Transcript Basic Components

Basic Components
At the Atomic Level
• Nucleus made up of Protons (+) and
Neutrons (no charge).
• Electrons occupy clouds of probability
around nucleus.
• Protons are about 1000 times bigger than
electrons.
Conductors, Semiconductors,
Insulators
• Properties due to bonding (sharing) of
electrons between atoms.
– Insulators – strong hold on electrons – not free
to move.
– Semiconductors – moderate hold on electrons
but will break loose under right conditions.
– Conductors – outer electrons form a sea of
electrons that are free to move within the sea.
Two Fundamentals of Electronics
1. Moving electrons create magnetic fields.
2. Moving or changing magnetic fields cause
electrons to move.
Basic Types of Current
• Direct Current (dc)
– Electrons move in one direction.
– Can fluctuate (pulse or ripple dc) in
magnitude, but still only in one direction.
• Alternating Current (ac)
– Electrons reverse direction with some
regularity.
– Constant fluctuation from positive-zeronegative.
Components of Electricity
• Voltage
• Current
• Resistance
E
I
R
(Water Pressure)
(Water Molecules)
(Friction)
Ohm’s Law
• Mathematical relationship between
components.
• E=I*R
Alternating Current Defined
• In alternating current (ac), electrons flow
back and forth through the conductor with
some periodicity.
AC Vocabulary
Crest
Wave
Length
Amplitude
Trough
Power
• Power is the ability to do work.
• Work is basically making something move.
– Force over a distance
or
– Pressure over a distance
• If something doesn’t move, there is no work
produced.
• Heat produced is also a measure of work.
Power in Electricity
•
•
•
•
The force is Voltage.
The things being moved are electrons.
Power therefore is Voltage times Current.
Power is measured in Watts.
Power in DC
• 12 volts pushing 2 amps = 24 W (watts).
• 1.5 volts pushing 300 milli amps = 450 milli W.
• This is great for dc, but what about ac when the
voltage and current are constantly changing?
Power in AC
Finding the Effective Voltage
• The voltage used in power calculations in ac
is the equivalent dc voltage value that
would do the same amount of work (or
heat).
• A simple average of ac voltage is not quite
good enough.
• A weighted average called Root Mean
Square (RMS) is more accurate.
Important Points about RMS
• RMS is the equivalent value of dc voltage
to do the same work.
• RMS is used in Power and Ohm’s Law
formulas.
• The RMS voltage is 0.707 times the peak
voltage.
Basic Components
(and What they Do)
• Resistors
– Impede the flow of electrons.
• Coils (inductors)
– Store energy in a magnetic field.
• Capacitors
– Store energy in an electrostatic field (electrons on one
side, voids on the other).
Resistors
• Values measured in Ohms.
– From fractions to millions.
– (kilo = 1,000; meg = 1,000,000)
• Ability to handle heat (or power or current).
– Physical size (1/4, 1/2, 1, 2, … watt)
Resistors
• Material
– Carbon
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•
•
Most common
High values (Ohms)
High precision
Low power
– Wire
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•
•
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•
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Long, thin wire wound in a coil
Not so common anymore
Low values (Ohms)
Low precision
High power
Lots of inductance (a coil of wire)
Coils (Inductors)
• Values in Henrys.
– Single Henry to very small fractions.
– (thousandths and millionths)
• Values depend on.
–
–
–
–
–
Diameter of the coil.
Diameter of the wire.
Spacing between windings.
Number of windings.
Core material.
Capacitors
• Values measured in Farads.
– From single to very small fractions.
– (millionths and billionths)
• Value depends on:
– Surface area of parallel conductive plates.
– Space between plates.
– Dielectric (material between plates).
Resistance and Reactance
• Resistance is one of the fundamental components of
electricity. It inhibits the flow of electrons.
• Inductors and capacitors react differently under dc and ac
conditions.
– Inductors offer zero resistance in dc environment.
– Capacitors offer infinite resistance in dc environment.
• They react quite differently in an ac environment.
• The resistance to electron flow in an ac environment
offered by inductors and capacitors is called
REACTANCE.
Project T.V. Remote Decoder Circuit
+9V
In
Out
Gnd
78L05
1N4001
SW6
330
.1uF
+5 Volts
to Relays
1
3
4
Vcc
GP5
GP4
GP3
12F675
2
4.7K
Gnd
GP0
GP1
GP2
8
7
6
Vcc
5
SW5
N.O.
SW4
Gnd
Out
SW3
SW2
+5V
K4
330
+5V
K3
LED
2N3904
4.7K
330
LED
2N3904
4.7K
+5V
330
K2
LED
4.7K
SW1
+5V
330
K1
LED
2N3904
Note:
 Internal pull-up resistors are used on 12F265 pins
GP0, GP1, GP2, GP4, GP5
 External pull-up resistor required on GP3
 Protection diodes are internal to K1 - K4
 Switchs SW1 - SW4 are internal to K1 - K4
4.7K
2N3904