I you know a bit about amateur radio probably you’ve heard or seen a telegraphic key. It is a small device with two push buttons “if we can say so” to transmit ‘dit’ and ‘dah’ signals that are used t encode information in to Morse code. Sebastian found them unergonomic and build one using capacitive touch based iambic key.
As a base for this project Sebastian used Attiny45 microcontroller which measures a time taken to charge sensor paddle. There is no other circuitry used as only detection of on and off values are needed. The internal pull up resistor is used to charge cap and then measure voltage with same pin. For more information about this process refer to Arduino CapSense library.