January 2024
Beginner to intermediate
560 pages
8h 38m
Japanese
Content preview from Raspberry Piクックブック 第4版
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14章 センサーSensors
この章では、さまざまな種類のセンサーを使ってRaspberry Piで温度や光などを測定するレシピを見ていこう。
ArduinoやRaspberry Pi Picoなどのボードとは違って、通常のRaspberry Piにはアナログ入力がない。つまり、多くのセンサーを使うには外付けのアナログ・デジタル変換器（ADC）が必要だ。幸い、ADCの使い方は比較的簡単だし、抵抗性のセンサーにはコンデンサーと抵抗を数個使って抵抗値を測定することもできる。
多くのレシピでは、ハンダ付け不要のブレッドボードとオス─メスのジャンパー線を使う必要がある［レシピ10.9を参照］。
レシピ14.1：抵抗性センサーを使う
●課題 Raspberry Piに可変抵抗器を接続し、Pythonプログラムから抵抗値を測定して可変抵抗器のつまみの位置がわかるようにしたい。
●解決 Raspberry Piと1個のコンデンサー、2本の抵抗、そして2本の汎用入出力（GPIO）ピンを使えば、抵抗値を測定できる。ここでは、小型の可変抵抗器（半固定抵抗）の一端と可動接点との間の抵抗値を測定することによって、つまみの位置を推定してみよう。
このレシピの製作には、以下のものが必要だ。
- ブレッドボードとジャンパー線（付録Aの「プロトタイピング用の器材とキット」を参照）
- 10kΩの半固定抵抗（付録Aの「抵抗とコンデンサー」を参照）
- 1kΩの抵抗を2本（付録Aの「抵抗とコンデンサー」を参照）
- 0.33μFのコンデンサー（付録Aの「抵抗とコンデンサー」を参照）
図14-1に、ブレッドボード上の実体配線図を示す。
図14-1 Raspberry Piで抵抗値を測定する
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