English for mechatronics engineering

English for Mechatronics Engineering Page 1

TABLE OF CONTENTS
TABLE OF CONTENTS 1

PART 1: DIGITAL LOGIC 3

CHAPTER 1: INTRODUCTION 3

LOGIC GATES 3

CHAPTER 2: APPLICATIONS OF LOGIC GATES 8

INTEGRATED CIRCUIT 8

APPLICATIONS 8

CHAPTER 3: BASIC ELECTRONIC COMPONENTS 10

RESISTANCE 10

CAPACITOR 11

DIODE 13

LIGHT EMITTING DIODE 15

BIPOLAR JUNCTION TRANSISTOR (BJT) 18

CHAPTER 4: MICROCONTROLLER 20

INTRODUCTION 20

IMPORTANT FEATURES 21

POWER SUPPLY CIRCUIT 22

HOW TO START WORKING? 23

PART 2: MECHANICAL ACTUATION SYSTEMS 26

CHAPTER 1: INTRODUCTION 26

MECHANISMS 26

TYPES OF MOTION 27

DEGREE OF FREEDOM 27

CHAPTER 2: CAMS 29

ECCENTRIC CAM 29

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DROP CAM 31

FLAT CAM 32

CHAPTER 3: GEARS 34

SPUR GEAR 35

HELICAL GEAR 36

DOUBLE HELICAL GEAR 37

BEVEL GEAR 38

WORM GEAR 39

RACK AND PINION 41

GEAR TRAIN 42

CHAPTER 4: BELT AND CHAIN DRIVES 44

PROS AND CONS 44

FLAT BELTS 45

ROUND BELTS 46

VEE BELTS 47

TIMING BELTS 48

CHAIN DRIVE 49

CHAINS VERSUS BELTS 50

CHAPTER 5: BEARINGS 51

DEEP-GROOVE 52

FILLING - SLOT 53

ANGULAR CONTACT 54

DOUBLE-ROW 55

SELF-ALIGNING 56

STRAIGHT-ROLLER BEARING 58

TAPER ROLLER 59

NEEDLE ROLLER 61


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PART 1: DIGITAL LOGIC
CHAPTER 1: INTRODUCTION
Many control systems are concerned with setting events in motion or stopping them
when certain conditions are met. For example, with domestic washing machine, the heater
is only switched on when there is water in the drum and it is to the prescribed level. Such
control involves digital signals where there are only two possible signal levels. Digital
circuitry is the basis of digital computers and microprocessor controlled systems. There
are two input signals which are either 1 or 0 signals and an output signal which is 1 or 0
signal. The controller is here programmed to only give a 1 output if both the input signals

are 1. Such an operation is said to be controlled by a logic gate .Logic gate is the basic
building blocks for digital electronic circuits. The term combinational logic is used for the
combining of two or more basic logic gates to form a required function.
LOGIC GATES
Logic gates are the basic components in digital electronics. They are used to create
digital circuits and even complex integrated circuits. For example, complex integrated
circuits may bring already a complete circuit ready to be used – microprocessors and
microcontrollers are the best example – but inside them they were projected using several
logic gates. In this tutorial we will teach you everything you need to know about logic
gates, with several examples.
As you may already know, digital electronics accept only two numbers, “0” and “1.”
Zero means a 0 V voltage, while “1” means 5 V or 3.3 V on newer integrated circuits. You
can think “0” and “1” as a light bulb turned off or on or as a switch turned off or on.
a. AND gate: Suppose we have a gate giving a high output only when both input A and
input B are high; for all other conditions it gives a low output. This is an AND logic gate.
We can visualize the AND gate as an electric circuit involving two switches in series.
Only when switch A and B are closed, there is a current.
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(a) Represented by switches

(b) Symbols
The relationship between the inputs and the outputs of an AND gate can be expressed
in the form of an equation, called Boolean equation. The Boolean equation for the AND
gate is written as
A . B = Y
An example is a burglar alarm in which it gives an output, the alarm sounding, when
the alarm is switched on and when a door is opened to active a sensor.

The relationships between inputs to a logic gate and the outputs can be tabulated in a
form known as truth table. This specifies the relationships between the inputs and outputs.
We can write the truth table as
A B Output
0
0

0 1
1 0
1 1

b. OR gate: An OR gate with inputs A and B gives an output of a 1 when A or B is 1. We
can visualize such a gate as an electric circuit involving two switches in parallel. When
switch A or B is closed, then there is a current. OR gates can also have more than inputs.
We can write the Boolean equation for an OR gate as:
A + B = Y

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(a) Represented by switches

(b) Symbols

A B Output
0 0
0
1

1 0
1 1

c. NOT gate: a NOT gate has just one input and one output, giving a 1 output when the
input is 0 and a 0 when input is 1. The NOT gate gives an output which is the inversion of
the input and is called an inverter. The 1 representing NOT actually symbolizes logic
identity, i.e. no operation, and the inversion is depicted by the circle on the output. Thus, if
we have a digital input which varies with time, the output variation with time is the
inverse.
The Boolean equation describing the NOT gate is
A Y

A bar over a symbol is used to indicate that the inverse, or complement, is being taken;
thus the bar over the A indicates that the output Y is the inverse value of A.


d. NAND gate: The NAND gate can be considered as a combination of an AND gate
followed by a NOT gate. Thus when input A is 1 and input B is 1, there is an output of 0,
all other inputs giving an output of 1.
Input Output
1
0
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The NAND gate is just the AND gate truth table with the outputs inverted. An alternative
way of considering the gate is as an AND gate with a NOT gate applied to invert both the
inputs before they reach the AND gate. The figure below shows the symbols used for the
NAND gate, being the AND symbol followed by the circle to indicate inversion.

The Boolean equation describing the NAND gate is:

A B Y 

The following is the truth table:
A B Output
0 0
0 1
1 0
1 1

e. NOR gate: The NOR gate can be considered as a combination of an OR gate followed
by a NOT gate. Thus when input A or input B is 1 there is an output of 0. It is just the OR
gate with the outputs inverted. An alternative way of considering the gate is as an OR gate
with a NOT gate applied to invert both the inputs before they reach the OR gate. The
figure below shows the symbols used for the NOR gate; it is the OR symbol followed by
the circle to indicate inversion.

The Boolean equation for NOR gate is:
A B Y 


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The following is the truth table for the NOR gate.
A B Output
0 0
0 1
1 0
1 1

f. XOR gate: XOR stands for exclusive OR. XOR gate compares two values and if they

are different its output will be “1.” XOR operation is represented by the symbol ⊕. So Y
= A ⊕ B is the Boolean equation for the XOR gate.

The following is the truth table for the XOR gate.
A B Output
0 0
0
1

1 0
1 1

g. XNOR gate: XNOR stands for exclusive NOR and is an XOR gate with its output
inverted. So, its output is at “1” when the inputs have the same value and “0” when they
are different. XNOR operation is represented by the symbol (·). The Boolean equation for
XNOR gate is:
A (·) B = Y





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CHAPTER 2: APPLICATIONS OF LOGIC GATES
INTEGRATED CIRCUIT
Logic gates are available as integrated circuits. The different manufacturers have
standardized their numbering schemes so that the basic part numbers are the same
regardless of the manufacturer. For example, Fig. 1(a) shows the gate systems available in
integrated circuit 7408; it has four two-input AND gates and is supplied in a 14-pin

package. Power supply connections are made to pins 7 and 14, these supplying the
operating voltage for all four AND gates. In order to indicate at which end of the package
pin 1 starts, a notch is cut between pins 1 and 14. Integrated circuit 7411 has three AND
gates which each having three inputs; integrated circuit 7421 has two AND gates with
each having four inputs. Figure 1(b) shows the gate systems available in integrated circuit
7402. This has four two-input NOR gates in a 14-pin package, power connections being to
pins 7 and 14. Integrated circuit 7427 has three gates with each having three inputs.

Figure 1: Integrated circuit (a) 7408, (b) 7402

APPLICATIONS
1. Digital comparator
A digital comparator is used to compare two digital words to determine if they are
exactly equal. The two words are compared bit by bit and a 1 output given if the words are
equal. To compare the equality of two bits, an XOR gate can be used; if the bits are both 0
or both 1 the output is 0, and if they are not equal the output is a 1. To obtain a 1 output
when the bits are the same we need to add a NOT gate, this combination of XOR and
NOT being termed an XNOR gate. To compare each of the pairs of bits in two words we
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need an XNOR gate for each pair. If the pairs are made up of the same bits then the output
from each XNOR gate is a 1. We can then use an AND gate to give a 1 output when all the
XNOR outputs are ones. Figure 2 shows the system.
A3
B3
A2
B2
A1
B1
A0

B0
A = B

Figure 2: Comparator
2. Coder
The Fig. 3 shows a simple system by which a controller can send a coded digital signal
to a set of traffic lights so that the code determines which light, RED, AMBER OR
GREEN, will be turned on. To illuminate the RED light we might use the transmitted
signal A = B = 0, for the AMBER light A = 0, B = 1 and for the GREEN light A = 1, B =
0. We can switch on the lights using these codes by using three AND gates and two NOT
gates.
AMBER
A
RED
B
GREEN

Figure 3: The traffic lights




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CHAPTER 3: BASIC ELECTRONIC COMPONENTS
RESISTANCE
The electrical resistance of an object is a measure of its opposition to the passage of a
steady electric current. An object of uniform cross section will have a resistance
proportional to its length and inversely proportional to its cross-sectional area, and
proportional to the resistivity of the material.

Discovered by Georg Ohm in the late 1820s, electrical resistance shares some
conceptual parallels with the mechanical notion of friction. The SI unit of electrical
resistance is the ohm, symbol Ω. Resistance's reciprocal quantity is electrical conductance
measured in Siemens, symbol S.
The resistance of a resistive object determines the amount of current through the object
for a given potential difference across the object, in accordance with Ohm’s laws:
V
I
R


where
R is the resistance of the object, measured in ohms, equivalent to J·s/C
2

V is the potential difference across the object, measured in volts
I is the current through the object, measured in amperes
We all know that voltmeter and ammeter are used for measuring the voltage and the
current respectively. For the resistance, the meters that use to measure it is the ohmmeter.
But what if we don't have an ohmmeter to use?
Color coding system for resistors consists of three colors to indicate the resistance
value in ohms of a certain resistor, sometimes the fourth color indicate the tolerance value
of the resistor. By reading the color coded in correct order and substituting the correct
value of each corresponding color coded as shown in the table below, you can
immediately tell all you need to know about the resistor. Each color band represents a
number and the order of the color band will represent a number value. The first 2 color
bands indicate a number. The 3
rd
color band indicates the multiplier or in other words the
number of zeros. The fourth band indicates the tolerance of the resistor. In most cases,

there are 4 color bands. However, certain precision resistors have 5 bands or have the
values written on them, refining the tolerance value even more.
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Color
1
st

Band
2
nd

Band
3
rd

Band
4
th
band
(multiplier)
5
th
Band
(Tolerance)
Black 0 0 0 10
0
Ω
Brown 1 1 1 10

1
Ω
Red 2 2 2 10
2
Ω
Orange 3 3 3 10
3
Ω
Yellow 4 4 4 10
4
Ω
Green 5 5 5 10
5
Ω
Blue 6 6 6 10
6
Ω
Violet 7 7 7 10
7
Ω
Gray 8 8 8 10
8
Ω
White 9 9 9 10
9
Ω



CAPACITOR

A capacitor (formerly known as condenser) is a passive two-terminal electrical
component used to store energy in an electric field. The forms of practical capacitors vary
widely, but all contain at least two electrical conductors separated by a dielectric
(insulator); for example, one common construction consists of metal foils separated by a
thin layer of insulating film. Capacitors are widely used as parts of electrical circuits in
many common electrical devices.
When there is a potential difference (voltage) across the conductors, a static electric
field develops across the dielectric, causing positive charge to collect on one plate and
negative charge on the other plate. Energy is stored in the electrostatic field. An ideal
capacitor is characterized by a single constant value, capacitance, measured in farads. This
is the ratio of the electric charge on each conductor to the potential difference between
them.
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The capacitance is greatest when there is a narrow separation between large areas of
conductor; hence capacitor conductors are often called "plates," referring to an early
means of construction. In practice, the dielectric between the plates passes a small amount
of leakage current and also has an electric field strength limit, resulting in a breakdown
voltage, while the conductors and leads introduce an undesired inductance and resistance.
Capacitors are widely used in electronic circuits for blocking direct current while
allowing alternating current to pass, in filter networks, for smoothing the output of power
supplies, in the resonant circuits that tune radios to particular frequencies and for many
other purposes.
A capacitor consists of two conductors separated by a non-conductive region. The non-
conductive region is called the dielectric. In simpler terms, the dielectric is just an
electrical insulator. Examples of dielectric mediums are glass, air, paper, vacuum, and
even a semiconductor depletion region chemically identical to the conductors. A capacitor
is assumed to be self-contained and isolated, with no net electric charge and no influence
from any external electric field. The conductors thus hold equal and opposite charges on
their facing surfaces, and the dielectric develops an electric field. In SI units, a capacitance

of one farad means that one coulomb of charge on each conductor causes a voltage of one
volt across the device.
The capacitor is a reasonably general model for electric fields within electric circuits.
An ideal capacitor is wholly characterized by a constant capacitance C, defined as the ratio
of charge ±Q on each conductor to the voltage V between them:
Q
C
V





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DIODE
A diode is a type of two-terminal electronic component with nonlinear resistance and
conductance (i.e., a nonlinear current–voltage characteristic), distinguishing it from
components such as two-terminal linear resistors which obey Ohm's law. A
semiconductor diode, the most common type today, is a crystalline piece of
semiconductor material connected to two electrical terminals. A vacuum tube diode (now
rarely used except in some high-power technologies) is a vacuum tube with two
electrodes: a plate and a cathode.
The most common function of a diode is to allow an electric current to pass in one
direction (called the diode's forward direction), while blocking current in the opposite
direction (the reverse direction). Thus, the diode can be thought of as an electronic version
of a check valve. This unidirectional behavior is called rectification, and is used to convert
alternating current to direct current, and to extract modulation from radio signals in radio
receivers—these diodes are forms of rectifiers.

A Zener diode is a special kind of diode which allows current to flow in the forward
direction in the same manner as an ideal diode, but will also permit it to flow in the
reverse direction when the voltage is above a certain value known as the breakdown
voltage, "Zener knee voltage" or "Zener voltage." The device was named after Clarence
Zener, who discovered this electrical property. A Zener diode exhibits almost the same
properties, except the device is specially designed so as to have a greatly reduced
breakdown voltage, the so-called Zener voltage. By contrast with the conventional device,
a reverse-biased Zener diode will exhibit a controlled breakdown and allow the current to
keep the voltage across the Zener diode close to the Zener breakdown voltage. For
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example, a diode with a Zener breakdown voltage of 3.2 V will exhibit a voltage drop of
very nearly 3.2 V across a wide range of reverse currents. The Zener diode is therefore
ideal for applications such as the generation of a reference voltage (e.g. for an amplifier
stage), or as a voltage stabilizer for low-current applications.

A diode bridge is an arrangement of four (or more) diodes in a bridge circuit
configuration that provides the same polarity of output for either polarity of input. When
used in its most common application, for conversion of an alternating current (AC) input
into direct current a (DC) output, it is known as a bridge rectifier. A bridge rectifier
provides full-wave rectification from a two-wire AC input, resulting in lower cost and
weight as compared to a rectifier with a 3-wire input from a transformer with a center-
tapped secondary winding.
The essential feature of a diode bridge is that the polarity of the output is the same
regardless of the polarity at the input. The diode bridge circuit is also known as the Graetz
circuit after its inventor, physicist Leo Graetz.

HW: Describing the basic operation of Diode Bridge?



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LIGHT EMITTING DIODE
A light-emitting diode (LED) is a semiconductor light source. LEDs are used as
indicator lamps in many devices and are increasingly used for other lighting. Introduced as
a practical electronic component in 1962, early LEDs emitted low-intensity red light, but
modern versions are available across the visible, ultraviolet, and infrared wavelengths,
with very high brightness.
When a light-emitting diode is forward-biased (switched on), electrons are able to
recombine with electron holes within the device, releasing energy in the form of photons.
This effect is called electroluminescence and the color of the light (corresponding to the
energy of the photon) is determined by the energy gap of the semiconductor. LEDs are
often small in area (less than 1 mm
2
), and integrated optical components may be used to
shape its radiation pattern. LEDs present many advantages over incandescent light sources
including lower energy consumption, longer lifetime, improved robustness, smaller size,
and faster switching. LEDs powerful enough for room lighting are relatively expensive
and require more precise current and heat management than compact fluorescent lamp
sources of comparable output.
Light-emitting diodes are used in applications as diverse as replacements for aviation
lighting, automotive lighting (in particular brake lamps, turn signals, and indicators) as
well as in traffic signals. LEDs have allowed new text, video displays, and sensors to be
developed, while their high switching rates are also useful in advanced communications
technology. Infrared LEDs are also used in the remote control units of many commercial

products including televisions, DVD players, and other domestic appliances.

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A seven-segment display (SSD), or seven-segment indicator, 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, and other electronic devices for displaying numerical information.

A seven segment display, as its name indicates, is composed of seven elements.
Individually on or off, they can be combined to produce simplified representations of the
Arabic numerals. Often the seven segments are arranged in an oblique (slanted)
arrangement, which aids readability. In most applications, the seven segments are of
nearly uniform shape and size (usually elongated hexagons, though trapezoids and
rectangles can also be used), though in the case of adding machines, the vertical segments
are longer and more oddly shaped at the ends in an effort to further enhance readability.
In a simple LED package, typically all of the cathodes (negative terminals) or all of the
anodes (positive terminals) of the segment LEDs are connected and brought out to a
common pin; this is referred to as a "common cathode" or "common anode" device. Hence
a 7-segment plus decimal point package will only require nine pins (though commercial
products typically contain more pins, and/or spaces where pins would go, in order to
match industry standard pinouts).
Integrated displays also exist, with single or multiple digits. Some of these integrated
displays incorporate their own internal decoder, though most do not – each individual
LED is brought out to a connecting pin as described. Multiple-digit LED displays as used
in pocket calculators and similar devices used multiplexed displays to reduce the number
of IC pins required to control the display. For example, all the anodes of the A segments
of each digit position would be connected together and to a driver pin, while the cathodes
of all segments for each digit would be connected. To operate any particular segment of
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any digit, the controlling integrated circuit would turn on the cathode driver for the
selected digit, and the anode drivers for the desired segments; then after a short blanking
interval the next digit would be selected and new segments lit, in a sequential fashion.
Often in pocket calculators the digit drive lines would be used to scan the keyboard as
well, providing further savings; however, pressing multiple keys at once would produce
odd results on the multiplexed display.

An LED matrix or LED display is a large, low-resolution form of dot matrix display,
useful both for industrial and commercial information displays as well as for hobbyist
human–machine interfaces. It consists of a 2-D matrix of LEDs with their cathodes joined
in rows and their anodes joined in columns (or vice versa). By controlling the flow of
electricity through each row and column pair it is possible to control each LED
individually. By scanning across rows, quickly flashing the LEDs on and off, it is possible
to create characters or pictures to display information to the user. By varying the pulse rate
per LED, the display can approximate levels of brightness. Multi-colored LEDs or RGB-
colored LEDs permit use as a full-color image display. The refresh rate is typically fast
enough to prevent the human eye from detecting the flicker.
A dot matrix display is a display device used to display information on machines,
clocks, railway departure indicators and many other devices requiring a simple display
device of limited resolution. The display consists of a matrix of lights or mechanical
indicators arranged in a rectangular configuration (other shapes are also possible, although
not common) such that by switching on or off selected lights, text or graphics can be
displayed. A dot matrix controller converts instructions from a processor into signals
which turns on or off lights in the matrix so that the required display is produced.

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BIPOLAR JUNCTION TRANSISTOR (BJT)
A bipolar junction transistor (BJT) is a three-terminal electronic device constructed of
doped semiconductor material and may be used in amplifying or switching applications.
Bipolar transistors are so named because their operation involves both electrons and holes.
Charge flow in a BJT is due to bidirectional diffusion of charge carriers across a junction
between two regions of different charge concentrations. This mode of operation is
contrasted with unipolar transistors, such as field-effect transistors, in which only one
carrier type is involved in charge flow due to drift. By design, most of the BJT collector
current is due to the flow of charges injected from a high-concentration emitter into the
base where they are minority carriers that diffuse toward the collector, and so BJTs are
classified as minority-carrier devices.
NPN TYPE
NPN is one of the two types of bipolar transistors, consisting of a layer of P-doped
semiconductor (the "base") between two N-doped layers. A small current entering the base
is amplified to produce a large collector and emitter current. That is, an NPN transistor is
"on" when its base is pulled high relative to the emitter.
Most of the NPN current is carried by electrons, moving from emitter to collector as
minority carriers in the P-type base region. Most bipolar transistors used today are NPN,
because electron mobility is higher than hole mobility in semiconductors, allowing greater
currents and faster operation. A mnemonic device for the remembering the symbol for an
NPN transistor is not pointing in, based on the arrows in the symbol and the letters in the
name. That is, the NPN transistor is the BJT transistor that is "not pointing in".
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PNP TYPE
The other type of BJT is the PNP, consisting of a layer of N-doped semiconductor
between two layers of P-doped material. A small current leaving the base is amplified in
the collector output. That is, a PNP transistor is "on" when its base is pulled low relative to

the emitter.
The arrows in the NPN and PNP transistor symbols are on the emitter legs and point in
the direction of the conventional current flow when the device is in forward active mode.
A mnemonic device for the remembering the symbol for a PNP transistor is pointing in
(proudly), based on the arrows in the symbol and the letters in the name. That is, the PNP
transistor is the BJT transistor that is "pointing in".

P-N-P Transistor



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CHAPTER 4: MICROCONTROLLER
INTRODUCTION
When we have to learn about a new computer we have to familiarize about the
machine capability we are using, and we can do it by studying the internal hardware
design (devices architecture), and also to know about the size, number and the size of the
registers.
A microcontroller is a single chip that contains the processor (the CPU), non-volatile
memory for the program (ROM or flash), volatile memory for input and output (RAM), a
clock and an I/O control unit. Also called a "computer on a chip," billions of
microcontroller units (MCUs) are embedded each year in a myriad of products from toys
to appliances to automobiles. For example, a single vehicle can use 70 or more
microcontrollers.
The Intel MCS-51 (commonly referred to as 8051) is a Harvard architecture, single
chip microcontroller (µC) series which was developed by Intel in 1980 for use in
embedded systems. Intel's original versions were popular in the 1980s and early 1990s.
While Intel no longer manufactures the MCS-51, binary compatible derivatives remain
popular today. In addition to these physical devices, several companies also offer MCS-51

derivatives as IP cores for use in FPGAs or ASICs designs.
Intel's original MCS-51 family was developed using NMOS technology, but later
versions, identified by a letter C in their name (e.g., 80C51) used CMOS technology and
consumed less power than their NMOS predecessors. This made them more suitable for
battery-powered devices.

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IMPORTANT FEATURES
The 8051 architecture provides many functions (CPU, RAM, ROM, I/O, interrupt logic,
timer, etc.) in a single package

8-bit ALU, Accumulator and 8-bit Registers; hence it is an 8-bit microcontroller

8-bit data bus – It can access 8 bits of data in one operation

16-bit address bus – It can access 216 memory locations – 64 KB (65536 locations)
each of RAM and ROM

On-chip RAM – 128 bytes (data memory)

On-chip ROM – 4 kByte (program memory)

Four byte bi-directional input/output port

UART (serial port)

Two 16-bit Counter/timers

Two-level interrupt priority


Power saving mode (on some derivatives)
For any electronics project the power supply plays a very important role in its proper
functioning. In this project we are using external A.C supply (220 v) as input, this high
voltage is converted into 12 Volts A.C by step down transformer, then we use voltage
regulators and filters with bridge rectifier to convert the A.C into D.C voltage. For voltage
regulation we are using LM 7805 and 7812 to produce ripple free 5 and 12 volts D.C
constant supply.
MCS-51 based microcontrollers typically include one or two UARTs, two or three
timers, 128 or 256 bytes of internal data RAM (16 bytes of which are bit-addressable), up
to 128 bytes of I/O, 512 bytes to 64 kB of internal program memory, and sometimes a
quantity of extended data RAM (ERAM) located in the external data space. The original
8051 core ran at 12 clock cycles per machine cycle, with most instructions executing in
one or two machine cycles. With a 12 MHz clock frequency, the 8051 could thus execute
1 million one-cycle instructions per second or 500,000 two-cycle instructions per second.
Enhanced 8051 cores are now commonly used which run at six, four, two, or even one
clock per machine cycle, and have clock frequencies of up to 100 MHz, and are thus
capable of an even greater number of instructions per second
Features of the modern 8051 include built-in reset timers with brown-out detection, on-
chip oscillators, self-programmable Flash ROM program memory, built-in external RAM,
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extra internal program storage, SPI, and USB host interfaces, CAN or LIN bus, PWM
generators, analog comparators, A/D and D/A converters, RTCs, extra counters and
timers, more interrupt sources, and extra power saving modes.
POWER SUPPLY CIRCUIT
There are two things worth attention concerning the microcontroller power supply circuit:
Brown out is a potentially dangerous state which occurs at the moment the
microcontroller is being turned off or when power supply voltage drops to the lowest level
due to electric noise. As the microcontroller consists of several circuits which have

different operating voltage levels, this can because it’s out of control performance. In
order to prevent it, the microcontroller usually has a circuit for brown out reset built-in.
This circuit immediately resets the whole electronics when the voltage level drops below
the lower limit.
Reset pin is usually referred to as Master Clear Reset (MCLR) and serves for external
reset of the microcontroller by applying logic zero (0) or one (1) depending on the type of
the microcontroller. In case the brown out is not built in the microcontroller, a simple
external circuit for brown out reset can be connected to this pin.




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HOW TO START WORKING?
A microcontroller is a good-natured “genie in the bottle” and no extra knowledge is
required to use it.
In order to create a device controlled by the microcontroller, it is necessary to provide
the simplest PC, program for compiling and simple device to transfer the code from PC to
the chip itself. Even though the whole process is quite logical, there are often some
queries, not because it is complicated, but for numerous variations. Let’s take a look.
Writing program in assembly language
In order to write a program for the microcontroller, a specialized program in the
Windows environment may be used. It may, but it does not have to When using such a
software, there are numerous tools which facilitate the operation (simulator tool comes
first), which is an obvious advantage. But there is also another ways to write a program.
Basically, text is the only thing that matters. Any program for text processing can be used
for this purpose. The point is to write all instructions in such an order they should be
executed by the microcontroller, observe the rules of assembly language and write
instructions exactly as they are defined. In other words, you just have to follow the

program idea. That’s all!
To enable the compiler to operate successfully, it is necessary that a document
containing this program has the extension, .asm in its name, for example: Program asm.
When a specialized program (mplab) is used, this extension will be automatically added. If
any other program for text processing (Notepad) is used then the document should be
saved and renamed. For example: Program.txt -> Program.asm. This procedure is not
necessarily performed. The document may be saved in original format while its text may
be copied to the programmer for further use.
Compiling a program
The microcontroller “cannot understand” the assembly language. That is why it is
necessary to compile the program into machine language. It is more than simple when a
specialized program (mplab) is used because a compiler is a part of the software. Just one
click on the appropriate icon solves the problem and a new document with .hex extension
appears. It is actually the same program, only compiled into machine language which the
microcontroller perfectly understands. Such documentation is commonly named “hex
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code” and seemingly represents a meaningless sequence of numbers in hexadecimal
number system.
In the event that other software for program writing in assembly language is used,
special software for compiling the program must be installed and used as follows - set up
the compiler, open the document with .asm extension and compile. The result is the same-
a new document with extension .hex. The only problem now is that it is stored in your PC.
Programming a microcontroller
In order to transfer a “hex code” to the microcontroller, it is necessary to provide a
cable for serial communication and a special device, called programmer, with software.
There are several ways to do it.
A large number of programs and electronic circuits having this purpose can be found
on the Internet. Do as follows: open hex code document, set a few parameters and click
the icon for compiling. After a while, a sequence of zeros and ones will be programmed

into the microcontroller through the serial connection cable and programmer hardware.
What's left is to place the programmed chip into the target device. In the event that it is
necessary to make some changes in the program, the previous procedure may be repeated
an unlimited number of times.

Development systems
A device which in the testing program phase can simulate any environment is called a
development system. Apart from the programmer, the power supply unit and the
microcontroller’s socket, the development system contains elements for input pin
activation and output pin monitoring. The simplest version has every pin connected to one
push button and one LED as well. A high quality version has LED displays, LCD
displays, temperature sensors and all other elements which can be supplied with the target
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device. These peripherals can be connected to the MCU via miniature jumpers. In this
way, the whole program may be tested in practice during its development stage, because
the microcontroller doesn't know or care whether its input is activated by a push button or
a sensor built in a real device.