K3ng Keyer — Schematic

K3NG Keyer Schematic — Full Post

Minimal Parts Addition

• 0.96" I²C OLED ($5)
• Passive piezo buzzer ($1)
• Optional: 1 red LED + 220Ω resistor (for error indicator)

No major changes to the original k3ng hardware required – just 4 extra wires and a small firmware update.

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2.3 PTT Output

• Separate transistor (e.g., 2N3904) or same optoisolator.
• Connected to radio’s PTT input (usually needs ground closure).
• Often programmable as CW/PTT delay in firmware.

B. Full-Featured "Shack Keyer"

• MCU: Arduino Mega 2560 (for pin-rich environment)
• 16x2 I2C LCD
• Rotary encoder (with built-in push button) for menu navigation.
• 4 message buttons + command button
• Separate PTT and KEY outputs (with optoisolation)
• Audio amplifier (LM386) with headphone jack.