INTERNAL GEAR PUMP

CONTENTS
Introduction
Stepper Motor
Introduction
Stepper Motor Types
Constructional Features
Principle of Operation
Data Sheet for Stepper Motor
Simulating the Basic Idea
Stepper Motor V/s D.C Motor
Stepper Motor Basics
Microcontroller
What is a microcontroller ?
Characteristics
Microcontrollers vs microprocessors: A comparison
Nomenclature
Architecture of Microcontrollers
Assembling and running of a 8051 program
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Project Description
Circuit Description
Robot Basics
Data Sheet for ATMEL AT89C51
Software
Assembly Language Program
C Code (Interrupt Based)
Conclusion
Bibliography and appendix
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INTRODUCTION
The most common problem we face when we use normal DC motors
is that we don’t have precise control over how much it rotates. To
rotate DC motors through a particular number of degrees what we
can do is either calibrate it for a delay based operation i.e. if we
switch it on for n seconds it moves 360 degrees; or what we can do
is attach n encoder to the shaft which gives us a feedback on how
much the motor shaft has rotated so that we can stop it when it
rotates through the desired angle. Home made encoders give good
results but don’t have such a high resolution and high resolution
encoders are costly.
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In such cases where we need to control the rotary position of the
motor we can use stepper motors.
Internal Gear Pumps
Internal Gear Pump Overview
Internal gear pumps are exceptionally
versatile. While they are often used on thin
liquids such as solvents and fuel oil, they excel
at efficiently pumping thick liquids such as
asphalt, chocolate, and adhesives. The useful
viscosity range of an internal gear pump is
from 1cPs to over 1,000,000cP.
In addition to their wide viscosity range, the pump has a wide
temperature range as well, handling liquids up to 750°F / 400°C.
This is due to the single point of end clearance (the distance
between the ends of the rotor gear teeth and the head of the
pump). This clearance is adjustable to accommodate high
temperature, maximize efficiency for handling high viscosity
liquids, and to accommodate for wear.
The internal gear pump is non-pulsing, self-priming,
and can run dry for short periods.
They're also bi-rotational, meaning that the same
pump can be used to load and unload vessels.
Because internal gear pumps have only two
moving parts, they are reliable, simple to operate, and easy to
maintain.
How Internal Gear Pumps Work
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1. Liquid enters the suction
port between the rotor (large
exterior gear) and idler
(small interior gear) teeth.
The arrows indicatethe
direction of the pump and
liquid.
2. Liquid travels through the pump between the teeth of the "gear-within-
a-gear" principle. The crescent shape divides the liquid and
acts as a seal between the suction and discharge ports.
3. The pump head is now nearly flooded, just prior to forcing the
liquid out of the discharge port. Intermeshing gears of the idler
and rotor form locked pockets for the liquid which assures volume
control.
4. Rotor and idler teeth mesh completely to form a seal equidistant
from the discharge and suction ports. This seal forces the liquid
out of the discharge port
Applications
Common internal gear pump applications include, but are not
limited to:
· All varieties of fuel oil and lube oil
· Resins and Polymers
· Alcohols and solvents
· Asphalt, Bitumen, and Tar
· Polyurethane foam (Isocyanate and polyol)
· Food products such as corn syrup, chocolate, and peanut
butter
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· Paint, inks, and pigments
· Soaps and surfactants
· Glycol
Materials Of Construction / Configuration Options
· Externals (head, casing, bracket) - Cast iron, ductile iron,
steel, stainless steel, Alloy 20, and higher alloys.
· Internals (rotor, idler) - Cast iron, ductile iron, steel,
stainless steel, Alloy 20, and higher alloys.
· Bushing - Carbon graphite, bronze, silicon carbide, tungsten
carbide, ceramic, colomony, and other specials materials as
needed.
· Shaft Seal - Lip seals, component mechanical seals,
industry-standard cartridge mechanical seals, gas barrier
seals, magnetically-driven pumps.
· Packing - Impregnated packing, if seal not required
Advantages
· Only two moving parts
· Only one stuffing box
· Non-pulsating discharge
· Excellent for high-viscosity
liquids
· Constant and even
discharge regardless of
pressure conditions
· Operates well in either
direction
· Can be made to operate
with one direction of flow
with either rotation
Disadvantages
· Usually requires moderate
speeds
· Medium pressure
limitations
· One bearing runs in the
product pumped
· Overhung load on shaft
bearing
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· Low NPSH required
· Single adjustable end
clearance
· Easy to maintain
· Flexible design offers
application customization
STEPPER MOTOR
Stepper motors are used for precision position control in many
applications like floppy drives, printers, process control instruments,
robotics and machine tool control.
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Here’s a stepper motor controller based on 89C51
microcontroller to control the rotation of a DC stepper motor in
clockwise and anti-clockwise directions. The controller is simple and
easy-to-construct, and can be used in many application including
machine control and robotics for controlling the axial rotation in XY
plane. A similar circuit can be added to control the rotation of the
motor in either XZ or YZ plane.
POWER
SUPPLY
Fig. 1: Block diagram of the stepper motor control system
TABLE I
Power Consumption of Microcontrollers
IC Voh Ioh Voi Ioi Vil Iil Vih Iih Pt
CMO
S
NMO
S
2.4V
2.4V
-60mA
-80mA
0.45V
0.45V
1.7
mA
1.7Ma
0.9V
0.8V
10mA
-800mA
1.9V
2.0V
10mA
10mA
50m
W
800m
W
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MICROCONTROLLER
89C51 STEPPER
MOTOR
CONTROL
SWITCH

Fig. 1 shows the block diagram of the stepper motor control system.
The power supply section (in fig. 2) consists of a step-down
transformer (7.5V AC, 1A), bridge rectifier (comprising diodes D1
through D4), filter capacitors (C1 and C2) and regulator IC 7805.
We have used here an Atmel Make low-power, high-performance,
8-bit CMOS microcontroller AT89C51 with 4 kb of
Flash programmable and erasable read-only memory n(PEROM). It
has a 128x8-bit internal RAM, 32 programmable input/output (I/O)
lines and two 16-bit timer/counters. The on-chip Flash allows the
program memory to be reprogrammed in-system or by a
conventional non-valuable memory programmer.
By combining a versatile 8-bit CPU with Flash on a monolithic
chip, Atmel AT89C51 is a powerful, highly flexible and cost-effective
solution to many embedded control applications. From traffic control
equipment to input devices, computer net working, products and
stepper motor controller, 89C51 microcontroller deliver a high
performance with a choice of configurations and options matched to
the specific need of each application.
STEPPER MOTOR BASIC
A stepper motor is a brushless motor whose rotor rotates in discrete
angular movements when its stator windings are energized in a
programmed manner. Rotation occurs because of magnetic
interaction between rotor poles and poles of sequentially energized
stator windings. The rotor has no electrical windings, but has salient
and magnetized poles.
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The input given to the motor is in the form of electrical pulses. For
every input pulse the motor shaft turns through a specified number of
degree called a step. The name stepping given to this motor is based
on its working principle i.e. one step rotation for one input pulse. The
range of step size may vary from 0.720 to 900. Actually a stepper
motor can be regarded as a digital electromechanical device, which
translates input digital information in form of electric pulses into
discrete steps of shaft rotation. In position control system if the
number of input pulses sent to the motor is known, the actual
position of driven job can be obtained. Thus a digital position control
system employing a stepper motor needs no rotor position sensors
and an expensive feedback loop.
A stepping motor differs from a conventional motor as
under:-
Input to stepper motor is in form of electric pulses whereas input a
conventional motor is invariably from a constant voltage source.
A conventional motor has a free running shaft whereas shaft of
stepper motor moves through angular steps.
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In control system applications, no feedback loop is required when
stepper motor is used but a feedback loop is required when
conventional motor is used.
A stepper motor is digital electromechanical device whereas a
conventional motor is an electromechanical device.
STEPPER MOTOR TYPES
There are three basic stepper motor types. They are: -
• Variable-reluctance
• Permanent magnet
• Hybrid
Variable-reluctance (VR)
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This type of stepper motor has been around for a long time. It is
probably the easiest to understand from a structural point of view.
Figure 1 shows a cross section of a typical V.R. stepper motor. This
type of motor consists of a soft iron multi-toothed rotor and a wound
stator. When the stator windings are energized with DC current the
poles become magnetized. Rotation occurs when the rotor teeth are
attracted to the energized stator poles.
Figure 1. Cross-section of a variable reluctance (VR) motor
Permanent Magnet (PM)
Often referred to as a “tin can” or “canstock” motor the permanent
magnet step motor is a low cost and low-resolution type motor with
typical step angles of 7.5° to 15°. (48 – 24 steps/revolution) PM
motors as the name implies have permanent magnets added to the
motor structure. The rotor no longer has teeth as with the VR motor.
Instead the rotor is magnetized with alternating north and south poles
situated in a straight line parallel to the rotor shaft. These magnetized
rotor poles provide an increased magnetic flux intensity and because
of this the PM motor exhibits improved torque characteristics when
compared with the VR type.
Hybrid (HB)
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The hybrid stepper motor is more expensive than the PM stepper
motor but provides better performance with respect to step
resolution, torque and speed. Typical step angles for the HB stepper
motor range from 3.6° to 0.9° (100 – 400 steps per revolution). The
hybrid stepper motor combines the best features of both the PM and
VR type stepper motors. The rotor is multi-toothed like the VR motor
and contains an axially magnetized concentric magnet around its
shaft. The teeth on the rotor provide an even better path, which helps
guide the magnetic flux to preferred locations in the airgap. This
further increases the detent, holding and dynamic torque
characteristics of the motor when compared with both the VR and
PM types.
The two most commonly used types of stepper motors are the
permanent magnet and the hybrid types. If a designer is not sure
which type will best fit his applications requirements he should first
evaluate the PM type as it is normally several times less expensive.
If not then the hybrid motor may be the right choice.
There also exist some special stepper motor designs. One is the disc
magnet motor. Here the rotor is designed as a disc with rare earth
magnets (Fig. 2). This motor type has some advantages such as
very low inertia and an optimized magnetic flow path with no coupling
between the two-stator windings. These qualities are essential in
some applications.
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Figure 5. Magnetic flux path through a two-pole stepper motor
with a lag between the rotor and stator.
INDUSTRIAL APPLICATION OF STEPPER MOTORS
Floppy Disk Drives.
Hard Disk Drives.
Printers, Plotters.
Electronic Watches.
Electronic Typewriters.
Teleprinter, Telex-machines.
Robotics.
CNC-System.
Instrumentation Control.
The main reason for the use of stepper motor instead of ordinary DC
motors in disk drives is requirement to position the read/write header.
Stepper motors can be rotated at a fixed angle and their angular
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rotation can be converted into linear movements to move the
read/write head over the disk surface in a fixed increment.
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CONSTRUCTIONAL FEATURES
A two-phase bipolar stepper motor has two coils A and B which are
wound around the upper and lower halves of stator as shown in
figure 1. The stator surrounds a rotor that contains specifically
aligned permanent magnets. The number of steps per revolutions is
determined by the number of pole pairs on the rotor and stator. The
cross sectional view of stator and rotor of the stepper motor are
clearly depicted in figure 1 and 2.
The stepper motor are clearly used in our circuit is having 10 pole
rotor structure but still 6 pole rotor structure has been depicted in
figure 2 for simplicity of the figure and easy understanding principle.
Stator :
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Stator of the stepper motor has salient poles on which concentrated
windings A and B are wound. These windings are appropriately
connected so as to result in two-phase windings on stator. The
salient pole structure of stator is continuous from one end to other
end of the rotor.
Rotor :
The rotor of stepping motor does not carry any winding. The
rotor is made up of ferromagnetic material.
A schematic view of a bipolar hybrid stepping motor is shown in
figure 2. It consists an axial permanent magnet at the two ends of
which are attached tow identical ferromagnetic stacks as shown.
These stacks consist of equal number of teeth and there are three
teeths on each stack. At one end the stack attains north magnetic
polarity and at other end stack gets south magnetic polarity. The two
stacks have an angular displacement of one half of the rotor tooth
pitch.
Once the voltage is applied to the windings, the permanent
magnet rotor of stepper motor assumes it unloaded holding position.
This means that the permanent magnet poles of rotor are aligned
according to the electromagnetic pole on the stator. The maximum
torque with which the excited motor can be loaded without causing a
continuous rotation is termed as stepper motor holding torque. A
torque can also be perceived with a non-excited motor. This is
because of the pole induction of permanent magnet on stator. This
effect known as cogging together with motor internal friction
produces detent torque, which is the torque with which a non-excited
motor can be statically loaded.
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PRINCIPLE OF OPERATION
The stepper motor is having a 10 pole rotor structure i.e. the rotor is
axial permanent magnet type with ferromagnetic stacks of opposite
polarities on the opposite ends. The numbers of stacks are 5 on each
end. But for simplicity of the explanation of underlining we will first
describe a simple PMDC stepper motor with two poles on rotor.
WORKING OF A SINGLE PMDC STEPPER MOTOR: -
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A simple PMDC motor with two coils A A' and B B' wound on
stator and the motor having a two pole structure is shown in figure
along side. The operation of this motor is clearly described in steps
below with the corresponding figure showing the magnetic flux
linkage between stator and rotor structures is shown along side:
Referring to figure 3. Now if the terminal A and B of stator windings
are connected to the positive voltage, then two stator magnetic
field vectors Fa and Fb will be produced as shown in fig.3. The rotor
will position itself in such a way as to lock its north pole to the
resulting stator south pole and vice versa. The rotor will move in anti-clockwise
direction.
Refer figure 4. When the voltage polarity of coil A A' is revered with
coil B B' energized a before, the resultant stator magnetic field vector
F will be at 900 from its former position. Hence the rotor will move
through a fixed angle of +900 as shown.
Refer figure 5. With coil A A' energized as before the voltage polarity
of coil B B' is reversed. The rotor will move through another 900 to
align itself with the resultant stator magnetic field F as shown.
Refer figure 6. With coil B B' energized as before, the voltage polarity
of coil A is again reversed. The motor will further move through
another 900 to align itself with the resultant stator magnetic field F as
shown.
Refer figure 6. With coil A A' energized as before the voltage polarity
of coil B B' is again reversed. The rotor will align itself as shown.
So the motor can be made to step in one direction by continuously
changing the direction of current through these coils. To step in
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reverse direction the direction of current should be changed in
reverse order through these coils. This method is called two phases
on full step drive since the two-phase coils are energized together.
PRINCIPLE OF A SINGLE PMDC STEPPER MOTOR :-
The principle of operation of PMDC stepper motor having been
clearly described above will now help us to have a clearer picture of
working of hybrid stepper motor. We take the simpler case of 6 pole
on the rotor structure and explain its working.
Referring to figure 7, 8, 9 the north poles are at the front end
shown with full lines whereas the south poles are at far end shown
with dotted lines.
When phase A winding is energized with current Ia North Pole
at A and South Pole at A' are created on the stator. Pole at A attracts
South Pole of far end and pole at A' attracts North Pole at front end
as shown in figure 7.
This equilibrium position of rotor structure results in maximizing
the flux linkages with the phase winding A. For turning the rotor
clockwise through a step de-energies phase winding A and excite
phase winding B so that North pole at B and South pole at B' are
created on the stator. Pole at B attracts the pole of rear end and pole
at B' attracts North Pole of front end, so a step angular rotation of
300 clockwise is achieved as in figure 8. In this equilibrium position,
maximum flux linkages are now linked with phase winding B. If
excitation is removed from phase winding B and reverse excitation is
applied to phase winding A, pole on A attracts North pole and pole at
A' attracts rear S pole as in figure 9. In this manner 12 steps will
complete one revolution. Sequence of exciting the phase windings
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for clockwise rotation is A B A' B' A and therefore for anticlockwise
rotation the sequence will be
A B' A' B A.
The magnitude of step angle
For Hybrid stepper motor = 3600/mP
Where m = number of stator phases
P = number of poles on rotor structure.
The working of actual bipolar hybrid stepper motor used in the
project can now be analogically understood. The only difference in
the hybrid stepper motor described earlier and the one used in our
project is that the numbers of poles on the rotor structure are
different. In our motor we have 10-pole rotor structure i.e. 5 pole of
North and South polarity on the two ends of an axial permanent
magnet.
Some terms applicable to stepping motors are as under :
Step angle is the angle through which the shaft rotates in response
to one input pulse.
Single step resolution is inversely proportional to step angle. Smaller
the step angle greater the number of steps per revolution and
therefore higher single step resolution.
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At stand still the excited motor opposes the rotor rotation due to load
torque. Holding torque is a term introduced for the measure of this
opposing torque.
Thus holding torque is defined as the maximum load torque that can
be applied to the shaft of an excited motor without continuous
rotation.
In case motor is unexcited the permanent magnet hybrid stepping
motors are able to develop a torque restricting the rotor rotation. The
term detent torque is defined as the maximum load torque that can
be applied to shaft of an unexcited motor without causing continuous
rotation.
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DATA SHEET
STEPPER MOTOR
Type : Bipolar hybrid PMDC stepper motor.
Source : Floppy disk drive of personal computer.
No. of windings : 2
on stator
Rated Current : 50 M amp. per winding.
Resistance per : 120 m
winding
Step angle : 180
No. of steps : 20
per revolution
DC SUPPLY
Type : Adapter
Make : Panasonic
Range : 10V, 500 mamp.
IC REGULATOR CHIP
Chip No. : L7805C
Make : ST
Vout : 5.0V
Tolerance : + 4%
Iout : 500 mamp.
Vin : 35 V
Package : T03
CONTROL CIRCUIT FOR STEPPER MOTOR WINDINGS
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SIMULATING THE BASIC IDEA
The basic control circuit for stepper motor can be easily
understood by referring to figure 3,4,5,6. The motor will step in one
direction if the voltages to the coil A coil B are applied as in table1.
TABLE -1
Step Coil A Coil B
1 +V +V
2 -V +V
3 -V -V
4 +V -V
5 +V +V
If the voltage to the coil A and coil B are applied as shown in table 2
then motor steps in reverse direction.
TABLE -2
Step Coil A Coil B
1 +V +V
2 -V +V
3 -V -V
4 +V -V
5 +V +V
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DC MOTORS VS. STEPPER MOTORS
Stepper motors are operated open loop, while most DC motors are
operated closed loop.
Stepper motors are easily controlled with microprocessors, however
logic and drive electronics are more complex.
Stepper motors are brushless and brushes contribute several
problems, e.g., wear, sparks, electrical transients.
DC motors have a continuous displacement and can be accurately
positioned, whereas stepper motor motion is incremental and its
resolution is limited to the step size.
Stepper motors can slip if overloaded and the error can go
undetected. (A few stepper motors use closed-loop control.)
Feedback control with DC motors gives a much faster response time
compared to stepper motors.
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ADVANTAGES OF STEPPER MOTORS
Position error is noncumulative. A high accuracy of motion is
possible, even under open-loop control.
Large savings in sensor (measurement system) and controller costs
are possible when the open-loop mode is used.
Because of the incremental nature of command and motion, stepper
motors are easily adaptable to digital control applications.
No serious stability problems exist, even under open-loop control.
Torque capacity and power requirements can be optimized and the
response can be controlled by electronic switching.
Brushless construction has obvious advantages.
DISADVANTAGES OF STEPPER MOTORS
They have low torque capacity (typically less than 2,000 oz-in)
compared to DC motors.
They have limited speed (limited by torque capacity and by pulse-missing
problems due to faulty switching systems and drive circuits).
They have high vibration levels due to stepwise motion.
Large errors and oscillations can result when a pulse is missed under
open-loop control.
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STEPPER MOTOR BASICS
STEPPER MOTOR STATES FOR MOTION
The above figure is the cross-section view of a single-stack variable-reluctance
motor. The stator core is the outer structure and has six
poles or teeth. The inner device is called the rotor and has four
poles. Both the stator and rotor are made of soft steel. The stator has
three sets of windings as shown in the figure. Each set has two coils
connected in series. A set of windings is called a “phase”. The motor
above, using this designation, is a three-phase motor. Current is
supplied from the DC power source to the windings via the switches
I, II, and, III.
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Starting with state (1) in the upper left diagram, note that in state (1),
the winding of Phase I is supplied with current through switch I. This
is called in technical terms, “phase I is excited”. Arrows on the coil
windings indicate the magnetic flux, which occurs in the air-gap due
to the excitation. In state I, the two-stator poles on phase I being
excited are in alignment with two of the four rotor teeth. This is an
equilibrium state.
Next, switch II is closed to excite phase II in addition to phase I.
Magnetic flux is built up at the stator poles of phase II in the manner
shown in state (2), the upper right diagram. A counter-clockwise
torque is created due to the “tension” in the inclined magnetic flux
lines. The rotor will begin to move and achieve state (3), the lower
left diagram. In state (3) the rotor has moved 15°.
When switch I is opened to de-energize phase I, the rotor will travel
another 15° and reach state (4). The angular position of the rotor can
thus be controlled in units of the step angle by a switching process. If
the switching is carried out in sequence, the rotor will rotate with a
stepped motion; the switching process can also control the average
speed.
STEP ANGLE
The step angle, the number of degrees a rotor will turn per step, is
calculated as follows:
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For this motor:
BASIC WIRING DIAGRAM
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TWO PHASE STEPPER-MOTOR WIRING DIAGRAM
The above motor is a two-phase motor. This is sometimes called
UNIPOLAR. The two-phase coils are center-tapped and in this case
they the center-taps are connected to ground. The coils are wound
so that current is reversed when the drive signal is applied to either
coil at a time. The north and south poles of the stator phases reverse
depending upon whether the drive signal is applied to coil 1 as
opposed to coil 2.
STEP SEQUENCING
There are three modes of operation when using a stepper motor. The
mode of operation is determined by the step sequence applied. The
three step sequences are:
WAVE STEPPING
The wave stepping sequence is shown below.
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Wave stepping has less torque then full stepping. It is the least stable
at higher speeds and has low power consumption.
FULL STEPPING
The full stepping sequence is shown below.
Full stepping has the lowest resolution and is the strongest at holding
its position. Clock-wise and counter clockwise rotation is
accomplished by reversing the step sequence.
HALF-STEPPING – A COMBINATION OF WAVE AND FULL
STEPPING
The half-step sequence is shown below.
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The half-step sequence has the most torque and is the most stable
at higher speeds. It also has the highest resolution of the main
stepping methods. It is a combination of full and wave stepping.
MICROCONTROLLER
What is a microcontroller?
A microcontroller is used to control some process or aspect of the
environment. A typical microcontroller application is the monitoring
of a house. As the temperature rises, the controller causes the
windows to open. If the temperature goes above a certain threshold,
the air conditioner is activated. In addition, upon detecting that my
computer is turned on, without any user interaction it should be
turned off etc.
A microcontroller is a highly integrated chip, which includes, on one
chip, all or most of the parts needed for a controller. The
microcontroller could be called a "one-chip solution". It typically
includes:
 CPU (central processing unit)
 RAM (Random Access Memory)
 EPROM/PROM/ROM (Erasable Programmable Read Only
Memory)
 I/O (input/output) - serial and parallel
 Timers
 Interrupt controller
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By only including the features specific to the task (control), cost is
relatively low. A typical microcontroller has bit manipulation
instructions, easy and direct access to I/O (input/output), and quick
and efficient interrupt processing. Microcontrollers are a "one-chip
solution" which drastically reduces parts count and design costs.
Microcontroller is also a general-purpose device that is meant to read
data, perform calculations on that data and control its environment
based on those calculations. The prime use of the microcontroller is
to control the operation of a machine using a fixed program that is
stored in the ROM and that does not change over the lifetime of the
system.
The microcontroller design uses a much more limited set of single
and double byte instructions that are used to move code and data
from internal memory to the ALU. Many instructions are coupled with
the pins on the integrated circuit package; the pins are
programmable i.e. capable of having several functions depending
upon the wish of the programmer. The microcontroller is concerned
with getting the data from and to its own pins; the architecture and
the instructions set are optimized to handle data in bit and byte size
CHARACTERISTICS OF MICROCONTROLLERS
· Microcontrollers are "embedded" inside some other device
(often a consumer product) so that they can control the
features or actions of the product.
· Microcontrollers are dedicated to one task and run one specific
program. The program is stored in ROM (read-only memory)
and generally does not change.
· Microcontrollers are often low-power devices.
· A microcontroller is often small and low cost. The components
are chosen to minimize size and to be as inexpensive as
possible.
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Common examples of the microprocessor are as follows:
 INTEL’S 8086, 80186,80286 through the PENTIUM 4
 MOTOROLA’S 6801 AND MC68HC11
Microcontroller vs microprocessor: A comparison
• The contrast between microcontroller and microprocessor is
the best exemplified from the fact that most microprocessors have
many operational codes (opcodes) for moving data from the external
memory to the CPU. But the microcontroller may have one or two
operational codes.
• Microprocessor may have one or two bit handling instructions
but the microcontroller has many bit handling instructions.
• Microprocessor is concerned with the rapid movement of the
data and the code from the external address to the chip and the
microcontroller is concerned with the rapid movement of the bits into
the chip.
• The microcontroller can function as a computer with addition of
no external digital parts whereas the microprocessor has many
additional parts to be operational.
• The microprocessor is intended to be special purpose digital
computer.
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FAMILIES & TYPES OF MICROCONTROLLERS:
THE INTEL 8051 FAMILY-It
was in the year 1980 that Intel Corporation introduced a powerful
series of microcontrollers, Intel 8051.
Family members of this series are:
80C51BH
80C31BH
87C51
8X52/54/58
8CX51FX
8XL52/54/58
8XL51FA/FB/FC
8XC51RA/RB/RC
8XC51GB
8XC51SL
8XC152JA/JB/JC
(X IS 0 FOR ROM LESS VERSIONS, 3 FOR VERSIONS WITH
ROM, 7 FOR VERSIONS WITH EPROM)
SOME OTHER MICROCONTROLLERS ARE:
#TEXAS INSTRUMENT’S TMS1000
#MOTOROLLAS 6801 AND MC68HC11
#ZILOG’S Z8
#NEC’S 7800 SERIES
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MERITS OF A GOOD MICROCONTROLLER:
A good microcontroller must satisfy the following criteria:
1.It should meet the computing needs of the task at hand both
efficiently as well as cost effectively. Other considerations include
#Speed
#Packaging
#Power consumption
#The size of RAMROM on the chip
#Number of input pins and timer on the chip
#Ease of up gradation to higher performance or lower power
consumption variants.
2. Easy availability of software development tools like compilers,
assemblers and debuggers using which the device can be
programmed easily.
3. Wide variety and reliable sources of procuring the microcontroller.
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NOMENCLATURE OF MICROCONTROLLERS:
The naming scheme of a microcontroller follows a set of rules that
gives vital information regarding the characteristics of that particular
microcontroller. For example the name AN83C51FA tells the
following about the microcontroller:
A N 8 3 C 51FA
PROGRAM MEMORY
0=ROMLESS
3=ROM
7=EPROM OR OTP
PACKAGE TYPE OPTION:
P=PLASTIC DIP, 40 PIN
N=PLASTIC,LEADEDCARRIER (PLCC),44
PIN
TEMPERATURE OPTION
ARCHITECTURE OF THE MICROCONTROLLER:
The architecture of the 8051 microcontroller consists of these
specific features:
 Eight bit CPU with registers A (accumulator) and B
 Sixteen bit program counter (PC) and data pointer (DPTR)
 Eight bit program status word (PSW)
 Eight bit stack pointer (SP)
 Internal RAM of 128 bytes
 Thirty two inputoutput pins arranged as four eight pin ports
 Two 16 bit timer counters
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 Full duplex serial data receivertransmitter
 Control registers
 Two external and three internal interrupt sources
 Oscillator and clock circuits
THE 8051 OSCILLATOR AND CLOCK:
The heart of the 8051 is the circuitry that generates the clock pulses
by which all internal operations are synchronized. Pins XTAL1 AND
XTAL2 are provided for connecting a resonant network to form an
oscillator.
Manufacturers make available 8051 designs that can run at
frequencies ranging from 1 MHz to 16 MHz. The oscillator generates
a pulse train at the frequency of the crystal. The clock frequency
establishes the smallest interval of time within the microcontroller
called the pulse, This pulse is used to synchronize and control all the
operations of the microcontroller.
PROGRAM COUNTER AND DATA POINTER:
A 8051 contains two 16 bit registers which are the program counter
(PC) and the data pointer (DPTR).
Each is used to hold the address of a byte in a memory. Program
instruction bytes are fetched from location in memory that are
addressed by the PC. The PC is automatically incremented after
every instruction byte is fetched and may also be altered by certain
instructions
The DPTR register is made of two 8 bit registers DPH & DPL which
are used to furnish addresses for internal &external code access
and external data access .
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A & B CPU REGISTERS:
These registers hold result of many instructions particularly of
mathematical and logical ones.
The A register is the most versatile of the two CPU registers and is
used for many operations like addition, subtraction, multiplication and
division and Boolean bit manipulations. It is also used for all data
transfers between the 8051 and external memory. The B register is
used in conjunction with the A register during multiplication and
division and is used as a data storage location.
INTERNAL MEMORY:
The 8051 has internal RAM & ROM memory which can be used for
program code bytes and to store variable data that can be altered as
the program runs.
The 8051 is also equipped with a stack .The stack refers to an area
of internal RAM that is used in conjunction with certain opcodes to
store and retrieve data quickly. The 8 bit stack pointer is used by the
8051 to hold an internal RAM address that is called top of the stack.
The address held in the SP register is the location in internal RAM
where the last byte of data was stored by a stack operation.
When data is to be placed on the stack, the SP increments before
storing data on the stack so that the stack grows up as data is
stored. As data is retrieved from the stack, byte is read and then the
SP decrements to point to the next available byte of stored data.
The 8051 operations that do not use the internal 128 byte RAM
addresses are done by a group of specific internal registers each
called a special function register (SFR) and may be addressed much
like the internal RAM.
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COUNTERS AND TIMERS:
Many microcontroller applications require the counting of external
events, which can be done using two 16 bit up counters
called T0 and T1. Each counter may be programmed to count
internal clock pulses, acting as timer or programmed to count
external pulses as a counter. Timers may be used in mode one, two
or three.
THE PSW REGISTER
The Program Status Word or the flag register an 8 bit register.
However only 6 bits are used. Four of these flags are conditional
flags. These are as follows:
 CY, The Carry Flag:
This flag is set if there is a carry out from the d7 bit. It is affected by
8-bit addition or subtraction. This can be set to 1 or 0.
 AC, The Auxiliary Carry Flag
If there is a carry from D3 to D4 during addition or subtraction this
bit is set.
 P, The Parity Flag
If the accumulator has odd number of ones then this flag is set to 1
or else it is equal to zero.
 OV, The Overflow Flag
This flag is set whenever the result of a signed number operation is
large causing the higher order bit to overflow into the sign bit.
The unconditional flags are RS0 and RS1 and are used to select a
register bank if one different from the default one is desired to be
used.
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CY AC RS0 RS1 OV P
THE PSW REGISTER
INTERRUPTS:
A computer program has only two ways to determine the conditions
in internal and external circuits. One method uses software
instructions and the other uses hardware signals called interrupts
that force the program to call a subroutine. Software techniques take
up the processor time that could be put to other uses while interrupts
take processor time action by the program is needed and are
therefore preferred.
Interrupts may be generated by internal chip operations or provided
by external sources. Any interrupt can cause the 8051 to perform a
hardware call to an interrupt handling subroutine that is located at a
predetermined absolute address in program memory.
ASSEMBLING AND RUNNING OF AN 8051 PROGRAM
In order to put the microcontroller to any use we need to program it
according to the need. Programs for microcontrollers are generally
written in assembly language. Many editors or word processors are
available that can be used to create and/or edit the program. A
widely used editor is the MS-DOS EDIT program (or the notepad in
Windows), which comes with all the Microsoft operating systems.
Notice that the editor must be able to produce an ASCII file. For
many assemblers, the file names follow the usual DOS conventions;
but the source file has the extension “asm” or “src”, depending on
which assembler is being used. An assembler in the next step uses
the “asm” extension for the source file.
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The “asm” source file containing the program code created in the
previous steps fed to an 8051 assembler. The assembler converts
the instructions into the machine codes.
The assembler will produce an object file and a list file. The
extension for the object file is “obj” while the extension for the list file
is “lst”.
Assemblers require a third step called linking. The link program takes
one or more object files and produces an absolute object file with the
extension “abs”. This abs file is used by the 8051 trainers that have a
monitor program. Next the “abs” file is fed into a program called “OH”
(object to hex converter) which creates a file extension “hex” that is
ready to burn into ROM.This program comes
with all 8051 assemblers.
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PROJECT DESCRIPTION
In this project, a bipolar stepper motor is used, which is used widely
in all kinds of floppy drives and CD drives. Specifications of the motor
follow:
Maximum voltage: 5V DC
Maximum revolutions per minute (RPM): 1000
Step resolutions: 18 degrees per pulse
The bipolar stepper motor uses two coils, which have two terminals
each.
There are three parameters of the stepper motor that can be
controlled: direction, speed and number of rotations.
Direction : -
To change the direction of the motor, you have to change the
sequence of pulses applied to its coils. The pulse sequence for
clock-wise and anticlockwise rotation is shown in the table on the
next page for better understanding. In the table, ‘0’ and ‘1’ indicate
low logic, and high logic, respectively.
Speed: -
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The speed of the motor can be changed by varying the pulse
repetition frequency (PRF). PRF is the frequency of pulses that are
applied to the motor coils in sequence. 20 PRF means 20 pulses will
be given to the stepper motor in one second. Now because step
resolution of the motor is 18° / pulse, the motor will rotate 20´18° =
360° (i.e., one complete revolution) in one second. So the speed of
the motor is 1 RPS (60 RPM). Now if you increase PRF from 20 Hz
to 40 Hz, the RPS will also double to 2 RPS (120 RPM).
Number of rotations: -
The step resolution is 18° / pulse. This means that if you apply
one pulse, the motor will rotate only 18°. If you apply 20 pulses in
series, the motor will rotate 360°, which means one complete
revolution. So if you limit the number of pulses applied to the motor,
you can restrict it to rotate the desired number of rotations.
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CIRCUIT DESCRIPTION
Fig. 1: Circuit of microcontroller-based stepper motor controller
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Fig. 1 shows the circuit of the microcontroller-based stepper motor
controller. Microcontroller AT89C51 (IC1) is at the heart of the circuit,
which can control all functions of the stepper motor. It is interfaced
with six tactile switches, five light-emitting diodes (LEDs) and coils of
the stepper motor. Port pins P0.0 through P0.4 of AT89C51 are
connected to LED1 through LED5 for indications of key-press,
clockwise rotation, anticlockwise rotation, RPM and number of
rotations, respectively. Port pins P1.0 through P1.5 are connected to
switches S2 through S7 to control clockwise and anticlockwise
rotation, in crement RPM, decrement RPM, increment the number of
rotations and decrement the number of rotations, respectively. Port
pins P2.0 through P2.7 are used to interface the stepper motor coils.
A 12MHz crystal produces clock frequency for the microcontroller.
Pin 21 through 28 of IC1 are connected to input pins of inverters N1
through N8. The outputs of inverters N1 through N8 are connected to
the bases of npn transistors 2N2222 through 1-kilo-ohm resistors.
These transistors are used for the H-bridge stepper motor driver
circuit.
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Fig. 2. Stepper motor driver circuit
Fig. 2 shows the stepper motor driver circuit. Since there are two
coils in the bipolar stepper motor, we need two H-bridge circuits, one
for each coil. The first H-bridge comprises transistors T1 through T4.
The first coil of the motor with red and blue terminals is connected to
this section as shown in Fig. 2. Transistors T5, T6, T7 and T8 from
another H-bridge and second coil of the motor with white and yellow
terminals is connected to this section as shown in Fig. 2. The high
input voltage to the base of the transistor will drive the transistor and
current will pass through the coil. The pulse sequence applied to the
coil is shown in the table.
Clockwise rotation::
Initially, blue and yellow terminals are high and red and white
terminals are low. So to rotate the motor clockwise, you have to
switch on transistor T2, T3, T6 and T7 and switch off the remaining
transistors. For this, apply hex data word CC (1100 1100).
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For the next sequence, red and yellow terminals are high and
blue and white terminals are low. So you have to switch on
transistors T1, T4, T6 and T7 and switch off the rest. For this apply
hex data word 3C (0011 1100).
Next, red and white terminals are high and blue and yellow
terminals are low. So you have to switch on transistors T1, T4, T5
and T8 and switch off the rest. The hex data word will be 33 (0011
0011).
Finally, red and yellow terminals are low and blue and white
terminals are on high logic. So transistors T2, T3, T5 and T8 should
be ‘on’ and the rest should be ‘off’. For this, apply hex data word C3
(1100 0011). Thus the complete sequence needed to rotate the
motor clockwise is CC-3C-33-C3.
Anticlockwise rotation::
As shown in the table for clockwise rotation, the only change
for anticlockwise rotation is that here the current changes its direction
in coil 2 first and then in coil1. So for anticlockwise rotation, the pulse
sequence will be CC-C3-33-3C. This pulse sequence is applied to
the motor with appropriate delay (depending upon the RPM) until the
motor completes the desired number of rotations.
Fig. 1 shows the circuit of the power supply. The AC mains is
stepped down by transformer X1 to deliver a secondary output of
7.5V at 500 mA. The transformer output is rectified by a full-wave
bridge rectifier comprising diodes D1 through D4, filtered by
capacitor C3 and regulated by IC4. Capacitor C4 bypasses any
ripple present in the regulated output. Regulated 5V DC is used to
power the circuit.
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The actual-size, single-side, single-side PCB for the
microcontroller-based stepper motor controller (Fig.1) is shown in
Fig.3 and its component layout in Fig.4.
Fig. 3: Actual-size, single-side PCB layout for microcontroller-based
stepper motor controller
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Fig. 4: Component layout for the PCB in Fig. 3
Clock and reset circuit – Two 33pF capacitors (C4 and C5 are
connected to pins 18 and 19 of the microcontorller, respectively, with
an 11.059MHz piezo electric crystal (XTALI) across them. The clock
frequency of the microcontroller depends on the frequency of the
crystal oscillator used. Typically, the maximum and minimum
frequencies are 1 MHz and 16 MHz, respectively, so we should use
a piezoelectirc crystal with a frequency in this range. The speed of
the stepper motor is proportional to the frequency of the input pulses
or it is inversely proportional to the time delay between pulses, which
can be achieved through software by making use of instruction
execution time.
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The time taken by any instruction to get executed can be
computed as follows:
Time = C ´ 12
F
Where ‘C’ is the number of cycles an instruction takes to execute and
‘F’ is the crystal frequency.
SOFTWARE
The software program is written in Assembly language and
assembled using 8051 cross-assembler (ASM 51). It is well
commented and easy to understand. Port P1 is initialized as the
input port. Data FFH is sent to port P1 and all its pins become high.
The program continuously checks port-P1 pins for low status. When
any port-P1 pin goes low, it goes into the comparison mode. After
comparison, it decides a particular action. LEDs glow to indicate the
action. Subroutines clkwise, aclkwise, incrpm, decrpm, incnum and
decnum are used for clockwise rotation, anticlockwise rotation,
incrementing RPM, decrementing RPM, incrementing the number of
rotations and decrementing the number of rotations, respectively.
Applied Pulse Sequence for Clockwise
And Anticlockwise Rotation
Clockwise rotation Anticlockwise rotation
Red Blue White Yellow Red Blue White Yellow
0 1 0 1 0 1 0 1
1 0 0 1 0 1 1 0
1 0 1 0 1 0 1 0
0 1 1 0 1 0 0 1
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PARTS LIST
Semiconductor:
IC1 AT89C51 microcontroller
IC2, IC3 7404 hex inverter
IC4 7805 5V regulator
T1- T8 2N2222 npn transistor
D1-D4 IN4007 rectifier diode
LED1-LED6 5mm light-emitting diode
Resistors (all ¼-watt, ± 5% carbon):
R1-R8 1-kilo-ohm
R9-R14 220-ohm
R15 4.7-kilo-ohm
Capacitors:
C1, C2 33pF ceramic disk
C3 1000mF, 16V electrolytic
C4 0.1mF ceramic desk
Miscellaneous:
X1 230V AC primary to 7.5V,
500mA secondary transformer
XTALPush-to-on tactile switch
S1-S7 Stepper motor 18° per step angle
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Robot Basics
The vast majority of robots do have several qualities in common.
First of all, almost all robots have a movable body. Some only have
motorized wheels, and others have dozens of movable segments,
typically made of metal or plastic. Like the bones in your body, the
individual segments are connected together with joints.
Robotic Arm Control
Robots have become important over a wide range of applications--
from manufacturing, to surgery, to the handling of hazardous
materials. Consequently, it's important to understand how they work,
and what problems exist in designing effective robots. This project
will address one of those problems: positional control.
One of a robot's functions is to move to a specified location or along
a predetermined path so it can perform a task. Motion may consist of
the robot itself moving, or of an articulated arm being actuated from a
fixed pivot position. Here we want to consider the problem of
controlling the motion of a very simple articulated arm--a two-segment
arm that can move only in the x-y plane and pivots about
the position x=0, y=0. A stepper motor M1 at (0,0) is attached to the
first arm segment L1 and controls the angle of L1 with respect to the
x-axis. A second stepper motor M2, afixed to the end of L1, is
attached to a second arm segment L2 and controls its angle with
respect to the x-axis. Each arm segment is 100 units long, for a total
maximum extension of 200 units. Neither of the arm segments may
move below the base, i.e., y = 0.
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DATASHEET
FOR ATMEL
AT89C51
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Assembly Language Program:
$MOD51
uf1 equ 2fh
uf2 equ 2eh
org 0000h
mov 2ah,#32h
mov 2bh,#01h
mov 2ch,#05h
mov 2dh,#01h
clr uf1
clr uf2
mov r0,#01h
mov p1,#0ffh
lop: mov a,p1
cjne a,#0ffh,jp
ajmp lop
jp: clr p0.0
loop: rrc a
jnc num
inc r0
sjmp loop
num: acall delay
setb p0.0
cjne r0,#01h,nxt
acall clkwise
sjmp over
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nxt: cjne r0,#02h,nxt2
acall aclkwise
sjmp over
nxt2: cjne r0,#03h,nxt3
jnb uf1,ledoff
setb p0.3
ledoff: acall incrpm
sjmp over
jnb uf1,ledof
setb p0.3
ledof: acall decrpm
sjmp over
jnb uf2,of
setb p0.4
of: acall incnum
sjmp over
nxt5: cjne r0,#06h,over
acall decnum
over: mov p2,#0ffh
mov p1,#0ffh
mov r0,#01h
sjmp lop
clkwise: mov r3,2ch
rot: clr p0.1
mov p2,#33h
acall delay
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mov p2,#3ch
acall delay
setb p0.1
mov p2,#0cch
acall delay
mov p2,#0c3h
acall delay
djnz r3,rot
ret
aclkwise: mov r3,2ch
rott: clr p0.2
mov p2,#33h
acall delay
mov p2,#0c3h
acall delay
setb p0.2
mov p2,#0cch
acall delay
mov p2,#3ch
acall delay
djnz r3,rott
ret
incrpm: clr p0.3
mov r4,2bh
cjne r4,#0ah,incr
setb uf1
ajmp out
incr: inc 2bh
mov b,2bh
mov a,#32h
div ab
mov 2ah,a
acall dely
setb p0.3
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out: ret
decrpm: clr p0.3
mov r4,2bh
cjne r4,#01h,decr
setb uf1
ajmp out1
decr: dec 2bh
mov b,2bh
mov a,#32h
div ab
mov 2ah,a
acall dely
setb p0.3
out1: ret
incnum: clr p0.4
inc 2dh
mov a,#05h
mov b,2dh
mul ab
mov 2ch,a
acall dely
setb p0.4
ret
decnum: clr p0.4
mov r4,2dh
cjne r4,#01h,decn
setb uf2
ajmp out2
decn: dec 2dh
mov a,#05h
mov b,2dh
mul ab
mov 2ch,a
acall dely
67 | P a g e

setb p0.4
out2: ret
delay: mov r1,2ah
lp5: mov r2,#0c8h
lp4: nop
nop
nop
djnz r2,lp4
djnz r1,lp5
ret
dely: mov r6,#0ffh
lp2: mov r7,#0c8h
lp1: nop
nop
nop
djnz r7,lp1
nop
nop
djnz r6,lp2
ret
end
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C Code For rotation (Interrupt based)
#include<c51rd2.h>
void clkwise(void);
void anticlk(void);
void delay(void);
void main(void)
{
P2=0xff;
P1=0xff;
while(1)
{
if(P1==0xbf)
{
clkwise();
}
else if(P1==0xdf)
{
anticlk();
}
}
}
void clkwise(void)
{
P2=0xcc;
delay();
P2=0x3c;
delay();
P2=0x33;
delay();
P2=0xc3;
delay();
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P2=0xff;
}
void anticlk(void)
{
P2=0xcc;
delay();
P2=0xc3;
delay();
P2=0x33;
delay();
P2=0x3c;
delay();
P2=0xff;
}
void delay(void)
{
int i=1,tick=0;
while(i)
{
tick++;
if(tick==200)
{
tick=0;
i=0;
}
}
}
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CONCLUSION
This project has been successfully completed. With the help of this
project, we can control various parameters of a stepper motor. This
can be used to precisely simulate a human arm.
In the world of automation, stepper motor is regarded as a milestone
in robotic industry. With its accuracy extending to small angles it is
used in almost every field of robotics.
Our project is a stepping stone towards complex robotics. This
project bridges the gap between diverse branches i.e. Electrical,
Electronics & Mechanical.
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BIBLIOGRAPHY
 “The 8051 Microcontroller and Embedded Systems “,Muhammad Ali Mazidi &
Janice Gillispie Mazidi , PEARSON Education
 “The 8051 microcontroller second edition”, Kenneth J. Ayala
 “Electronics For you“ , November 2006, Stepper Motor Controller using
AT89C51, A.M. Bhatt, Page 66
 “Robotics”, K.S. Fu, R.C. Gonzales, C.S.G Lee, Mc-Graw Hill International
Editions.
 http:// www.wikipedia.com
 http://computer.how stuffworks.com/microprocessor1.htm/
 http://www.atmel.com
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