Repurpose a Cash Register into a Hotkey Keypad with Arduino
One of the awesome things you can do with Arduino and compatible boards is use them as the heart of recycling older technology into something fun and different - or even useful.
An excellent example of this has been demonstrated by Instructables member Fwacer who has salvaged the mechanical keyboard from an old cash register, and converted it into a USB keyboard for PC hotkey use.
This involved determining the keypad circuit, and then connecting it to an Arduino Pro micro-compatible board via a 74HC595 shift register. The use of Arduino HID USB example code takes care of the PC interface. Once cleaned up, the keyboard looks great:
For complete details, please check out the project Instructable page. And if you're interested in doing this yourself, PMD Way can help you with the parts, such as: