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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. 2 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) 3 Pre-cut wires: long red (2), short red (1), blue (2), white (1), yellow (1) Battery pack with wire leads (1) 4 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. 5 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. 6 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. 7 7. Check that the power circuit matches the following picture. 8 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. 9 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). 10 7. Check that the signaling circuit matches the following picture. 11 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. 12 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. 13 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! 14 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 15 Figure 3: Morse Code Translation Sheet 16