K3ng Keyer Schematic [repack]

Because the K3NG keyer is modular, you can add or remove features at any time. For example, if you initially built the keyer without a display, you can later add a 20×4 LCD and simply uncomment #define FEATURE_LCD_4BIT before re‑uploading the firmware. The same applies to a keyboard, memories, or a CW decoder.

Symptom: Your radio keys constantly, except when you press the paddle. Cause: Your radio uses "Active High" keying (common on some homebrew rigs), but the K3NG schematic is "Active Low" (Grounded). Fix: Change the configuration in k3ng_keyer.ino from KEYER_ACTIVE_LOW to KEYER_ACTIVE_HIGH . No hardware change needed.

The simplest schematic uses a USB cable (5V). For portable operation, you need an .

Connect a normally-open momentary push button between a digital pin (typically D5) and GND. LCD / OLED Displays (Optional) k3ng keyer schematic

If your input power is greater than 5 V (e.g., 12 V), install the Mini‑360 buck regulator (U2) set to output 5 V. Place a jumper on JP1 only when you are supplying exactly 5 V externally. Always double‑check the voltage before connecting the Arduino Nano.

Connecting an Arduino directly to a radio's key jack is risky due to high voltages, reverse polarity, and ground loops.

For high-voltage tube rigs, the schematic may include an optocoupler (e.g., 4N35) or a relay to provide absolute galvanic isolation. Because the K3NG keyer is modular, you can

Always include 0.1µF decoupling capacitors near the power pins of your Arduino and optocouplers to filter out high-frequency noise.

For high-voltage or vintage tube rigs, it is highly recommended to use an optically isolated

To the uninitiated, a schematic looks like a plate of spaghetti. To a ham, it’s a map. But Elias had been depending on online "how-to" guides and forums, blindly copying pin connections without understanding why . He decided to strip it back to basics and actually read the schematic as if it were a story. Symptom: Your radio keys constantly, except when you

If your rig does not have a built-in sidetone, or you want to practice offline, the K3NG code features an audio output pin.

Uses a transistor (like a 2N2222) or an optoisolator to safely key the rig's PTT or Key line. Speed Control:

A digital output pin (e.g., D13) connects to the base/gate of the transistor through a 1k-ohm to 2.2k-ohm resistor. The collector/drain connects to the positive key line of the rig, and the emitter/source connects to the rig's ground.

: The preferred choice for a comprehensive build. The expanded flash memory and high I/O pin count allow you to run all options simultaneously. Understanding the Schematic: Key Circuit Modules

The schematic varies based on the features you want to unlock. Selecting the correct Arduino micro-controller is the first design choice: