August 2016
Beginner to intermediate
336 pages
6h 28m
Chinese
Content preview from iPhone & iPad電子專案製作｜透過techBasic開發Arduino、感測器與藍牙應用
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第三章：打造金屬探測器
使用 iPhone 或 iPad 作為金屬探測器
先前我們曾提過，電流可產生磁場，磁場可產生電流，而金屬也會影響磁場。金屬這種
物質，其原子至少擁有一個連結力道寬鬆的電子，因此電子從這個原子移動到另一個電
子，相對而言較為容易，所有可移動的電子都會致使磁場稍稍彎曲，改變其強度與方向，
而這正是能夠把 iPhone 轉為金屬探測器的背後原理。
首先，讓我們先迅速進行幾項實驗，證明上述所說是否可行。地球磁場強度在每個地方
都不相同，在阿布奎基城約為 50 µT，那麼，一塊小小金屬物扭曲磁場的程度，是否夠
大能為我們所用呢？我執行第 2 章的磁力計範例，然後拿著 iPhone，在底下 6 英吋遠的
地方放著我的鍵盤，鍵盤外層包覆著一層鋁，圖 3-2 秀出實驗結果。
圖 3-2 iPhone 經過金屬物上方時的磁場變化 1
譯註：圖 3-2 與圖 3-3 從上到下的線條顏色是：紅色、藍色、綠色。
使用 iPhone 或 iPad 作為金屬探測器
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OK ！不錯，看起來應該可以派上用場。當我拿著 iPhone 經過鍵盤的邊緣時，會出現第
一個紅色與藍色的突起，以及綠色突起的前導邊緣，然而以此例而言資訊太多了，我並
不想要三個方向的磁場強度；移動時若翻轉 iPhone，則
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.