if they found me doing that in my garage…!
Some posh gas hobs have thermocouples as a flame detect.
The output of the thermocouple holds the secondary gas valve open, so the ring stays alight. If the flame should blow out, then it goes cold, looses current and so the valve shuts.
However there is still a manually operated gas valve. So a human is in the loop.
Gas is dangerous, this is why in the UK we have strict rules on gas-fitting. See what happened at Ronan Point; gas can easily destroy not just your house but other peoples’ too.
For the sake of a few beers I would use electric heating.
I dont know much about the UK but electricity is rather dangerous in some parts of the world
isn’t this an educational blog?
You mean teaching the basics of industrial sensing and control (heat, flame, temperature, gas throttle valve, design for noise immunity) are not educational?
These sensors (or at least rather more advanced versions of these) are used as the primary control feedback for gas turbines.
I remember a particular site where flame failure detection was used in the startup sequence of a gas turbine that was older than me (>28 years). The startup procedure was the following:
1) Obtain footstool
2) rack out the flame failure unit so that the circuit boards were exposed
3) push the start button on the turbine
4) lick your fingers and briefly touch them across the optocouplers responsible for translating the signal from the ultraviolet flame detection eyes so that the flame detector would render “valid” during the idle time.
The sensors were terrible. The slightest amount of coking would render them randomly intermittent which would cause a flame failure detection and turbine trip.
By teaching kids how to make beer reliably, we can teach them how to design gas turbines.
Clearly there is no Mrs. Hale who will be driving into the garage at any moment after hitting the garage door opener while looking in her purse … ;)
Detecting a flame’s plasma by conductivity? Whatever happened to a high-temperature wire with a predictable temperature-vs.-electrical-conductivity profile? Then you could also detect the actual temperature of the flame in case you wanted fine-grain control of the fuel consumption.
JBeale – what, you don’t invite your insurance agent over to enjoy his favorite craft beer you’ve made just for him to ensure continued heavy discounts he signs for on policies after enjoying too many brewskies??? Oh, the humanity! :lol:
Leo Williams – a modification of the same process can be used to make non-alcoholic root beer, birch bark beer, sassafras, etc. Chemistry is a highly educational subject, and it also involves studying stuff that burns, explodes, and gives off stinky smells, among other less practical uses :lol:
Jim – you truly have your finger on the pulse of this blog. Uncommon insight! I’m impressed and love the humor that you inject into the conversation.
Will the new website have ‘flame detection logic’?
It already does, it’s called the banhammer…
I can see the attraction of using a propane heater – a bit like making your own fireworks, or a building a man lifiting balloon filled with methane. But wouldn’t an electric heater have been, well, esaier?
PS I vaguely remember the beer drinking future gas turnine designers propping up the bar…
“Two beer posts in a week is too much, isn’t it.”
Two Raspberry Pi posts in a week is too much, isn’t it….
What planet are you on? :-))
I love this post. Even reading the comments has been educational. I didn’t know that plasma was conductive, for instance.
I don’t know much about shielded audio cable, but I suspect it’s expensive precisely because of the shielding. You will find that most Cat5 cable is unshielded. (Look for UTP printed on the sheath. It means “Unshielded Twisted Pair”.) Cat5 and Cat6 cables can achieve their high transmission rates through a clever method of twisting four pairs of wire and use of balanced signals sent down those paired wires. The balance makes the signal electromagnetically neutral on average and the twisting is done in such a way as to minimize cross-talk among the pairs. At any rate, the lack of shielding means the cable can be made relatively inexpensively but it also means that UTP will probably not help with damping the sort of noise seen by igniting the flame.
As a fellow home brewer I must cation you not to use you’re brew pot as a fermentor. There’s no seals to keep the bad bacteria out and can cause skunked beer. Also northern brewer sells an electric heating pad that wraps around your fermentor that plugs right in to a temperature controller or a wall outlet. Good luck and happy brewing. Cheers buddy.
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