(image: cyclopian overload magic eye)

It was in Boston, and I was wandering up and down Center St. in search of a cup-o-joe and a bun. My spidey sense tingled and I turned: across the street, the silent siren-song for makers: a big, handwritten sign 'FREE' above a pile of electronics. Hello, nurse. Took a Twit-pic and posted my discovery.

Almost immediately, pal CTP pointed out that two out of the three contraptions had Magic Eye tubes. I had never heard of them, so I powered up google. Needles to say- these are right up there with Nixie tubes in electronic awesomeness.

More info and pics behind the jump..

(image: Magic Eye tube box via Philip Rheinschild, Jr.)

Magic Eye tubes were an offshoot on the CRT evolutionary tree. They were used mainly as indicators- tuning, volume, etc. The all glow green, but there are many, many different variations. They all provide a visual indication by altering the active and shadow areas of the 'iris'. The one above is a tube-tester- if the tube is good, the shadow area closes in to the 'good' lines. There are several great websites that include base diagrams, types/shapes of different magic eyes, and history.

I've yet to complete a project with them (I'm still on the road) but just playing around with the wiring it looks like potentiometers can trigger the iris (albeit with varied results). I tried this with a IR sensor and a mic, both of which showed  promise. It'll be at the top of the project list when I get back- I'd love to see how bend and touch sensors could be involved.