Something related to a project i was doing for someone is to implement a control system for an oil burning water heater where you have to use a closed loop control system to control the oil pressure to the burner and the fan speed for the flue in order to maintain the water temperature at some set point under varrying loads.Oil burners are difficult to control at the best of times and can be very dangerous when they go wrong so there are lots of variables to monitor and complex ignition proceedures for the processor to handle as well as the PID control loop for the actual burner.