Best PLC Programming Practices 1 (using multiple outputs with the same address)

Recently this subject came up and even though a PLC will let you use the same output address (location) several times in the program its a bad habit to get into or bad idea to do so, for many reasons such as and this is one of them, most people in the industry when troubleshooting a machine they will look for the output in the program and work backwards, well if you have several places in the program that this can happen its very hard to find the issue.

Troubleshooting 101 (this is how I do it) Lets say... you have a machine that the motor does not run, you get out your meter and check the contact and you dont have power pulling in the contact, you check the LED on the PLC and yep... its off, so now hook up the laptop and search the output and you find 1 output, well simple just work backwards until you find what is stopping that output from energizing, 99% of the time its an input but starting at the output is the fastest way to find that input.

So lets say the logic is LARGE... there are so many conditions that this one output will come on or needs to come on that its impossible to not have more than one rung, use the PLC memory bits, every PLC has internal holding registers so make several rungs where your scenarios playout and make a holding register true (on) see the attached PIC, we made a simple program in a CLICK PLC where the first 3 rungs make C1, C2 and C3 turn on and then use the 4th rung where all three of the holding register outputs are used to energize the output Y001 and since they are parallel anyone of the three different holding registers will make the rung true.