Download Crash Protection System

Project Report
on
“CRASH PROTECTION ”
SUBMITTED IN PARTIAL FULFILLMENT OF REQUIRED FOR BTECH IN “Electronics & communication” under Punjab state board of
technical education and industrial training Chandigarh
Submitted by:-
RIMT
(Mandi Gobindgarh)
Submitted To:DEPARTMENT OF “ ELECTRONICS AND COMMUNICATION”
RIMT- Near floating side, Mandi Gobindgarh. Punjab (147301)
1
ON
CRASH PROTECTION
2
INDEX
SR. NO.
CHAPTER NAME
PAGE NO.
1
Acknowledgement
4
2
Introduction
5
3
Component List
6
4
Block Diagram
Mechanical drawing and description
6
7
Power Supply
12
Microcontroller
13
Circuit and working
Advantage
32
11
Disadvantage
33
12
Application
34
13
Precaution
35
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CHAPTER – 1
ACKNOWLEDGEMENT
Many individual have proudly influenced us during our Studies (B.E) at
RIMT ENGINEERING College,Mandi Gobindgarh and it is pleasure to
acknowledge their guidance and support. At RIMT Polytechnic, We learned
many things like the project training is mainly aimed at enabling the student
to apply their theoretical knowledge to practical as "The theory is to know
how and practical is to do how" and to appreciate the limitation of
knowledge gained in the class room to practical situation and to appreciate
the importance of discipline, punctuality, team work, sense of responsibility,
money, value of time, dignity of labour.
I will like to express my gratitude towards Mrs. Talwar who took
keen interest in our project, who helped me in every possible way and is
source of inspiration for all the group members.
I would also like to thank Mr. Talwar (HOD), Electronics &
Communication who motivated us to complete our project with enthusiasm
and hard work.
Components:Iron Strip Lenth-10 fit, depth-30mm and width-12mm
Iron Strip Lenth- 2 fit, Depth-25mm and width-6mm
1. diode 4007
2. 1000uF, 25 V
2
1
4
3. 470uF, 16 V
4. 7805
5. LED
6. 470 ohm
1. 40 pin base
2. 12 Mhz
3. 22 pF
4. 89s52
5. 10uF, 10 V
6. 10K
1. 8 Pin base
2. 817
3. 1K
4. 470 ohm
5. 4.7 K
6. 547
7. 558
Bateery
Battery connecter
Motor Dc gear
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1
1
1
1
1
2
1
1
1
2
2
2
2
2
2
2
2
2
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PROCREDURE TO MAKE PROJECT:1. IDEA OF PROJECT
In this stage student select the topic of the project of the
project. It’s the main stage of project work.its the area where
talented students shows their innovative ideas. Innovative
students make project with a new idea then others. We
selected this project because we want to do something in with
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our own hands. We drop idea because there was little bit
practical.
2. STUDY RAW MATERIAL AND LAYOUT DIAGRAM
In this section we collected the study Raw Material. We
searches about our project on
google.com,www.yahoo.com,www.msn.com and
www.ludhianaprojects.com. But we find many Layout and
theory Raw Materials for our project. We were not sure about
the Layout and Raw Material used in it. Because Layout
diagram available on the site were provided by students. So we
can really on them. Then we saw www.ludhianaprojects.com a
project help provider site. Its help us lot. They helped us lot in
our project. We find the proper layout Project of our project in
that site.
3. Trail TESTING OF MAIN PROJECT- Then we collect the Raw
Material of project. It was not a easy task. Because no shop in
our area have all parts used in projects. Then after collection of
Raw Material we test the projects working by temporary made
project.- step by step. Because we want to sure about the
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Project. We checked it in different steps beacuuse it was a big
project and was not possible to check it in a single step.
4. COMPONENT MOUNTING- we have also some parts of
electronic circuit. So we kept the pcb for circuit with hole size
from 0.8mm yo 1 mm for leads of Raw Material. Then we insert
Raw Material according ton their pitches.
5. SODERING- Afgter mounting Raw Raw Material we solder the
Raw Raw Material ane by one. We kept the temperature of iron
at 250 degree to 400 degree. Because above this temperature
it can damage to component. We used general iron available in
the market of siron company. Its temperature was nearly 350
degree acc to company specifications. We used soldering wire
of 22 gauge with flux inbuilt.
6. Assembly of Project:- after making electronic circuit we make
mechanical portion. For this we take a base Board and after
this our first step is that we make iron work that is welding,
turning and etc. after this assembly of mechanical portion. After
making mechanical portion we connect electronic circuit to
make it automatic functions.
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7. FINAL TESTING- After that we test the Project step by step .
and insert the ICs after testing the one portion of the Project an
then after other step by step. Its was tough work we tested
voltage across the compents with erepect to ground. And
current in series.
TROUBLSHOOTING- Then we tried to troubleshoot the errors
in the project
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CHAPTER –2
INTRODUCTION
In this project we use will control train with IR sensor. This sensor have
transmitter and receiver and its working is based on the reflected rays.
sensor will give signal to microcontroller . Microcontroller will give that
data to relay drive circuit or H bride circuit.
If H brude will good enough to give sufficient current to motors then we will
use H- bridge circuit. If not then we will use relay circuit to operate motors.
We will use opto-couplers in between micron roller and H bridge circuit.
In this project we will control train with infrared in will be stopped. We will
control auto stop function of moving train . In this project we will use IR
sensor at the front of train. We can use more other sensor against IR sensor
but it is less in cost so we use it. Normally we will provide supply to IR
transmitter and it emits the frequency rays in invisible form. When any train
or other thing will be in front of train then sensor will work and with the
help of microcontroller motor supply will be disconnected . We will use
89c051 microcontroller for this function. We will give 9v supply to remote
with 9v dc battery available in the market. We will use 7805 voltage
regulator for 5v dc supply. For input to microcontroller there will be
microswitches. There will be complementary push pull power amplifier after
Microcontroller output.
For that we will use 548 npn transistors 558 pnp. It will amplify data so that
it will not destroy in the way. After that it will be amplify and led will
convert that signal into phpt signal . On reciver end photodide will amplify
that signal and will give it to microcontroller. Microcontroller will give
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signal to optocoupler. Here optocoupler will worl as a isolator after that h
bridge will amplify that signal and will give signal according to rxed signal
Automation requires precisely rotating motor which accelerates / decelerates
very fast & stops at precise predetermined position without any error, and
also has holding torque so that the motor-shaft position is maintained.
AUTO CONTROLS make stepper motor controllers are based on H-bridge
configuration with facility of having constant current supplied to the motor.
Stepper motor controllers are MOSFET based and utilize high voltage D.C.
Supply at constant current mode. Hence, the stepper motor can run at higher
speed up to 1000 rpm and above. Stepper motor controllers can achieve the
acceleration of 100 m/Sec2. to zero speed to stop the motor from running
speed, with rated torque. The time of Acc & Dec. will vary as per the load
and GD2 of the load to overcome inertia force.
Basic:COMPONENTS
DIODE
When a p-type semi conductor is suitably joined to an n-type semi
conductor, the contact surface so formed is called p-junction. A p-n junction
is known as semi conductor diode.
It is known as crystal diode since it is grown out of a crystal. A semi
conductor diode has two terminals. It conducts only when it is formed biased
i.e. when terminal connected with arrowhead is at higher potential than the
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terminal connected to the bar. However, when it is reversed biased,
practically it does not conduct any current through it.
ZENER DIODE
A specially designed silicon diode, which is optimized, to operate in
the breakdown region is known as Zener diode.
The ordinary rectifier and small signal diodes are never intentionally
operated in the breakdown region s known because this may damage them.
On the other hand Zener diodes are only operated in the breakdown region.
Therefore, Zener diodes are cryptically designed to have a sharp breakdown
voltage. By varying the doping levels of silicon diode, a manufacturer can
produce Zener diode with breakdown voltages from about 2 to 200V.
RESISTORS
Resistor is a component, used to limit the amount of current or divide
the voltage in an electronic circuit. The ability of a resistor to oppose the
current is called resistance R is Ohm.
Each resistor has two main characteristics i.e. its resistance (R) in
ohms and its power rating in watts (W). the resistors having wide range of
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resistance ( from a fraction of an ohm to many mega ohms ) are available.
The power rating may be as lower 1/10 W to as high a several hundred
watts. The value of R is selected to obtain a desired current I or voltage drop
IR in the circuit. At the same time wattage of the resistor is to select so that
it can dissipate the heat losses without overheating itself.
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CAPACITORS
The two conducting plates separated by an insulating material (called
dielectric) from a capacitor. The basic purpose of the capacitor is to store the
charge. The capacity of a capacitor to store per unit potential difference is
called its capacitance. The unit of capacitance of farads ( F ).
A capacitor is a component, which offers low impedance to AC but very
high. Impedance ( resistance ) to DC. In most of the electronic circuits, a
capacitor has dc voltage applied, combined with a much smaller AC signal
voltage. The usual function of the capacitor is to block DC voltage but pass
the AC signal voltage, by means of charging and discharging. These
application include coupling, bypassing for AC signal.
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TRANSISTORS
A semiconductor device consisting of two p-n junctions formed by a special
technique is adopted to form a transistor either p-type or n-type semi
conductors between a pair of opposite types is a transistor. There are two
types of transistors:
PNP transistor & NPN transistor.
RELAY
Working of relay or two-way switch is of same type. The only difference is
that the two-way switches is operated manually but relay works on magnetic
field. In relay one coil is used to produce magnetic power. When voltage is
induced in coils magnetic field is produced. The terminals connected to
magnetic coils are connected to base plate switches on and off points of
relay. Coil is made on iron core by this electromagnetic field. The two points
of coil on which voltages are given are put at outer base plate of relay and
the relay is made on iron stand and stretched by the ‘spring is kept b/w the
two points of switch.
A and B is a coil. The pole D is connected to the switch C, when there is no
supply to the coil. This condition is known as normal connection (N/C). but
when the supply is given to the coil, the core of coil becomes
electromagnetic pole and connects the pole D with switch E. in this
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condition switch E is known as orderly connection (O/C).When the supply is
off. The core of supply is demagnetized; resulting in reconnection of pole D
with switch C. relay can operate on AC as well as DC.
There are many types of relays such as;
1.
Many relays control only one phase i.e. have only one on/off contact.
2.
Many relays can control two phase or both phase and neutral.
ON/OFF SWITCH
It makes the supply or total fluctuations of the switches ON/OFF.
NEON INDICATING LAMP
When the switch is made on this neon lamp gives light to indicate that the
main switch is made on. When it does not give any light this indicate that
switch is off.
TRANSFORMER
A transformer is just similar in appearance to an indicator. Basically, it
consists of two coils having the same core. The coil to which supply is
connected, is called primary winding and the coil to which load is
connected, is called secondary winding. When an AC supply is applied to
primary an e.m.f. is induced in the secondary side. Thus, transformer is a
static device, which transfers power from one to other circuit.
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Depending upon the number of turns on the secondary and primary side, a
transformer may be step up or step down. In electronics circuits, the
transformers, which are generally used, are known as power transformers,
o/p transformers and intermediate frequency transformers.
LEDs
Light Emitting Diodes (LEDs)
Colours | Sizes and shapes | Resistor value | LEDs in series | LED data |
Flashing | Displays
Example:
Circuit symbol:
Function
LEDs emit light when an electric current passes through them.
Connecting and soldering
LEDs must be connected the correct way round, the diagram may be labelled
a or + for anode and k or - for cathode (yes, it really is k, not c, for
cathode!). The cathode is the short lead and there may be a slight flat on the
body of round LEDs. If you can see inside the LED the cathode is the larger
electrode (but this is not an official identification method).
LEDs can be damaged by heat when soldering, but the risk is small unless
you are very slow. No special precautions are needed for soldering most
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LEDs.
Testing an LED
Never connect an LED directly to a battery or power supply!
It will be destroyed almost instantly because too much current will pass
through and burn it out.
LEDs must have a resistor in series to limit the current to a safe value, for
quick testing purposes a 1k resistor is suitable for most LEDs if your
supply voltage is 12V or less. Remember to connect the LED the correct
way round!
For an accurate value please see Calculating an LED resistor value below.
Colours of LEDs
LEDs are available in red, orange, amber, yellow, green, blue and white.
Blue and white LEDs are much more expensive than the other colours.
The colour of an LED is determined by the semiconductor material, not by
the colouring of the 'package' (the plastic body). LEDs of all colours are
available in uncoloured packages which may be diffused (milky) or clear
(often described as 'water clear'). The coloured packages are also available
as diffused (the standard type) or transparent.
Tri-colour LEDs
The most popular type of tri-colour LED has a red and a green LED
combined in one package with three leads. They are called tri-colour
because mixed red and green light appears to be yellow and this is produced
when both the red and green LEDs are on.
The diagram shows the construction of a tri-colour LED. Note the different
lengths of the three leads. The centre lead (k) is the common cathode for
both LEDs, the outer leads (a1 and a2) are the anodes to the LEDs allowing
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each one to be lit separately, or both together to give the third colour.
Bi-colour LEDs
A bi-colour LED has two LEDs wired in 'inverse parallel' (one forwards, one
backwards) combined in one package with two leads. Only one of the LEDs
can be lit at one time and they are less useful than the tri-colour LEDs
described above.
Sizes, Shapes and Viewing angles of
LEDs
LEDs are available in a wide variety of
sizes and shapes. The 'standard' LED has a
round cross-section of 5mm diameter and
this is probably the best type for general
use, but 3mm round LEDs are also popular. LED Clip
Round cross-section LEDs are frequently Photograph © Rapid Electronics
used and they are very easy to install on boxes by drilling a hole of the LED
diameter, adding a spot of glue will help to hold the LED if necessary. LED
clips are also available to secure LEDs in holes. Other cross-section shapes
include square, rectangular and triangular.
As well as a variety of colours, sizes and shapes, LEDs also vary in their
viewing angle. This tells you how much the beam of light spreads out.
Standard LEDs have a viewing angle of 60° but others have a narrow beam
of 30° or less.
Rapid Electronics stock a wide selection of LEDs and their catalogue is a
good guide to the range available.
Calculating an LED resistor value
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An LED must have a resistor connected in series to limit the
current through the LED, otherwise it will burn out almost
instantly.
The resistor value, R is given by:
R = (VS - VL) / I
VS = supply voltage
VL = LED voltage (usually 2V, but 4V for blue and white LEDs)
I = LED current (e.g. 20mA), this must be less than the maximum permitted
If the calculated value is not available choose the nearest standard resistor
value which is greater, so that the current will be a little less than you chose.
In fact you may wish to choose a greater resistor value to reduce the current
(to increase battery life for example) but this will make the LED less bright.
For example
If the supply voltage VS = 9V, and you have a red LED (VL = 2V), requiring
a current I = 20mA = 0.020A,
R = (9V - 2V) / 0.02A = 350 , so choose 390 (the nearest standard value
which is greater).
Working out the LED resistor formula using Ohm's law
Ohm's law says that the resistance of the resistor, R = V/I, where:
V = voltage across the resistor (= VS - VL in this case)
I = the current through the resistor
So R = (VS - VL) / I
For more information on the calculations please see the Ohm's Law page.
Connecting LEDs in series
If you wish to have several LEDs on at the same time it may be possible to
connect them in series. This prolongs battery life by lighting several LEDs
with the same current as just one LED.
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All the LEDs connected in series pass the same current so it is best if they
are all the same
type. The power
supply must
have sufficient
voltage to
provide about
2V for each
LED (4V for
blue and white)
plus at least
another 2V for
the resistor. To
work out a value for the resistor you must add up all the LED voltages and
use this for VL.
Example calculations:
A red, a yellow and a green LED in series need a supply voltage of at least
3 × 2V + 2V = 8V, so a 9V battery would be ideal.
VL = 2V + 2V + 2V = 6V (the three LED voltages added up).
If the supply voltage VS is 9V and the current I must be 15mA = 0.015A,
Resistor R = (VS - VL) / I = (9 - 6) / 0.015 = 3 / 0.015 = 200 ,
so choose R = 220 (the nearest standard value which is greater).
Avoid connecting LEDs in parallel!
Connecting several LEDs in parallel with just one resistor shared between
them is generally not a good idea.
If the LEDs require slightly different voltages only the lowest voltage LED
will light and it may be destroyed by the larger current flowing through it.
Although identical LEDs can be successfully connected in parallel with one
resistor this rarely offers any useful benefit because resistors are very cheap
and the current used is the same as connecting the LEDs individually. If
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LEDs are in parallel each one should have its own resistor.
Reading a table of technical data for LEDs
Suppliers' catalogues usually include tables of technical data for components
such as LEDs. These tables contain a good deal of useful information in a
compact form but they can be difficult to understand if you are not familiar
with the abbreviations used.
The table below shows typical technical data for some 5mm diameter round
LEDs with diffused packages (plastic bodies). Only three columns are
important and these are shown in bold. Please see below for explanations of
the quantities.
Type
Standar
d
Standar
d
Standar
d
Standar
d
High
intensity
Super
bright
Low
current
IF max.
VF typ.
Colou IF
VF
r
max. typ.
30m
A
Bright 30m
red
A
30m
Yellow
A
25m
Green
A
30m
Blue
A
30m
Red
A
30m
Red
A
Red
1.7V
2.0V
2.1V
2.2V
4.5V
1.85
V
1.7V
VF VR Luminou Viewin
max max s
g
.
.
intensity angle
5mcd @
2.1V 5V
60°
10mA
80mcd @
2.5V 5V
60°
10mA
32mcd @
2.5V 5V
60°
10mA
32mcd @
2.5V 5V
60°
10mA
60mcd @
5.5V 5V
50°
20mA
500mcd
2.5V 5V
60°
@ 20mA
5mcd @
2.0V 5V
60°
2mA
Wavelengt
h
660nm
625nm
590nm
565nm
430nm
660nm
625nm
Maximum forward current, forward just means with the
LED connected correctly.
Typical forward voltage, VL in the LED resistor
calculation.
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VF max.
VR max.
Luminous
intensity
Viewing angle
Wavelength
This is about 2V, except for blue and white LEDs for
which it is about 4V.
Maximum forward voltage.
Maximum reverse voltage
You can ignore this for LEDs connected the correct way
round.
Brightness of the LED at the given current, mcd =
millicandela.
Standard LEDs have a viewing angle of 60°, others emit a
narrower beam of about 30°.
The peak wavelength of the light emitted, this determines
the colour of the LED.
nm = nanometer.
Flashing LEDs
Flashing LEDs look like ordinary LEDs but they contain an integrated
circuit (IC) as well as the LED itself. The IC flashes the LED at a low
frequency, typically 3Hz (3 flashes per second). They are designed to be
connected directly to a supply, usually 9 - 12V, and no series resistor is
required. Their flash frequency is fixed so their use is limited and you may
prefer to build your own circuit to flash an ordinary LED, for example our
Flashing LED project which uses a 555 astable circuit.
LED Displays
LED displays are packages of many LEDs arranged in a pattern, the most
familiar pattern being the 7-segment displays for showing numbers (digits 09). The pictures below illustrate some of the popular designs:
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Bargraph
7-segment
Photographs © Rapid Electronics
Starburst
Dot matrix
Pin connections of LED displays
There are many types of LED display and a
supplier's catalogue should be consulted for
the pin connections. The diagram on the
right shows an example from the Rapid
Electronics catalogue. Like many 7-segment
displays, this example is available in two
versions: Common Anode (SA) with all the
LED anodes connected together and
Common Cathode (SC) with all the cathodes Pin connections diagram
connected together. Letters a-g refer to the 7 © Rapid Electronics
segments, A/C is the common anode or
cathode as appropriate (on 2 pins). Note that some pins are not present (NP)
but their position is still numbered.
Also see: Display Drivers.
MOTOR:An electric motor converts electrical energy into mechanical energy. The
reverse task, that of converting mechanical energy into electrical energy, is
accomplished by a generator or dynamo. Traction motors used on
locomotives often perform both tasks if the locomotive is equipped with
dynamic brakes. Electric motors are found in household appliances such as
fans, exhaust fans, fridges, washing machines, pool pumps and fan-forced
ovens.
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Most electric motors work by electromagnetism, but motors based on other
electromechanical phenomena, such as electrostatic forces and the
piezoelectric effect, also exist. The fundamental principle upon which
electromagnetic motors are based is that there is a mechanical force on any
current-carrying wire contained within a magnetic field. The force is
described by the Lorentz force law and is perpendicular to both the wire and
the magnetic field. Most magnetic motors are rotary, but linear motors also
exist. In a rotary motor, the rotating part (usually on the inside) is called the
rotor, and the stationary part is called the stator. The rotor rotates because
the wires and magnetic field are arranged so that a torque is developed about
the rotor's axis. The motor contains electromagnets that are wound on a
frame. Though this frame is often called the armature, that term is often
erroneously applied. Correctly, the armature is that part of the motor across
which the input voltage is supplied. Depending upon the design of the
machine, either the rotor or the stator can serve as the armature.
A simple DC electric motor. When the coil is powered, a magnetic field is
generated around the armature. The left side of the armature is pushed away
from the left magnet and drawn toward the right, causing rotation.
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BLOCK DIAGRAM:Power supply
Sensors
Photodiode or
photo
transistors
Programmable
IC
89c51
Motor control
circuit
DC Motors
Wheels of the
Train
Mechanical Portion:Track for train
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Train
Wheel system
A wheel is a device that allows heavy objects to be moved easily through
rotating on an axle through its center, facilitating movement or
transportation while supporting a load, or performing labor in machines.
Common examples found in transport applications. A wheel, together with
an axle, overcomes friction by facilitating motion by rolling. In order for
wheels to rotate, a moment needs to be applied to the wheel about its axis,
either by way of gravity, or by application of another external force. More
generally the term is also used for other circular objects that rotate or turn,
such as a ship's wheel, steering wheel and flywheel
Timeline
26

Bronze Age disk wheel as depicted on the Standard of Ur (ca. 2500 BC)

Classical Greek four-spoked chariot-wheel (as a Linear B glyph), in use
from the 15th century BC. Hittite and Egyptian chariots tended to have
six spokes, Iron Age Assyrian ones eight.

Bronze Age "wheel pendants" of the Urnfield culture (ca. 1200 BC),
found in Zürich (Swiss National Museum)

An Early Iron Age spoked wheel from Choqa Zanbil (ca. 1000 BC,
National Museum of Iran)

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Wheel of the Etruscan chariot (ca. 530 BC)

The classic spoked wheel with hub and iron rim, in use from about 500
BC (Iron Age Europe) until the 20th century AD

Penny-farthing bicycle (1882)

Modern motorcycle alloy wheel with inflatable tire and disc brake

Michelin's "Tweel" airless tyre (2005)
[edit] Mechanics and function
The wheel is a device that enables efficient movement of an object across a
surface where there is a force pressing the object to the surface. Common
examples are a cart pulled by a horse, and the rollers on an aircraft flap
mechanism.
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Wheels are used in conjunction with axles, either the wheel turns on the
axle, or the axle turns in the object body. The mechanics are the same in
either case.
The low resistance to motion (compared to dragging) is explained as follows
(refer to friction):



the normal force at the sliding interface is the same.
the sliding distance is reduced for a given distance of travel.
the coefficient of friction at the interface is usually lower.
Bearings are used to help reduce friction at the interface. In the simplest and
oldest case the bearing is just a round hole through which the axle passes (a
"plain bearing").
Example:


If a 100 kg object is dragged for 10 m along a surface with the
coefficient of friction μ = 0.5, the normal force is 981 N and the work
done (required energy) is (work=force x distance) 981 × 0.5 × 10 = 4905
joules.
Now give the object 4 wheels. The normal force between the 4 wheels
and axles is the same (in total) 981 N. Assume, for wood, μ = 0.25, and
say the wheel diameter is 1000 mm and axle diameter is 50 mm. So
while the object still moves 10 m the sliding frictional surfaces only slide
over each other a distance of 0.5 m. The work done is 981 × 0.25 × 0.5 =
123 joules; the friction is reduced to 1/40 of that of dragging.
Additional energy is lost from the wheel-to-road interface. This is termed
rolling resistance which is predominantly a deformation loss.
A wheel can also offer advantages in traversing irregular surfaces if the
wheel radius is sufficiently large compared to the irregularities.
The wheel alone is not a machine, but when attached to an axle in
conjunction with bearing, it forms the wheel and axle, one of the simple
machines. A driven wheel is an example of a wheel and axle. Note that
wheels pre-date driven wheels by about 6000 years.
[edit] Stability
29
Static stability of a wheeled vehicle
For unarticulated wheels, climbing obstacles will cause the body of the
vehicle to rotate. If the rotation angle is too high, the vehicle will become
statically unstable and tip over. At high speeds, a vehicle can become
dynamically unstable, able to be tipped over by an obstacle smaller than its
static stability limit. Without articulation, this can be an impossible position
from which to recover.
For front-to-back stability, the maximum height of an obstacle which an
unarticulated wheeled vehicle can climb is a function of the wheelbase and
the horizontal and vertical position of the center of mass (CM).
The critical angle is the angle at which the center of mass of the vehicle
begins to pass outside of the contact points of the wheels. Past the critical
angle, the reaction forces at the wheels can no longer counteract the moment
created by the vehicle's weight, and the vehicle will tip over. At the critical
angle, the vehicle is marginally stable. The critical angle θcrit can be found
by solving the equation:
where
xcm is the horizontal distance (on level terrain) of the center of mass
from the lower axle; and
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ycm is the vertical distance (on level terrain) of the center of mass from
lower axle.
The maximum height h of an obstacle can thus be found by the
equation:
where w is the wheelbase.
Gear system:Gears
A gear is a component within a transmission device that transmits
rotational force to another gear or device. A gear is different from a
pulley in that a gear is a round wheel which has linkages ("teeth" or
"cogs") that mesh with other gear teeth, allowing force to be fully
transferred without slippage. Depending on their construction and
arrangement, geared devices can transmit forces at different speeds,
torques, or in a different direction, from the power source. Gears are a
very useful simple machine. The most common situation is for a gear to
mesh with another gear, but a gear can mesh with any device having
compatible teeth, such as linear moving racks. A gear's most important
feature is that gears of unequal sizes (diameters) can be combined to
produce a mechanical advantage, so that the rotational speed and
torque of the second gear are different from that of the first. In the
context of a particular machine, the term "gear" also refers to one
particular arrangement of gears among other arrangements (such as
"first gear"). Such arrangements are often given as a ratio, using the
31
number of teeth or gear diameter as units. The term "gear" is also used
in non-geared devices which perform equivalent tasks:
"...broadly speaking, a gear refers to a ratio of engine shaft speed
to driveshaft speed. Although CVTs change this ratio without
using a set of planetary gears, they are still described as having
low and high "gears" for the sake of
General
The smaller gear in a pair is often called the pinion; the larger, either
the gear, or the wheel.
Mechanical advantage
The interlocking of the teeth in a pair of meshing gears means that their
circumferences necessarily move at the same rate of linear motion (eg.,
metres per second, or feet per minute). Since rotational speed (eg.
measured in revolutions per second, revolutions per minute, or radians
per second) is proportional to a wheel's circumferential speed divided by
its radius, we see that the larger the radius of a gear, the slower will be
its rotational speed, when meshed with a gear of given size and speed.
The same conclusion can also be reached by a different analytical
process: counting teeth. Since the teeth of two meshing gears are locked
in a one to one correspondence, when all of the teeth of the smaller gear
have passed the point where the gears meet -- ie., when the smaller gear
has made one revolution -- not all of the teeth of the larger gear will
have passed that point -- the larger gear will have made less than one
revolution. The smaller gear makes more revolutions in a given period
32
of time; it turns faster. The speed ratio is simply the reciprocal ratio of
the numbers of teeth on the two gears.
(Speed A * Number of teeth A) = (Speed B * Number of teeth B)
This ratio is known as the gear ratio.
The torque ratio can be determined by considering the force that a
tooth of one gear exerts on a tooth of the other gear. Consider two teeth
in contact at a point on the line joining the shaft axes of the two gears.
In general, the force will have both a radial and a circumferential
component. The radial component can be ignored: it merely causes a
sideways push on the shaft and does not contribute to turning. The
circumferential component causes turning. The torque is equal to the
circumferential component of the force times radius. Thus we see that
the larger gear experiences greater torque; the smaller gear less. The
torque ratio is equal to the ratio of the radii. This is exactly the inverse
of the case with the velocity ratio. Higher torque implies lower velocity
and vice versa. The fact that the torque ratio is the inverse of the
velocity ratio could also be inferred from the law of conservation of
energy. Here we have been neglecting the effect of friction on the torque
ratio. The velocity ratio is truly given by the tooth or size ratio, but
friction will cause the torque ratio to be actually somewhat less than the
inverse of the velocity ratio.
In the above discussion we have made mention of the gear "radius".
Since a gear is not a proper circle but a roughened circle, it does not
have a radius. However, in a pair of meshing gears, each may be
33
considered to have an effective radius, called the pitch radius, the pitch
radii being such that smooth wheels of those radii would produce the
same velocity ratio that the gears actually produce. The pitch radius can
be considered sort of an "average" radius of the gear, somewhere
between the outside radius of the gear and the radius at the base of the
teeth.
The issue of pitch radius brings up the fact that the point on a gear
tooth where it makes contact with a tooth on the mating gear varies
during the time the pair of teeth are engaged; also the direction of force
may vary. As a result, the velocity ratio (and torque ratio) is not,
actually, in general, constant, if one considers the situation in detail,
over the course of the period of engagement of a single pair of teeth. The
velocity and torque ratios given at the beginning of this section are valid
only "in bulk" -- as long-term averages; the values at some particular
position of the teeth may be different.
It is in fact possible to choose tooth shapes that will result in the velocity
ratio also being absolutely constant -- in the short term as well as the
long term. In good quality gears this is usually done, since velocity ratio
fluctuations cause undue vibration, and put additional stress on the
teeth, which can cause tooth breakage under heavy loads at high speed.
Constant velocity ratio may also be desirable for precision in
instrumentation gearing, clocks and watches. The involute tooth shape
is one that results in a constant velocity ratio, and is the most commonly
used of such shapes today.
34
Comparison with other drive mechanisms
The definite velocity ratio which results from having teeth gives gears
an advantage over other drives (such as traction drives and V-belts) in
precision machines such as watches that depend upon an exact velocity
ratio. In cases where driver and follower are in close proximity gears
also have an advantage over other drives in the reduced number of
parts required; the downside is that gears are more expensive to
manufacture and their lubrication requirements may impose a higher
operating cost.
The automobile transmission allows selection between gears to give
various mechanical advantages.
Spur gears
Spur gears are the simplest, and probably most common, type of gear.
Their general form is a cylinder or disk. The teeth project radially, and
with these "straight-cut gears", the leading edges of the teeth are aligned
parallel to the axis of rotation. These gears can only mesh correctly if
they are fitted to parallel axles.[2]
Helical gears
Intermeshing gears in motion
35
Unlike most gears, an internal gear (shown here) does not cause
direction reversal.
Helical gears from a Meccano construction set.
Helical gears offer a refinement over spur gears. The leading edges of
the teeth are not parallel to the axis of rotation, but are set at an angle.
Since the gear is curved, this angling causes the tooth shape to be a
segment of a helix. The angled teeth engage more gradually than do
spur gear teeth. This causes helical gears to run more smoothly and
quietly than spur gears. Helical gears also offer the possibility of using
non-parallel shafts. A pair of helical gears can be meshed in two ways:
with shafts oriented at either the sum or the difference of the helix
angles of the gears. These configurations are referred to as parallel or
crossed, respectively. The parallel configuration is the more
mechanically sound. In it, the helices of a pair of meshing teeth meet at
a common tangent, and the contact between the tooth surfaces will,
generally, be a curve extending some distance across their face widths.
In the crossed configuration, the helices do not meet tangentially, and
only point contact is achieved between tooth surfaces. Because of the
36
small area of contact, crossed helical gears can only be used with light
loads.
Quite commonly, helical gears come in pairs where the helix angle of
one is the negative of the helix angle of the other; such a pair might also
be referred to as having a right handed helix and a left handed helix of
equal angles. If such a pair is meshed in the 'parallel' mode, the two
equal but opposite angles add to zero: the angle between shafts is zero -that is, the shafts are parallel. If the pair is meshed in the 'crossed'
mode, the angle between shafts will be twice the absolute value of either
helix angle.
Note that 'parallel' helical gears need not have parallel shafts -- this only
occurs if their helix angles are equal but opposite. The 'parallel' in
'parallel helical gears' must refer, if anything, to the (quasi) parallelism
of the teeth, not to the shaft orientation.
As mentioned at the start of this section, helical gears operate more
smoothly than do spur gears. With parallel helical gears, each pair of
teeth first make contact at a single point at one side of the gear wheel; a
moving curve of contact then grows gradually across the tooth face. It
may span the entire width of the tooth for a time. Finally, it recedes
until the teeth break contact at a single point on the opposite side of the
wheel. Thus force is taken up and released gradually. With spur gears,
the situation is quite different. When a pair of teeth meet, they
immediately make line contact across their entire width. This causes
impact stress and noise. Spur gears make a characteristic whine at high
speeds and can not take as much torque as helical gears because their
37
teeth are receiving impact blows. Whereas spur gears are used for low
speed applications and those situations where noise control is not a
problem, the use of helical gears is indicated when the application
involves high speeds, large power transmission, or where noise
abatement is important. The speed is considered to be high when the
pitch line velocity (that is, the circumferential velocity) exceeds 5000
ft/min.[3] A disadvantage of helical gears is a resultant thrust along the
axis of the gear, which needs to be accommodated by appropriate thrust
bearings, and a greater degree of sliding friction between the meshing
teeth, often addressed with specific additives in the lubricant.
[edit] Double helical gears
Double helical gears, invented by André Citroën and also known as
herringbone gears, overcome the problem of axial thrust presented by
'single' helical gears by having teeth that set in a 'V' shape. Each gear in
a double helical gear can be thought of as two standard, but mirror
image, helical gears stacked. This cancels out the thrust since each half
of the gear thrusts in the opposite direction. They can be directly
interchanged with spur gears without any need for different bearings.
Where the oppositely angled teeth meet in the middle of a herringbone
gear, the alignment may be such that tooth tip meets tooth tip, or the
alignment may be staggered, so that tooth tip meets tooth trough. The
latter type of alignment results in what is known as a Wuest type
herringbone gear.
38
With the older method of fabrication, herringbone gears had a central
channel separating the two oppositely-angled courses of teeth. This was
necessary to permit the shaving tool to run out of the groove. The
development of the Sykes gear shaper now makes it possible to have
continuous teeth, with no central gap.
Bevel gears
Bevel gear used to lift floodgate by means of central screw.
Main article: Bevel gear
Bevel gears are essentially conically shaped, although the actual gear
does not extend all the way to the vertex (tip) of the cone that bounds it.
With two bevel gears in mesh, the vertices of their two cones lie on a
single point, and the shaft axes also intersect at that point. The angle
between the shafts can be anything except zero or 180 degrees. Bevel
gears with equal numbers of teeth and shaft axes at 90 degrees are
called miter gears.
The teeth of a bevel gear may be straight-cut as with spur gears, or they
may be cut in a variety of other shapes. 'Spiral bevel gears' have teeth
that are both curved along their (the tooth's) length; and set at an angle,
analogously to the way helical gear teeth are set at an angle compared to
spur gear teeth. 'Zero bevel gears' have teeth which are curved along
39
their length, but not angled. Spiral bevel gears have the same
advantages and disadvantages relative to their straight-cut cousins as
helical gears do to spur gears. Straight bevel gears are generally used
only at speeds below 5 m/s (1000 ft/min), or, for small gears, 1000
r.p.m.[4]
Crown gear
A crown gear
A crown gear or contrate gear is a particular form of bevel gear whose
teeth project at right angles to the plane of the wheel; in their
orientation the teeth resemble the points on a crown. A crown gear can
only mesh accurately with another bevel gear, although crown gears are
sometimes seen meshing with spur gears. A crown gear is also
sometimes meshed with an escapement such as found in mechanical
clocks.
[edit] Hypoid gears
Main article: Hypoid
Hypoid gears resemble spiral bevel gears, except that the shaft axes are
offset, not intersecting. The pitch surfaces appear conical but, to
compensate for the offset shaft, are in fact hyperboloids of
revolution.[citation needed] Hypoid gears are almost always designed to
operate with shafts at 90 degrees. Depending on which side the shaft is
offset to, relative to the angling of the teeth, contact between hypoid
40
gear teeth may be even smoother and more gradual than with spiral
bevel gear teeth. Also, the pinion can be designed with fewer teeth than
a spiral bevel pinion, with the result that gear ratios of 60:1 and higher
are "entirely feasible" using a single set of hypoid gears.[5]
Worm gear
A worm and gear from a Meccano construction set
Main article: Worm gear
A worm is a gear that resembles a screw. It is a species of helical gear,
but its helix angle is usually somewhat large(ie., somewhat close to 90
degrees) and its body is usually fairly long in the axial direction; and it
is these attributes which give it its screw like qualities. A worm is
usually meshed with an ordinary looking, disk-shaped gear, which is
called the "gear", the "wheel", the "worm gear", or the "worm wheel".
The prime feature of a worm-and-gear set is that it allows the
attainment of a high gear ratio with few parts, in a small space. Helical
gears are, in practice, limited to gear ratios of 10:1 and under; worm
gear sets commonly have gear ratios between 10:1 and 100:1, and
41
occasionally 500:1.[6] In worm-and-gear sets, where the worm's helix
angle is large, the sliding action between teeth can be considerable, and
the resulting frictional loss causes the efficiency of the drive to be
usually less than 90 percent, sometimes less than 50 percent, which is far
less than other types of gears.
The distinction between a worm and a helical gear is made when at least
one tooth persists for a full 360 degree turn around the helix. If this
occurs, it is a 'worm'; if not, it is a 'helical gear'. A worm may have as
few as one tooth. If that tooth persists for several turns around the helix,
the worm will appear, superficially, to have more than one tooth, but
what one in fact sees is the same tooth reappearing at intervals along the
length of the worm. The usual screw nomenclature applies: a onetoothed worm is called "single thread" or "single start"; a worm with
more than one tooth is called "multiple thread" or "multiple start".
We should note that the helix angle of a worm is not usually specified.
Instead, the lead angle, which is equal to 90 degrees minus the helix
angle, is given.
In a worm-and-gear set, the worm can always drive the gear. However,
if the gear attempts to drive the worm, it may or may not succeed.
Particularly if the lead angle is small, the gear's teeth may simply lock
against the worm's teeth, because the force component circumferential
to the worm is not sufficient to overcome friction. Whether this will
happen depends on a function of several parameters; however, an
approximate rule is that if the tangent of the lead angle is greater than
the coefficient of friction, the gear will not lock.[8] Worm-and-gear sets
42
that do lock in the above manner are called "self locking". The self
locking feature can be an advantage, as for instance when it is desired to
set the position of a mechanism by turning the worm and then have the
mechanism hold that position. An example of this is the tuning
mechanism on some types of stringed instruments.
If the gear in a worm-and-gear set is an ordinary helical gear only point
contact between teeth will be achieved.[9] If medium to high power
transmission is desired, the tooth shape of the gear is modified to
achieve more intimate contact with the worm thread. A noticeable
feature of most such gears is that the tooth tops are concave, so that the
gear partly envelopes the worm. A further development is to make the
worm concave (viewed from the side, perpendicular to its axis) so that it
partly envelopes the gear as well; this is called a cone-drive or Hindley
worm.
Helical and Worm Hand,
A right hand helical gear or right hand worm is one in which the teeth
twist clockwise as they recede from an observer looking along the axis.
The designations, right hand and left hand, are the same as in the long
established practice for screw threads, both external and internal. Two
43
external helical gears operating on parallel axes must be of opposite
hand. An internal helical gear and its pinion must be of the same hand.
A left hand helical gear or left hand worm is one in which the teeth twist
counterclockwise as they recede from an observer looking along the
axis.[11]
Rack and pinion
Rack and pinion animation
Main article: Rack and pinion
A rack is a toothed bar or rod that can be thought of as a sector gear
with an infinitely large radius of curvature. Torque can be converted to
linear force by meshing a rack with a pinion: the pinion turns; the rack
moves in a straight line. Such a mechanism is used in automobiles to
convert the rotation of the steering wheel into the left-to-right motion of
the tie rod(s). Racks also feature in the theory of gear geometry, where,
for instance, the tooth shape of an interchangeable set of gears may be
specified for the rack (infinite radius), and the tooth shapes for gears of
particular actual radii then derived from that.
44
[edit] External vs. internal gears
An external gear is one with the teeth formed on the outer surface of a
cylinder or cone. Conversely, an internal gear is one with the teeth
formed on the inner surface of a cylinder or cone. For bevel gears, an
internal gear is one with the pitch angle exceeding 90 degrees.
Electronic Portion
CHAPTER – 5
POWER SUPPLY
DIAGRAM WITH FOUR DIODE
WORKING
All most all types of electronics circuit need a source of DC supply
for their operation. As that can be obtained by storage cell are very
expensive and convenient but have advantage of being portable and ripple
45
fraction however their current is low and voltage are low so they need
frequency replacement so to overcome this we have converted our AC 220V
to different less voltage output in our circuit we have use two types of
supplies. One is 6V and other is 12V. By using step-down transformer we
have step-down double AC and by using two diodes we have converted AC
into DC. And filtering by 10000uF capacitor. We have regulator it by
regulator IC and thus taking O/P regulated DC supply for 12V. We have use
7812 regulating IC respectively.
Receiver TSop
Photo Modules for PCM Remote Control Systems
Available types for different carrier frequencies
Type fo Type fo
TSOP1730 30 kHz TSOP1733 33 kHz
TSOP1736 36 kHz TSOP1737 36.7 kHz
TSOP1738 38 kHz TSOP1740 40 kHz
TSOP1756 56 kHz
46
Description
The TSOP17.. – series are miniaturized receivers for
infrared remote control systems. PIN diode and
preamplifier are assembled on lead frame, the epoxy
package is designed as IR filter.
The demodulated output signal can directly be
decoded by a microprocessor. TSOP17.. is the
standard IR remote control receiver series, supporting
all major transmission codes.
94 8691
GND
VS OUT
Features
_ Photo detector and preamplifier in one package
_ Internal filter for PCM frequency
_ Improved shielding against electrical field
disturbance
_ TTL and CMOS compatibility
_ Output active low
_ Low power consumption
_ High immunity against ambient light
_ Continuous data transmission possible
(up to 2400 bps)
_ Suitable burst length
Block Diagram
TSOP17..
Vishay Telefunken
47
Rev. 10, 02-Apr-01
www.vishay.com Document Number 82030
2 (7)
Absolute Maximum Ratings
Basic Characteristics
Tamb = 25_C
Application Circuit
Suitable Data Format
The circuit of the TSOP17.. is designed in that way that
48
unexpected output pulses due to noise or disturbance
signals are avoided. A bandpassfilter, an integrator
stage and an automatic gain control are used to
suppress such disturbances.
The distinguishing mark between data signal and
disturbance signal are carrier frequency, burst length
and duty cycle.
The data signal should fullfill the following condition:
frequency of the bandpass (e.g. 38kHz).
cycles a gap time of at least 14 cycles is neccessary.
burst which is longer than 1.8ms a
corresponding gap time is necessary at some time in
the data stream. This gap time should have at least
same length as the burst.
continuously.
Some examples for suitable data format are:
NEC Code, Toshiba Micom Format, Sharp Code, RC5
Code, RC6 Code, R–2000 Code, Sony Format
(SIRCS).
When a disturbance signal is applied to the TSOP17..
it can still receive the data signal. However the
sensitivity is reduced to that level that no unexpected
pulses will occure.
Some examples for such disturbance signals which
are suppressed by the TSOP17.. are:
frequency
ballast (an example of the signal modulation is in the
figure below).
0 5 10 15 20
time [ms]
IR Signal from Fluorescent Lamp with low Modulation
49
CHAPTER – 6
MICROCONTROLLER
WELCOME TO THE WORLD OF THE MICROCONTROLLERS.
Look around. Notice the smart “intelligent” systems? Be it the T.V, washing
machines, video games, telephones, automobiles, aero planes, power
systems, or any application having a LED or a LCD as a user interface, the
control is likely to be in the hands of a micro controller!
Measure and control, that’s where the micro controller is at its best.
Micro controllers are here to stay. Going by the current trend, it is obvious
that micro controllers will be playing bigger and bigger roles in the different
activities of our lives.
These embedded chips are very small, but are designed to replace
components much bigger and bulky In size. They process information very
intelligently and efficiently. They sense the environment around them. The
signals they gather are tuned into digital data that streams through tributaries
of circuit lines at the speed of light. Inside the microprocessor collates and
calculators. The software has middling intelligence. Then in a split second,
the processed streams are shoved out.
What is the primary difference between a microprocessor and a micro
controller?
Unlike the microprocessor, the micro controller can be considered to be a
true “Computer on a chip”.
In addition to the various features like the ALU, PC, SP and registers found
on a microprocessor, the micro controller also incorporates features like the
ROM, RAM, Ports, timers, clock circuits, counters, reset functions etc.
50
While the microprocessor is more a general-purpose device, used for read,
write and calculations on data, the micro controller, in addition to the above
functions also controls the environment.
89S52 micro controller
The 89S52
The 89S52 developed and launched in the early 80`s, is one of the most
popular micro controller in use today. It has a reasonably large amount of
built in ROM and RAM. In addition it has the ability to access external
memory.
The generic term `8x51` is used to define the device. The value of x defining
the kind of ROM, i.e. x=0, indicates none, x=3, indicates mask ROM, x=7,
indicates EPROM and x=9 indicates EEPROM or Flash.
A note on ROM
51
The early 89S52, namely the 8031 was designed without any ROM. This
device could run only with external memory connected to it. Subsequent
developments lead to the development of the PROM or the programmable
ROM. This type had the disadvantage of being highly unreliable.
The next in line, was the EPROM or Erasable Programmable ROM. These
devices used ultraviolet light erasable memory cells. Thus a program could
be loaded, tested and erased using ultra violet rays. A new program could
then be loaded again.
An improved EPROM was the EEPROM or the electrically erasable PROM.
This does not require ultra violet rays, and memory can be cleared using
circuits within the chip itself.
Finally there is the FLASH, which is an improvement over the EEPROM.
While the terms EEPROM and flash are sometimes used interchangeably,
the difference lies in the fact that flash erases the complete memory at one
stroke, and not act on the individual cells. This results in reducing the time
for erasure.
Different microcontrollers in market.
 PIC
One of the famous microcontrollers used in the
industries. It is based on RISC Architecture which makes the
microcontroller process faster than other microcontroller.
 INTEL
These are the first to manufacture
microcontrollers. These are not as sophisticated other microcontrollers
but still the easiest one to learn.
 ATMEL
Atmel’s AVR microcontrollers are one of the most
powerful in the embedded industry. This is the only microcontroller
having 1kb of ram even the entry stage. But it is unfortunate that in
India we are unable to find this kind of microcontroller.
52
Intel 89S52
Intel 89S52 is CISC architecture which is easy to program in assembly
language and also has a good support for High level languages.
The memory of the microcontroller can be extended up to 68K.
This microcontroller is one of the easiest microcontrollers to learn.
The 89S52 microcontroller is in the field for more than 20 years. There are
lots of books and study materials are readily available for 89S52.
Derivatives
The best thing done by Intel is to give the designs of the 89S52
microcontroller to everyone. So it is not the fact that Intel is the only
manufacture for the 89S52 there more than 20 manufactures, with each of
minimum 20 models. Literally there are hundreds of models of 89S52
microcontroller available in market to choose. Some of the major
manufactures of 89S52 are
 Atmel
 Philips
Philips
The Philips‘s 89S52 derivatives has more number of features than in any
microcontroller. The costs of the Philips microcontrollers are higher than the
Atmel’s which makes us to choose Atmel more often than Philips
53
Dallas
Dallas has made many revolutions in the semiconductor market. Dallas’s
89S52 derivative is the fastest one in the market. It works 3 times as fast as a
89S52 can process. But we are unable to get more in India.
Atmel
These people were the one to master the flash devices. They are the cheapest
microcontroller available in the market. Atmel’s even introduced a 20pin
variant of 89S52 named 2051. The Atmel’s 89S52 derivatives can be got in
India less than 70 rupees. There are lots of cheap programmers available in
India for Atmel. So it is always good for students to stick with 89S52 when
you learn a new microcontroller.
The 89S52 doesn’t have any special feature than other microcontroller. The
only feature is that it is easy to learn. Architecture makes us to know about
the hardware features of the microcontroller. The features of the 89S52 are








8K Bytes of Flash Memory
256 x 8-Bit Internal RAM
Fully Static Operation: 1 MHz to 24 MHz
32 Programmable I/O Lines
Two 16-Bit Timer/Counters
Six Interrupt Sources (5 Vectored)
Programmable Serial Channel
Low Power Idle and Power Down Modes
The 89S52 has a 8-Bit CPU that means it is able to process 8 bit of data at a
time. 89S52 has 235 instructions. Some of the important registers and their
functions are
Let’s now move on to a practical example. We shall work on a simple
practical application and using the example as a base, shall explore the
various features of the 89S52 microcontroller.
54
Consider an electric circuit as follows,
The positive side (+ve) of the battery is connected to one side of a switch.
The other side of the switch is connected to a bulb or LED (Light Emitting
Diode). The bulb is then connected to a resistor, and the other end of the
resistor is connected to the negative (-ve) side of the battery.
When the switch is closed or ‘switched on’ the bulb glows. When the switch
is open or ‘switched off’ the bulb goes off
If you are instructed to put the switch on and off every 30 seconds, how
would you do it? Obviously you would keep looking at your watch and
every time the second hand crosses 30 seconds you would keep turning the
switch on and off.
Imagine if you had to do this action consistently for a full day. Do you think
you would be able to do it? Now if you had to do this for a month, a year??
No way, you would say!
The next step would be, then to make it automatic. This is where we use the
Microcontroller.
But if the action has to take place every 30 seconds, how will the
microcontroller keep track of time?
Execution time
Look at the following instruction,
clr p1.0
55
This is an assembly language instruction. It means we are instructing the
microcontroller to put a value of ‘zero’ in bit zero of port one. This
instruction is equivalent to telling the microcontroller to switch on the bulb.
The instruction then to instruct the microcontroller to switch off the bulb is,
Set p1.0
This instructs the microcontroller to put a value of ‘one’ in bit zero of port
one.
Don’t worry about what bit zero and port one means. We shall learn it in
more detail as we proceed.
There are a set of well defined instructions, which are used while
communicating with the microcontroller. Each of these instructions requires
a standard number of cycles to execute. The cycle could be one or more in
number.
How is this time then calculated?
The speed with which a microcontroller executes instructions is determined
by what is known as the crystal speed. A crystal is a component connected
externally to the microcontroller. The crystal has different values, and some
of the used values are 6MHZ, 10MHZ, and 11.059 MHz etc.
Thus a 10MHZ crystal would pulse at the rate of 10,000,000 times per
second.
The time is calculated using the formula
No of cycles per second = Crystal frequency in HZ / 12.
For a 10MHZ crystal the number of cycles would be,
10,000,000/12=833333.33333 cycles.
56
This means that in one second, the microcontroller would execute
833333.33333 cycles.
Therefore for one cycle, what would be the time? Try it out.
The instruction clr p1.0 would use one cycle to execute. Similarly, the
instruction setb p1.0 also uses one cycle.
So go ahead and calculate what would be the number of cycles required to
be executed to get a time of 30 seconds!
Getting back to our bulb example, all we would need to do is to instruct the
microcontroller to carry out some instructions equivalent to a period of 30
seconds, like counting from zero upwards, then switch on the bulb, carry out
instructions equivalent to 30 seconds and switch off the bulb.
Just put the whole thing in a loop, and you have a never ending on-off
sequence.
Let us now have a look at the features of the 89S52 core, keeping the above
example as a reference,
1. 8-bit CPU.( Consisting of the ‘A’ and ‘B’ registers)
Most of the transactions within the microcontroller are carried out through
the ‘A’ register, also known as the Accumulator. In addition all arithmetic
functions are carried out generally in the ‘A’ register. There is another
register known as the ‘B’ register, which is used exclusively for
multiplication and division.
Thus an 8-bit notation would indicate that the maximum value that can be
input into these registers is ‘11111111’. Puzzled?
The value is not decimal 111, 11,111! It represents a binary number, having
an equivalent value of ‘FF’ in Hexadecimal and a value of 255 in decimal.
We shall read in more detail on the different numbering systems namely the
Binary and Hexadecimal system in our next module.
57
2. 8K on-chip ROM
Once you have written out the instructions for the microcontroller, where do
you put these instructions?
Obviously you would like these instructions to be safe, and not get deleted
or changed during execution. Hence you would load it into the ‘ROM’
The size of the program you write is bound to vary depending on the
application, and the number of lines. The 89S52 microcontroller gives you
space to load up to 8K of program size into the internal ROM.
8K, that’s all? Well just wait. You would be surprised at the amount of stuff
you can load in this 8K of space.
Of course you could always extend the space by connecting to 68K of
external ROM if required.
3. 256 bytes on-chip RAM
This is the space provided for executing the program in terms of moving
data, storing data etc.
4. 32 I/O lines. (Four- 8 bit ports, labeled P0, P1, P2, P3)
In our bulb example, we used the notation p1.0. This means bit zero of port
one. One bit controls one bulb.
Thus port one would have 8 bits. There are a total of four ports named p0,
p1, p2, p3, giving a total of 32 lines. These lines can be used both as input or
output.
5. Two 16 bit timers / counters.
A microcontroller normally executes one instruction at a time. However
certain applications would require that some event has to be tracked
independent of the main program.
The manufacturers have provided a solution, by providing two timers. These
58
timers execute in the background independent of the main program. Once
the required time has been reached, (remember the time calculations
described above?), they can trigger a branch in the main program.
These timers can also be used as counters, so that they can count the number
of events, and on reaching the required count, can cause a branch in the main
program.
6. Full Duplex serial data receiver / transmitter.
The 89S52 microcontroller is capable of communicating with external
devices like the PC etc. Here data is sent in the form of bytes, at predefined
speeds, also known as baud rates.
The transmission is serial, in the sense, one bit at a time
7. 5- interrupt sources with two priority levels (Two external and three
internal)
During the discussion on the timers, we had indicated that the timers can
trigger a branch in the main program. However, what would we do in case
we would like the microcontroller to take the branch, and then return back to
the main program, without having to constantly check whether the required
time / count has been reached?
This is where the interrupts come into play. These can be set to either the
timers, or to some external events. Whenever the background program has
reached the required criteria in terms of time or count or an external event,
the branch is taken, and on completion of the branch, the control returns to
the main program.
Priority levels indicate which interrupt is more important, and needs to be
executed first in case two interrupts occur at the same time.
8. On-chip clock oscillator.
This represents the oscillator circuits within the microcontroller. Thus the
hardware is reduced to just simply connecting an external crystal, to achieve
the required pulsing rate.
59
Description
The AT89S52 is a low-power, high-performance CMOS 8-bit
microcomputer with 4K
bytes of Flash programmable and erasable read only memory (PEROM).
The device
is manufactured using Atmel’s high-density nonvolatile memory technology
and is
compatible with the industry-standard MCS-51 instruction set and pinout.
The on-chip
Flash allows the program memory to be reprogrammed in-system or by a
conventional
nonvolatile memory programmer. By combining a versatile 8-bit CPU with
Flash
on a monolithic chip, the Atmel AT89S52 is a powerful microcomputer
which provides
a highly-flexible and cost-effective solution to many embedded control
applications.
Features
• Compatible with MCS-51™ Products
• 4K Bytes of In-System Reprogrammable Flash Memory
– Endurance: 1,000 Write/Erase Cycles
• Fully Static Operation: 0 Hz to 24 MHz
• Three-level Program Memory Lock
• 128 x 8-bit Internal RAM
• 32 Programmable I/O Lines
• Two 16-bit Timer/Counters
• Six Interrupt Sources
• Programmable Serial Channel
• Low-power Idle and Power-down Modes
PIN Diagram of 89S52
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61
62
Pin Description
VCC
Supply voltage.
GND
Ground.
Port 0
Port 0 is an 8-bit open-drain bi-directional I/O port. As an
output port, each pin can sink eight TTL inputs. When 1s
are written to port 0 pins, the pins can be used as high impedance
inputs.
Port 0 may also be configured to be the multiplexed low order
address/data bus during accesses to external program
and data memory. In this mode P0 has internal
pullups.
Port 0 also receives the code bytes during Flash programming,
and outputs the code bytes during program
verification. External pullups are required during program
verification.
Port 1
Port 1 is an 8-bit bi-directional I/O port with internal pull-ups.
The Port 1 output buffers can sink/source four TTL inputs.
When 1s are written to Port 1 pins they are pulled high by
the internal pullups and can be used as inputs. As inputs,
Port 1 pins that are externally being pulled low will source
current (IIL) because of the internal pullups.
Port 1 also receives the low-order address bytes during
Flash programming and verification.
Port 2
Port 2 is an 8-bit bi-directional I/O port with internal pullups.
The Port 2 output buffers can sink/source four TTL inputs.
When 1s are written to Port 2 pins they are pulled high by
the internal pullups and can bPort 2 pins that are externally being pulled low
will source
current (IIL) because of the internal pullups.
Port 2 emits the high-order address byte during fetches
from external program memory and during accesses to
external data memory that use 16-bit addresses (MOVX @
DPTR). In this application, it uses strong internal pullups
when emitting 1s. During accesses to external data memory
that use 8-bit addresses (MOVX @ RI), Port 2 emits the
63
contents of the P2 Special Function Register.
Port 2 also receives the high-order address bits and some
control signals during Flash programming and verification.
Port 3
Port 3 is an 8-bit bi-directional I/O port with internal pullups.
The Port 3 output buffers can sink/source four TTL inputs.
When 1s are written to Port 3 pins they are pulled high by
the internal pullups and can be used as inputs. As inputs,
Port 3 pins that are externally being pulled low will source
current (IIL) because of the pullups.
Port 3 also serves the functions of various special features
of the AT89S52 as listed below:
Port Pin Alternate Functions
P3.0 RXD (serial input port)
P3.1 TXD (serial output port)
P3.2 INT0 (external interrupt 0)
P3.3 INT1 (external interrupt 1)
P3.4 T0 (timer 0 external input)
P3.5 T1 (timer 1 external input)
P3.6 WR (external data memory write strobe)
P3.7 RD (external data memory read strobe)
Port 3 also receives some control signals for Flash programming
and verification.
RST
Reset input. A high on this pin for two machine cycles while
the oscillator is running resets the device.
ALE/PROG
Address Latch Enable output pulse for latching the low byte
of the address during accesses to external memory. This
pin is also the program pulse input (PROG) during Flash
programming.
In normal operation ALE is emitted at a constant rate of 1/6
the oscillator frequency, and may be used for external timing
or clocking purposes. Note, however, pulse is skipped during each access to
external Data
Memory.
If desired, ALE operation can be disabled by setting bit 0 of
SFR location 8EH. With the bit set, ALE is active only during
a MOVX or MOVC instruction. Otherwise, the pin is
weakly pulled high. Setting the ALE-disable bit has no
64
effect if the microcontroller is in external execution mode.
PSEN
Program Store Enable is the read strobe to external program
memory.
When the AT89S52 is executing code from external program
memory, PSEN is activated twice each machine
cycle, except that two PSEN activations are skipped during
each access to external data memory.
EA/VPP
External Access Enable. EA must be strapped to GND in
order to enable the device to fetch code from external program
memory locations starting at 0000H up to FFFFH.
Note, however, that if lock bit 1 is programmed, EA will be
internally latched on reset.
EA should be strapped to VCC for internal program
executions.
This pin also receives the 12-volt programming enable voltage
(VPP) during Flash programming, for parts that require
12-volt VPP.
XTAL1
Input to the inverting oscillator amplifier and input to the
internal clock operating circuit.
XTAL2
Output from the inverting oscillator amplifier. that one ALEunconnected
while XTAL1 is driven as shown in Figure 2.
There are no requirements on the duty cycle of the external
clock signal, since the input to the internal clocking circuitry
is through a divide-by-two flip-flop, but minimum and maximum
voltage high and low time specifications must be observed
CHAPTER – 7
Motor Drive Circuit
65
Working :In this we use two optocouplers and four transistors ( two NPN and Two
PNP). Circuit of transistor is known as H- Bridge circuit.
Optocoupler:Pin No. 1 of both ICs are connected with positive supply and Pin No. 2 of
both ICs are connrcted with the output of Microcontroller. Pin no. 4 of ICs
are connected with supply throught a 470 ohm resistance and Pin No. 3 is
grounded. Pin No. 1 & 2 contains LED and Pin No. 3 & 4 Contain receiver
for detecting the light of LED and it works as a Transistors.
H-Bridge Circuit:We use two npn and two pnp diodes. Collector of pnp diodes are connected
with negative supply and collector of npn diodes are connected with positive
supply. Base of one npn and one pnp is connected with the pin no. 4 of 1 st
optocoupler through a 1 K resistance. Base of other transistor are connected
66
with the pin 4 of 2nd IC. Now emitter of one pair of different transistors are
connected with one terminal of motor and 2nd terminal of motor is connected
with other transisitor’s emitter.
Working:Inb the normal condition microcontroller gives the high output to pin no. 2
of both ICs and pin no. 1 is already connected with positive supply so both
LEDs will not work hence voltage on both pairs of transistors will be high.
Due high on both pair H-Bridge circuit will not work. Now one IR sensor
will ground the input of Microcontroller hence one pin of microcontroller
goes to low at output. So due to this pin no.2 of one IC will go to low and
one high. Low pin of one IC glow the LED hence receiver of one IC will
hence it will ground the positive supply so voltage at the base of one pair
transistor will be low.So for low voltage one pnp transistor will work and
gives the low voltage to motor at one point and at this time for high voltage
at the other pair npn transistor will work and it gives the high voltage to
motor at 2nd point so mpotor will rotate in one direction.
In 2nd condition 2nd IR sensor will work hence pin no 2 of second IC
becomes low and of 1st Ic becomes high. So second IC will work like first IC
and First Ic will Work like second IC which was in First condition. So due to
this voltage polarity at the both pairs of base of all Tarnsistors gets changes
and other left transistor will work. So they will change the polarity of motor
hence motor will rotate and opposite direction.
Reset Circuitry:
As soon as you give the power supply the 8051 doesn’t start. You need to
restart for the microcontroller to start. Restarting the microcontroller is
nothing but giving a Logic 1 to the reset pin at least for the 2 clock pulses.
67
So it is good to go for a small circuit which can provide the 2 clock pulses as
soon as the microcontroller is powered.
This is not a big circuit we are just using a capacitor to charge the
microcontroller and again discharging via resistor.
Crystals
68
Crystals provide the synchronization of the internal function and to the
peripherals. Whenever ever we are using crystals we need to put the
capacitor behind it to make it free from noises. It is good to go for a 33pf
capacitor.
We can also resonators instead of costly crystal which are low cost and
external capacitor can be avoided.
But the frequency of the resonators varies a lot. And it is strictly not advised
when used for communications projects.
Using Keil C.
There is nothing much different from the Turbo C we used and Keil C we
are going to use. The only difference is that we need to change the header
file of the microcontroller we are going to use.
69
#include<AT89x51.h>
Here in the above code I was using At89c51 so I am including this file for
compiling.
After including the file we must declare main function and start writing the
code.
#include<AT89x51.h>
void main()
{
int i;
while(1){
for (i = 0;i< 9000;i++)
P1_1=0;
for (i = 0;i< 9000;i++)
P1_1=1;
}
}
DC Motor
70
These are the motors that are commonly found in the toys and the tape
recorders. These motors change the direction of rotation by changing the
polarity. Most chips can't pass enough current or voltage to spin a motor.
Also, motors tend to be electrically noisy (spikes) and can slam power back
into the control lines when the motor direction or speed is changed.
Specialized circuits (motor drivers) have been developed to supply motors
with power and to isolate the other ICs from electrical problems. These
circuits can be designed such that they can be completely separate boards,
reusable from project to project.
A very popular circuit for driving DC motors (ordinary or gearhead) is
called an H-bridge. It's called that because it looks like the capital letter 'H'
on classic schematics. The great ability of an H-bridge circuit is that the
motor can be driven forward or backward at any speed, optionally using a
completely independent power source.
The H-Bridge Circuit
71
This circuit known as the H-bridge (named for its topological similarity to
the letter "H") is commonly used to drive motors. In this circuit two of four
transistors are selectively enabled to control current flow through a motor.
72
opposite pair of transistors (Transistor One and Transistor Three) is enabled,
allowing current to flow through the motor. The other pair is disabled, and
can be thought of as out of the circuit.
By determining which pair of transistors is enabled, current can be made to
flow in either of the two directions through the motor. Because permanentmagnet motors reverse their direction of turn when the current flow is
reversed, this circuit allows bidirectional control of the motor.
73
The H-Bridge with Enable Circuitry
It should be clear that one would never want to enable Transistors One and
Two or Transistors Three and Four simultaneously. This would cause
current to flow from Power + to Power - through the transistors, and not the
motors, at the maximum current-handling capacity of either the power
supply or the transistors. This usually results in failure of the H-Bridge. To
74
prevent the possibility of this failure, enable circuitry as depicted in Figure is
typically used.
In this circuit, the internal inverters ensure that the vertical pairs of
transistors are never enabled simultaneously. The Enable input determines
whether or not the whole circuit is operational. If this input is false, then
none of the transistors are enabled, and the motor is free to coast to a stop.
By turning on the Enable input and controlling the two Direction inputs, the
motor can be made to turn in either direction.
Note that if both direction inputs are the same state (either true or false) and
the circuit is enabled, both terminals will be brought to the same voltage
(Power + or Power - , respectively). This operation will actively brake the
motor, due to a property of motors known as back emf, in which a motor that
is turning generates a voltage counter to its rotation. When both terminals of
the motor are brought to the same electrical potential, the back emf causes
resistance to the motor's rotation.
Stepper motors
Stepper motors are special kind of heavy duty motors having 2 or 4 coils.
The motors will be stepping each time when it get the pulse. As there are
many coils in the motors we need to energize the coils in a specific sequence
75
for the rotation of the motor. These motors are mostly used in heavy
machines. The figure shown below consists of a 4 coil stepper motor and the
arrow mark will rotate when the coils are energized in the sequence.
Unlike DC motors stepper motors can be turned accurately for the given
degrees.
Servo motors
Servo motors unlike the stepper motor it has to be controlled by the timing
signal. This motor has only one coil. It is mostly used in train s for its
lightweight and low power consumption. The servo motors can also be
accurately rotated by the making the control signal of the servo motor high
76
for a specific time period. Actually the servo motor will be having 3 wires
where 2 are for power supply and another one is for the control signal.
Driving the servomotors is so simple that you need to make the control
signal high for the specific amount of time. The width of the pulse
determines the output position of the shaft
Object Detection
Detecting objects without whiskers doesn’t require anything as sophisticated
as machine vision. Some train s use RADAR or SONAR (sometimes called
SODAR when used in air instead of water). An even simpler system is to use
infrared light to illuminate the train ’s path and determine when the light
reflects off an object.The IR illuminators and detectors are readily available
and inexpensive.
Infrared As Headlights
The infrared object detection system we’ll build on the Bot is like a car’s
headlights in several respects. When the light from a car’s headlights reflects
off obstacles, your eyes detect the obstacles and your brain processes them
77
and makes your body guide the car accordingly. We will be using infrared
LEDs for headlights. They emit infrared, and in some cases, the infrared
reflects off objects and bounces back in the direction of the detecter. The
eyes of the Bot( mobile) are the infrared detectors. The infrared detectors
send signals to the Microcontroller indicating whether or not they detect
infrared reflected off an object. The brain of the Bot, the microcontroller
makes decisions and operates the motors based on this sensor input.
78
CHAPTER - 9
CIRCUIT DIAGRAM
79
WORKING
First of all we give a 12 volt supply to the train then power supply circuit
will convert it in 5 volt which is required for microcontroller and all parts of
circuit. this supply goes to microcontroller. Positive voltage at 40 no. pin
and 20 no. is connected with Ground. We give a 5 volt supply at pin no. 9
for reset purpose through a reset circuit. Reset circuit is constructed by 10uF
capacitor and 10 K resistance. Pin no, 18 and 19 is connected with 12 Mhz
crystal oscillator and 2 ceramic capacitor respected the ground. Now we use
a TSOP 1738 of which pin no. 1 is connected with GND and 2nd pin is
connected with Positive 5 volt. It gives output at pin no. 3 which is
connected with P3.3 which receives the data in serial form. After this
programming works and gives output at port 2. Port 2 is connected with
motor circuit. One motor circuit is connected with P2.0 and P2.1 and second
motor is connected with P2.2 and P2.3. for forward direction MCU gives
low at P2.0 and P2.2 and high at other two pins. Due to this both motors will
rotate in same direction. To understand this functioning of motors above
working of motor circuit is descrived. For reverse direction P2.1 and P2.3
goes low and respectively P2.0 and P2.2 goes high so both motors will rotate
same but in different direction as that of previous direction. For left or right
turning of train we give low signal at Pin no. P2.0 and P2.3 or P2.1 and
P2.2. due to this both motors will rotate in opposite direction hence train
will turn in one direction.
To control the function of stop we use IR transmitter and receiver at front
of Train. IR transmitter is connected with 5 volt supply through a 100 ohm
resitance permanently. IR receiver used as a switching circuit for
microcontroller. First of all we provide 5 volt supply at P1.0 through 10 k
resistor and also we connect IR reciver at this pin without any resistance. So
80
when receiver detect the rays ( which are reflected by other train In the front
of main train) provide low signal to the microcontroller. So its starts its
programming working and provide high signal at all pins of motor circuit
and that happen motor get stop.
To movement of this train we use wheels direct with motor or in some
situations gears are used with motor and wheel to create torque and speed of
train .
Programming
/*************************************************************
********ir train new modified
*************************************************************
*********/
VAR1
equ r7
TEMP
equ 10H
;Temp variable
COUNT
equ 11H
;Count
ADDR
equ 12H
;Device address
CMD equ 13H
FLIP bit 00H
TOG bit 01H
;Temporary Variable
;Command
;Flip bit
;Temp bit for flip
81
IR
equ P3.3
;IR Receiver connected to this pin
SW1 equ P2.0
;Switch 1 connected here
SW2 equ P2.1
;Switch 2 connected here
SW3 equ P2.2
;Switch 3 connected here
SW4 equ P2.3
;Switch 4 connected here
SW5 equ P2.4
;Switch 5 connected here
SW6 equ P2.5
;Switch 6 connected here
SW7 equ P2.6
;Switch 7 connected here
SW8 equ P2.7
;Switch 8 connected here
SWport
org 00H
equ P1
;Port at which switches are connected
;Start of prog
main:
nop
fcmd:
nvalid:
82
ljmp main
valid:
;Key press check
clr a
mov c,FLIP
rlc a
mov TEMP,a
clr a
mov c,TOG
rlc a
cjne a,TEMP,valid1
sjmp nvalid
valid1:
mov c,FLIP
mov TOG,c
mov a,CMD
clr c
cjne a,#1,skip1
;Check for SW1
acall moto1
ljmp main
83
isset1:
clr SW1
ljmp main
moto1:
clr p2.0
setb p2.1
clr p2.2
setb p2.3
acall delay
acall delay
setb p2.0
setb p2.1
setb p2.2
setb p2.3
ret
skip1:
cjne a,#2,skip2
;Check for SW2
acall moto2
84
ljmp main
isset2:
clr SW2
ljmp main
moto2:
setb p2.0
clr p2.1
setb p2.2
clr p2.3
acall delay
acall delay
setb p2.0
setb p2.1
setb p2.2
setb p2.3
ret
skip2:
85
cjne a,#3,skip3
;Check for SW3
acall moto3
ljmp main
isset3:
clr SW3
ljmp main
moto3:
clr p2.0
setb p2.1
setb p2.2
clr p2.3
acall delay
acall delay
setb p2.0
setb p2.1
setb p2.2
setb p2.3
ret
86
skip3:
cjne a,#4,skip4
;Check for SW4
acall moto4
ljmp main
isset4:
clr SW4
ljmp main
moto4:
setb p2.0
clr p2.1
clr p2.2
setb p2.3
acall delay
acall delay
setb p2.2
setb p2.3
setb p2.0
setb p2.1
87
ret
skip4:
cjne a,#5,skip5
;Check for SW5
acall moto5
ljmp main
isset5:
clr SW5
ljmp main
moto5:
setb p2.4
clr p2.5
acall delay
setb p2.4
setb p2.5
ret
skip5:
cjne a,#6,skip6
;Check for SW6
acall moto6
88
ljmp main
isset6:
clr SW6
ljmp main
moto6:
clr p2.4
setb p2.5
acall delay
setb p2.4
setb p2.5
ret
skip6:
cjne a,#7,skip7
;Check for SW7
jb SW7,isset7
setb SW7
ljmp main
isset7:
clr SW7
89
ljmp main
skip7:
cjne a,#8,skip8
;Check for SW8
jb SW8,isset8
setb SW8
ljmp main
isset8:
clr SW8
ljmp main
skip8:
cjne a,#0CH,exit ;Check for all switches
mov SWport,#00H
ljmp main
exit:
ljmp main
delay:
acall delay1
acall delay1
acall delay1
acall delay1
90
acall delay1
ret
delay1:
MOV R6,#255
AGAIN22: MOV R7,#255
BACK22: DJNZ R7,BACK22
DJNZ R6,AGAIN22
RET
END
;End of program
91
CHAPTER – 10
ADVANTAGES
92
CHAPTER – 11
DISADVANTAGES
CHAPTER – 12
APPLICATION
93
CHAPTER – 13
PRECAUTIONS
1. According to circuit all the different components for their services,
ability.
2. During soldering on the PCB, one should be very careful regarding
short circuit, dry units, etc.
3. Components direction especially electrolytic capacitor, transistor,
must be kept in mind for their actual position.
94
4. Put each and every component on the PCB according their actual
position.
5. Proper care must be taken by solders on transistor so that these are not
to be damaged due to leakage of current.
6. Put each and every component of the same value on the PCB as per
diagram.
Bibliography:
www.ludhianaprojects.com/train ics
http://www.sciencejoywagon.com/physicszone/lesson/otherpub/wfendt/el
ectricmotor.htm
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