Morse Code Transmission by Laser

In this project I present to you the construction of a small device that decodes the light signals received in Morse code and displays the characters in the letters of the alphabet on a display. This technique was often used in the world war II between battle submarines or cruisers.

1.Arduino Nano

2.ST7735 or 64X128 Oled display

3.Mini solar panel(max voltage 5v)

4.passive buzzer

5.resistor 22...33k (optional)

6.Visuino software

7.Arduino IDE

8.Breadboard and jumper wires

Two types of display can be used in this project, an SPI ST7735 model or an Oled 64x128 model. Both schemes are attached, for each option chosen.

The electrical diagram shows the presence of an optional resistor. It is installed when using the device when the light level is high. Used in the evening or at night, this resistor is not mounted. Its value varies depending on the mini solar panel used and varies between 22...33k.

• Attention: the solar panel can be recovered from various toys, but it must not exceed the voltage at the 5-volts terminals in strong light in order not to destroy the Arduino board.
• You can also use a panel with a higher voltage at the terminals by using a resistive divider between its terminals and the Arduino board, but a mini solar panel is easy to find and most have a voltage of less than 5 volts.
• Notice in the electrical diagram the connection of the solar panel with the Arduino, the + terminal to GND and the - terminal to D2

• The code is compiled in the Visuino program. Find the code in Visuino and IDE format in the attachment. If you want to edit the code, you will have to install the program. If you want to load from the Arduino IDE, copy the "Mitov" folder that contains the "h" files into the library folder as you can see in the images or video.
• The code for Visuino only works in the attached version because the project is an older, modified project. The code's working principle is simple: A generator sends pulses as long as the solar panel is illuminated. Depending on the time it is illuminated and depending on the set frequency of the generator, it sends a number of pulses that are read by two comparators. When the number of pulses is less than 6, the comparator reads it as "dot" when the generator sends a number between 6 and 20, the comparator reads it as "lines".
• Furthermore, a series of logical AND gates changes its state from "false" to "true" depending on the number of lines or points and their order. Each logic gate is assigned to a letter of the alphabeth
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• The logic gates command a series of "char" values ​​that are sent to the display and shown as text on the screen, thus obtaining the decoding.
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• So, if you are more experienced in Morse code, you can increase the frequency of the generator for a higher transmission speed. At the same time, slightly reduce the delay time of the "Delay" component, components circled in red in the attached photos.
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• If you don't want to make changes in the code, load the code into the Arduino by choosing the correct port and the "Old Bootloader" option from the Visuino or Arduino IDE program. Find both code formats in the attachment.

• Find the folder with the "h" files and the functional version of Visuino, here: https://app.box.com/s/m8vdzf3gefd0hrh01si0tor21ut6yr2b

• As soon as the electrical connections have been made, the device is ready for operation. If it is used in the evening or at night, the optional resistance may be missing.
• The communication distance can exceed 1km in the case of using a stand for the laser and a solar panel measuring about 20-30cm.
• The longer distance between characters is interpreted by the device as a "pause" and when the screen is full, send 5..6 points to the panel and the device will reset
• You can use a flashlight instead of a laser beam, but the communication distance decreases significantly.
• The device only displays the letters of the alphabet, numbers and punctuation marks, subject to a future update

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• ATTENTION: THE USE OF A LASER BEAM REQUIRES PRECAUTIONARY MEASURES! DO NOT LOOK DIRECTLY INTO THE LASER BEAM, YOU CAN BE HURT! DO NOT LEAVE THE LASER BEAM OUT OF REACH OF CHILDREN, USE THE DEVICE WITH A SMALL FLASHLIGHT IN THIS CASE!

Thank you!