Metal detector applications in smartphone use magnetometer to detect the variation of magnetic field strength. Since magnetic field influence decays with distance, it is important to make the magnetometer close to the target as much as possible. However, magnetometer IC is a small block sealed inside of the phone. How can we know its location? If you look the part I of the following video, it gives some tips.
The proposed approach is to move a steel bar around the phone and find the spot generating the strongest magnetic strength reading. The phone used in the video is Nexus One produced by Google. The conclusion is that lower left corner of the phone is the approximate location of magnetometer sensor IC.
To provide more evidence, we checked various teardown reports of Nexus One smartphone. One interesting image we found is from ifixit teardown repot (http://www.ifixit.com/Teardown/Nexus-One-Teardown/1654/2).AK8973 is the magnetometer IC name. This PCB board is at lower part of the phone and it is bottom view of the board. Therefore, we know that the magnetometer is located near lower left corner of Nexus One phone. Same as what we find by steel bar.
I also tried the same steel bar trick with iPhone 3GS. It turns out that we should use the upper right part of 3GS for metal detector. To confirm, we searched 3GS teardown reports and find the this picture fromhttp://www.appleinsider.com/articles/09/06/24/cost_to_build_apples_new_iphone_3g_s_estimated_at_179.html
This page shows the main PCB board. The left part of this picture corresponds to the top of the phone. Also, this is the bottom view of the board. So the location of the magnetometer IC (AK8973) is the upper right edge of the 3GS phone. Same as we found by steel bar!
(original post published in Dec 19, 2010)
No comments:
Post a Comment