I have built an ultra-compact DIY iambic Morse code keyer for a dual-paddle key based on the work of PA3HCM. The keyer uses an Arduino Uno and a few components such as a potentiometer for adjusting the words per minute (WPM), a small speaker, some resistors, and LED indicators. I housed the circuitry in a neat enclosure and added some terminals (for signal line-out and an auxiliary connection for a second key). I then attached a dual-paddle key onto the enclosure, making the keyer and key setup a very portable trainer for code practice.
Night Sky in Focus Astronomy and Amateur Radio © Anthony Urbano (Manila, Philippines)