Specifications

RSLinx – Training Guide C - 15
Example & Strategies for a Debug File
As a brief example, consider the following…In normal machine operation, to manipulate a
part, an output from the programmable controller might open a solenoid which extends an
arm attached to a hydraulic cylinder. As the arm reaches the end of its travel, a limit switch
trips which de-energizes the output, which closes the valve and stops arm travel (if all goes
well). Now that the arm is "in position" the machine continues through its cycle.
That would be the way that the system would operate if there was a PLC-5 processor, I/O
racks, power supplies, a valve, etc.
With Emulation, checkout can be more convenient, and even more thorough (it can be
done in your office instead of the shop floor). It does, however, require a rather thorough
understanding of your machine operation since you must also build the debug files that will
"respond" to the main ladder logic. This is far easier than it sounds because when you
developed the original software, you probably had a type of script in mind. A typical script
might have gone something like this:
"First, the output is energized which energizes the solenoid which starts the arm moving.
The arm continues to move for a few seconds, finally tripping the end-of-travel limit
switch. When the end-of-travel limit switch is tripped, the arm should stop and the heater
should come on."
Now, as you begin developing the "Debug" file, which is what actually models the process,
you visualize what sequence of events the machine would normally go through (as you did
when you wrote the actual control logic). The Debug file in our example must recognize
when the Robot Arm Solenoid output is energized, and introduce some delay while the arm
would be extending, and then at the conclusion of that delay, turn on an input bit that
simulates the limit switch closing.
The Debug file rungs, and the instructions that would be programmed on those rungs, are
first described and then pictured on the following page: