A CW Automatic Keyer

You may be thinking: Just what the world needs, another Arduino-based keyer. True, there are dozens of circuits for CW keyers based on several of the Arduino family of boards. However, using an Arduino board for something as simple as a CW keyer is an H-bomb-to-kill-an-ant approach to the problem. You could probably design your own keyer circuit using just three or so I/O pins. For that reason, we’re going to depart slightly from our usual Arduino project and consider using one of the minimal Atmel μC chips: The ATtiny85.

Another wrinkle we’re going to use to make our keyer a little different is that it uses capacitive reactance to activate the keyer circuit. This means you do not need to implement (or buy) a set ...

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