1.
Project Title: Propeller Clock
Student: Darren Rodrigues (BE ETC 2011 passout)
About the
project:
This project
displays the time in digital formaton a two
dimensional cylindrical display created by using a single column consisting of seven
LED’s in three different colors.
How it
works:
The column of
LED’s is controlled by a microcontroller PIC16F877A. To display a particular
digit the microcontroller divides it into a number of vertical sections and
each vertical section into seven units. For example the number ‘2’ is divided
into:
Then the
microcontroller takes each vertical section and turns on the LED column in the
same way as the pattern. It holds the LED’s in this state for a particular time
and then displays the next vertical section. Thus for the above example the
output would be:
By revolving
this vertical column around a parallel axis at sufficient speed the illusion of
the number is created. This is done by using a 12V DC motor. To get the display
right the revolution speed must match the speed at which the microcontroller
switches the LED’s. Thus the speed of the motor is varied by using a 555 Timer
based PWM circuit.
Blocks
of the project
Power
Supply
The entire
project requires a regulated DC power supply. For this a Bridge Rectifier
circuit is used. The Step-Down Transformer delivers 12V unregulated AC voltage
to the bridge rectifier. The unregulated output of the rectifier is filtered by
a 1000µF/16V capacitor. From here the supply is split to the motor control
circuit and the microcontroller circuit placed on the motor shaft. The motor
control circuit uses a 7806, 6V voltage regulator to get 6V regulated DC
voltage with peak output current of approximately 1A. The microcontroller circuit
takes the filtered 12V DC voltage through a commutator
system comprising of a copper brush and ring. Ground (0V) is available through
the metallic shaft of the motor. The voltage obtained from the ring is filtered
from contact spikes by a 470µF/25V capacitor and then regulated by a 7805, 5V
voltage regulator to power the onboard microcontroller circuitry.
Motor
Control
The motors
speed must be adjusted to the right value till the revolution speed of the LED column
matches the microcontroller output rate. Thus a 555 Timer based PWM circuit is
used. This circuit outputs a pulse wave of fixed frequency but the duty cycle
can be varied by changing the value of the potentiometer.
The output
current of the 555 Timer is insufficient to drive the DC Motor which will be
taking some load due to the weight of the microcontroller circuit mounted on
its shaft. Thus a driver is to control the motor based on the PWM output of the
555 Timer.
The driver
used is the TIP122 NPN Darlington Transistor. The maximum current that it can
handle is 5A. It is wired to the 555 Timer in a simple configuration. The
TIP122 has internal Back EMF protection diodes.
Microcontroller
Circuit
Since the
project intends to display a digital clock by using just seven LED’s a
Microcontroller is used to control the LED’s
The LED’s used
are common cathode (negative) bicolor LED’s i.e. a green and red LED in one
package with a common N terminal.
The microcontroller
used is PIC16F877A which has 8kb of serial programmable FLASH memory. Along
with this it has five I/O ports of which two 8bit ports are used. It also
features a 16bit Timer Module with interrupt capability.
The
Microcontroller maintains six RAM locations for each digit of the display. It
contains a lookup table for all decimal numbers. Each number is divided into
vertical sections as explained earlier and the microcontroller by accessing the
value present in each RAM location goes to the lookup table to access the
display code for each section. Thus it accesses the lookup table of each number
at least four or five times to complete displaying the entire number. Two ports
are used to load the code for each section. One port is connected to the red
side of the LED while the green side is connected to the other port. Common
terminals of all LED’s are grounded. LSB’s of both
ports are not used since these are 8 bit and only 7 bits are required for seven
LED’s. Thus the microcontroller runs through all six RAM locations for one
color. Then repeats the above for another color and then repeats it again for
both colors. Thus RED, GREEN and RED + GREEN = YELLOW are the three colors
obtained.
For
timekeeping a 16 bit timer is used to give an interrupt every half a second.
Half second interrupt is used to flash the time separator ‘:’ every second so
at occurrence of the interrupt the state of the separator is complemented.
After two interrupts the time value in the RAM location is incremented by 1
second.
2. Project Title: PRE PROGRAMMED PATH FOLLOWING ROBOT
DESIGNED, CONSTRUCTED AND
PROGRAMMED BY
CLIFFORD
RODRIGUES (BE ETC 2011 passout)
This robot is constructed using microcontroller PIC16F877A , a keypad
is interfaced to the micro controller , using which one can enter the required
path for the robot to follow and then to play the path . A motor driver IC
L293D is interfaced to the micro controller to drive the 12V dc motors.
The PIC16F877A is programmed to receive the entered path (forward,
backward, left and right) and store the path in a RAM location of the micro
controller, then later, when commanded to play the path, the micro controller
reads each data from the RAM location and drives the motors for the specified
path .For the LEFT direction the left motor is made to run reverse and the
right motor runs forward, and for the RIGHT direction the left motor is made to
run forward and the right motor runs
reverse.
Video link: www.youtube.com/watch?v=lYQnV37TZd8
3. Project Title: GOING WIRELESS THROUGH AIR AND
WATER
Student: Frenoy Osburn Madre Deus (TE ETC 2012
passout)
Communication is something that human life probably cannot
do without. Also many researchers are working towards wireless power transfer.
The theme for my project was “going wireless through AIR and WATER” and
prototypes have been designed for the same.
-LASER BASED COMMUNICATION-
Laser based communication has proved to be reliable in many
sub-domains of communication. Its advantages include non requirement of
broadcast rights and buried cables, speeds of several gigabits per second are
offered while being free from radio interference. It also can be used in the
digital communication.
The disadvantage is of course the line-of-sight requirement
between the transmitter and receiver; however this is a cleverly disguised
benefit, any attempts of tapping the laser beam would not go un-noticed as it
would reflect in the received signal, as opposed to radio broadcasting (FM and
the like) since many receivers can “listen into” a single transmitter without
being noticed, causing major privacy and security issues for transmissions. The
line-of-sight problem can be overcome using fiber optic cable if the
application provides for it; we thus would have a very basic form of optic
communication.
(Left) The prototype designed to
demonstrate Laser Based Communication. The yellow cardboard is a visual aid for
a better grasp behind the theory. Music has been transmitted from the media
player.
The transmitter is designed using the basic 741 op-amp and a
BD139 transistor whose output is fed to a laser diode (a modified commonly
available laser torch pointer).
The receiver is designed around LM386 with a suitable
transistor pre-amp. Higher power audio outputs can be achieved using audio
amplifiers like TDA2050 or similar chips. The above units where capable of
audio transmission with no noticeable loss, which was impressive taking into account the simplicity of the circuits.
This can be adapted to form a very basic means of fiber
optic communication. Applications include high speed communication between
computers at home or in office, communication links in A/C vents, on the
ceiling in hallways and passages. Other applications include temporary
connectivity needs as sporting events, conventions and also space
communication. Microcontrollers can also be used to send coded data or digital
signals. The possibilities are endless.
-WIRELESS POWER TRANSFER-
Wireless power transfer is a topic that many people believe
is really hard to achieve practically. But as they say “Something’s are worth waiting for” and more importantly “Worth trying for”. One approach to solve the problem is through inductive
coupling.
In a ‘crude’ way it can be visualized using the transformer
principle, whereby the primary and secondary windings are coupled through
magnetic flux. The current approach uses a 555 timer IC as an oscillator and
two resonant circuits consisting of an inductor and capacitor.
(Left) Block diagram for the prototype;
developed during initial stages of design.
The frequency chosen was 145 KHz and primary consisted of a
series resonant circuit containing 140uH and 8.6nF inductor and capacitor
respectively. The secondary is a parallel resonant circuit consisting of a
430uH/2.8nF. It is noted that a primary coil with larger diameter and fewer
turns compared to the secondary would be more efficient for my purpose.
(Left) The prototype demonstrating wireless power, the plastic
encloses the entire secondary circuit and the four LED’s are lit.
The set-up generated a voltage of around 4V at a distance of
couple of centimeters which was more than enough to power 4 LED’s. It proved
its worth even under WATER, something that could spark new highs in water proof
electronic gadgets.
The output obtained was more than satisfactory since the
circuit was designed around just the KHz range and inductor wire used was
ordinary magnet wire, much more efficient transmission would be possible with litz wire and higher frequencies.
Current research shows an efficiency of 40% which is bound
to increase. Applications aim at decreasing the cables needed in everyday life.
Also it can be used in waterproof devices where power is provided wirelessly.
This technology could very well be on its way to eliminate the traditional
power cable, something which was not thought possible until now.
(Left) Picture of primary and
secondary coil
and container filled with water.
(Right) Wireless power transfer
under water
4. Project
Title: Obstacle
Avoiding Robot
Student: Pratik Krishnanand Powar (BE ETC 2011 passout)
It is a 2 wheeled robot with a rear support wheel. It has
IR-Photodiode pair as an obstacle detector on its front end. Normally, the
robot moves in forward direction. When there is an obstacle in front of the
sensor, IR beam emitted by the IR LED gets reflected from the obstacle surface
and falls on the photodiode. This causes a change in the photodiode sensor
output. This change is sensed by the microcontroller (89s52) which controls the
motors. The robot stops moving in forward direction once the obstacle is
detected, moves away from the obstacle(both motors rotate in reverse direction)
by some distance and takes a turn by an angle (less than 180 degrees by making
the motors to rotate in opposite directions) and then starts moving again in
forward direction.
The advantage of using 2 wheels for locomotion is that it can a turn while standing at the same place in a restricted
space.
Since the robot is designed to move in a random manner with
the primary objective being avoiding obstacles, it can have varied
applications.
An example would be to use it used like a automatic robot
floor cleaner by attaching a cleaning unit(like a brush)and by varying the
degrees by which the robot turns each time it detects an obstacle according to
the area supposed to be cleaned.
Another example would be to use it for surveillance by
mounting a camera on it.
5. Project Title: DEVICE
ENERGIZER AND TIMER USING PIC16F877A
Student: Anup Shenai (BE ETC
2011 passout)
CONCEPT
In this project I have made a device energizer and timer,
which lets a user start a device at a particular time and run it for a time
which again can be specified by the user.
INSPIRATION
I wanted to listen to
music when I get up in the morning, at that time I didn’t have a fancy mobile
phone, all I had was a old tape recorder, so I decided to make a system which
will play music instead of the boring alarm ring, and the idea took shape. So now
if I connect a tape recorder to my invention I can play music at a specified
time and for a specified time
Apparatus
PIC16F877A (MICROCONTROLLER), NE555 (TIMER)
WORKING
·
NE555 timer is configured to operate in the astable mode with pulse duration of 2 sec
·
Two timers in pic16f877a timer1 and timer2 are used
·
Timer1 is used to specify the time after which
the device is to be energized,timer1 is configured in counter mode(so as to
count the pulses generated by pic microcontroller)
·
Timer2 is used to specify the time for which the
device is supposed to run
·
When the value stored in the counter is equal to
the value in the timer1 after counting the pulses from NE555,the device starts
and runs for a time specified by the
user
·
Timing of 24 hrs can be achieved using this
device, and timer can run continuously as long as there is uninterrupted power
supply
Figure1. when device starts Figure2 when the timer is running