PROPELLER LED DISPLAY
AJMAL BlN MUHAMAD SAZALI
This Report Is Submitted In Partial Fulfillment of Requirements for the Bachelor
of Electronic Engineering (Industrial Electronic) with honours.
Fakulti Kejuruteraan Elektronik dan Kejuruteraan Komputer
Universiti Teknikal Malaysia Melaka
April 2007
vii
ABSTRACT
Conventional methods of displaying images to public are using LCD display and
dot-matrix LED board. Propeller LED display is a device that project an image or time
as if the images are floating in the air. The floating image is received because of human
eye limitation. Actually the floating images emerge by synchronizing LED'S blink to
form an image at particular time and rate.
The programming of PIC is using Assembly Language. This project consist two
main circuit; motor controller circuit and LED circuit. 9VDC will be used to supply the
power for motor controller circuit. Then the motor controller circuit will provides power
to LED circuit and DC motor. When DC motor is rotating, the floating image will
appear. The synchronization of DC motor speed and LED blink cause the image visible
to human eyes. So the desired image such as clock, date or symbol can be programmed
and displayed.
ABSTRAK
Antara kaedah konvensional untuk memaparkan imej adalah menggunakan
papan LCD dan papan LED dot-matrik. Paparan Berputar LED adalah alat untuk
menayangkan imej atau masa seolah-olah imej tersebut terapung di udara. Imej yang
terbentuk ini dapat diterima kerana batasan mata manusia. Sebenarnya, imej ini timbul
kerana keselarian kerlipan LED untuk membentuk imej pada masa dan kadar yang
khusus.
Bahasa pengaturcara Assembly digunakan untuk diprogramkan kedalam PIC.
Projek ini terbahagi kepada dua litar utama, iaitu litar pengawal litar motor dan litar
LED. 9VDC digunakan untuk membekalkan voltan kepada litar pengawal motor.
Apabila motor DC berpusing, imej yang terapung akan terhasil. Keselarian di antara
kelajuan motor DC dan kelipan LED akan mengakibatkan imej yang nyata untuk dilihat
oleh mata manusia. Oleh itu, imej seperti jam, tarikh dan simbol boleh diprogramkan
dan dipaparkan.
CHAPTER I
INTRODUCTION
1.1
PROJECT SYNOPSIS
Nowadays, there are so many way to displaying a message such as using 7
segment, Frosted Light Bar (RGB 16.7 millions true colows), digital clock and etc.
These kind of device are used to advertise or displaying some sort of message in
order to attract people. It is different than a conventional method such as poster,
banner and etc. These projects are cheaper, easier and even carry out the same
purpose as any display apparatus.
1.2
PROBLEM STATEMENTS
From other article and project, there are some problems which are effected
the outcome of the image displayed. The main problem is concerning the motor. A
VCR motor has to be used as a motor in order to prevent noise. The circuit also have
to use photo transistor to generate precise index pulse. In order to display the date
and clock, the circuit must have memory capacitor to keep the clock ticking even
when the power is not supplied to the circuit. The memory capacitor is expensive
plus, it bigger and heavy. To replace the memory capacitor, a small, cheap and light
3V lithium battery is used as a replacement. A voltage regulator also has to be used
in order to allow rotation speed change without effecting the circuit and displayed
images.
1.3
OBJECTIVES
The objectives of this project are:
i.
To design a display system using LEDs which rotate on a motor.
ii.
To design a program using Assembly language.
iii.
To display clock, date and symbol using LEDs.
iv.
To develop software that can generate LEDs display with accurate
synchronization and timing.
1.4
SCOPES OF PROJECT
The scopes of this project are:
i.
The circuit is mounted on DC motor.
ii.
LED'S are used to display clock, date and symbol.
...
111.
PICF84A is used to control and transmit the signal and utilizing the
Assembly language.
1.5
CHAPTER SUMMARY
CHAPTER I will describe the definition of this project will be explained in
this chapter. Also in this chapter there will be summary the project progress.
CHAPTER I1 will discuss about research and information which are related to
this project. Every fact and information are gained from different references will be
discussed so that the best technique and method can be implemented on this project.
CHAPTER I11 will be describing how this project is separated to small
partition. The elements which are used to build each circuit are described by concept
and theory. Plus, figures are provided to ensure the understanding.
CHAPTER IV is describing about the project result and outcome discovery.
The project outcome discovery will be presented from the many data analysis results.
The final chapter, CHAPTER V will be explaining about the conclusion of the
whole project which includes project finding, achievement analysis and conclusion
about the research implementation which have been used. The project suggestion for
enhancement also discussed.
CHAPTER I1
LITERATURE REVIEW
2.1
INTRODUCTION
This chapter is all about discussing the theory and concept from the past
projects. The objective is to explain the perspective and method which has been used
in the past projects and to observe how this project can be related with existing
research and theory. This shows how the theory and concept have been implemented
in order to solve project problem. The theory understanding is crucial as a guidance
to start any project. The result of a project cannot be assessed if it's not compared to
the theory.
2.2
HENK'S PROPELLER CLOCK ON A MIRROR PROJECT
Figure 2.1 : Displaying Clock And Date.
The LEDs turn on and turn off, one after another, very rapidly. Due to the
slow response of the human eye, the impression that the lights are on all together is
obtained and the display can be read. Scanning in this clock is mechanically. A
limited number of LEDs are placed in a row and attached to a rotating arm. The arm
spins at 1500rpm (or more) and the LEDs are turned on and off at very precise times
and places. This gives the impression that there are several hundred LEDs making up
a complete display. The fact that the arm is spinning at 1500rpm the LEDs, the
electronics and the arm itself are hardly visible. The visible things are the lighted
dots from the LEDs making a readable display that seems to float.
Depending on the form of the arm, the display is either a cylinder or a disc.
The cylinder shaped display can only show digits. With the disc shaped display it is
also possible to simulate analog hands. The electronics is used to drive the LEDs and
to keep time are located on the rotating arm. Early versions used buttons on this arm.
Other designs use a reed-switch that can be actuated by holding a magnet
near the rotating arm. Chester Lowrey's Propeller Clock using one visible light, one
infrared, to create a two-button system. This made settings the time a lot easier.
But Henk wanted to display time and date. To set time and date with just
two buttons would not be very efficient. So an infrared sensor is connected to the
CPU and programmed it to decode signals from a remote control. This opened up a
lot more possibilities. The remote can be used to set time and date. It can also be
used to set different display modes. The successful project is shown in Figure 2.1.
2.3
BOB BLICK'S PROPELLER CLOCK PROJECT
Figure 2.2: Seven Light Emitting Diodes Spin.
Bob Blick made the clock spinning on a piece of perfboard. The power is
provided from the spinning armature of a plain DC motor. In order to run the wires
out of the motor, the bearing is removed from one end of the motor, leaving a big
hole. There are three terminals inside most small DC motors, and it acts a lot like
three-phase alternating current, so it must be rectified back to DC. A nice side effect
of this is that the position of the motor can be detected by taking one of the phases
straight into the microprocessor.
Bob Blick used perfboard (Vectorboard) and handwired the circuit together.
Use an 18-pin socket for the 16C84 is used because it needs to be programmed
before putting it in the circuit. For the 7 current-limit resistors a DIP resistor array is
used, because it made it easy to experiment with LED brightness. He settled on 120
ohms. Seven regular resistors also can be used, because 120 ohms works fine, though
it puts the peak current right at the limit for the 16C84. To keep the clock running
after turning it off a 47000uf is used, so the time can be set. The LED'S gets power
separate from this circuit. The result is shown in Figure 2.2.
CHAPTER I11
PROJECT METHODOLOGY
3.1
INTRODUCTION
This project consist two different circuits. There are motor controller circuit
and LED circuit. At early stage, circuit designs are being done. After that, using a
software called 'Proteus-ISIS', both circuit simulation are implemented. After the
simulation process is proceeded, both circuit will be designed to be printed in PCB
board using 'Proteus-ARES'. Next, circuit construction and testing are using
multimeter. If the circuit malfunction, designing and modifying circuit process has to
be done to ensure both circuits working properly. The programming language design
process is using MPLAB-IDE. Finally after the programming is finished, the
program is burned into PICF84A using WinPic800.
3.2
BLOCK DIAGRAM
LED Circuit
PIC
LED
A
9v
A
A
4
Motor
+ Controller
Circuit
DC
Motor
- Motor
Shaft
-
Figure 3.2: Block Diagram of Propeller LED Display
From the Figure 3.2, the 9V DC is supplied to Motor Controller Circuit.
Motor Controller circuit is controlling the DC motor speed and the speed is
adjustable. In order to rotate the circuit, DC motor is used. PIC microcontroller
purposed is to execute the program and transmit the signal to LED. As output, a line
of LED is used to transmit the desired signal. In order to display the images, DC
motor will rotate the circuit board. If the displayed image is not clear, the DC motor
speed is adjusted until the displayed image is visible.
3.3
ACTIVITY FLOW CHART
With the aim of completing this project on time, all activities have been
planned as shown in the activity flow chart with the intention that everything is
completed step by step.
Discussing the scope
Literature research
Circuit Design
Simulation
1
Construct Circuit
PIC
Programming
No
Finalized PCB
Figure 3.3: Project Activities Flow Chart
3.4
COMPONENT AND SOFTWARE EXPLANATION
The PIC16F84A is a high-performance, low-cost, CMOS, fully-static 8-bit
microcontroller with 1K x 14 EEPROM program memory and 64 bytes of EEPROM
data memory. It is the second member of an enhanced family of PICl6CXX
microcontrollers.
Its high performance is due to instructions that are all single word (14-bit
wide), which execute in single cycle (400 ns at lOMHz clock) except for programbranches which take tow cycles (800ns). The PIC16C84 has four interrupt sources
and an eight level hardware stack. The peripherals include an 8-bit timerlcounter
with an 8- bit prescaler (effectively a 16 bit timer) and 13 bi- directional I10 pins.
The high current drive (25 mA max. sink, 20 mA max source) of the I10 pins help
reduce external drivers and therefore, system cost. The PIC16C84 product is
supported by an assembler, an in-circuit emulator and a production quality
programmer. These tools are supported on the IBM PC and compatible machines.
3.4.1.1 Peripheral Features
13 110 pins with individual direction control
High current sinklsource for direct LED drive 25 mA sink max. per pin
20 mA source max. per pin
8-bit real time clock/counter (RTCC) with 8-bit programmable prescaler
Special Microcontroller Features
- Power-on reset
- Power up timer
- Oscillator start-up timer
- Watchdog timer (WDT) with its own on-chip RC oscillator for reliable
operation
- Security EPROM fuse for code-protection
- Power saving SLEEP mode
- User selectable oscillator options:
RC oscillator: RC
Crystallresonator: XT
High speed crystallresonator: HS
Power saving low frequency crystal: LP
- Serial, In-System Programming (ISP) of EPROM program memory
using
only two pins
3.4.1.2 Pin Diagram of PIC16F84A
-
POIF, SOIC
RAZ
R83
WPaMCICKI
MCLR
vs
flmm
ma
R52
WB3
-
The PIC16F84A belongs to the mid-range family of the PICmicroB
microcontroller devices. A block diagram of the device is shown in Figure 3.4.
Figure 3.4: PIC 16F84A Block Diagram.
3.4.2
MOTOR
Motors come in many sizes and types, but their basic function is the same.
Motors of all types serve to convert electrical energy into mechanical energy. They
can be found in VCR's, elevators, CD players, toys, robots, watches, automobiles,
subway trains, fans, space ships, air conditioners, refrigerators, and many other
places. The performance of the motor is very important in circuit design. This is
because the electrics motors directly affect its speed and pushing capability. Motor
performance information is needed to select the required speed. The current
requirements from the motor will dictate what type and size batteries will need and
they are also a factor in determining the minimum current requirements for motor
speed controllers.
3.4.2.1 DC Motor
DC motors seem quite simple. Apply a voltage to both terminals, and it will
spins. DC motors are non-polarized which means that it can reverse voltage so the
motor will rotate in two directions, forward and backward. Typical DC motors are
rated from about 6V-12V. The larger ones are often 24V or more but for the purpose
of this project, it is necessary to use 6V-12V range motor. Voltage is directly related
to motor torque. The more voltage supplied, the higher the torque will be produce.
Specifications of most DC motors show high revolutions per minute (rpm) and low
torque.
The DC motor is popular in a number of drive applications due to its simple
operation and control. By referring Figure 3.5, it has 2 main parts which is rotor and
stator. Stator is the part where the permanent magnet situated and used to generate the
magnetic field and it is static. Rotor is the rotary part in the motor and contains block of
core and wire loops. It also called the armature.
Figure 3.5: DC Motor
The rotor is placed inside the magnetic field caused by two permanent magnets.
By referring to the situation that shown in Figure 3.6, both sides of the wire loop will
have a force on them. trying to make the wire loop rotate. The current is applied to the
loop through the commutator, which is shown as two pieces of metal formed into a ring
in the figure. Current is applied to the commutator by stationary graphite blocks, called
brushes, which rub against the commutator ring. The loop will continue to rotate
anticlockwise until it is vertical. At this point, the stationary brushes won't be applying
current around the loop any more because they will be contacting the gap between the
commutator segments, but the inertia of the loop keeps it going a little more, until the
DC supply reconnects to the commutator segments, and the current then goes around the
loop in the opposite direction. The force though is still in the same direction. and the
loop continues to rotate.
Figure 3.6: The Operation of DC Motor
3.4.2.2 DC Motor Voltage
DC motors are non-polarized - meaning that one can reverse voltage without
any bad things happening. Typical DC motors are rated from about 6V-12V. The
larger ones are often 24V or more. But for the purposes of this project, do stay in the
6V-12V range. It is stated that voltage is directly related to motor torque. High
voltage produces higher torque. A DC motor is rated at the voltage it is most efficient
at running. If very few volts are applied, it just won't work. If too much is applied, it
will overheat and the coils will melt. So the general rule is to apply as close to the
rated voltage of the motor. But do not surpass 12V motors unless the torque is
required badly.
3.4.2.3
DC Motor Current
As with all circuitry, one must pay attention to current. Too little, and it just
won't work. Too much, the motor will meltdown. When buying a motor, there are
two current ratings one should pay attention to. The first is operating current. This
is the average amount of current the motor is expected to draw under a typical
torque. Multiply this number by the rated voltage and the average power draw
required to run the motor is obtained. The other current rating which one needs to
pay attention to is the stall current. This is when the motor is power up, and enough
torque is put to force it to stop rotating. This is the maximum amount of current the
motor will ever draw, and hence the maximum amount of power too. So, one must
design all control circuitry capable of handling this stall current. Also, if the motor
is constantly run, or run it higher than the rated voltage, it is wise to heat sink to
keep the motor's coils from melting.
3.4.2.4 DC Motor Power Rating
Basically, all motors are rated at certain wattage. Wattage is energy.
Inefficiency of energy conversion directly relates to heat output. Too much heat, the
motor coils melt. So the manufacturers of motors know how much wattage will cause
motor failure, and post this on the motor specification sheets.
The equation is:
Power (watts) = Voltage * Current
Increase voltage and measure current until the power is about -90% below the given
power rating.
3.4.2.5
DC Motor Torque
Torque is defined as that force which tends to produce and maintain rotation.
The function of torque in a DC motor is to provide the mechanical output or drive the
piece of equipment that the DC motor is attached to. There are two torque value ratings
which must been pay attention to. The first is the operating torque. This is the torque the
motor was designed to give. Usually it is the listed torque value. The other rated value is
stall torque. This is the torque required to stop the motor from rotating. he torque which
is developed by the motor can be determined using Equation:
T = KQI,
where
T
= torque
K
=a
Q
= field
1,
= armature
constant depending on physical size of motor
flux, number of lines of force per pole
current
When buying a DC motor, there are two torque value ratings which must be
Pay attention to. The first is operating torque. This is the torque the motor was
designed to give. Usually it is the listed torque value. The other rated value is stall
torque. This is the torque required to stop the motor from rotating.
If one need a little more speed, going 20% above the rated motor voltage
value is fairly safe. But, that this is less efficient, and the motor should be heatsinked.
3.4.2.6 Velocity
Velocity is very complex when it comes to DC motors. The general rule is
motors run the most efficient when run at the highest possible speeds. Obviously
however this is not possible. There are times to run the motor slowly. Just like car, it
won't to keep the car constantly at high speed. The voltage and applied torque
resistance obviously also affects speed.
Instead using a Multisim as a simulator, Proteus-ISIS is used. Proteus-ISIS is
suitable to simulate a circuit which consist PIC or motor. It can simulate the blinking
LED and the rotating motor as shown in Figure 3.7. The analyses are done from this
software which is very useful to verify the circuit.
Figure 3.7: Layout of Proteus-ISIS.
Proteus-ARES is used to design the PCB board. Using this software, a user
has to know the scale of the product because in ARES, there's no scale indicator. So
a user has to well familiar with proto board and component size. The layout of
Proteus-ARES is shown in Figure 3.8.
Figure 3.8: Layout of Proteus-ARES.
3.4.5
MPLAB IDE
MPLAB IDE is software to construct and compile the programming language
as shown in Figure 3.9. This software is crucial to verify the programming language.
If there's error while compiling, the program can't be burned into PIC.
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WinPic800 is used to burn the complete program language into PIC.
WinPic800 are capable to burn a complete programming language such as Assembly,
C++, Visual Basic, C and etc. All the programming language will be converted to
Hex file before burning into PIC. WinPic800 layout is shown in Figure 3.10.
Figure 3.10: Layout of WinPic800.
3.4.7 ASSEMBLY LANGUAGE
An assembly language is a low-level language used in the writing of
computer programs. Assembly language uses mnemonics, abbreviations or words
that make it easier to remember a complex instruction and make programming in
assembly an easier task. The goal of using mnemonics in the writing of assembly
language programs is to replace the more error prone, and time consuming, effort of
directly programming in a target computer's numeric machine code that had been
used with the very first computers. An assembly language program is translated into
the target computer's machine code by a utility program called an assembler. The
assembler performs a (more or less) one-to-one (isomorphic) translation from
mnemonic statements into machine instructions and data. The purpose is to free the
Programmer from tedious tasks such as remembering codes, calculating addresses
and offsets, as well as various other constants, while still retaining full control over
the machine.
On the other hand, a translator that takes a program written in a high-level
language and translates it to an equivalent executable machine code (andlor assembly
code) is called a compiler.
A "translator" that directly execute (i.e. perform) the sequence of declarations and
actions in a written (high or low-level) program is called an interpreter.
Assembly language programs are tightly coupled with (and specific to) a
target computer architecture
-
as opposed to higher-level programming languages,
u-hich are generally platform-independent. More sophisticated assemblers extend the
basic translation of program instructions with mechanisms to facilitate program
development, control the assembly process, and aid debugging.
Assembly language was once widely used for all aspects of programming, but
today it tends to be used more narrowly, primarily when direct hardware
manipulation or unusual performance issues are involved. Typical uses are device
drivers, low-level embedded systems, and real-time systems. These applications
benefit from the increased speed of processing assembly program instructions.
The programming flow chart is shown in Figure 3.1 1. When the program
started, it will go to "Displaying Message 1". After that it will go to "Count 50
cycle". If the cycle doesn't count finish till 50, it will loop back to "Displaying
Message 1". If it does, it will proceed to the next process. When this process finished
the final block, it will start again at "Displaying Message 1". This process continues
until the power is off.