The task at hand is to design and successfully implement a series of structured ladder logic codes using the TIA Portal/Step 7 software package that is capable to control a tabletop gantry crane apparatus. The desired program is meant to fully automate this crane. It can be designed from any methods available although, it will only be able to run once in a test like manner on the apparatus itself. All the necessary codes will be designed using simulators as there will be no opportunities to test the actual gantry crane apparatus.
The puzzle like task in made up of 6 disks varying in height stack in 5 possible locations. These disks are; 3 single height, 2 double height and 1 triple height. These six disks are initially placed in two piles on top of each other forming of stacks of 5 disks high, however the location and order of these disks stacks. The initial position of the stacks will be chosen just prior to the start of each demonstration by the tutor and in fact the program may be restarted with the stacks put in different positions.
The specific requirement is to “distribute” these disks, so that the triple height disk is placed by itself at the end horizontal position, the two double height disks are also placed by themselves at the next horizontal position and the 3 single height disks are all placed on top of each other in the middle position. Once this is completed, the program should flash all lights and the buzzer at a rate of 10 Hz, until the stop button is pressed.
The program may be run several times using the START & STOP buttons as previously described. To determine the correct operation and robustness of the program along with possibly different arrangements of discs prior to each START.[5]
The picture below shows an example of the to stacks placed at random. 
