Use an NPN transistor. The base goes to the Arduino (via a resistor), emitter to ground, and collector to the transmitter key jack.
A 3.5mm mono jack connected to the drain (for MOSFET) or collector (for BJT) of the transistor. 4. Optional but Recommended Features k3ng keyer schematic
Optional LCD/I2C displays, potentiometers for speed control, and pushbuttons for memories. Basic K3NG Keyer Schematic Diagram Use an NPN transistor
Connects to Digital Pin 2 (Internal pull-up resistor enabled). emitter to ground
A permanent, low-cost solution. You can solder a female pin header socket for an Arduino Nano, solder your 2N2222 transistor circuit, and run wires to 3.5mm jacks for your paddle and transmitter lines.
Connects to Arduino Digital Pin D5 and GND .