The principle of the lights controller is to provide an automated function; of activating and deactivating specific lamps used in reptile vivariums and fish aquariums.

 

The controller maintains a 24 hour clock, and stores the hour and minutes values for sunrise and sunset. When the clock reaches either sunrise, sunset or one hour past these times, a series of triggers are initiated to 'switch on' or 'switch off' specific lamps.

 

The microcontroller used is the Microchip PIC18F14k22 microprocessor running at 5v. Internal processor clock is 8 MHz, and Timer1 (auto incrementing register used to maintain the clock) is controlled via an external 32.768 kHz quartz crystal. This microcontroller provides all the control functions of the unit. The microprocessor outputs the time and day period to a backlit 8 column, 2 row alphanumeric display (HD44780) , reads the user input buttons (Menu/Enter, Increase and Decrease), drive a series of status LEDs (Day lamps and heat/blue lamps active as green and yellow respectively) and provide a 3 - 5v control signal for the solid state relays.