Hardware Reference
In-Depth Information
DHT11 humidity and temperature sensor
Breadboard
Wires
10 kilohm resistor
You can i nd the code download for this chapter at http://www.wiley.com/
go/arduinosketches on the Download Code tab. The code is in the Chapter 10
folder and the i lename is chapter10.ino .
NOTE The Wireless technology name is Wi-Fi with a hyphen, but in the Arduino
library, where it is unable to use hyphens, it is called WiFi. For this chapter, Wi-Fi refers
to the technology, and WiFi to the Arduino library capable of using WiFi cards.
Introduction
All aspects of computers have evolved at an incredible rate. A high-end com-
puter from 10 years ago is, by today's standard, easily surpassed by a mobile
telephone. Processors, memory, and storage have all increased, and component
size has drastically decreased. Mobile computers used to be rare; today, laptop
computers are seen just about everywhere, as are tablets, smartphones, and even
smart watches. The need for mobility has been driving the industry for years,
but the need for data even more so.
Early networks were slow, complicated, cabled systems. Today, Ethernet
technology can be found in almost every house. On the back of most Internet
modems is a small Ethernet switch, providing four or more “ports”; connect-
ing a computer is as simple as plugging an Ethernet cable in the ports. To add
another computer, just plug in another cable in the next open port. This is perfect
for households, and the same technology also powers huge companies with
thousands of computers, including the Internet. Networks have become fast and
reliable, but until recently, the need for physical wiring conl icted with mobility.
Mobile users had data on the go. Commercial teams could have documents
on their computer with them, and engineers could have development tools and
diagnostics with them. However, to get access to the Internet, or even to transfer
documents, they had to plug in their laptop to the company's network. Most
meeting rooms had an Ethernet switch with a few cables, just in case anyone
needed quick access. Mobile devices would never be truly mobile until they got
rid of the cables tethering them to the desk, and so Wi-Fi was born.
 
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