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Everything I know about interaction design I learned by making a scratch-n-sniff television

My favorite thing about my Scratch-n-Sniff TV is the conversations it spawns. I showed it recently at Maker Faire NY, and as at previous showings at ITP and at Greylock Arts, reactions were divided. About 70% of people were totally incredulous until they tried it, and then were delighted and had to find out how it worked. Of the remaining 30%, half looked at it suspiciously and rebuffed invitations to try it and the other half tried to predict how it worked before using it and then complained that the smells weren’t “accurate.” All of these reactions reveal an underlying attitude towards technology and its possibilities: the first, marvel—the what will they think of next effect; the second, suspicion—this has got to be a trick; the third, which shares elements of the second, a need to establish that we control technology—not the other way around.


Smell is subjective, it’s ephemeral, and it’s not binary. What smells like citrus to one person smells like air freshener to another; smells can’t be turned on and off, they waft, so getting people to believe that their actions resulted in equal and opposite smell reactions required some clever sleight of nose. First of all, I gave people clear visual cues. When you scratch a picture of chocolate, you’re much more likely to interpret the resulting smell as chocolate. I also made the screen respond to being scratched by fading, just as scratch-n-sniff stickers do after vigorous scratching. This tie-in to a direct physical analogue was key, as people were much more likely to smell the screen where they’d scratched it and the one-to-one correspondence between action and reaction primed people to smell. A couple of times I ran out of scents, and several people still swore they’d smelled scents that simply weren’t there!



  1. I found that the transistor-based model of the Glade Flameless Candle automatic air freshener would fire once approximately every two seconds if powered for 500 milliseconds (as opposed to the earlier version that relies on a resonant circuit that requires ten seconds before firing), so I hooked up its battery terminals to an Arduino, and voila! Controllable atomization of non-oil based scents!


  1. Trying to create an effective scent disperser from scratch is madness. One of the benefits of piggybacking on all of Glade’s hard work is that it’s easy to fill the provided smell canisters with other scents. I got most of mine from the nice folks at Demeter.


  1. I aligned the scent dispensers under a touchscreen sending touch coordinates to the Arduino via Processing sketch. Thanks to the hydrostatic properties of the fine particle mist, when emitted, it flows up the screen and across it, sticking to it until the scent evaporates a few seconds later.



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