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Old 04-19-2013, 06:04 AM   #1
sarink
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Default Automated Soda Dispenser

Hey guys, I'm working on an automatic soda dispenser...

I've got an arduino uno (running a node.js web interface that sends serial commands to the board as the UI), a simple aquarium pump (for now), and a bunch of cheap solenoid valves to select/dispense a measured amount of bag in box syrup into your glass on demand. This portion all works fine.

Where I'm having trouble, is on the soda side. I've got a 2.5 gal corny keg at 50psi full of carbonated water at room temperature (it's been carbed for about 2 weeks now, and I shook the hell out of it the first 15 min). Coming off the corny keg I've got about 3' of tubing, at the end of the tube I have this solenoid valve http://www.ebay.com/itm/1-4-Electric.../290721876966? which is also controlled by the arduino.

Now there are two big problems... One, the soda comes flying out like a fire hose, and two, it loses all its carb and goes flat the second it violently splashes into your glass.

Side note: I plan on keeping the keg at room temperature and just leaving the co2 on+hooked up all the time. I figure by over carbing a bit and maybe using a bit more syrup or something I can balance out the fact that you have to water it down with ice. Eventually I'd like to get a fridge, but that just can't happen at this time.

I've read a lot of stuff, such as using epoxy mixers, and using a ton of tubing (probably like 35' in my case) to fix this. But I'd love to get some more info. Also, let's say I purchased a bunch of tube and some epoxy mixers, will that reduce it enough so that valve will work and not create a ton of bubbles? Will those two things certainly fix it? What other concerns are there? Is there any way to accomplish this without a huge run of tube? What about some sort of flow/pressure regulator? (I used to work at a dive shop when I was younger and I remember we had to dispense pure o2 verrrry slowly off of needle valve - I'm imagining something like this?) And I'm not opposed to the huge run of tube, but if there's another way that's great!

Thanks!!

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Old 04-19-2013, 03:59 PM   #2
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Now there are two big problems... One, the soda comes flying out like a fire hose, and two, it loses all its carb and goes flat the second it violently splashes into your glass.
This is both because of the tube length and the fact that it's at room temperature. My guess is you'll need at least 15-20 feet of 3/16 tubing to bring the pressure down, your 35 foot number might be closer. And the water will need to be cold, really cold. In regular installations they run the water lines thru an aluminum block that sits under the ice bucket to cool the water and the syrup as it flies by. The carbonator is at room temperature tho.
Quote:
Is there any way to accomplish this without a huge run of tube? What about some sort of flow/pressure regulator? (I used to work at a dive shop when I was younger and I remember we had to dispense pure o2 verrrry slowly off of needle valve - I'm imagining something like this?) And I'm not opposed to the huge run of tube, but if there's another way that's great!
Thanks!!
Well it's going to be hard to find a valve/regulator/contraption thats cheaper than 35 feet of tubing. Then it has to be food safe and you have to clean it, etc.

The big thing though is you'll need to cool that water before it comes out or all the gas is going to fly out anyway. Also you'd have warm soda which seems undesirable.
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Old 04-19-2013, 06:08 PM   #3
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So even with 30' of tubing it's still going to come out flat because the keg isn't cold? Are you saying there is no possible way, at all, to accomplish this at room temp?

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Old 04-19-2013, 06:25 PM   #4
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Originally Posted by sarink View Post
So even with 30' of tubing it's still going to come out flat because the keg isn't cold? Are you saying there is no possible way, at all, to accomplish this at room temp?
The keg doesn't HAVE to be cold, but the amount of CO2 that can be dissolved in a liquid is in part determined by the temperature of the liquid, so it has to be cooled in the tube if not before. If you're cooling it in the tube it also means you'll need metal tubes, since plastic does such a terrible job of conducting heat.

Open a warm cake of coke and pour it over ice cubes. It'll be flat and hard to pour without overflowing the cup. The easiest way is to cool the liquid is to cool the keg

It'll help to have the syrup cold as well.
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Old 04-19-2013, 10:16 PM   #5
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Yeah, I do understand that. Every time I fill the keg it will be with ice cold water, and then I'll carb it by shaking it, maybe insulate the keg as best I can while it sits and finishes carbing. I plan to eventually be able to have a fridge or a way to cool all this, but it's just not possible at this time....

So, that being said... I know that is, very strongly, recommended to chill it. But what I'm asking is if it's possible to make it work without? Can I initially carb it cold, overcarb (at 50 psi), use extra long metal lines like this http://www.nybrewsupply.com/stainles...bing-coil.html and actually get a room temperature soda dispenser to work?

Or should I give up and put the entire project on the back burner until I can figure out a fridge setup?

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