Arduino code for the Arethusa watering system.
The hardware must be powered by a 12V power 'wall-wart' to ensure there is enough power to drive the pump.
The system will deploy a small dose of water to the target plant/s at the interval specified by the potentiometer.
The interval is measured in hours, and can be any value from 1 hour to 72 hours (3 days).
The time remaining until the next dose is indicated by the dots on the LCD.