ChApTEr 2 ■ hArdwArE for IoT SoluTIonS- Speed sensors: Similar to flow sensors, simple speed sensors like those found
on many bicycles use a magnet and a reed switch to generate a Hall effect. The
frequency combined with the circumference of the wheel can be used to calculate
speed and, over time, distance traveled. Yes, a bicycle computer is yet another
example of a simple sensor network: the speed sensor on the wheel and fork
provides the data for the monitor on your handlebars. - Switches and pushbuttons: These are the most basic of digital sensors used to detect
if something is set (ON) or reset (OFF). - Tilt switches: These sensors can detect when a device is tilted one way or another.
Although simple, they can be useful for low-cost motion-detection sensors. They are
digital and are essentially switches. - Touch sensors: The touch-sensitive membranes formed into keypads, keyboards,
pointing devices, and the like are an interesting form of sensor. You can use
touch-sensitive devices like these for sensor networks that need to collect data
from humans. - Video sensors: As mentioned previously, it’s possible to obtain small video sensors
that use cameras and circuitry to capture images and transmit them as digital data. - Weather sensors: Sensors for temperature, barometric pressure, rainfall, humidity,
wind speed, and so on, are all classified as weather sensors. Most generate digital
data and can be combined to create comprehensive environmental sensor networks.
Yes, it’s possible to build your own weather station from about a dozen inexpensive
sensors, an Arduino (or a Raspberry Pi), and a bit of programming to interpret and
combine the data.
Computer Systems
A complete discussion of IOT hardware (at least hardware for the nodes in the network) would be
incomplete without mentioning computer systems. Desktop or server computers can be used in your IOT
solutions in a number of ways, from providing a reliable platform for a database server, web server, firewall
to the Internet, or cloud gateway (or all of these).
I typically try to avoid using computer systems in my IOT solutions mainly to keep cost down but also
because low-cost computer boards and microcontroller boards are more than adequate for the solutions I’ve
built (or dream about building).
However, if you do want to use a computer system in your IOT solution, you should do so. Just consider
the added cost (even small shoebox computers are many times the cost of a Raspberry Pi), physical size
and mounting or location, and additional power requirements (they’re not easy to run off of batteries or
solar power).
Finally, make sure you take necessary precautions in securing your computer systems so that they are
not vulnerable to intrusion or invite attacks. Hackers can generally wreak much more havoc with a computer
system than, say, an Arduino. However, don’t dismiss low-cost computer boards as safe; they aren’t. Most
are also good targets for hackers given they often run powerful Linux operating systems.