OVERVIEW OF PROJECT
What is PROPELLER LED DISPLAY???
Propeller :
Propeller is a term associated with a circular rotating object. As this project needs to rotate whole circuit assembly, there must be some prime mover attached to it. So, the term ‘Propeller’.
LED Display:
This project using bright light emitting diodes for displaying the characters and symbols on its assembly.
That’s why this project is named as ‘PROPELLER LED DISPLAY’
BASIC PRINCIPLE BEHIND THIS PROJECT :
POV (Persistence Of Vision):
This is the phenomenon which is related to vision capability of human eye by which an after- image is thought to persist for approximately 1/25th of a second.
So, if someone is observing the images at a rate of 25 images per second, then they appear to be continuous. The best example of this property is the red circle we observe when we rotate the firecracker or incense stick in circle
CIRCUIT DIAGRAM :
Microcontroller
AT89C2051
This project is based around the microcontroller AT89C2051, which is a derivative of 8051 family, from Atmel Inc. This is a 20 pin IC packaged in DIP package. This small sized IC is used, mainly because of its reduced weight. This improves the performance of the display, because reduced weight gives advantage of increased RPM.
LED MODULE
LED module consisting of 8 bright LED is fixed in another side of the arm of our project. These LEDs are connected with each of the port pin of microcontroller, with a series current limiting resistor of 470 ohm. Shown in Fig. at Right side .
Speed of the LED's (Frame rate) :
The rotational speed of the LED's affects directly how many pictures can be displayed in a second. This corresponds to the frame rate .On a modern TV, the frame rate is 100Hz. The more frame rate, the less flickering of the picture.
Because on the Propeller Display the picture is scanned mechanically, it is not easy to achieve high frame rates. For me it isn't possible to mechanics that can rotate the LED's 100 times a second.
The propeller has to be very well balanced to keep vibrations as low as possible and keep the speed of the rotating LED's as high as possible.
Introduction & Principle :
Before the text can be displayed, it has to be converted to a bitmap and stored in an array .Because the H8S/2633 has a lot of RAM store the whole text as a bitmap in it. After the conversion, the bitmap can simply transferred periodically to the LED's which displays the picture column by column.
The eye of the visitor puts these column together to the complete picture. To convert a string to a bitmap it's necessary to have a font. Every possible character is stored in the flash. A little routine copies the single characters together to obtain a whole string.
Have a look to this principle:
Because the motor of the propeller turns clockwise, the microcontroller has to output the picture from the right side to the left. If the direction would be wrong, the text appears mirrored.
Scrolling :
Scrolling is relatively easy to implement too. A window which complies to the pixel count of one round of the propeller is moved over the picture.
Only the pixels in this window are putted out bye the LED's.
When this window moves, also the displayed text moves and it looks like scrolling.
Remarks :
For a nicer picture the LED's only flashes a short time when the propeller is on a position.
Then they are darkly while the propeller move the LED's to the next pixel position and they flash again. This is done with the divider.
RESULT
Circuit Module
Rotating Display
Mechanical assembly plays a vital role in proper functioning of this project. The display is scanned each time, by rotating the whole assembly in a circular path. The basic idea we developed is on our own, by implementing and modifying different ways to do this.
Following diagram shows the most reliable way, that we finally selected.
Here, one major challenge was how to bring +5V supply to the spinning circuit. We tried the same by adopting two-three different methods, but finally concluded on the method, as shown in the figure.
As seen in the diagram, one supply connection (GND) is provided
through the motor’s shaft. Other terminal (Vcc) is connected, by arranging a friction disc-brush arrangement. The brush keeps its contact with the disc, so that current can be supplied.
PRINTED CIRCUIT BOARD:
Much modern electronic system would be virtually impossible to package without incorporating printed circuit board. A printed circuit board popularly known as PCB, is a piece of plastic insulating board, on one side of which a complete layout diagram of an electronic circuit consisting of copper as conductive layer is printed by a special photo generation process.
On the other side of PCB are mounted electronic components like capacitor, resister, inductor and IC's. The metal conducting part serves as conducting medium for the electronic components that are assembled on the opposite side of board.
PCB MAKING
Take proper scale of components and according to such scale make component lay out of project circuit, on a paper. This layout is simple as well as small in size. Then draw mirror image of PCB layout.
STEPS FOR PCB DESIGNING
The following checklist uses the major area of concern in the process of PCB design:
a) Optimum size and shape of board should be ensured.
b) The substrate should be selected properly by taking into consideration its cost, mechanical properties and electrical properties.
c) Layout of conductor pattern should be taken care from cross talk, leakage, shielding, numbers of jumpers required and their placement.
d) Selection of conductor width, thickness and spacing should be done after analyzing their placement.
e) Proper productive coating should be selected.
f) Thermal consideration should be analyzed properly.
g) Proper mounting of heavy and unstable component should be ensured Most critical objective was to achieve pristine balance and overall good mechanical strength. For weight adjustment, we have provided one long screw, and weight can be attached or removed by adding / removing metallic bolts. If the assembly is balanced perfect, then it can achieve stability, and rotate at high RPMs too. This will improve the overall efficiency of this display.
Some Troubleshooting in Project :
1. DC motor is not rotating
~> Check the current flowing through the motor. If it reaches above 750mA, then the motor is short,Repeat it. In case of jamming, try to grease the bearing and shaft.
2. The display rotates, but not displaying garbage values.
~> Check the red strip (Interrupt) is in proper position or not. If not, adjust it.
3. Some or all LED not glowing.
~> Check the connector, that connects the LED module to the microcontroller.
~> Otherwise, check the continuity through each wire.
~> If the connections are OK, then replace the particular LED.
ENJOY... ; )
What is PROPELLER LED DISPLAY???
Propeller :
Propeller is a term associated with a circular rotating object. As this project needs to rotate whole circuit assembly, there must be some prime mover attached to it. So, the term ‘Propeller’.
LED Display:
This project using bright light emitting diodes for displaying the characters and symbols on its assembly.
That’s why this project is named as ‘PROPELLER LED DISPLAY’
BASIC PRINCIPLE BEHIND THIS PROJECT :
POV (Persistence Of Vision):
This is the phenomenon which is related to vision capability of human eye by which an after- image is thought to persist for approximately 1/25th of a second.
So, if someone is observing the images at a rate of 25 images per second, then they appear to be continuous. The best example of this property is the red circle we observe when we rotate the firecracker or incense stick in circle
This project is based around the microcontroller AT89C2051, which is a derivative of 8051 family, from Atmel Inc. This is a 20 pin IC packaged in DIP package. This small sized IC is used, mainly because of its reduced weight. This improves the performance of the display, because reduced weight gives advantage of increased RPM.
LED MODULE
LED module consisting of 8 bright LED is fixed in another side of the arm of our project. These LEDs are connected with each of the port pin of microcontroller, with a series current limiting resistor of 470 ohm. Shown in Fig. at Right side .
Speed of the LED's (Frame rate) :
The rotational speed of the LED's affects directly how many pictures can be displayed in a second. This corresponds to the frame rate .On a modern TV, the frame rate is 100Hz. The more frame rate, the less flickering of the picture.
Because on the Propeller Display the picture is scanned mechanically, it is not easy to achieve high frame rates. For me it isn't possible to mechanics that can rotate the LED's 100 times a second.
The propeller has to be very well balanced to keep vibrations as low as possible and keep the speed of the rotating LED's as high as possible.
Moving Message Display
Before the text can be displayed, it has to be converted to a bitmap and stored in an array .Because the H8S/2633 has a lot of RAM store the whole text as a bitmap in it. After the conversion, the bitmap can simply transferred periodically to the LED's which displays the picture column by column.
The eye of the visitor puts these column together to the complete picture. To convert a string to a bitmap it's necessary to have a font. Every possible character is stored in the flash. A little routine copies the single characters together to obtain a whole string.
Have a look to this principle:
Because the motor of the propeller turns clockwise, the microcontroller has to output the picture from the right side to the left. If the direction would be wrong, the text appears mirrored.
Scrolling :
Scrolling is relatively easy to implement too. A window which complies to the pixel count of one round of the propeller is moved over the picture.
Only the pixels in this window are putted out bye the LED's.
When this window moves, also the displayed text moves and it looks like scrolling.
Remarks :
For a nicer picture the LED's only flashes a short time when the propeller is on a position.
Then they are darkly while the propeller move the LED's to the next pixel position and they flash again. This is done with the divider.
RESULT
MECHANICAL ASSEMBLY
Mechanical assembly plays a vital role in proper functioning of this project. The display is scanned each time, by rotating the whole assembly in a circular path. The basic idea we developed is on our own, by implementing and modifying different ways to do this.
Following diagram shows the most reliable way, that we finally selected.
Here, one major challenge was how to bring +5V supply to the spinning circuit. We tried the same by adopting two-three different methods, but finally concluded on the method, as shown in the figure.
As seen in the diagram, one supply connection (GND) is provided
through the motor’s shaft. Other terminal (Vcc) is connected, by arranging a friction disc-brush arrangement. The brush keeps its contact with the disc, so that current can be supplied.
PCB LAYOUT
PRINTED CIRCUIT BOARD:
Much modern electronic system would be virtually impossible to package without incorporating printed circuit board. A printed circuit board popularly known as PCB, is a piece of plastic insulating board, on one side of which a complete layout diagram of an electronic circuit consisting of copper as conductive layer is printed by a special photo generation process.
On the other side of PCB are mounted electronic components like capacitor, resister, inductor and IC's. The metal conducting part serves as conducting medium for the electronic components that are assembled on the opposite side of board.
PCB MAKING
Take proper scale of components and according to such scale make component lay out of project circuit, on a paper. This layout is simple as well as small in size. Then draw mirror image of PCB layout.
STEPS FOR PCB DESIGNING
The following checklist uses the major area of concern in the process of PCB design:
a) Optimum size and shape of board should be ensured.
b) The substrate should be selected properly by taking into consideration its cost, mechanical properties and electrical properties.
c) Layout of conductor pattern should be taken care from cross talk, leakage, shielding, numbers of jumpers required and their placement.
d) Selection of conductor width, thickness and spacing should be done after analyzing their placement.
e) Proper productive coating should be selected.
f) Thermal consideration should be analyzed properly.
g) Proper mounting of heavy and unstable component should be ensured Most critical objective was to achieve pristine balance and overall good mechanical strength. For weight adjustment, we have provided one long screw, and weight can be attached or removed by adding / removing metallic bolts. If the assembly is balanced perfect, then it can achieve stability, and rotate at high RPMs too. This will improve the overall efficiency of this display.
TROUBLESHOOTING
Some Troubleshooting in Project :
1. DC motor is not rotating
~> Check the current flowing through the motor. If it reaches above 750mA, then the motor is short,Repeat it. In case of jamming, try to grease the bearing and shaft.
2. The display rotates, but not displaying garbage values.
~> Check the red strip (Interrupt) is in proper position or not. If not, adjust it.
3. Some or all LED not glowing.
~> Check the connector, that connects the LED module to the microcontroller.
~> Otherwise, check the continuity through each wire.
~> If the connections are OK, then replace the particular LED.
FINAL ORIGINAL OUTPUT OF THIS PROJECT
LED MODULE TURN ON
DISPLAY WORD "WELCOME TO EC"
ENJOY... ; )
