Since its rebirth, our trusty VaxTap has matured, becoming a true mission-critical network component--serving any client, regardless of the language spoken. This year, our little VaxTap has become even more popular and, as a result, increasingly difficult to manage. Unfortunately, we cannot watch over it 24x7, so our VaxTap is often left alone, unprotected, and the thought of just any thirsty schmo wandering into the lab for a mug's worth made us cringe. Worse yet, without proper management, our VaxTap could fall victim to every VAXTap's worst nightmare: a downed keg.

The Right Ingredients

So this year, we wired the VaxTap 2000 Pro to the Web. Now we can keep tabs on keg levels and beer temperature, and maintain accurate logs for every pull of the tap--from anywhere in the world via our favorite Web browser. It just goes to show that anything can be managed. How did we do it? Well, when you start with a starving electrical engineering student, a staff programmer with way too much time on his hands and a keg full of beer, just about anything is possible.

The idea behind calibrating beer levels is relatively simple. A scale, or strain gauge, is used to measure the decreasing weight of the contents of the keg, a.k.a. beer. It's a fairly simple equation: Subtracting the weight of the empty keg (Kempty) from the weight of a partially empty keg (Kcurrent) will give you the weight of the contents (Beer) remaining in the keg: Kcurrent-Kempty=Beer.

It's important to recalibrate Kfull each time a new type of beer is placed in the keg, since the Kfull weight will vary from beer to beer. And Kfull must be known to determine the exact number of glasses of beer that remain. The math is left as an exercise for the reader. For even greater accuracy, and longevity, we chose an electronic scale. For the same reasons, we decided to go with a digital thermometer to measure beer temperature (Beert).

Now the Tricky Part

Our biggest challenge was interfacing the strain gauge and digital thermometer with a PC to produce interpretable values. For this, our University of Wisconsin electrical engineering team whipped up an A-D (analog to digital) circuit to convert the strain gauge and digital thermometer readings into digital values that are transmitted via a serial port common to PC architecture. The values reported from the circuit for keg weight are reported in a series of 255 increments.

Both the strain gauge and thermometer reside in the refrigerated compartment along with the keg, while the circuitry and power supply remain outside, thus preventing moisture and extreme temperatures from affecting their performance. The 8-bit A-D circuit provides 255 discrete values, and is specifically tuned for accuracy for weights near 10 pounds (when the keg is nearly empty) and near 42 degrees Fahrenheit.

To develop usage logs, we built a contact/closure switch that we attached to the tap handle v ia a push-pull rod. All of this runs inside a Vax VT220 monitor that also houses the tap mechanism, making the tap both a ttractive and functional. This also put the VaxTap 2000 Pro in perfect position for the next hardware upgrade: a servo-operated, audio-recognition-activated, autopour mechanism. We have a prototype working now that uses the Clapper for activation. However, early beta tests have exposed a problem: The user has but one free hand for activation since one hand is already holding the mug under the tap. This has forced users to smack their forehead twice to activate the tap. Feedback suggests that voice activation is the only way to go.

The VaxTap 2000 Pro instrument-monitoring hardware is connected through a serial port to our Web server--an Intel/Windows NT machine running IIS (Internet Information Server). We developed a Visual C++ program that listens to the serial port on the Web server. If an event occurs, such as the opening or closing of the tap, then the program logs an event description, along with the time of the event. Every 60 seconds the program polls the VaxTap circuitry, checking and then recor ding the keg's weight and temperature. The weight and temperature are sent to the server as hexadecimal numbers, and the program converts these numbers into approximate number of pints remaining and temperature in Fahrenheit.

Inquiring Minds Want to Know What did we do with all this information? You can access the VaxTap 2000 Pro Web page at www.NetworkComputing.com/822/822f3.html. There you'll find up-to-date data on keg volume and keg temperature, and be able to see if someone's logged into the keg at that very moment. We've also tracked our "pour" habits with some nice graphs. And, yes, we've even gone to the trouble of writing a program that will build charts from the log files, just so management (and you, loyal reader) can make sure our progress does not wane. You may notice, as we have, that the quantity of beer consumed increases as the end of the week approaches and shortly afte r editorial deadlines. This is even better than following stock market trends!

Jeff Newman can be reached at jnewman@nwc.com.