Building iPhone and iPad Electronic Projects

Chapter 3. Creating a Metal Detector

About This Chapter

Prerequisites

Read Chapter 1 and the end of Chapter 2 (the section on the techBASIC help system) if you need some help with techBASIC. If you are already comfortable with techBASIC, jump right in.

Equipment

You will need an iPhone, iPod, or iPad running iOS 5 or later.

Software

You will need a copy of techBASIC or techBASIC Sampler.

What You Will Learn

This is a project chapter, using knowledge from Chapter 1 and Chapter 2 to develop a metal detector. There’s also a lot of background material explaining why the metal detector works and, in some cases, why it doesn’t. It always helps to know the limitations of an instrument!

The magnetometer in the iPhone is an amazing instrument that gives you the magnetic field strength along three axes in microteslas (µT). Apple software uses this instrument to find the direction in which the iPhone is pointed. This chapter looks at how the magnetometer works, shows you how to access the data from techBASIC, and illustrates using the magnetometer to develop a metal detector.

The iPhone/iPad Magnetometer

If you’re like me, just using a metal detector is not all that much fun. I want to know how it ticks. That’s what the first few parts of this chapter are about. If you don’t care, skip to Using the iPhone or iPad as a Metal Detector, where you’ll find a description of how to use the metal detector app.

Starting with the iPhone 3GS, all iPhones have a built-in magnetometer. All iPads have ...