Four Kegs One Tap

[mattd2]

So thinking outside the box on both your issues here...

What if, rather than using low pressure CO2 to push the left-over beer out of the tap, you use higher pressure CO2 to push the beer BACK into the keg through the same line. IE - select your beer, valve opens. Open tap handle, beer flows out tap. Close tap handle, and the HP CO2 back-purge line that's connected to your main trunk line close to the tap opens up. Because the solenoid valve for the original beer is still open, you push all the left over beer back into the line. A few second burst would take care of things, and then the valve closes and everything resets. Now you have mostly empty trunk line and no wasted beer.

As for figuring out what's left in the kegs - rather than flow sensors, which are quite costly (last I checked), throw a load-cell under each keg. Empty kegs should all be in the same weight range, and the average density / weight per pint of your various brews should be close enough for estimating. You'll at least be able to tell whether the keg is mostly empty or only half gone.

Good luck to you - keep us updated.
-Kevin

Like the idea, my only comment would be to make sure that the solenoid valves you use can handle flow in both directions.

 

[BadNewsBrewery]

Solenoid valve is open or closed. The check valve is s concern.

 

[mattd2]

Solenoid valve is open or closed. The check valve is s concern.

A lot of the solenoid valves I have seen are direction and will leak if pressurised in the oposite direction. Saying that it probably doesn't matter much are there will be pressure still against the other side of the shut valves on the other lines and the amount that did leak would not likely affect the other lines greatly.

 

[BadNewsBrewery]

A lot of the solenoid valves I have seen are direction and will leak if pressurised in the oposite direction.

This I did not know. Well, if OP can find valves that work, my idea would still be viable. If you dispense your kegs at around 10-12PSI, you'd only need maybe 15-18PSI (guessing ) to push the beer back down the line into the keg.

 

[sharp63]

Update:

I'll be putting this together this weekend. I have everything ready to go for the most part. All of the components are in, except for a few fittings that I'll be getting tomorrow and Saturday. My custom programming on the Arduino controller board is functional and I just have a few things to do on the Raspberry Pi to get it talking to the Arduino and serving web pages to the iPad. The iPad will be used to show the graphical interface of all the beers and will use the touchscreen to actually select a beer to pour.

I'll have to grab some picture of it operating and then begin the process of posting the all details on my blog. Very excited to finally see it in action!

 

[texwake]

Please post photos as you do this. SUBSCRIBED!

 

[DrewschBag]

Also subbed for pictures. You brainy smarties.

 

[grathan]

Don't forget manual option. Suck if you forget to charge the tablet...

 

[DustyTheBrewer]

Dude, this is going to be amazing. Awaiting updates.

 

[sharp63]

Don't forget manual option. Suck if you forget to charge the tablet...

I had to create a fairly convoluted system to get the iPad to communicate with the other electronics. The drawback is it adds a bunch of bulky equipment. The good news is that I am able to use my iPhone or any other smart phone should the iPad not be charged!

An update on the system:

After hoping to have it put together last weekend, I ran into some unexpected software glitches that were causing intermittent errors. I also ran into some issues stemming from sloppy soldering. After hacking away an hour here and there in between family stuff over this holiday week, I've got things in pretty good working order. Once I figure out a way (good or otherwise) to actually organize all the cables that are running in the tap box and get it attached my keezer, I'll post some picks.

I've had to make a few sacrifices in order to get the basic system up and running and plan to make extensive revisions after summer homebrew season is over, but I'm still very happy with how it currently is.

 

[BadNewsBrewery]

So of all the plans discussed, what did you end up going with? Something set up to back-clear the line, or just accepting that you'll get a bit of a mixture for the first pour?

 

[nextgenxx]

You should build something like these new coke mixing/making machines!

http://mashable.com/2011/08/24/coke...-own-drink-on-facebook-and-in-the-real-world/

 

[sharp63]

So of all the plans discussed, what did you end up going with? Something set up to back-clear the line, or just accepting that you'll get a bit of a mixture for the first pour?

I'm trying to limit the amount of liquid left in the main line. After the check-valves on each line, there is about 5 inches of each line the go down into the manifold. The manifold is fairly small and then the output attaches almost directly to the tap. I'm relying on gravity to pull the liquid in the main line down, which seems to be working.

One major problem, however, is that I'm getting a lot of foam. The foam is either coming from the solenoids or the check valves. I bought more expensive solenoids because reviews had them not creating foam, so it may be the check valves. I have no plans to deconstruct anything until my four kegs are out, so I won't begin tinkering with the hardware for another two or three months.

 

[sharp63]

Here are some photos...

#1 - This is where all the connections come in. The manifold has four inputs at the top and one at the bottom. The one at the bottom is immediately connected to the faucet. One of the first revisions I'll make later this year is adding in a digital flow meter before the faucet so I can measure how much is being poured.

#2 - A photo to give you some idea of how close the check valves are to the manifold.

#3 - A photo of when I was putting everything together in the box. I don't currently have a back cover to the box, as I plan to make a lot of adjustments over the next few months. I have two work boxes installed inside the box. The top one with the weatherproof cover houses the Arduino board and the Raspberry Pi computer. The second box is just to help keep the mess of wires somewhat organized. I'm going to need a bigger box as all the stuff doesn't fit into that second box.

You can see the four solenoid valves at the bottom. Long-term, I'd like to separate the electronics from the dispensing system. I'll probably make a box that doesn't attach to the keezer lid to hold that stuff and then another box that does attach to the lid to hold the manifold and tap.

#4 - Photo of the iPad interface. I made this part of the interface very simple. You see a small icon with a headline of each of the beers. There is also some brief info on each of the hombrews. I'll probably expand this out to more detail to help educate our guests who might not know what a beer is from the title. You can touch anywhere on each of the four boxes to "arm" the system.

#5 - Photo of the iPad interface once a beer is "armed". It brings up a modal window with buttons to start and stop pouring. My initial plan was to have a physical toggle switch on the box that you would have to click on and off, but I ran into too many unexpected problems that needed fixed and that fell off my priorities list. Some of the people who got to use the system this week thought it was cool to control the pouring with the iPad, but I'd prefer to rig up a tap handle that's actually a toggle switch so you only use the iPad to select a beer to pour and then open and close the tap handle to actually pour.

#6 - Photo of system in operation. You can see the hillbilly nature of this current setup with the router sitting on top of the keezer

Because I didn't have time to figure out how to make the iPad talk directly to the Arduino (programable microcontroller that controls the solenoid valves), I came up with this networked approach. The way this works is that the Arudino attaches to a Raspberry Pi (a tiny, but fully functional linux computer). The Raspberry Pi runs a web server and sends commands to the Arduino over USB. The Pi attaches to the router via an ethernet cable. The iPad then just uses its Safari web browser to load the web page from the Raspberry Pi web server. The web page uses Javascript/AJAX to make server calls to the Raspberry Pi telling it what beer to select and then the Raspberry Pi tells the Arduino which valve to turn on.

The drawback to this system is that I need to use a router to do this, which is cumbersome. The benefit is that I can actually use any smart device with wi-fi to control the keg system, so I could use my iPhone or iPad and others can use their Galaxies, Kindle Fire's, etc.

 

[sharp63]

Electronics:

#1 - Raspberry Pi

#2 - Arduino - Note the disgustingly bent capacitors sticking out. I had to replace a few that were nicely soldered in and realized my desoldering skills were non-existent and could get it to the point where I could actually get the full capacitor lead through the hole on the circuit board. I'll definitely be soldering up a new board soon and already have the parts to do so.

#3 - Solenoid valve up close.

 

[cjhammel]

Using this table you could just draw off that the beer in the line drink it then continue the pour. But this probably only an issue when going from a dark to light beer.
3/16” ID = 1/6 oz/ft
1/4” ID = 1/3 oz/ft
5/16” ID = 1/2 oz/ft
3/8” ID = 3/4 oz/ft

Cool idea love tech.

 

[BadNewsBrewery]

Maybe I'm not thinking straight, but what are the check-valves doing for you, other than foaming the beer? If you have 4 solenoids to select which beer is pouring, then the check-valve isn't doing a whole lot. I suppose it's keeping the beer that's pouring from mixing too far with the beer in the other lines, but I'm still pretty sure you're going to get mixing because your check valves are a short distance away from the manifold.

I'm guessing the check valves are causing huge amounts of foam as they're a giant pressure reducer and turbulance causer. If they're not doing anything for you, why not get rid of them and see what happens.

 

[BadNewsBrewery]

So I haven't done the research to see if you can get a solenoid valve that is bi-directional (IE no check valve) to make this work, but this is still how I'd do it. I've attached a picture of how I would set it up, to allow you to totally clear the line and not have to worry about beer mixing at the manifold or in your line. It also gives you the option of having a lot of line after the manifold, to get a smoother pour.

One option that would be cool to program in - rather than having the CO2 clear the line after ever "end pour", only have it clear the line when someone switches to a different beer. So that way if you pour 5 of the same beer, there's no CO2 used and the system works like a normal keg/tap. Only when someone wants something else would the CO2 purge happen. You'd just have to have a count down timer on the display saying "STANDBY - SWITCHING BEERS" so they didn't open the tap while the CO2 was trying to purge.

Anywho - I know it's not how you're currently set up, but I figured a quick picture might help show you some different ideas / ways to tackle the project.

-Kevin

 

[sharp63]

The check valves sit right above the manifold and were put there to eliminate mixing beers anywhere other than inside the manifold. Gravity takes care of purging what little does sit in the manifold and between the manifold and the check valves.

I did spend a little extra on solenoids that were known to not cause foaming. I'm not 100% reliant on that anecdotal evidence, but I do suspect that cheap check valves are most likely the culprit. I'll probably do a modification soon to eliminate the check valves and see if putting the solenoids closer to the manifold cuts down on foam.

If that doesn't work and I need the solenoids closer to the keg, I'll need to experiment with using another solenoid to handle the co2 clear out. I was hoping to avoid that for sake of simplicity in my initial prototype.

 

[hubbs]

Would you mind providing links where you purchased some of the hardware, in particular the solenoids.

I love this project and want to give it a go.

Also, could you not use a $10 USB wifi dongle for the rasberry pi to do away with the router?

Thanks

 

[tsl346]

If it were possible to put the solenoid outlets directly into the manifold I think you would be able to remove the check valves and basically use the solenoids to prevent the backflow of beer into the other lines. You might need a larger manifold to accomplish this but I bet it would be worth it.

 

[twistr25]

Any chance we could see your code for the webpage?

 

[Brewmech]

You will need flow back prevention valves on the lines or any change in pressure from one keg to any other will cause you to mix beers. Interesting project.

 

[sharp63]

A few blog posts going into slightly more detail:

Intro: http://scottsharp.me/blog/introducing-ikeg/
Software: http://scottsharp.me/blog/ikeg-software-overview/
Plumbing: http://scottsharp.me/blog/ikeg-plumbing/

 

[RTL]

First, that is awesome!

Second, in addition to the check valves you may be foaming because your serving tower does not appear to be cooled or insulated. Correct me if I am wrong there.

While pouring does the beer come out foamy then gradually get better as the lines cool? Can you draw a glass of beer, then draw another glass of beer with less foam from the same keg without switching?

Just a thought. Keep the pics coming!