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How to Build a Simple Circuit
and Signal in Morse Code
Josh Noble, Jen Bayly, Aneesh Deoras - Instruction Set, ENGL 202C, Section 018
Introduction
Morse code is a type of alphabet in
which letters are represented by a
series of long and short signals (dots
and dashes), where the signals are
either light, sound, or electricity. It is
an international code that can be
understood by any skilled observer
and, compared to voice, is less
susceptible to poor conditions.
Furthermore, no type of decoding
device is needed as long as you know
the code!
Figure 1: A replica Morse telegraph device
Morse code has a long history stretching back to the early 1800’s. It was first used
in conjunction with telegraphs. Telegraphs were devices that sent long-distance
messages through electrical currents traveling through wires between stations. On
the receiving end, these electrical currents produced a series of dots and dashes on
a paper tape. However, a method of translating these messages was needed, and
thus the Morse code was developed.
Radio communication soon made use of Morse code by adapting the dots and
dashes into sound, where the signals were sent as short and long pulses
respectively. This became especially important during World War II, where Morse
code was used to send messages between warships and naval bases, as well as by
warplanes. Additionally, until 1999, Morse code was the international standard for
maritime communication. Even the Titanic used Morse code to signal for help!
One important application of Morse code that everyone should know is how to
signal “SOS,” a distress signal used to ask for help. In order to do this, you will
first learn how to set up a simple circuit. This circuit will result in a lit up LED light,
and using this light you will send a Morse code message. Finally, you will be given a
chance to sign your own message in Morse code. From start to finish, give yourself
about fifteen minutes.
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Materials
You will need the following materials:
Morse code translation sheet (see
page 16) (1)
Breadboard with Velcro sticker
attached (1)
Red LED (1)
150Ω resistor (1)
Button switch (1)
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Pre-cut wires: long red (2), short red
(1), blue (2), white (1), yellow (1)
Battery pack with wire leads (1)
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How to Assemble the Signaling Device
Morse code can be sent through by
electricity, sound, or light. Light is a
particularly good choice because it
can be observed over great
distances without a physical
connection between the signaler and
the receiver. This set of instructions
will explain how to build your own
LED Morse code signaling device
using common electrical
components. The end result will be
an LED with a button on-off switch.
Please take note of the number
indicators along the long edge of the
breadboard, as these refer to the
rows. There are also letter
indicators along the short edge, as
well as (+) and (-), signifying
columns. These indicators will be
used as a coordinate system when
directing where to insert wires.
Column Letters
Figure 2: Definitions of Breadboard Layout
CAUTION
Improper wire placement may damage the circuit.
Ensure wires are in correct holes before placement.
Press all wires firmly into the breadboard.
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Assembling the Battery Pack Power Supply
These first steps will set up the battery pack.
1.
Attach the battery pack
to the breadboard using
Velcro.
The long side of the battery
pack should be parallel to
the short side of the
breadboard.
2.
1.
2. Insert one end of the
black wire into the white
terminal attached to the
battery pack.
Use the terminal hole that
is attached to the red wire.
3.
Insert the white wire
into the white terminal
attached to the battery
pack.
Use the terminal hole that
is attached to the black
wire.
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4.
Connect the wires just
inserted to the
breadboard, with the
white wire to the right
(+) column and the
black wire to the right () column, both in row
25.
5.
Connect one red wire
between the left (+)
column and the right (+)
column in row 30.
6.
Connect the other red
wire between the left (-)
column and the right (-)
column in row 30.
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7.
Check that the power
circuit matches the
following picture.
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Assembling the Signaling Circuit
These steps will set up the LED.
1.
Connect the yellow wire
between the left (+)
column in row 51 and 51a.
Ensure that the connection
and further connections are
secure by pressing down on
the ends of the wire.
2.
Insert the resistor
between holes 51b and
52b.
3.
Place one blue wire
between holes 52e and
58e.
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4.
Place the other blue wire
in holes 60e and 60i.
The wire will cross over the
center rut.
5.
Connect the LED between
hole 60j and right (-)
column in row 60.
The LED has two different leg
lengths. The longer leg
should face the blue wires
and the shorter leg should be
in the (-) column.
6.
Attach the button such
that its pins are in holes
57a, 58b, and 60d.
The pins will move down and
to the right, with two pins on
the upper half (closer to the
battery).
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7.
Check that the signaling
circuit matches the
following picture.
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Using the Signaling Device
The signaling device is set up such that the LED will be off when the button is left
alone. This is to prevent unnecessary power draw. If the LED does not turn on
when you press the button, please see the troubleshooting section.
1.
Hold the breadboard so that the components face upwards and
the battery pack is towards you.
This arrangement makes the circuit comfortable to hold and the button
easy to access.
2.
To turn the LED on, press the button.
The LED will be on during the dots and dashes of Morse code.
3.
To turn the LED off, release the button.
The LED will be off during the pauses between the dots and dashes of
Morse code.
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How to Send Morse Code
Each letter in the English alphabet corresponds to the series of dots and
dashes indicated on the Morse code translation sheet. Signing in Morse code
simply involves spelling out your message through the dots and dashes. In
this case, we’ll use light as our signal. Therefore, a dot is a quick flash of
light, whereas a dash is a longer flash. This section will walk you through
signing your own message, and then provide you with a specific example. It
is recommended that two people partake in these steps.
Sending Your Own Morse Code Signal
When signing in Morse code, there are a few points that you should keep in mind.
●
●
●
●
●
1.
The length of a dot is one unit. For our purposes, this will amount to the
time it takes to quickly press and release the button.
A dash is three units.
The space between parts of the same letter is one unit.
The space between letters is three units.
The space between words is seven units.
Write out your word or sentence
This will help you keep track of what you are trying to signal.
2.
Use the chart to find out the sequence of dots and dashes that
correspond to each letter.
When you go to signal, each dot will equal pressing the button briefly
(press and release) while each dash will equal pressing the button for
about a second (press and hold).
3.
Sign your message in Morse code.
Test your abilities by seeing if a partner can decode your message!
Print two copies of the attached Morse code translation sheet to simplify
decoding.
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Sending a Distress Signal
This example will explain how to send SOS, a distress signal. It consists of three
dots (S), followed by three dashes (O), and followed by three dots (S).
1.
Turn the light on and off three times in quick succession. Keep
off for about a second.
Press the button down to activate the light. This will signal the letter ‘S’.
2.
Turn the light on and off three times for about one second each
time. Keep off for about a second.
The length of these pulses should be longer than the previous. This will
signal the letter ‘O’.
3.
Turn the light on and off three times in quick succession.
This will signal the letter ‘S’. You’ve just signaled SOS!
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Troubleshooting
The LED won’t turn
on.





The LED becomes
hot after use.


The LED is dim.

Review all steps and ensure that wires are
inserted into the correct positions.
Press the button firmly in the center.
The LED only works in one direction. Its longer
leg should face toward the button.
Check the button orientation. The single pin
should face away from the battery pack.
Replace the batteries.
The LED will heat up only after frequent button
presses. Allow the LED to cool if the heat is
uncomfortable.
Review all steps and ensure that wires are
inserted into the correct positions.
Replace the batteries.
References
Morse Code History, White River Valley Museum and the Mary Olson Farm.
http://www.wrvmuseum.org/morsecodehistory.htm. Accessed 6 November 2012.
Figure 1: Automatic Telegraph Receiver by cliff1066TM on Flickr, used under Creative
Commons Attribution license.
Morse Code Sheet: Public Domain, Wikimedia Commons
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Figure 3: Morse Code Translation Sheet
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