Example research essay topic: In-depth Explanation Of How Microcontrollers Work – 1,844 words

Microcontrollers are hidden inside a surprising
number of products these days. If your microwave
oven has an LED or LCD screen and a keypad, it
contains a microcontroller. All modern automobiles
contain at least one microcontroller, and can have
as many as six or seven: The engine is controlled
by a microcontroller, as are the anti-lock brakes,
the cruise control and so on. Any device that has
a remote control almost certainly contains a
microcontroller: TVs, VCRs and high-end stereo
systems all fall into this category. Nice SLR and
digital cameras, cell phones, camcorders,
answering machines, laser printers, telephones
(the ones with caller ID, 20-number memory, etc.),
pagers, and feature-laden refrigerators,
dishwashers, washers and dryers (the ones with
displays and keypads)… You get the idea.
Basically, any product or device that interacts
with its user has a microcontroller buried inside.
In this edition of HowStuffWorks, we will look at
microcontrollers so that you can understand what
they are and how they work.

Then we will go one
step further and discuss how you can start working
with microcontrollers yourself — we will create a
digital clock with a microcontroller! We will also
build a digital thermometer. In the process, you
will learn an awful lot about how microcontrollers
are used in commercial products. What is a
Microcontroller? A microcontroller is a computer.
All computers — whether we are talking about a
personal desktop computer or a large mainframe
computer or a microcontroller — have several
things in common: All computers have a CPU
(central processing unit) that “executes
programs.” If you are sitting at a desktop
computer right now reading this article, the CPU
in that machine is executing a program that
implements the Web browser that is displaying this
page. The CPU loads the program from somewhere. On
your desktop machine, the browser program is
loaded from the hard disk. The computer has some
RAM (random-access memory) where it can store
“variables.” And the computer has some input and
output devices so it can talk to people.

On your
desktop machine, the keyboard and mouse are input
devices and the monitor and printer are output
devices. A hard disk is an I/O device — it
handles both input and output. The desktop
computer you are using is a “general purpose
computer” that can run any of thousands of
programs. Microcontrollers are “special purpose
computers.” Microcontrollers do one thing well.
There are a number of other common characteristics
that define microcontrollers. If a computer
matches a majority of these characteristics, then
you can call it a “microcontroller”:
Microcontrollers are “embedded” inside some other
device (often a consumer product) so that they can
control the features or actions of the product.
Another name for a microcontroller, therefore, is
“embedded controller.” Microcontrollers are
dedicated to one task and run one specific
program. The program is stored in ROM (read-only
memory) and generally does not change.
Microcontrollers are often low-power devices.

A
desktop computer is almost always plugged into a
wall socket and might consume 50 watts of
electricity. A battery-operated microcontroller
might consume 50 milliwatts. A microcontroller has
a dedicated input device and often (but not
always) has a small LED or LCD display for output.
A microcontroller also takes input from the device
it is controlling and controls the device by
sending signals to different components in the
device. For example, the microcontroller inside a
TV takes input from the remote control and
displays output on the TV screen. The controller
controls the channel selector, the speaker system
and certain adjustments on the picture tube
electronics such as tint and brightness. The
engine controller in a car takes input from
sensors such as the oxygen and knock sensors and
controls things like fuel mix and spark plug
timing.

A microwave oven controller takes input
from a keypad, displays output on an LCD display
and controls a relay that turns the microwave
generator on and off. A microcontroller is often
small and low cost. The components are chosen to
minimize size and to be as inexpensive as
possible. A microcontroller is often, but not
always, “ruggedized” in some way. The
microcontroller controlling a car’s engine, for
example, has to work in temperature extremes that
a normal computer generally cannot handle. A car’s
microcontroller in Alaska has to work fine in -30
degree F weather, while the same microcontroller
in Nevada might be operating at 120 degrees F.
When you add the heat naturally generated by the
engine, the temperature can go as high as 150 or
180 degrees F in the engine compartment.

On the
other hand, a microcontroller embedded inside a
VCR hasn’t been ruggedized at all. The actual
processor used to implement a microcontroller can
vary widely. For example, the cell phone shown on
this page contains a Z-80 processor. The Z-80 is
an 8-bit microprocessor developed in the 1970s and
originally used in “home computers” of the time.
The Garmin GPS shown in How GPS Receivers Work
contains a low-power version of the Intel 80386, I
am told. The 80386 was originally used in desktop
computers. In many products, such as microwave
ovens, the demand on the CPU is fairly low and
price is an important consideration.

In these
cases, manufacturers turn to dedicated
microcontroller chips — chips that were
originally designed to be low-cost, small,
low-power, embedded CPUs. The Motorola 6811 and
Intel 8051 are both good examples of such chips.
There is also a line of popular controllers called
“PIC microcontrollers” created by a company called
Microchip. By today’s standards, these CPUs are
incredibly minimalistic; but they are extremely
inexpensive when purchased in large quantities and
can often meet the needs of a device’s designer
with just one chip. A typical low-end
microcontroller chip might have 1,000 bytes of ROM
and 20 bytes of RAM on the chip, along with eight
I/0 pins. In large quantities, the cost of these
chips can sometimes be just pennies. You certainly
are never going to run Microsoft Word on such a
chip — Microsoft Word requires perhaps 30
megabytes of RAM and a processor that can run
millions of instructions per second.

But then, you
don’t need Microsoft Word to control a microwave
oven, either. With a microcontroller, you have one
specific task you are trying to accomplish, and
low-cost, low-power performance is what is
important. Using Microcontrollers In How
Electronic Gates Work, you learned about
7400-series TTL devices, as well as where to buy
them and how to assemble them. What you found is
that it can often take many gates to implement
simple devices. For example, in the digital clock
article, the clock we designed might contain 15 or
20 chips. One of the big advantages of a
microcontroller is that software — a small
program you write and execute on the controller —
can take the place of many gates.

In this article,
therefore, we will use a microcontroller to create
a digital clock. This is going to be a rather
expensive digital clock (almost $200!), but in the
process you will accumulate everything you need to
play with microcontrollers for years to come. Even
if you don’t actually create this digital clock,
you will learn a great deal by reading about it.
The microcontroller we will use here is a
special-purpose device designed to make life as
simple as possible. The device is called a “BASIC
Stamp” and is created by a company called
Parallax. A BASIC Stamp is a PIC microcontroller
that has been customized to understand the BASIC
programming language. The use of the BASIC
language makes it extremely easy to create
software for the controller.

The microcontroller
chip can be purchased on a small carrier board
that accepts a 9-volt battery, and you can program
it by plugging it into one of the ports on your
desktop computer. It is unlikely that any
manufacturer would use a BASIC Stamp in an actual
production device — Stamps are expensive and slow
(relatively speaking). However, it is quite common
to use Stamps for prototyping or for one-off demo
products because they are so incredibly easy to
set up and use. They are called “Stamps,” by the
way, because they are about as big as a postage
stamp. Parallax makes two versions of the BASIC
Stamp: the BS-1 and the BS-2. Here are some of the
differences between the two models: Spec BS-1 BS-2
RAM 14 bytes 26 bytes EEPROM 256 bytes 2 kilobytes
Max program length about 75 instructions about 600
instructions Execution speed 2,000 lines/sec 4,000
lines/sec I/O pins 8 16 The specific BASIC Stamp
we will be using in this article is called the
“BASIC Stamp Revision D” (pictured below).

The
BASIC Stamp Revision D is a BS-1 mounted on
carrier board with a 9-volt battery holder, a
power regulator, a connection for a programming
cable, header pins for the I/O lines and a small
prototyping area. You could buy a BS-1 chip and
wire the other components in on a breadboard. The
Revision D simply makes life easier. You can see
from the previous table that you aren’t going to
be doing anything exotic with a BASIC stamp. The
75-line limit (the 256 bytes of EEPROM can hold a
BASIC program about 75 lines long) for the BS-1 is
fairly constraining. However, you can create some
pretty neat stuff, and the fact that the Stamp is
so small and battery operated means that it can go
almost anywhere.

Programming the BASIC Stamp You
program a BASIC Stamp using the BASIC programming
language. If you already know BASIC, then you will
find that the BASIC used in a Stamp is
straightforward but a little stripped-down. If you
don’t know BASIC, but you do know another language
like C, Pascal or Java, then picking up BASIC will
be trivial. If you have never programmed before,
you probably want to go learn programming on a
desktop machine first. Here is a quick rundown on
the instructions available in Stamp BASIC. (For
complete documentation, go to the Parallax site
and click on the “Downloads” button in the toolbar
on the left.) Standard BASIC instructions:
for…next – normal looping statement gosub – go
to a subroutine goto – goto a label in the program
(e.g.

– “label:”) if…then – normal if/then
decision let – assignment (optional) return –
return from a subroutine end – end the program and
sleep Instructions having to do with I/O pins:
button – read a button on an input pin, with
debounce and auto-repeat high – set an I/O pin
high input – set the direction of an I/O pin to
input low – set an I/O pin low output – set the
direction of an I/O pin to output pot – read a
potentiometer on an I/O pin pulsin – read the
duration of a pulse coming in on an input pin
pulsout – send a pulse of a specific duration out
on an output pin pwm – perform pulse width
modulation on an output pin reverse – reverse the
direction of an I/O pin serin – read serial data
on an input pin serout – ….

Research essay sample on In depth Explanation Of How Microcontrollers Work