08-Chapter 8 - Microcontrollers

bendembarrassElectronics - Devices

Nov 2, 2013 (3 years and 7 months ago)

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Chapter 8

Microcomputers


Micro
computer




Micro
controller

What’s the difference?

Homework 7

1.
What is a microcontroller?

What are some common applications of these?



A microcontroller is a simple computer on a single
silicon chip that cost only a few dollars.



They are useful in washing machines, toasters, and
cars.

Microcontrollers in Cars and Trucks?

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.

Interesting…

Any device that has a
remote control

almost certainly contains a
microcontroller: TVs, VCRs and high
-
end stereo systems all fall
into this category.


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.


Basically, any product or device that interacts with its user has a
microcontroller buried inside.

PIC Microcontroller


We will use the
16F84A

microcontroller made by
Microchip for the team project. Use the Internet to
research these chips.



Acronyms



IC


RAM


ROM


PROM


EPROM


EEPROM


PIC

IC


Integrated Circuits

RAM


Random Access Memory

ROM


Read Only Memory

ROM cannot be modified (at least not very quickly or easily),

ROM


Read Only Memory

ROM cannot be modified (at least not very quickly or easily),

PROM


Programmable Read Only Memory


setting of each bit is locked by a fuse

Google “PROM Memory”

EPROM


Erasable Programmable Read Only Memory

EEPROM


Electronically Erasable Programmable Read Only Memory

EEPROM


Electronically Erasable Programmable Read Only Memory

PIC


Programmable Integrated Circuits

The SFA Rover

Team Project

The Vehicle Course

50
-
feet

6
-
feet

The Vehicle Course

50
-
feet

6
-
feet

Extra Credit

Scoring

D = Distance traveled in feet in 10 minutes



(the maximum distance is 50
-
feet)

R = 15 if the vehicle successfully demonstrates avoiding an obstacle on


the right and 0 if it is not demonstrated

L = 15 if the vehicle successfully demonstrates avoiding an obstacle on


the left and 0 if it is not demonstrated

T =
-
10 each time the vehicle is touched by a team member during the


course


Grade = T + L + R + D
×

70/(50ft)


Bonus: For each extra left or right obstacle avoided, 2 points of extra
credit will be earned for each member of the team. A maximum of 20
extra points can be earned in this manner.

Left
Button

Right
Button

PIC
Microcontroller

H
-
Bridge

9
-
Volt
Battery

Right
Motor

Left
Motor

Voltage
Regulator

SFA Rover Circuit Diagram

Key Concepts

Note that the parts used in the team
project are discussed in your text book.


Chapter 7
-

Logic Circuits


Chapter 8
-

Microcomputers


Chapter 10
-

Diodes (Voltage Regulator)


Chapter 12
-

Transistors (H
-
Bridge)


Chapter 16
-

DC Machines (Motors)

Key Concepts

Other key ideas used in this team project
include:


Battery Power Management


Torque


Friction


Gearboxes


We will now design circuits that will be used in
lab next week.

Chapter 10

Diodes

Semiconductors


Germanium


32 protons


Silicon


14 protons


Most commonly used


How many electrons can be in the ground state of
an atom?


Answer: 2 (s level)



...in the first excited state?


Answer: 8 (s and p levels)



…in the second excited state?


Answer: 8 (s and p levels)

Atomic Physics

Valence Electrons


Valence electrons

are electrons in the
outermost shell of the atom that can
participate in forming chemical bonds with
other atoms.



How many valence electrons does Silicon
have?


Answer: 4


How many electrons are needed to fill the
outermost energy level of Silicon?


Answer: 4


2
-
D representation of Silicon Crystal



How many valence electrons does Phosphorus
(
15
P) and Aluminum (
13
Al) have?


Answers: 5 and 3

Diodes


Conduct electricity in one direction



Two terminal devices


anode and cathode



Primarily made of silicon


Doping

The adding of impurities


n
-
type crystal


e.g. Silicon doped with Phosphorous


negative charge carriers


electrons



p
-
type crystal


e.g. Silicon doped with Aluminum


positive charge carriers


vacancy or hole

Diodes

p
-
type

n
-
type

Circuit Symbol

Flapper Valve Analogy

Flapper

Valve

Analogy

Diode Characteristics


Forward
-
Bias Condition


Good Conductor



Reverse
-
Bias Condition


High Resistance



I

versus
V

Plot


Ideal Diode and Real Diode


“Knee” and Breakdown Voltage


Three Regions

Shockley Equation


Shockley Equation on Excel


Common LED have a maximum recommended
current of 20mA.


What resistor value is needed in series with an LED
and a 5
-
Volt power supply so that the LED does not
burn up?


Answer: _______ or ________

What does the circuit symbol for an
LED look like?

Diode Circuits


rec∙ti∙fi∙er


Pronunciation: 'rek
-
t&
-
"fI(
-
&)r

Function:
noun

Date: 1611

:

one that
rectifies
;
specifically

:

a device for
converting alternating current into direct current



Half
-
Wave Rectifier



Full
-
Wave Rectifier



Bridge Rectifier

Smoothing Capacitors


Ripple Voltage (V
r
)




DC Component (V
DC
)




Ripple Factor

Concept Test


Is a high or low value for the ripple voltage

V
desirable?


Answer: Low


What are three ways to achieve low ripple
voltages?


Answers:


Low Current


High Frequency


High Capacitance

Zener Diodes


Zener Diodes are intended to operate in the
breakdown region.



Manufacturers set the
breakdown voltage

by
modifying the doping.



Zener diodes can make good
voltage regulators
.



Circuit Symbol



Clarence Zener once visited SFA.



What is a Zener diode? How do the
circuit symbols for a diode and a Zener
diode differ?


Zener diodes are intended to operate in the
breakdown region
-
usually as voltage
regulators.


Manufacturers set the breakdown voltage by
careful doping.

How do you convert AC to DC?

Voltage Regulators remove the ripple.

Diode

Rectifier

Smoothing

Capacitor

Voltage

Regulator

AC Input

DC Output

Concept Question


What components to you need to convert a 110
-
Volt AC
signal to a 9
-
Volt DC signal?


Answers:


Transformer


to step down the voltage


Diodes


to rectify the waveform (make +)


Capacitor


to smooth the rectified waveform


Voltage Regulator


to remove the ripple


Note that the device connected to this 9
-
Volt power supply
acts as a resistor.


For this reason the device is sometimes called the “load” or
“load resistance”.

Example Questions


10.32, 35


Homework Questions?


10.55, 56, 57, 35


What is an ideal diode?


An ideal diode is a perfect conductor
with zero voltage drop in the forward
bias direction…


…and a perfect insulator in the reverse
bias direction.

Stop Here

What element from the periodic
table are diodes made of?




Silicon