Okay, so we may have lied in our last post. Although iButtons have long been our preferred way to authenticate to Kegbot, we've actually come up with something that is even more fun to use. Now presenting: the RFID-controlled Kegbot!
The reader itself costs about $50, and it is probably possible to get one cheaper. I use self-adhesive EM4102 (125 KHz) RFID tags, which cost about a buck each -- less expensive than a DS1920 iButton and FOB by a few dollars. Initial support for the RFID reader as an authentication device
has been checked in to kegbot.
HOWTO build your own RFID pint glass readerYou will need the following basic components:
- A USB RFID reader; I use the Phidget reader.
- A plastic drip tray. A steel tray might work, but may require some modification.
- A disposable food storage container.
Here's a pictoral overview.
Above: plastic drip tray, Phidgets USB RFID reader, disposable plastic food storage container.
Pop open the drip tray.
To get a feel for where the reader will go, you can place it inside. We'll mount it upside-down (so that the USB socket doesn't get in the way), around the center of the tray (right where the glassware would be placed).
Now, it is time to build a protective beer raincoat for our little "RFID reader that could". Here's where the food storage container comes in. Eat last night's leftovers, wash out the container, and discard the lid.
We're going to slice off most of the container, so that we're left with about 1/2" tall hood.
Using the plastic drip tray as an approximate guide, slice off the top of the container. I found that scissors actually work better, once you have a starter slice:
You will be left with something that looks like this:
Next, you are going to want to test your surgical prowess by trying to fit the grille portion of the drip tray back into place, with the hood sitting in the tray.
If your tray is like mine, you'll need to hack off a plastic standoff to make room for the hood:
When properly assembled, the grille should fit atop the hood like so:
Next, you will need to create something to prop the reader up off the bottom of the drip tray, so that it is a safe distances away from drip tray muck (and as close as possible to the top of the drip tray). At this point, some screw-in plastic standoffs would be great, but I did not have any handy.
I attempted to build standoffs out of leftover Ikea bookshelf dowels and small nails; this was a total failure. Instead, I managed to build a support out of something much more plentiful: party cup!
As you can see, no plastic foodware was spared the wrath of my "de-topping" rampage on this afternoon.
Next, I duct taped the little party-cup riser to the RFID reader, flipped the whole assembly over, and placed it in the top. I cut out a notch for the USB cable.
Finally, I found USB cable that I was comfortable dooming to a slow, sticky decline, and placed the entire assembly in the drip tray. (I opted to simply thread the cable out of the tray's top rather than drilling something in the side, since I didn't want to compromise the tray's ordinary liquid capacity.
Here's a close-up of the finished assembly:
And another, once assembled back together:
Finally, I stuck a little RFID sticker on the bottom of my mug and poured a drink:
Touchless beer authentication saves the day! Or.. something.
Conclusions & Future IdeasOverall, this is a lot of fun; it compliments the iButton reader (both happily coexist at the same time), and it definitely adds a "magic" factor to the kegbot, especially when the LCD greets you by name after swinging your glass into position.
The longevities of the adhesive on the RFID, and of the ID itself, still remain to be seen. The
tags I've used seem pretty sturdy, and I've put my mug through a couple of hot washes and the tag still works, but I wouldn't be surprised if it falls off one day.
If you have a mug you use regularly, adding an RFID tag to it could be lots of fun. Though the tags are probably less robust (and more likely to fall off or get lost) compared to an iButton, their price is low enough that I could see them still being useful in party situations: buy a bunch of tags for $1 each, charge people up front for cups for at least that much, and expect the tag and cup to be thrown away at the end of the night.
Taking the party concept one step further, the Kegbot core could even grow to support a 'gift card' type mode, where a particular authentication token is credited for a certain amount of beer, and no specific user account.
Finally, there are plenty of other tag types (including sturdier keychain fob packages), so there's no requirement that the RFID be in the pint glass, or even the drip tray.
I'm sure we will think of plenty of other fun things to do with this. Time to order some more tags!
