While not in the classic schematic, the "Next Generation" K3NG adds an ESP8266. The schematic routes RX/TX (Pins 18/19) to the ESP. This allows you to key via a web browser.
For total electrical isolation between the Arduino and the rig, use an optocoupler (like the 4N25 or 4N35). The Arduino drives the internal LED, which optically triggers the output phototransistor, keeping your transceiver safely isolated. 3. Sidetone Audio Circuit
If your rig doesn't have a built-in sidetone, or you want to practice offline: k3ng keyer schematic
This circuit often uses a switching transistor, such as the 2N2222 , or an optocoupler to isolate the keyer from the radio’s circuitry.
Required if you want to enable all software features simultaneously (e.g., display, ethernet, extensive command sets) due to its larger flash memory. While not in the classic schematic, the "Next
An onboard sidetone lets you monitor your sending without needing the transceiver’s audio. The simplest schematic approach is to drive a small speaker or piezo buzzer directly from a microcontroller digital pin. To get better volume and tone quality, many schematics add a transistor stage and a volume control potentiometer. The , for example, includes a 2N3904 transistor to drive the speaker and a 500 Ω trimmer to adjust the volume.
The Dit and Dash lines connect to individual digital I/O pins (commonly D2 and D5, though customizable in the code). The paddle's common ground connects to the Arduino GND. For total electrical isolation between the Arduino and
: Connect the Arduino's hardware TX/RX lines to a USB-to-Serial chip (like the CH340 or FTDI) to interface seamlessly with logging software like N1MM or HRD.
Building your own keyer from a schematic is a rewarding DIY project that results in a piece of gear perfectly tailored to your operating style. By understanding the schematic's blocks and carefully following build instructions, you can successfully construct a versatile K3NG keyer for your station.