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2011-03-16

How the iPad 2 Smart Cover performs its magic

iFixit has figured out how Apple’s Smart Cover for the iPad 2 works. This blog post summarizes the findings.
The Smart Cover folded as a keyboard stand. [Source: Apple]
The Smart Cover is one of the iPad’s most important features. It has several intriguing characteristics:
  • When you magnetically attach the Cover hinge to the iPad, it automatically “finds” the right place.
  • When you open the cover, the iPad is immediately switched on. There is no button to press and no on-screen widget to swipe.
  • The Cover also snaps closed and stays attached to the surface of the iPad. Upon closing, the iPad goes to sleep.
  • You can fold the Cover behind the iPad to prop it up slightly for typing (see image above) or to position it vertically for video viewing.
  • To get the Cover out of the way while holding the iPad, you can turn it over and it stays flat against the iPad’s back. The hinge remains attached while doing so.
iFixit has disected the Cover and the iPad to figure out how they work together. Here is a summary:
  • iPad
    • Left side (on the back): Magnets to attach the hinge.
    • Right side: Magnets to keep the Cover closed. These magnets are also needed to offset the reduction of rigidity caused by the segments.
    • A sensor in the bezel (on the right) registers whether a magnet is currently attached. Changes lead to the iPad going to sleep or waking up. There is a smaller magnet in the Cover dedicated to this purpose.
  • Smart Cover
    • Hinge: The hinge magnets alternate between positive and negative polarity. Those polarities are matched by the iPad magnets and are responsible for the Cover automatically attaching at the right place. The hinge actually consists of two hinges, to enable folding.
    • Left side: A metal plate works with the magnets at the right side to keep things in place when the Cover is folded up.
    • Right side: In addition to magnets assisting the right side of the iPad in keeping the Cover closed, there are several magnets with the sole purpose of increasing attachment strength during folding. The same effect could have been achieved by making the left side magnetic, but that might have adversely affected the iPad.

The Cover contains a metal plate on the left side and 14 large magnets on the right side. Of these, 4 attach to the iPad, the other 10 are only used to hold the metal plate during folding. An extra small magnet (top left corner of the yellow rectangle) is used for switching the iPad on or off. [Source: iFixit]
I am surprised that Apple has actually built magnets into the iPad, but apparently that was necessary to make the attachment strong enough. It just goes to show how iPad and Cover have been designed in tandem.

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