Project keezerPints, Or How Much Beer Do I Have Left?

Kevin59

This is going to fall under the category "No I don't need it, but I thought it'd be cool/fun/etc to do!"...

I know the topic has been brought up here before (or I think it has), but I decided I was going to try and implement some sort of keezer tap monitoring system for my 12-tap keezer. Sure I can open the lid and pick up a given keg for a rough "feel" check, but being a gadget-loving EE I want something cooler.

So I have embarked on an Arduino-based solution that will display the number of pints remaining for each keg in the keezer. The Arduino side of things is pretty much done as far as coding and the display and menu/button system. I've attached a few pics below.

The tricky/questionable part remains, that is implement the sensor system. At this time I'm planning to try a 50kg weight sensor similar to the one shown below. It will form half a Wheatstone bridge with two additional 1K resistors to complete the bridge, and a TI INA125P instrumentation amplifier to send a voltage to an ADC input on the Arduino. The idea would be to have one of these sensors & amps per keg such that the Arduino can poll the values based on timed code it's running. I have never messed with one of these weight sensors before, but I know there are a lot of concerns expressed out there regarding creep over time, constantly loaded sensors, etc. But at 4 for $10 on Amazon why not play around with it right?

Anyway the Arduino EEPROM will store 3 values per keg in the keezer: gravity points (SG), ADC value of empty keg and ADC value of keg with 5 gallons of water. All of my kegs are the same so I'm not worrying about minimal variances between kegs. Each of these parameters can be adjusted through a menu system that's displayed on the Arduino. There's also a menu selection where I can see the present ADC value for purposes of setting the empty/full ADC values.

From there pints-per-keg (PPK) can be calculated as:

PPK = ((ADC value from sensor - ADC value empty) / ((ADC value full * (1+SG)/1000) - ADC value empty))) * 40

The ADC value of a keg of 5 gal of water is adjusted upward before calculation based on the given beer's SG. The EEPROM gravity points defaults to 12 to start.

Each keg will sit on a 9-inch square board that's elevated and hinged on one side above a base board that runs the full width of the keezer, with the sensor set under the side opposite the hinge, or perhaps moved slightly inward to get a lever effect to drive up the sensor value change as the keg will at most weigh half of what the sensor can handle. The 9-inch square board will have a recessed circle routed in place to ensure the keg always sits in the same spot.

Here's hoping it works, but even if it doesn't it's been a blast to finally play with the Arduino. I suspect it's going to find its way into some other area of my homebrewing down the road!

Cheers!

Kevin

P.S. The Arduino code is for the most part complete except for the fact I'm currently using an Arduino Uno with only 4 available analog inputs (due to the I2C communication with the display). Any of you that like to tinker with an Arduino are welcome to have it if you'd like to take a look and play with it on your own. The LCD display values can also be viewed via a serial monitor window.

P.P.S. This is what happens when a homebrewer that wanted to open a microbrewery has given up his plans to do so! Sad

foomench

Cool.

**kal** · Posted: Fri Oct 03, 2014 12:32 am Post subject:

I like the weight idea a lot more than flow sensors as you know that over time they're going to get gummed up and impossible to clean. (Most are not meant for food use to begin with).

Let us know how it works out!

I still use the old method of "carefully lifting a keg and inch or so to see how heavy it is" to know how much beer is left. Or more importantly, I always have ~6 kegs carb'ed and ready to go so when on pops in the keezer there's always a replacement available.

Kal

Kevin59

18DPA · Joined: 14 Nov 2011 Posts: 135 Location: Kuwait

Kevin59