Raspberry Pi Cookbook, 4th Edition

Chapter 14. Sensors

14.0 Introduction

In this chapter, we look at recipes for using sensors of various types that will enable the Raspberry Pi to measure temperature, light, and more.

Unlike boards such as the Arduino and the Raspberry Pi Pico, a regular Raspberry Pi lacks analog inputs. This means that for many sensors, it is necessary to use additional analog-to-digital converter (ADC) hardware. Fortunately, this is relatively easy to do. It is also possible to use resistive sensors with a capacitor and a couple of resistors.

Many of the recipes will require the use of a solderless breadboard and male-to-female jumper wires (see Recipe 10.9).

14.1 Using Resistive Sensors

Problem

You want to connect a variable resistor to a Raspberry Pi and measure its resistance to determine the position of the variable resistor’s knob in your Python program.

Solution

You can measure resistance on a Raspberry Pi using nothing more than a capacitor, a couple of resistors, and two general-purpose input/output (GPIO) pins. In this case, you will be able to estimate the position of the knob on a small variable resistor (trimpot) by measuring its resistance from its slider contact to one end of the pot.

To make this recipe, you’ll need the following:

• Breadboard and jumper wires (see “Prototyping Equipment and Kits”)

• 10kΩ trimpot (see “Resistors and Capacitors”)

• Two 1kΩ resistors (see “Resistors and Capacitors”)

• 330 nF capacitor (see “Resistors and Capacitors” ...