Electronic valve on beer tap

I've got pretty much this exact setup: http://www.midwestsupplies.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/c/o/cornelius-keg-system-with-5-lb-co2-tank-comes-empty.jpg

On the tap end where you would normally squeeze it to make the liquid come out and into your glass, I'd like to put a valve, so that I can dispense via software from the computer.

What sort of valve would I use to do this? I need it to be able to handle pressure (up to 50 psi), and not cause any foaming. I've looked around at solenoid valves but I don't exactly know what I would be looking for or the right terminology.


I and not cause any foaming.

You might check the cellar of your local pub. I’m not an expert, but the stuff you see looks so complicated that there has to be a reason for it and I have speculated that it is some sort of positive displacement device to specifically avoid foaming. The stuff in your link is the sort of thing used on the firemens’ annual picnic, where everybody is an expert, nobody knows what they are doing, and all they drink is froth - until somebody turns up with a ute-load of slabs.

Well some foaming is alright I suppose, but I don't want to be wasting TOO much.

I also plan to use this for soda water, so if there isn't anything that can prevent beer from foaming, would the soda water have the same problem?

I feel as if this is a simple problem which has been solved many times before. A solenoid valve possessing this ability has to exist somewhere. I just don't know what I should be searching to find it. Any ideas? Something like this? http://www.amazon.com/Electric-Solenoid-Replacement-Pipelines-Applications/dp/B00827FP26/ref=pd_sim_indust_4

I actually have one of these http://www.amazon.com/Vdc-Normally-Closed-Solenoid-Valve/dp/B007D1U64E and I tried to put it in place of the standard "thumb" tap/valve, but for some reason nothing would come out?? I verified the valve was open and getting voltage. Something to do with the line being pressurized? The valve being so small maybe? I don't really understand...

I guess you have to look at the geometry of the inside of the valve and see what path it provides for the fluid when it’s open. If there’s only a small opening and there is not much pressure behind the fluid, you may find that surface tension, buoyancy or some other effect is enough to hold the fluid back. I suppose it’s even possible that you haven’t actually got the valve fully open.

The valve is definitely open. And there's about 50 psi of pressure behind it...

sarink: The valve is definitely open. And there's about 50 psi of pressure behind it...

You say it's definitely open, but how can you tell? If it's not allowing fluid through, that's a pretty strong sign that it's NOT open. The solenoid may be energised, but that doesn't mean the valve is open.

50 PSI is very high and could be enough for the pressure of the fluid to overcome the force of the solenoid and jam the valve shut, depending on the internal design. That advert doesn't say what the maximum rated pressure is but it may not be that high. Have you tried opening the valve and just dribbling water through it? Presumably it does flow correctly at low pressure when it's open, and you haven't got the wrong part as some of the comments on that advert suggested.

I say it's definitely open only because it flows fine at low pressure. If I disconnect the hoses from the pressurized line, I can blow/suck through the valve. I also have a diaphragm (aquarium) pump which can pump a steady amount of liquid through the valve just fine.

I guess it's more like 40-45 PSI, but still.

If this valve doesn't work because the high pressure is jamming it shut or something that's fine, in fact I am using it for other purposes and just grabbed it as a test. But I would like to know what I need to purchase in order to get this setup to work properly??

Thanks again!

sarink: But I would like to know what I need to purchase in order to get this setup to work properly??

A solenoid valve rated for the pressure, flow rate and type of fluid that you want to pass through it and with the right electrical characteristics to be operated via your power supply + driver circuit + Arduino.

If the fluid is for human consumption then there may be additional requirements for the valve to be food-safe and to be capable of being cleaned and sterilised.

Pretty much nailed it, but what would you call such a thing? If you google "normally closed solenoid valve" you never really find ones with characteristics stated like that. I'm clueless on where to find/how to find it. What about the link I posted above?

what would you call such a thing?

Google turned up lots of hits for ‘food grade solenoid valve’ including lots for brewing related projects that make me suspect this is quite a common requirement. I suggest you simply click a few promising links and see whether any of them seem suitable for your application.

You might want to look at the kegbot.org project. There’s a forum post with all the parts used to build a kegbot. https://kegbot.org/kegbb/index.php?p=/discussion/comment/762 In short I’m using the McMaster Carr solenoid cut off valve. You can see me controlling it with an iPhone and an Arduino, http://www.youtube.com/watch?v=KjOugSK-vZw