Kegbot project

Figured this would fit in Bar Sport as well as anywhere else :slight_smile:

I’m working on an Arduino powered Kegbot for my kegerator. I’ve made several attempts to contact makers of the original kegbot with no luck so I’m just going at it on my own.

My main problem is sourcing parts for less than hundreds of dollars. So I’m looking for suggestions from the community for where to find a plastic(brass makes beer taste funky) valve(probably solenoid based) with as close to a 3/16" inner diameter as possible. There are several places that appear to sell valves like this but they are all > $100US. I can’t imagine needing to spend more than about $30US.

Then there’s the problem of flow metering. Remag ( sells a nice flowmeter (Vision 2000) but their US distributor resells it for $100. C’mon! A transistor hooked to a propeller in a tube should not cost this much! So if anyone has any ideas on how to measure flow to a reasonable degree of accuracy let me know!

Any and all ideas welcome, specifically those that have links to real live part sources that I can afford. I’ll be quite happy to post my build progress and plans/part lists when I get this thing finished.

Apparently I’m not the only one at a loss when it comes to sourcing these parts, although I must admit I thought I would hear some alternative ideas from the Arduino crowd.

So rather than looking for part numbers I’ll word this in a more conversational manner:

  • How would you determine how much beer is left in a keg?
  • How would you measure (or estimate) how much beer left the keg on each pour?
  • How would you deny access to said beer until a user is authenticated?

First 2, place the keg on some sort of scale then wire it to an Arduino Analog pin.

^^ Pressure sensor from Sparkfun, little expensive, and might be tough mapping it out to keg size(How much does a Keg weigh?)

For the third, depends on what kind of auth system you want.

A simple, but un-modifiable way would be to set up a bunch of nested If statements,

<<<if 1st button pressed>
<Else, red LEd>
Else red LED>>

ETC, and the first/second button would be exchanged for your “password”

I hadn’t considered a weight sensor like that one. A 1/2 barrel keg weighs about 150lbs when full and 15lbs when empty. I’d have to figure out some way to divide the weight in a reliable manner.

I already have a TTL magnetic card reader based authentication system that works okay, what I’m looking for is authorization. i.e. a solenoid valve inline with the output tube. A pinch valve of some sort would be much preferred however since pinching the flexible plastic tube wouldn’t require parts to come in contact with the beer.

Bleh, couple months ago, I had a list of like 5 similar projects, but they used bottled beverages, and auto-mixed em.

And there were whole forums dedicated to this.

but I can’t seem to find a single one.

You’re looking the right way with a solenoid, but again, knowing nothing about beer, I don’t know what kind of pressure is in the keg, and if a standard solenoid would work.

P.S. I’m pretty sure “Authentication system” means a method to control entry/access, ie your scan cards.
What you need is a flow control/dispensing control system.

For the flowmeter try B Meters. I have used them before and are quite reliable (with water anyway), you have to be careful when using other liquids, especially beer with suspended solids, as they can clog up. I wouldn’t expect to pay too much under $100 though.

However if you just need the flowmeter for control, try a flowswitch. This will switch at a particular flowrate and should be much cheaper.

A solenoid I think would be ideal, but a solenoid pinch valve would be even better. One of the tougher problems with solenoids however is they can’t contain brass, and they tend to have very restrictive and oddly-shapen (ie foam generating) flow areas. The ones that don’t cost hundreds of dollars, which is silly, I’m looking for a very hacky diy type job. As for pressure, that shouldn’t be a problem. Its between 6 and 12psi in the keg depending on the beer, and slightly less in the output tube.

Spankyham, the meters from B Meters seemed a little on the enormous side for this application. The inner diameter of the tube in question is 3/16" (4.7mm).

A flowswitch might not be a bad idea. I could get a reasonable estimate based on pressure and flow over time I suppose. Any recommendations for suppliers for these?

lilpunk: Authentication system would in fact be the magnetic card reader. However Authorization system would be a solenoid. The first identifies if a user can get access, the second does the work of granting it.

It occurred to me that kegs are made of metal and filled with a semi conductive fluid. I wonder if there are any measurable electrical properties that change with the fluid level? Capacitance?

I think it’d be less headache to just put it on a scale, Assuming you can’t open it all the way and stick varying lengths of wire in, there aint much you can do.