Technologist Keith has documented his LED calculator - based around an Arduino, a rotary encoder, LCD and other circuitry. With it the user can set the LED parameters with the required data being displayed on the LCD. Purists will say nothing beats simple arithmetic and a data sheet, but it's fun to make an electronic version, for example:
For more information, code downloads and design history - check out Keith's bloghere. And we're on twitter and Google+, so follow us for news and product updates as well.
When making your own Arduino projects with a character LCD - save time and move forward with the Freetronics LCD & Keypad shield which contains a bright 16x2 character LCD and five buttons that can be read from only one analog input pin: