The simplest schematic uses a USB cable (5V). For portable operation, you need an .
Elias traced the lines on the paper with a highlighter. The schematic centered around the ATmega328P microcontroller. He realized he had been obsessing over features—memory buttons, LCD screens, PS2 keyboards—while ignoring the basics.
He had been tempted to just use a relay, but the schematic showed the optocoupler was faster and quieter. He built the output circuit exactly as drawn. He keyed the transmitter. The relay on the old rig clicked in perfect rhythm. k3ng keyer schematic
The core of the K3NG keyer is an Arduino board (Arduino Uno or Mega), which serves as the "brain." The schematic is modular, meaning you can build a basic keyer or a feature-rich unit. Core Components of the Schematic
Internal pull-up resistors are enabled via software, but standard schematics include a 0.01µF to 0.1µF capacitor from each line (Dit and Dash) to ground to filter out RF interference (RFI) straying from your transmitter. 2. Transmitter Keying Output Circuit The simplest schematic uses a USB cable (5V)
Most radios (Icom, Yaesu, Kenwood) have a "key line" that sits at +5V, +8V, or even +12V. The Arduino can only handle 40mA and 5V. Hooking it directly will release the "magic smoke."
The K3NG Arduino CW Keyer, designed by Anthony Good (K3NG), is the gold standard for amateur radio operators seeking a powerful, customizable Morse code keyer. This open-source project transforms a basic Arduino development board into a feature-rich CW powerhouse that rivals commercial units costing hundreds of dollars. The schematic centered around the ATmega328P microcontroller
| Feature | Description | |---------|-------------| | | Decodes dots, dashes, and spaces using standard Morse timing (Farnsworth/Paris). Shows decoded text on a 16x2 LCD or OLED. | | Input validation & error flagging | Lights an LED or shows “ERR” if the input is stuck high (short circuit), low (always closed), or if timing is inconsistent (e.g., dash shorter than dot). | | Sidetone with integrity beep | Generates audio feedback via a piezo – normal sidetone plus a distinct “error beep” when invalid input is detected. | | Serial output for debugging | Prints decoded characters + timing stats to Serial Monitor (helps tuning and troubleshooting). |
A 2N2222 or 2N3904 NPN transistor is required to interface the Arduino's 5V logic with the transceiver's keying circuit (which might be higher voltage). Wiring: Base: Connected to an Arduino pin (e.g., D11) through a Emitter: Connected to Ground (GND).
Never omit the transistor/MOSFET for keying the radio.