How can I use RFIDs and some sort of detector to create a city-wide treasure hunt?

May 9, 2007 8:13 AM

How can I use RFIDs and some sort of detector to create a city-wide treasure hunt?

For my wife's birthday, I'd like to create a treasure hunt around the city we live in (Boston), taking us to different places we've gone. Is it possible to buy some sort of wand/detector/geiger counter type thingy that I can use to find the clues? I was thinking of something involving RFIDs that would make the device beep louder as we got closer (within a reasonable distance, like 30 feet or something). That way I could hide clues at different places and not have to worry about the impossible-ness of finding them. Is this at all possible?

They wouldn't be big clues, probably just a sheet of paper folded in half, in an envelope, either taped to a wall or something, or being held by a person at a restaurant or hotel or something. Is that enough room to put the RFID thing in? I really have no idea how this all would work technically, but I think that the concept is cool! If anyone has any ideas, please let me know.

posted by ab5000 to technology (9 comments total)

Do you know about Geocaching?
posted by Cat Pie Hurts at 8:19 AM on May 9, 2007 [1 favorite]

You probably don't want to be leaving electronic devices lying around Boston after what happened to the last people that did that.

I second the geocaching or letterboxing, though RFID specifically isn't used there, the city-wide treasure hunt definitely fits.
posted by DU at 8:24 AM on May 9, 2007

If your aim is to get people to a specific location before giving them a clue describing treasure in the vicinity then why not just tell them explicitly to go to the initial location?

If you want to get more elaborate then GPS would be useful as other have suggested. So would an ordinary paper map with a grid reference.

If you do want to use electronics then I would suggest that RFID is probably too short range. RADAR transponders or even Wifi base stations might be more effective.
posted by rongorongo at 9:01 AM on May 9, 2007

Most RFID devices have a range of about 4 inches. Scratch that :)

I'd suggest those little hotwheels-sized RC cars you get for $10 at toy stores. Take the circuit board out of the car, power it with a AAA battery, and wire the outputs to LEDs or motors or something that Gives A Clue. Dress it up like a geiger counter or what ever you want. This device can be key-chain sized, since the circuit board is tiny. Then, the transmitter can just have one of the buttons wired close, so it constantly transmits that signal, and when the receiving device is nearby, it will respond.

Buy multiple toy cars on the same frequency, and you can set each transmitter to be transmitting a different signal (forward, back, left, or right. You can also do combos - forward-left, etc), which will produce a different response in the receiving device. If it lights up different LEDs, maybe which LEDs light up gives the clue, for example, by indicating which things on a list to look for.
posted by -harlequin- at 9:28 AM on May 9, 2007

I forgot to add - the range of those little $10 RC cars is about 15 feet, but there are various hacks you can do to boost that a bit.
posted by -harlequin- at 9:30 AM on May 9, 2007

Another potentially useful trick - a directional antenna, such as putting a tin can around the antenna ("cantenna") on the receiver. This would mean the receiver needs to be pointed at things to see if the signal appears, making it more interactive. You need to Know Stuff to design a directional antenna for a frequency, but for many standard frequencies you can find info/plans online.
posted by -harlequin- at 9:42 AM on May 9, 2007

About bang on your suggested 30-foot radius are those little FM transmitters for MP3 players. They're about $30, and a super-cheap mp3 player is about $12. The receiving device could then be a simple radio, and the sound it makes would be whatever it's receiving, be it a beeping that gets louder as the signal improves with decreasing distance, or pop music with the lyrics being further clues, ala that "Help me Rhonda" Short Circuit movie scene.
posted by -harlequin- at 9:50 AM on May 9, 2007

RFID kits are available but I think that leaving electronic devices laying around is just begging for another Mooninite panic.
posted by chairface at 10:40 AM on May 9, 2007

RFID chips can be read at far more than a few inches, I believe the current record is 69 feet at one of the Black Hat cons. That said, the reader/trigger is likely to be substantially larger than a normal rfid device.

I'd go with the RF cars idea, but other ideas might include bluetooth or more diy wireless. Hell, if you're a real hardware hacker, ZigBee is almost designed for this kind of thing.
posted by Skorgu at 2:32 PM on May 9, 2007