K3ng Keyer Schematic Repack [patched] May 2026

The Ultimate Guide to the K3NG Keyer Schematic Repack: Organizing Open-Source Morse Code Excellence

Key Improvements in This Repack

| Original K3NG Issue | Repacked Solution | |---------------------|-------------------| | Paddle inputs share ground with high-current key line | Separate analog/digital ground with a ferrite bead | | No pull-up resistor values specified | 10k for paddles, 4.7k for I2C, 1k for transistors | | Display wiring changes with LCD type | Standardized on I2C (only 4 wires: VCC, GND, SDA, SCL) | | Sidetone output is just a pin | RC filter (1k + 10µF) + buffer transistor before LM386 |

Sheet 3: User Interface (Minimal & Maximal)

Instead of one messy diagram, two sub-blocks: k3ng keyer schematic repack

• Minimal: 3 buttons (Tune, Command, Function) + 1 pot for speed.
• Maximal: 16x2 LCD via PCF8574 I2C backpack (saves 6 wires), rotary encoder with hardware debouncing (74HC14), and a 3-LED status bar.

2. The Input Protection Stage

A professional repack includes a small circuit to protect the Arduino pins from static (ESD) and RFI. The Ultimate Guide to the K3NG Keyer Schematic

• Schottky diodes (e.g., BAT54S) to clamp voltage.
• 1k-10k pull-up resistors on paddle inputs.
• Optional optocoupler for the key output to isolate the keyer from high-voltage tube transmitters.

2.1 The Core Microcontroller Section

The heart of the repack is the microcontroller pinout table. A good repack will include: Minimal: 3 buttons (Tune, Command, Function) + 1

• Arduino Uno / Nano (ATmega328P) pin column
• Arduino Mega 2560 pin column
• Teensy 3.2/4.0 column (if supported)
• For each key function: CW output, Paddle Left, Paddle Right, Dit/Dah memory, Speed pot, PTT out, Beacon enable.

Example entry from a repack:

| Function | Uno/Nano Pin | Mega Pin | Firmware #define | |----------------|--------------|----------|-----------------------------| | CW Output | D13 (or D8) | D13 | #define cw_output_pin 13 | | Paddle Left | D3 | D3 | #define paddle_left_pin 3 | | Paddle Right | D2 | D2 | #define paddle_right_pin 2| | Speed Pot | A0 | A0 | #define speed_pot_pin 0 |

A repack typically presents this as a large table or multi-page diagram with clear cross-references.