Page 18 - ARM Based Microcontroller Projects Using MBED

4 1. INTRODUCTION

FIG. 1.3 Adding a keypad and an LCD.

The system shown in Fig. 1.2 is a very simplified liquid level control system with no user
interaction. In a more sophisticated system we may include a keypad to set the desired liquid
level and an LCD (liquid crystal display) to see the desired and/or the actual liquid levels in
the tank. Fig. 1.3 shows the block diagram of our upgraded system. Notice that here we are
using two inputs and two outputs from our microcontroller.
We can make our system even more sophisticated as shown in Fig. 1.4 by adding an au-
dible alarm to indicate when the water level is above the desired point. Also, a PC can be
interfaced to the microcontroller so that, for example, the actual liquid levels can be sent
to the PC at regular intervals and graphs of liquid level variations can be plotted on the
PC between the required intervals.
In Fig. 1.5, wireless interface is added to our system in the form of Bluetooth or Wi-Fi. With
the help of the wireless interface we can, for example, send and save the liquid level readings
on a Cloud. Additionally, we can monitor and/or control the liquid level remotely through
the Cloud using, for example, a mobile phone. Because the microcontrollers are programma-
ble and in general offer many input and output ports, we can make our system as simple or as
complex as we like.
The power of microcontrollers is obvious from the simple example given in this section.
Microcontrollers are classified by the number of bits they process at a time. Although some
of the early microcontrollers were only 4 bits, the 8-bit devices are still the most popular and
commonly used devices. Examples of some 8-bit microcontrollers are PIC16, PIC18, Arduino,
8051, and so on. The 16-bit and 32-bit microcontrollers are faster, have more memories, and
are more powerful, but at the same time they are more expensive and their use may not be