LogixPro Scan Time

A quick question:



I have been playing with the LogixPro Sim for some time now and have found some programs to be very dependent upon the scan speed setting. Does anyone else have this problem or understand why?



For instance, I have completed the bottle plant project but my program only works correctly at about the 75 percent scan speed setting. Just a few clicks higher or lower results in various parts of the program to loose sync causing broken bottles. Different speeds cause different bad effects. Not sure if it adjusts the timer clocks differently then say the belt speed.

Any help is appreciated.

Ray,

The Bottle Line Simulation program is sensitive to the overall speed of the line. The main reason is that the Fill Tubes work at a set speed, so if you speed up the conveyor, the Filler will not be all the way retracted before the bottle starts to move again.

The "scan" time on the LogixPro is user-adjustable. For a real system, the scan time is not directly adjustable, but depends on the size of the program and how many subroutines and other interrupts are used. This scan-time adjustment is merely a way to demonstrate that the actual real-life speed of various equipment (relative to the PLC scan time) is a factor to consider when writing a PLC program. Instead of scan time, you should view this setting as an equipment speed setting. The thing you are supposed to learn from this is: In general, the faster equipment has to run, the more likely something is to break or malfunction.

By the way, I have not been able to figure out how to make the Bottle Line run at 100% on my XP computer. On my old Windows 95 computer, it would run at about 90%. So the speed setting is also dependent on the speed of the computer you are using.