Apple's spiffy iPad 2 display protector, dubbed Smart Cover, has proven to be a hit among early reviewers. But the curious folks at iFixit wanted to know, "How does it work?" So they took it apart to find out.
It almost seems like overkill, because at first glance, there doesn't seem to be much to the Smart Cover. It's a set of folding polyurethane or leather panels, and it attaches unerringly -- some might be tempted to say "magically" -- in place with magnets to protect the touchscreen. You can see the Smart Cover clicking slickly into place in this Apple YouTube video.
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But how exactly did Apple pull off this bit of magic? Was it with breakthrough high-tech wizardry, perhaps using something called "correlated magnets," which make use of signal correlation and coding theory to allow magnetic forces to be very precisely controlled, and even programmed to interact with each other in specific ways? (Check out the pioneer in this field, Correlated Magnetics Research).
As it turns out, Smart Cover is almost low-tech, and its magic lies in some very clever design decisions. Here's what the iFixit teardown (the complete report is online) revealed:
* The four same-size panels of a Smart Cover consist, from left, of a steel plate, two all-plastic panels, and a large collection of magnets in the far-right panel. All four are sheathed in either polyurethane or leather.
* Apple used a lot of magnets: The Smart Cover is actually a system of 31 quite strong magnets: 10 in the tablet itself, and 21 magnets inside the Smart Cover, arranged on the left and right sides of both products.
The accompanying photo, courtesy of iFixit and shot with magnetic sensitive film, shows the cluster of magnets on the right side of both the Smart Cover and the iPad2. Both the cover and the tablet have another row of magnets on their left sides.
* Despite the magic, the magnets themselves are completely conventional, two-pole magnets.
* On the right side of the cover is a round magnet, circled in red in the photo, which triggers the built-in sleep sensor on the tablet, turning off the iPad 2 screen when the cover snaps in place.
* The rest of the magnets in this right-side grouping are used in two ways: four to clamp to matching magnets on the iPad's right side, and the rest to hold the panels in the triangular shape that forms the iPad 2 stand.
* The triangle forms by folding the sections from right to left, to bring the Smart Cover's right-hand group of 15 magnets into contact with the steel plate on the left-hand side. "A steel-to-magnet bond is weaker than a magnet-to-magnet bond, and so they needed lots more magnets to prevent the case from literally falling apart during use," according to iFixit.
* Because the iPad 2 has an aluminum case, the Smart Cover magnets wouldn't "stick." Apple added a set of magnets in the tablet itself, and these magnets match with the magnets in the Smart Cover to hold together. Cleverly, the tablet's magnets have alternating polarities, which match with the corresponding reverse polarity of magnets in the Smart Cover. The result: The cover always snaps into place correctly.
* A similar approach on the left side of cover and tablet means the two clamp together properly and securely.
John Cox covers wireless networking and mobile computing for Network World.
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