How to Build a Simple Arduino Morse Code Transmitter From Scratch

Building a simple Arduino-based Morse code transmitter from scratch is a fun electronics project that can be completed in just a few hours. With minimal components, I can make a device that allows me to transmit Morse code wirelessly using radio frequency (RF) signals.

What I Will Need

• An Arduino microcontroller board (Uno, Nano, Mega, etc.)
• A Morse code key or button
• A resistor (1kΩ to 10kΩ)
• A NPN transistor (2N2222 or similar)
• A length of hookup wire
• A 433MHz RF transmitter module
• A 433MHz RF receiver module (optional, for receiving transmitted signals)

How It Works

The Arduino acts as the brains of the transmitter, reading input from the Morse code key and turning the radio transmitter on and off rapidly to produce the Morse code patterns.

The NPN transistor acts as a switch, allowing the Arduino to control the higher current draw of the transmitter module. When the Arduino sets a pin high, it allows current to flow through the transistor to the transmitter's data pin, turning it on.

The resistor is used to limit current flow and prevent damage to the Arduino or transistor. The RF transmitter module generates the 433MHz signal which can be picked up by a receiver.

Circuit Diagram

Here is a circuit diagram showing how to connect the components:

The Morse key or button connects to a digital pin on the Arduino, the transistor base to another pin, and the emitter to ground. The collector connects to the data pin on the transmitter module.

Steps to Build

1. Prepare the Components

• Solder header pins onto the RF transmitter module to make connections easier.
• Cut and strip both ends of hookup wires to make connections.
• Insert the Arduino board into a solderless breadboard.

2. Connect the Morse Key

• Connect one pin of the Morse key or button to Arduino pin 2.
• Connect the other pin to ground (GND) on the Arduino.

3. Connect the Transistor

• Connect the collector pin to the data pin on the RF transmitter module.
• Connect the emitter pin to Arduino GND.
• Connect the base pin to Arduino pin 3 through a 1kΩ resistor.

4. Connect the RF Transmitter

• Connect VCC on the transmitter module to Arduino 5V pin.
• Connect GND to Arduino GND.

5. Load and Test the Code

• Install the VirtualWire library.
• Load the sample Arduino Morse code sketch to the board.
• Open the serial monitor and press the Morse key or button to transmit letters.
• Hold the key down slightly longer to transmit words spaced apart.

If using a receiver module, tune it to the same 433MHz frequency and verify the transmissions. Now I have a wireless Morse code transmitter to practice sending messages!

Going Further

To take this project further:

• Add a buzzer to audibly play the code being transmitted.
• Create messages using a string variable instead of single letters.
• Add a potentiometer to control transmission speed.
• Use a photoresistor and LED to detect received signals.
• Print received messages on an LCD display.

With just a few basic components, the Arduino is a handy platform for learning Morse code and radio communication. This simple transmitter is the perfect starting point before moving on to more advanced projects! Let me know if you build your own.