March 3, 2011 [R-B] designed a 555 timer circuit to scan a keypad. Keypads are common interfaces for small projects and require row and column scanning by a microcontroller.

The timer is based on an Arduino Pro Mini and an HX1230 LCD with a simple piezo speaker for audible alerts.

The OONTZ uses a 3D printed case, a 16 button keypad, an Arduino Leonardo, a monochrome driver, and a few potentiometers. It's actually a pretty simple thing to build yourself provided you can the ...