ti530 one shots

aholmes

Member
Join Date
Aug 2003
Location
England
Posts
3
hi

i have a problem with a ti530 plc, it seems the one shots only work occasionally. think it's from some kind of memory conflict with something else but don't know what. anyone got any ideas?
 
One shots are not doubled up - sometimes they work sometimes they don't. It isn't localised to just a few one shots either - it's across the configured range (0-255)
 
How do you know that the problem is due to the one shots not behaving as they should? Are you arriving at that conclusion by watching the performance of the machine or have you programmed traps to verify that the one shots never pulsed? One shots are notoriously difficult to troubleshoot because you can't count on seeing them pulse on the monitor.

One shots require an additional table in memory to keep track of the previous state of the bit. I don't know the details of this PLCs' architecture, but if the problem is in hardware, you'll need to replace the module where the transition table is located. Before replacing any hardware, I'd make sure the problem is not in the application program.
 
Put in traps to identify the problem - apparently it is to do with the long scan time, been advised to update the hardware anyway

thanks for the help though
cheers
 
I can't come up with a reason why a long scan time would have any impact on the operation of a one shot.

The only thing that comes to mind is a one shot controlled by a hardwired input. If the physical input is a rapid pulse whose duration is close to the PLC's scan time, you could have problems, but they wouldn't be caused by the one shot.
 

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