[Sebastian] is learning Morse code and CW radio, and of course he needed a telegraph key. Instead of using the terribly unergonomic paddle style key, he built a capacitive touch iambic key over the course of a few evenings.
An iambic key usually has two switches. When one switch is closed, it will transmit a ‘dit’. When the other switch is closed, it will transmit a ‘dah’. Instead of using mechanical paddles, [Sebastian] brought his iambic key into the 21st century by using a touch sensor. An ATtiny45 measures the time it takes for a single metal plate to fully charge. It’s the same idea behind the wonderful Arduino CapSense library.
This isn’t the first capacitive-touch iambic key we’ve seen; this little guy is just a pair of metal contacts and resistors that plug right into an Arduino. With an ATtiny45, [Sebastian]’s build is a full-blown iambic telegraph key that plugs right into his CW rig. You can check out the walk through of the project along with [Sebastian] trying out his iambic key after the break.