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BM-305
Mikrodenetleyiciler
Güz 2016
(2. Sunu)
(Yrd. Doç. Dr. Deniz Dal)
Akım, Gerilim, Direnç ve Ohm Kanunu
An electric circuit is formed when a conductive path is created to allow free electrons to
continuously move. This continuous movement of free electrons through the conductors of a
circuit is called a current, and it is often referred to in terms of “flow,” just like the flow of a liquid
through a hollow pipe.
The force motivating electrons to “flow” in a circuit is called voltage. Voltage is a specific
measure of potential energy that is always relative between two points. When we speak of a
certain amount of voltage being present in a circuit, we are referring to the measurement of how
much potential energy exists to move electrons from one particular point in that circuit to
another particular point. Without reference to two particular points, the term “voltage” has no
meaning.
Free electrons tend to move through conductors with some degree of friction, or opposition to
motion. This opposition to motion is more properly called resistance. The amount of current in a
circuit depends on the amount of voltage available to motivate the electrons, and also the
amount of resistance in the circuit to oppose electron flow. Just like voltage, resistance is a
quantity relative between two points. For this reason, the quantities of voltage and resistance
are often stated as being “between” or “across” two points in a circuit.
Ohm Kanunu
Ohm's Law (named after German physicist Georg Ohm, 1825) deals with
the relationship between voltage and current in an ideal conductor. This
relationship states that:
The potential difference (voltage) across an ideal conductor is
proportional to the current through it.
The constant of proportionality is called the "resistance", R.
Ohm's Law is given by:
V = I.R
where V is the potential difference between two points which include a
resistance R. I is the current flowing through the resistance.
Kirşof Kanunları
In 1845, a German physicist, Gustav Kirchoff developed a pair or set of
rules or laws which deal with the conservation of current and energy
within Electrical Circuits. These two rules are commonly known as:
Kirchoff’s Circuit Laws with one of Kirchoff’s laws dealing with the
current flowing around a closed circuit, Kirchoff’s Current Law, (KCL)
while the other law deals with the voltage sources present in a closed
circuit, Kirchoff’s Voltage Law, (KVL).
Kirşof’un Akımlar Kanunu
Kirchoff’s Current Law or KCL, states that the “total current or charge entering a
junction or node is exactly equal to the charge leaving the node as it has no other
place to go except to leave, as no charge is lost within the node“. In other words
the algebraic sum of ALL the currents entering and leaving a node must be equal to
zero, I(exiting) + I(entering) = 0. This idea by Kirchoff is commonly known as the
Conservation of Charge. We can use Kirchoff’s current law when analysing parallel
circuits.
Kirşof’un Gerilimler Kanunu
Kirchoff’s Voltage Law or KVL, states that “in any closed loop network, the total
voltage around the loop is equal to the sum of all the voltage drops within the
same loop” which is also equal to zero. In other words the algebraic sum of all
voltages within the loop must be equal to zero. This idea by Kirchoff is known as
the Conservation of Energy.
Starting at any point in the loop continue in
the same direction noting the direction of
all the voltage drops, either positive or
negative, and returning back to the same
starting point. It is important to maintain
the same direction either clockwise or anticlockwise or the final voltage sum will not
be equal to zero. We can use Kirchoff’s
voltage law when analysing series circuits.
Dirençler İçin Renk Kodları
Dirençlerde Tolerans
The tolerance of a resistor is the deviation that a resistor may vary from its nominal value
resistance, measured at 25°C with no load applied. In other words, the resistor tolerance is
the amount by which the resistance of a resistor may vary from its stated value. The larger
the resistor tolerance, the more it may vary, either up or down, from its nominal value. The
smaller the resistor tolerance, the less it varies from its nominal value and, thus, the more
stable it is.
The most common way of specifying resistor tolerance is by percentage. When specified by
percentage value, this percentage means the amount by which a resistor may vary from its
nominal value. For example, a resistor which has a tolerance of 10% may vary 10% from its
nominal value.
Typical resistor tolerances are 1 percent, 2 percent, 5 percent, 10 percent and 20 percent.
The value can even be lower than 1 percent with high-precision resistors.
Consider a 500 ohm resistor with a 10 percent tolerance. This means that the resistance of it
can be anywhere from as low as 450 ohm to as high as 550 ohm. On the other hand, if the
same 500 ohm resistor has a 1 percent tolerance, its resistance can be between 495 ohm and
505 ohm. Lower percent tolerances equal more precision (less variance) in resistance values.
Gerilim Bölücü
Değişken Direnç (Potansiyometre)
A potentiometer,
informally a pot, is a threeterminal resistor with a
sliding or rotating contact
that forms an adjustable
voltage divider.
Potentiometers are
commonly used to control
electrical devices such as
volume controls on audio
equipment.
Potentiometers operated
by a mechanism can be
used as position
transducers, for example,
in a joystick.
Geçici Anahtar
Normalde Açık veya Normalde Kapalı
Momentary switches are
switches which only remain
in their on state as long as
they’re being actuated
(pressed, held, magnetized,
etc.).
Most often momentary
switches are best used for
intermittent user-input
cases; stuff like reset or
keypad buttons.
Kalıcı Anahtar
DIP switches are through-hole switches
designed in the same mold as a throughhole DIP IC. They can be placed in a
breadboard, in the same manner a
through-hole IC might, by straddling the
center area.
These switches often come in arrays of
eight or more separate SPST switches,
with tiny little sliding levers. They were
widely used in the olden days of
computing, but they’re still useful for
configuring devices via hardware.
An 8-position DIP switch
Pull-up Direnci (Resistor to Vcc)
User input is one of the most
common applications for switches.
For example, if you want to connect
a switch to a microcontroller input
pin, a simple circuit like this is all
you would need.
When the switch is open, the MCU
pin is connected through the
resistor to 5V. When the switch is
closed, the pin is tied directly to
GND. The resistor in that circuit is a
pull-up resistor, required to bias the
input high, and prevent a short to
ground when the switch is closed.
Pull-down Direnci (Resistor to Gnd)
Pull-down resistors work in the same
manner as pull-up resistors, except that
they pull the pin to a logical low value.
They are connected between ground and
the appropriate pin on a device. An
example of a pull-down resistor in a digital
circuit can be seen in the figure.
A pushbutton switch is connected between
the supply voltage and a microcontroller
pin. In such a circuit, when the switch is
closed, the micro-controller input is at a
logical high value, but when the switch is
open, the pull-down resistor pulls the input
voltage down to ground (logical zero value),
preventing an undefined state at the input.
Işık Yayan Diyot (LED)
A light-emitting diode (LED) is a
semiconductor device that emits visible
light when an electric current passes
through it. LEDs, being diodes, will only
allow current to flow in one direction.
And when there’s no current-flow,
there’s no light. Luckily, this also means
that you can’t break an LED by plugging
it in backwards. Rather, it just won’t
work. The positive side of the LED is
called the “anode” and is marked by
having a longer “lead,” or leg. The
other, negative side of the LED is called
the “cathode.” Current flows from the
anode to the cathode and never the
opposite direction.
Akım Sınırlayan Direnç
If you connect an LED directly to a current
source it will try to dissipate as much
power as it’s allowed to draw, and it will
destroy itself. That’s why it’s important to
limit the amount of current flowing across
the LED.
For this, we employ resistors. Resistors limit
the flow of electrons in the circuit and
protect the LED from trying to draw too
much current.
RGB (Red-Green-Blue) LED
Ortak Katot ve Anot
At first glance, RGB (Red, Green, Blue) LEDs look just like regular LEDs, however, inside
the usual LED package, there are actually three LEDs, one red, one green and yes, one
blue. By controlling the brightness of each of the individual LEDs you can mix pretty much
any color you want.
Işığa Bağımlı Direnç (LDR)
A photoresistor or lightdependent resistor (LDR) or
photocell is a light-controlled
variable resistor. The resistance
of a photoresistor decreases
with increasing incident light
intensity; in other words, it
exhibits photoconductivity.
A photoresistor can be applied
in light-sensitive detector
circuits, and light- and darkactivated switching circuits.
Diyot
A diode is a device that only allows for the
flow of electricity to pass in one direction.
These components are often used to isolate
the effect of one component from another.
Flyback diodes do a similar job of suppressing
voltage spikes, specifically those induced by an
inductive component, like a motor. When current
through an inductor suddenly changes, a voltage
spike is created, possibly a very large, negative spike.
A flyback diode placed across the inductive load, will
give that negative voltage signal a safe path to
discharge, actually looping over-and-over through
the inductor and diode until it eventually dies out.
Kapasitör
A capacitor is a device that can store and
release electrical charge in a circuit.
Typically a capacitor consists of two
charging plates with a material in between
that prevents electrical discharge.
These devices can be used to smooth out
signals in a circuit. Additionally, large
capacitors can be used as storage systems
for current. Their ability to store charge is
measured in Farads [F].
Tranzistör
A transistor is a device that restricts or allows
the flow of current between two contacts
based on the presence or absence of current
on a third contact. A transistor has three leads:
collector, emitter and base. The collector and
emitter act as the input and output for the
transistor. While the base is the trigger for the
signal.
Two common types of transistors are:
PNP - If the base voltage is less than the
emitter voltage, then current flows from the
emitter to the collector.
NPN - If the base voltage is greater than the
emitter voltage, then current flows from the
collector to the emitter.
Note: The P stands for P-type semiconductor
and the N stands for N-type semiconductor
Two common uses for transistors are to act as
an electrically activated switch. Also transistors
can be used to increase (amplify) the output
current.
7 Parçalı Gösterge (Ortak Katot veya Anot)
A seven-segment display (SSD) is a form of electronic
display device for displaying decimal numerals that is
an alternative to the more complex dot matrix
displays. Seven-segment displays are widely used in
digital clocks, electronic meters, basic calculators,
and other electronic devices that display numerical
information.
Sıvı Kristal Gösterge (LCD)
LCD (Liquid Crystal Display) screen is an
electronic display module and find a wide
range of applications. A 16x2 LCD display is
very basic module and is very commonly
used in various devices and circuits. These
modules are preferred over seven segments
and other multi segment LEDs. The reasons
being: LCDs are economical; easily
programmable; have no limitation of
displaying special & even custom characters
(unlike in seven segments), animations and
so on.
A 16x2 LCD means it can display 16 characters
per line and there are 2 such lines. In this LCD
each character is displayed in 5x7 pixel matrix.
This LCD has two registers, namely, Command
and Data.
The command register stores the command instructions given to the LCD. A command is an
instruction given to LCD to do a predefined task like initializing it, clearing its screen, setting
the cursor position, controlling display etc. The data register stores the data to be displayed
on the LCD. The data is the ASCII value of the character to be displayed on the LCD.
Breadboard
A breadboard is a construction base for
prototyping of electronics. In the 1970s the
solderless
breadboard
became
available.
"Breadboard" is also a synonym for "prototype".
Because the solderless breadboard does not
require soldering, it is reusable. This makes it easy
to use for creating temporary prototypes and
experimenting with circuit design. For this reason,
solderless breadboards are also extremely popular
with students and in technological education. A
variety of electronic systems may be prototyped by
using breadboards, from small analog and digital
circuits to complete central processing units
(CPUs).
Fritzing is an open-source
software initiative to
support designers and
artists ready to move
from physical prototyping
to actual product. It was
developed
at
the
University of Applied
Sciences of Potsdam. The
software is created in the
spirit of the Processing
programming language
and
the
Arduino
microcontroller
and
allows a designer, artist,
researcher, or hobbyist to
document their Arduinobased prototype and
create a PCB layout for
manufacturing.
Fritzing Yazılımı