[B Gallagher]

Hey all,

Does anyone know exactly how the Sudden Motion Sensor in the PB's work?

I've found the following:

Sudden Motion Sensor technology is designed to help protect the PowerBook's internal hard drive -- a tri-axis accelerometer determines if the notebook is accidentally dropped.

"This system is unique to the PowerBook itself -- it's built in to the motherboard." As a result, Apple isn't dependent on any specific hard disk drive manufacturer, Russell told MacCentral.


But can anyone explain exactly what a tri-axis accelerometer is, and how it works? Thanks!

[analogika]

"tri-axis accelerometer" is just a device that measures acceleration in three dimensions - up/down, forward/back, and left/right.

This kind of thing *used to* be done with gyroscopes.

Nowadays, apparently, not.

Plugging "sudden motion sensor" into google (can you buy internet with google in NZ? Mine here came with it.) gives me, on the very first link to show up:

While I have no knowledge of how AMS works internally, it quite likely uses a "silicon sensor based on integrated micro-electromechanical systems (iMEMS) technology Acceleration or inclination causes an electrical property of the sensor, say capacitance, t be altered. The sensor's interface can appropriately translate these tiny changes to presen them as acceleration "readings".

FWIW.

[B Gallagher]

Originally Posted by analogika

(can you buy internet with google in NZ? Mine here came with it.)

[drprat]

i think he's simply wondering why you just didn't use google to answer your question....

[B Gallagher]

Hehe yes... there have been occasions where I've searched for something on here, not found it, and then proceded to post, without searching google. But everyone here seems prety helpful and friendly, and knows what they're talking about, so I prefer to ask a friendly forum group than google.

But yes, I will remember to use google in the future!

[chabig]

Originally Posted by analogika

This kind of thing *used to* be done with gyroscopes.

Not exactly. This has always been done with accelerometers. Gyroscopes measure rotation, not acceleration.

As for the motion sensor...when you are simply using your machine the accelerometer senses 1 g (force of gravity). When you drop it, the accelerometer feels 0 g. This signals the hard drive to park its heads.

Chris

[analogika]

ah, but the internal sms can be used to determine the orientation of the 'book - there's been tech demos where people you could turn and move the powerbook, and the view on the screen would move through a landscape accordingly...

[chabig]

Yes, you're right. I have a new Powerbook and I have played with the app that shows the orientation. With three linear accelerometers, you can resolve the orientation of the powerbook in three dimensions, without gyroscopes.

Chris

[madmacgames]

I guess Apple has just recently put these on their powerbooks? I've got a 12" 1GHz and it doesn't appear to have it.... a shame to, cause IBM has been putting similar technology in their Thinkpads for a few years now.

[Simon]

Yeah, it's a new feature on the rev D 12"/17" and on the rev C 15" as well as on the latest iBooks.

[madmacgames]

wonder if they got from help with the technology from IBM

[ibook_steve]

Originally Posted by madmacgames

wonder if they got from help with the technology from IBM

No, it was all Apple developed. I don't know if it's the same chip or not, but IBM had nothing to do with it.

Steve