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Another Beer Please

Posted by michael on from the brooklyn-lager dept.

jmichaelg writes "What do you get when you combine a glass, a PIC computer, two capacitors, a coil and a zener Diode? A wireless beer glass that signals your waiter when you need a refill. The circuit is an RFID transponder that measures the fluid level in a glass and transmits a globally unique ID coupled to the fluid level reading when queried by an antenna hidden in your table. The query provides enough power to drive the circuit so no batteries are needed. A technical paper describes the circuitry in the table and the glass." This hit the news over a year ago, but we didn't have the technical details.

3 of 333 comments (clear)

  1. Low tech solution by Matthias+Wiesmann · · Score: 5, Informative
    I like high tech stuff, but sometimes, there is a simple low-tech solution that is simpler, cheaper and often more robust.

    Do you know that there is a low tech solution that is in use for years? In germany beer mugs have a lid. If the lid is open, the waiter knows you want a refill, if not you don't want a refill...

    This solution is also wireless...

  2. Re:Definitely neat. But... by BadDoggie · · Score: 4, Informative
    And you've never actually worked as a server there. There are about 10,000 guests in each tent, being served by about 50-80 women who have to carry up to a dozen freshly-filled 1-liter mugs (Maßkruüge), each weighing in at 2.2kg. Calm down and wait your turn. Maybe if you tried tipping more than the 12 cents to round it up to the next full euro you'd get better service.

    This advice on Oktoberfest bears repeating:

    1. Put your butt on a bench and they'll bring you a beer. You will NOT be served at Oktoberfest unless you are seated. Everyone will let you sit down for the two or three minutes necessary to order a beer if you ask nicely and tell them that's what you're doing.
    2. Tourists go to the HB (Hofbräuhaus); the best beer is Augustiner.
    3. To be sure to get faster service, fuller beer steins and better food, tip 15% or more. The women work HARD (and if you had to listen to the "Hey, Baby" song 3 times an hour, 13 hours a day for 2 1/2 weeks straight, you'd understand).
    I don't need a mug that tells the staff I need another beer; I need one that tells me I don't!

    woof.

  3. Re:Inductive coupling by edhall · · Score: 3, Informative

    Read the article; it's far more ingenious than that. The coil is just feed into two PIC inputs, and the PIC's static-protection diodes do the rectification. A zener and a cap across the power pins complete the power supply.

    It gets better. They use the clock pin as one of those inputs. Thus the chip is clocked by the received RF. And by briefing switching the other input to an output, they communicate pulses back to the sender. (That right -- no separate RFID chip, the PIC does all the sending as well as the sensing.)

    Speaking of sensing, it gets even better. The capacitance measurement used to determine the fluid level is done by switiching two other input/output pins and a fixed capacitor to create a charge pump measurement. By counting the number of times a charge on the fluid-measuring capacitance has to be transfered to the fixed capacitor to bring it up to a logic level, they measure picofarad differences corresponding to changing fluid levels easily.

    An utterly amazing bit of minimalist engineering!

    -Ed