MINISTRY OF EDUCATION AND TRAINING
Report No.1: Introduction
Supervisor
Mr. Huỳnh Anh Dũng
Group Members
Student ID
Name
Role
00347
Nguyễn Minh Đức
Team leader, Document Management
00463
Trần Quang Huy
Hardware Designer, Tester
00718
Bùi Hoàng Vượng
Software Designer, Developer, Tester
01157
Ngô Anh Vũ
Software Designer, Developer, Tester
01215
Trần Xuân Sáng
Hardware Designer, Tester
Initial Idea
Embedded System (ES) is a specialized study in FPT university. Since we are new in ES
and our knowledge is little, we do not expect to do something new and widely
applicable. Through research and realization of Capstone project, we simply hope to
gain more knowledge and experience in ES field for future bigger project. So we
decided to make a Propeller Clock which we were interested in
Definition
Propeller Clock is a linear array of light emitting diodes, rotating at a high angular
velocity to generate a circular screen. By synchronizing these light emitting diodes,
and keeping in mind the concepts of persistence of vision and limit of resolution, we
can display an analog clock
Figure 1: A propeller clock is sticked to rotation axis of a fan
Persistence Of Vision
Persistence of vision is the phenomenon of the eye by which an afterimage is
thought to persist for approximately one twenty-fifth of a second on the retina
The myth of persistence of vision is the belief that human perception of motion (brain
centered) is the result of persistence of vision (eye centered). The myth was
debunked in 1912 by Wertheimer but persists in many citations in many classic and
modern film-theory texts. A more plausible theory to explain motion perception (at
least on a descriptive level) are two distinct perceptual illusions: phi phenomenon
and beta movement
A visual form of memory known as iconic memory has been described as the cause of
this phenomenon. Although psychologists and physiologists have rejected the
relevance of this theory to film viewership, film academics and theorists generally
have not. Some scientists nowadays consider the entire theory a myth
In contrasting persistence of vision theory with phi phenomena, a critical part of
understanding that emerges with these visual perception phenomena is that the eye
is not a camera. In other words vision is not as simple as light registering on a
medium, since the brain has to make sense of the visual data the eye provides and
construct a coherent picture of reality. Joseph Anderson and Barbara Fisher argue
that the phi phenomena privileges a more constructionist approach to the cinema
(David Bordwell, Noël Carroll, Kirsten Thompson), whereas the persistence of vision
privileges a realist approach (André Bazin, Christian Metz, Jean-Louis Baudry)
The discovery of persistence of vision is attributed to the Roman poet Lucretius,
although he only mentions it in connection with images seen in a dream. In the
modern era, some stroboscopic experiments performed by Peter Mark Roget in 1824
were also cited as the basis for the theory
In conclusion, what we see is a blend of what we are viewing and what we viewed a
fraction of a second before
Figure 2: Display “1” by series of lighting up of diodes
Phi Phenomenon
The phi phenomenon is an optical illusion defined by Max Wertheimer in the Gestalt
psychology in 1912, in which persistence of vision formed a part of the base of the
theory of cinema, applied by Hugo Münsterberg in 1916. This optical illusion is based
in the principle that the human eye is capable of perceiving movement from pieces of
information, for example, a succession of images. In other words, from a slideshow of
a group of frozen images at a certain speed of images per second, we are going to
observe constant movement
The phi phenomenon is an optical illusion of our brains and eyes that allows us to
perceive constant movement instead of a sequence of images. We are supplying
information that does not exist (between image and image) that creates the illusion
of a smooth movement. The phi phenomenon, which might be considered the basis
of the correct working of the cinema, is only a limitation of the human eye, which
depends on the persistence of visual sensations
(This animated image can only be viewed in web browser)
Figure 3: An example of Phi Phenomenon
Beta Movement
The beta movement is an optical illusion, first described by Max Wertheimer in 1912.
Its illusion is that fixed images seem to move, even though of course the image does
not change. It might be considered similar to the effects of animation. Wertheimer
wrote his paper in the early days of motion pictures, and this may account for some
of his findings, as people were unfamiliar with images moving at all
Of course the static images do not physically change but give the appearance of
motion because of being rapidly changed faster than the eye can see
This optical illusion is caused by the fact that the human optic nerve responds to
changes in light at about 10 cycles per second, so changes about double of this are
registered as motion instead of being separate distinct images
(This animated image can only be viewed in web browser)
Figure 4: An example of Beta Movement
Distinguish Phi Phenomenon & Beta Movement
Although both cause sensation of movement, the phi phenomenon can be considered
to be an apparent movement caused by luminous impulses in sequence (that is to say,
it is lights going on and off at regular intervals), whereas the beta movement is an
apparent movement caused by luminous stationary impulses (lights that do not move,
but seem to)
Literature Review
Nowaday, there are many projects on propeller clock, we will discuss the theory and
concept from the 2 typical past projects
1. Henk's propeller clock on a mirror project
Figure 4: An example of Henk's propeller clock
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
2. Bob blick's propeller clock project
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
Figure 4: An example of Bob Blick’s propeller clock
Proposal
This is summary of the features that team members proposed in ascending order of
difficulty and descending order of priority:
1. Display an analog clock with three hands
We build the first version of Propeller Clock that is possible to perform the
most basic functions:
- Connecting the circuit board to the power supplier
- Lighting up the LEDs
- Controling each LED
- Balancing the circuit board to make the whole system rotational
- Controling the rotation velocity
Basically, it has 2 units:
- Rotating circuit board
- DC motor with power supply unit
When the circuit board rotates at high speed it LEDs light forms a circular
screen and we can customize the embedded code to display the 60 scales as
60 minutes in one hour respectively, the hour scales are marked as numbers
from 1 to 12. Three hands indicate hour, minute and second in which the
long hand indicates hour, the medium hand indicates minute and the short
hand indicates second
Figure 4: Analog clock
We intend to use PIC16F887 as the microcontroller of the project. The
PIC16F887 is one of the latest products from Microchip. It features all the
components which modern microcontrollers normally have. For its low price,
wide range of application, high quality and easy availability, it is an ideal
solution in applications such as: the control of different processes in
industry, machine control devices, measurement of different values…
2. Display date
Next step is adding information of date below the center of the clock.
Obviously this step mostly relates to coding
The display convention is mm-dd-yyyy
3. Display multiple colors
This feature is optional. We use RGB LED instead of single color LED to
create multicolor as we want. Of course controling RGB LED is much more
difficult than single color LED. Moreover it refers to art design
Figure 5: An RGB LED
4. Optimize the product
Reliability: the product should have no defect, especially the defects relate
to safety. Test it over and over again to ensure the reliability
Minimization: we minimize the clock as much as possible. To do this it is a
must that the circuit board is designed carefully with respect to space
Portability: finally we pack the product to make it portable
5. Add more advanced features
This is optional. We would like to advance our product as much as we can.
Let say that this step belongs to the future. At the moment we propose
wireless power
Wireless energy transfer or wireless power is the transmission of
electrical energy from a power source to an electrical load without
interconnecting manmade conductors. Wireless transmission is useful in
cases where interconnecting wires are inconvenient, hazardous, or
impossible. The problem of wireless power transmission differs from that
of wireless telecommunications, such as radio. In the latter, the
proportion of energy received becomes critical only if it is too low for the
signal to be distinguished from the background noise. With wireless
power, efficiency is the more significant parameter. A large part of the
energy sent out by the generating plant must arrive at the receiver or
receivers to make the system economical
The most common form of wireless power transmission is carried out
using direct induction followed by resonant magnetic induction. Other
methods under consideration include electromagnetic radiation in the
form of microwaves or lasers
Figure 6: Illustration of wireless power
Benefits Of The Expected Product
 For our group:
 Understand the process from start to finish to complete an embedded
product that have practical applications
 Use the things our group learned from class into real products
 Understand the way to analyze, design the architecture of a system, write
document and organize the database by a given request
 About embedded systems, we will learn how to design functions for
printed circuit, components embedded code on our circuit
 Increase the skills of teamwork as well as independent research of each
member
 For commercial use
 The main target of the system is casual consumers and mass-market. In
Vietnam, there isn’t any similar product, so we hope it can be successful
Risk Management
ID
1
Risk Description
Serious
High
Modera
te
Status
Very high
Ask for support
from our
supervisor and
experienced
Potential acquaintances.
High
Ask members
to rearrange
their schedules.
After that find
a time when
everyone can
work together
Serious
Occured
Serious
Add buffer
Potential time to the
project plan.
Human resource:
Some members still
have to work at
Action
Team leader
prepares
knowledge
from text book
Occurred
and ask for
advise from
experienced
PM
Human resource:
It’s hard to work
together, as each
team member has
very different
schedule.
4
High
Hardware
knowledge:
There might be
problems with
hardware design
due to the lack of
knowledge in this
matter
3
Effect
Project
Management
skill:
Team leader lacks
of project
management skill
2
Probability
Contingency
Fsoft, they could
have to work overtime in the future
References
http://www.mikroe.com/chapters/view/2/chapter-1-pic16f887-microcontrollerdevice-overview/
http://users.skynet.be/fc052475/henks_hobbies.htm
http://www.bobblick.com/techref/projects/propclock/propclock.html
Persistence Of Vision: http://en.wikipedia.org/wiki/Persistence_of_vision
Phi Phenomenon: http://en.wikipedia.org/wiki/Phi_phenomenon
Beta Movement: http://en.wikipedia.org/wiki/Beta_movement
Wireless Power: http://en.wikipedia.org/wiki/Wireless_energy_transfer