Download digital mini project

1.0 Objective and scope of work:

To design the lighthouse and make a structure of that as a practical
design in the lab.

To use some materials and components to build this system and to
make it real project.

Doing this project is to accomplish the scope of work which is to
navigate for pilots at sea or on inland waterways.
2.0 Methodology:
Power is on
Pulses with a specific width are provided to the counter using the timer.
counts pulses provided by the timer with (Q0 , Q9) outputs.
Timer
Counter
are connected to some specific outputs (Qs) or pins of the counter to get
Diodes
some specific sequences.
are connected together to a transistor to amplify the current
Diodes
to power the LED
will on according to the sequences specified by the diodes connected to
LED
the counter.
3.0 Results and discussion
3.1 Results
The output of our circuit can be shown through the LED we have used as our result’s
indicator. The LED will be emitting in a specific sequence which is shown in the
following waveform :
The connection behind this specific waveform is going to be explained later.
In our project we have used the following list of components :

resistors: 470, 2k2, 22k, 100k

capacitors: 0.1µF, 1µF 16V radial

diodes: 1N4148 ×4

transistor: BC108 (or equivalent)

1M preset, horizontal

6V 60mA MES lamp

MES lamp holder

555 timer IC, such as NE555

4017 counter IC

DIL sockets for ICs: 8-pin, 16-pin

on/off switch

battery clip

9V battery box for 6 AA cells

Strip board: 19 rows × 21 holes
The NE555 timer is an astable operated timer and its circuit internal diagram is shown
below:
Initially when the power is turned on, the capacitor (C1) is uncharged and thus the trigger
voltage pin(2) is at 0 V. This cause the output of comparator B to be HIGH and the
output of comparator A to be LOW, forcing the output of the latch, and thus the base of
Q1, LOW and keeping the transistor off. Now, C1 begins charging through R1 and R2, as
indicated in figure shown above. When the capacitor voltage reaches 1/3 Vcc, comparator
B switches to its LOW output state; and when the capacitor voltage reaches 2/3 Vcc,
comparator A switches to its HIGH output state. This resets the latch, causing the base of
Q1 to go HIGH and turning on the transistor. This sequence creates a discharge path for
the capacitor through R2 and the transistor, as indicated. The capacitor now begins to
discharge, causing comparator to go LOW. At the point where the capacitor discharges
down to 1/3 Vcc, comparator B switches HIGH; this sets the latch, making the base of Q1
LOW and turning off the transistor. Another charging cycle begins, and the entire process
repeats. The result is rectangular wave output whose duty cycle depends on the values of
R1 and R2. By selecting R1 and R2, the duty cycle of the output can be adjusted. Since
C1 charges through R1+R2 and discharges only through R2, duty cycles approaching a
minimum of 50% can be achieved if R2 << R1 so that the charging and discharging times
are approximately equal. An expression for the duty cycle is developed as follows. The
time that the output is HIGH (tH) is how long it takes C1 to charge from 1/3 Vcc to 2/3
Vcc. It is expressed as :
tH = 0.7(R1+R2)C1
The time that the output is LOW (tL) is how long it takes C1 to discharge from 1/3 Vcc
to 2/3 Vcc. It is expressed as :
tL = 0.7R2C1
the period, T, of the output waveform is the sum of th and tL. It is expressed as :
T = 0.7(R1+2R2)C1
In our project by adjusting the variable resistance to a specified value we have set the
period (T) to one second (1S) as calculated below :
T = 0.7(R1 + 2R2)C1
1 S = 0.7(100K + 2R2)(1X10^-6 F)
1 S = 0.7(100000 + 2R2)(1X10^-6 F)
1 S = (70000 + 1.4R2)(1X10^-6 F)
1 S = 0.07 S +(1.4X10^-6 F)R2
R2 = (1 S – 0.07 S)X10^6/1.4 F
R2 = (0.93 S)X10^6/1.4 F
R2 = 930000 S/1.4 F
; where ,
Second = Ohm x Farad
R2 = 664285.7143 Ohms
The 4017 counter that we have used has the function of controlling the one-second period
sequence provided by the timer. The operation done in our project is that we have
connected outputs Q0,Q1,Q3 and Q4 to four diodes connected to a 108 transistor, the
transistor is then connected to a resistor before the current reaches the LED and the turns
it on. Choosing the outputs of the counter depends on the sequence required. The outputs
mentioned above indicates that we have activated them only, others are not used, and we
can see that it is logic when QO represents one second, another second is followed by
connecting from Q1, the total time of the two outputs is two seconds so the LED will be
emitting for two seconds,Q2 is not used and we that each output is representing one
second (illustrated above) so the LED will be turned off for this one second, after that Q3
and Q4 are used so the LED will be turned on for another two seconds, Q5 to Q9 are not
used so the LED will be turned off for five seconds. The sequence repeats itself until the
power is turned off.
3.2 Discussion:
Our mini project has been designed for a model lighthouse to flash a lamp in a simple
sequence: two flashes of 2s with a short gap of 1s, followed by a longer gap of 5s before
repeating the sequence. We have connected the circuit as shown in the circuit diagram
attached with the proposal submitted previously. The 555 timer is connected as an astable
to provide clock pulses for the 4017 counter. We have controlled the pulse width the
timer provide the counter using the 1M preset (horizontal)(variable resistance), by
varying this variable resistance to a specified value which has been calculated above we
could approximately fix the pulse width to be (1 second), this specified value has been
calculate according to the following formula : T=0.7(R1+2R2)C1, these clock pulses
will be then supplied to the 4017 counter, this counter has ten outputs (QO to Q9) and
each and every one of them becomes high (‘on’) in turn as the clock pulses are received.
We only have used outputs Q0,Q1,Q3 and Q4 and they have been combined with diodes
to produce the flash sequence. A transistor has been used to amplify the current to power
the lamp, or the LED. In order to make easy for us to analyze and maybe to detect and
discover the errors we tried to make the circuit as tidy and neat as we could, this has been
done by using different jumpers colors, we have used red-colored jumpers to connect
from the components to the ground, yellow-colored jumpers to connect from the
components to the power supply which is the 9V battery, and gray-colored jumpers for
the internal connection between the components and that was really powerful for
detecting the connection failures. Each and every experiment must have errors and for
sure we have faced some such as muchness of the jumpers, the impossibility of
controlling the variable resistance to the truly calculated value, and other errors that were
out of our control (random errors) such as uncontrolled variables, for example
temperature and external noise.
Conclusion :
All objectives were obtained and satisfied, the lighthouse circuit design was constructed
successfully, result as a specified desired waveform that was shown using our indicator in
the circuit which is the LED was correctly obtained. Using the Multisim was also an
advantage to show how the circuit works in a software program in addition to the
hardware that was constructed. MultiSIM is a chief competitor with the Cadence OrCAD
package, another tool for electronic schematic design and simulation. MultiSIM now
features a microcontroller module called MultiMCU, as well as integrated import and
export features to National Instruments' PCB layout software, Ultiboard. The light
emitting diode display is very useful for displaying how the project works and it can be
found easily.