Morse code was one of the earliest forms of encoding telecommunications messages, and still remains one of the most versatile. While other communications methods certainly perform better under the appropriate conditions, Morse code can be transmitted in a number of different situations and by varying means. It can be transmitted via telegraph (electric current), sound, radio, or light. This Raspberry Pi-based device is capable of transmitting Morse code over miles using light.
This project was built by the owner of DMTechTalk, who developed it for a client that was looking for a way to transmit Morse code via light. The client wanted to be able to type in a message in plain text, and have the device translate that message into Morse code. They wanted the light to be bright enough to be visible for more than a mile, wanted the device to be self-contained, portable, and water resistant, and to be able to transmit Morse code at between 5 WPM (Words Per Minute) and 75 WPM. Those are some pretty specific requirements, but a Raspberry Pi single-board computer (SBC) turned out to be perfect for the job.
The Raspberry Pi 3 Model B is housed inside of a Seahorse SE-720 waterproof protective hard case. Also inside of that case is an 11.6” 1080p IPS LCD display, a Logitech K400 Plus wireless keyboard with a built-in touchpad, and everything needed for power. That power was a particular concern, because the LED—a 100W truck spotlight that can consume up to 8 amps of current—requires between 12V and 30V of DC. The Raspberry Pi and other components can only accept 5V of DC power, which means a simple battery pack wasn’t sufficient.
The solution was to accept 12V from a car’s electrical system, but to still account for the 24V that some heavy duty trucks produce. That provides power to the LED spotlight through a fast-switching solid state relay. Power from the vehicle is reduced to 5V a buck converter voltage regulator for the Raspberry Pi. The Raspberry Pi controls the LED spotlight’s relay to transmit Morse code. A custom application was written in C to translate plain text into the relay controls that adhere to Morse code timing. It was expensive to build at about $800, but the result is a portable device that can easily transmit Morse code over long distances using light.