Two common variations appear in K3NG schematics:
Additionally, the group (k3ngkeyer) has user-contributed KiCad and Eagle files. k3ng keyer schematic
The brain is typically an (ATmega328P) or a Mega 2560 for more I/O. The schematic shows: The schematic shows a : | Arduino Pin
You cannot key a 100W tube transmitter directly from an Arduino pin (3.3V or 5V). The schematic shows a : Its schematic is not just a wiring diagram;
| Arduino Pin | Function | Schematic Detail | |-------------|------------------------|-------------------------------------------------| | D2 | Paddle Dit | 10k pull-up + 1N4148 to +5V | | D3 | Paddle Dah | Same as D2 | | D4 | LCD RS (if parallel) | Direct connection | | D5 | LCD Enable | Direct connection | | D6 | LCD D4 | Direct | | D7 | LCD D5 | Direct | | D8 | LCD D6 / PS/2 Clock | Shared? Check compile options | | D9 | LCD D7 / PS/2 Data | Shared | | D10 | Key Output (transistor)| 1k base resistor + 2N2222 + 1N4007 | | D11 | Sidetone out | To LM386 input (via 10k pot) | | D12 | PTT output | Second transistor stage | | D13 | Status LED (built-in) | Optional | | A0 | Speed pot | 10k pot + 0.1µF cap | | A1 | Command pot (mode) | Optional | | A4 (SDA) | I2C LCD / Rotary Encoder| 4.7k pull-ups | | A5 (SCL) | I2C LCD / Rotary Encoder| 4.7k pull-ups |
In the world of amateur radio, the ability to send clean, precise Morse code is paramount. While commercial keyers are plentiful, the open-source —designed by Anthony Good (K3NG)—has become the de facto standard for Arduino-based CW generation. Its schematic is not just a wiring diagram; it is a masterclass in balancing legacy hardware compatibility with modern microcontroller flexibility. This piece dissects the core architecture of that schematic, explaining why each section is critical for producing perfect "fist" quality code.