We will now look at another way of programming our palletizer using the PLC. How many ways can you program the PLC for the same function? The answer is a lot of different ways. You can have ten different programmers working on the same program and get ten different automatic control PLC programs. Sure they may have similarities but, they are all unique in their code within the PLC. As a system integrator, you will see many different ways of programming the PLC. We will now look at reprogramming our palletizer example using drum instructions. (Sequencer)
Last time we applied the five steps to PLC program development to a palletizer example. We will review our steps and then change our programming code to incorporate the drum instructions. Like our original example, we will allow the operator to change the layers of boxes you want on each skid. We will also add in this example a manual operation sequence to cycle through each of the steps for troubleshooting the program.
Developing the PLC program is a process that can be clearly defined. In our series on the five steps to PLC program development, we have done some similar practical examples.
PLC Programming Examples – Five Steps to PLC Program Development – Press
– Process Mixer
– Shift Register (Conveyor Reject)
– Paint Spraying
– Delay Starting of 7 Motors – Pick and Place
– Sorting Station (Shift Register)
Define the task: (1) – PLC Programming Example Palletizer using Drum
Using the PLC we will sort items on a conveyor using shift register instructions. We will apply the five steps to a PLC example program development of a sorting station. The program will use shift registers to track colored parts down a conveyor and sort depending on color into one of three locations.
Understanding how the PLC will scan and update your program is critical in programming and troubleshooting your system. Typically a PLC will solve your logic from left to right, top to bottom. The status of the memory from the previous rung, are available for the next rung to use. We will look at a few examples to determine how the PLC will solve logic to illustrate the above program scanning. Keep on Reading!