Shading Controller

 In normal operation the controller monitors the positions of the two curtain motors 
by the analog inputs.  
  If the motor positions deviate by more than a set amount, the controller will adjust the
curtains to be equal.
  If the motor positions deviate by more than the allowed amount for longer than 
the delay period, the alarm relay will go off, the output signal to both motors 
will be cut, and the corresponding fault relay will activate.