Author: Emery Premeaux & Brian Evans
Aimed at: Hardware enthusiasts
Pros: A great idea
Cons: Not enough projects
Reviewed by: Harry Fairhead
This is a really nice idea. All you have to do to save the world is create sensor packages that are cheap enough and robust enough to be used everywhere. Of course, knowing what is going on isn't quite enough to save the world. After measurement has to come action but it is a good first step.
The main author starts the book off by describing the effect, personal effect that is, of the recent Tokyo earthquake and the way a Japanese hackerspace created a GPS position-locating Geiger Counter. Alas there is no project of this size described in the book. There is also no Geiger Counter, if this is what you are looking for. In fact as an attempt to save the world, even with sensors the whole book is a bit limited.
It has only seven chapters and it goes over the same ground quite a few times. What there is is good, but it hardly gets off the launch pad.
Chapter 1 is a general orientation chapter. It tells you about the Arduino and its Analog to Digital Converter in particular. It introduces the problem of setting a reference voltage, a topic that is repeated in other chapters. What it assumes the reader knows is also very variable. One minute we have a discussion of a range of sensor chips and then we have a discussion of a simple voltage divider. The chapter finishes with how to build a breadboard shield.
Chapter 2 is where the construction of sensor systems really gets started. Its a simple six probe temperature measuring system. There is an interesting discussion of using the standard temperature chips - LM35D and MCP9700. How to mount them and how to calibrate. A simple test program is reasonably well explained. Then we have adding a display and powering the whole thing using a battery - and comments on the reference voltage problem.
The next chapter isn't a sensor-based project, but looks at how to keep an Arduino running on solar and other power sources. After a general overview of harvesting power, we return to solar with a very simple circuit. Again we have a discussion of the reference voltage problem and an introduction of a DC/DC converter. There is an interesting discussion of power saving modes and the Arduino plus sensors before we move on to a solar-powered project complete with realtime clock sleep controller. Quite a few pages are all about how to measure the current drain of the project, i.e. how to insert a multimeter to measure current into the power lead. Again the level of knowledge expected of the reader varies a lot.
Chapter 4 is about using wireless and the author tends to prefer the simple and easy to use Chibi over the more complex Zigbee. After wasting lots of time on Zigbee radio modules, I think I agree. The rule seems to be to keep it simple, very simple. The big problem is that in this chapter the reasonable explanations of the code give way to listings that only have comments to help you understand. This is a difficult topic made more difficult by the compressed presentation and the long code listings.
Chapter 5 is about getting data onto the web and it is essentially about using Pachube. The only problem is that Pachube was recently taken over and renamed Cosm. However the URL quoted in the book redirect to the new site and most of the information given works. The chapter provides an example project of connecting an Arduino to Pachube/Cosm.
Chapter 6 presents the most interesting and innovative of the projects - a digital seismometer. If you are expecting big massive weights to act as resonant devices, then think again. This project is based on a simple accelerometer that is added to an Ardino and then burried in the ground. It is a simple project apart from the details of how you seal it in a jar and then bury it in the ground. The readings from the accelerometer are in G force experienced and this is converted to earthquake intensity. At best the sensor is going to detect an intensity 3 or 4 tremor. Unfortunately, this is going to be sensitive to high frequency vibration generated by things like passing cars, trucks and so on. To be really effective the system should be tuned to pick up frequencies below 1Hz or so and 10 to 100 Hz if you are interested in "microquakes". What this all means is that the device is a fun project but probably not going to work well - except for big close earthquakes.
The final chapter is about measuring power consumption using a current sensing transformer. This basically replicates the function of the pre-packaged plugin power meters that can be bought cheaply. A project that took one of these and simply hacked into its display would probably have been more practical, but not as interesting. This chapter is written by the second author and the change of style shows.
The book finishes suddenly without an overview or a "where next". Of the projects that it presents, only the seismometer is novel and exciting. In a book about building sensors to save the world we don't get to measure much - where's the humidity, rainfall, solar energy, pollution, chemical detectors and, most missed, where is the Geiger counter?
Ok probably too much for a single author or even two authors but its what you might expect from a the title. Also with the range of sensors you now find in a mobile phone it all looks a little underpowered. This isn't a completely useless book and there were sections of it I enjoyed reading but it just didn't go far enough in any direction. The theory was limited and the practice tended to repeat basic ideas. It you are interested in using an accelerometer, building a solar powered Ardiuno module or using some simple wireless communication then you might want to read this book - but only if you are a beginner.
The final verdict has to be "nice idea, but shame about the execution".