Timers

[dgwill 0]

Question - is it possible for a timer to go faulty? I had an issue whereby I had the problem of a timer appearing not to operate, even though conditions said it ought to work. As I am a beginner when it comes to programming I overcame the problem by wiring in an external timer. This had the desired result and the equipment is functioning as intended.

[panic mode 246]

I guess everything could fail one way or another. But it's quite hard to imagine that something designed to be robust enough for industrial applications like PLC would continue to operate and yet have nonfunctional timers. Since you say you are newbee, it is possible that for example you don't know yet how to use them or that you have same timer used more than once. Thats where you start using cross reference to see if one coil is used and where. I would suggest to post your code so we can take a closer look at it and help you find the culprit.

[dgwill 0]

Just to clarify - this programme has been operational for years ( long before I joined the company) so it is not a new issue.

[Sergei Troizky 26]

You did not provide fault details for the best recommendations. Try to check the following obvious and not so obvious things: - You may judge it as a regular timer while it is a retentive one. - Verify your project file with the PLC contents, in order to be sure that you are monitoring the real program operation, not a close but different one. - If the timer conditions contain normally closed contacts, they may be one scan pulses and you cannot monitor a contact open for one scan. - A timer will not count if it is within an inactive STL state, or within a portion of program, bypassed by a jump. Also, a timer in subroutine or interrupt behaves specifically. - If the timer setting is not a constant but a register, invalid value in the register may cause the timer faults. - If elsewhere in the program there is an indexed timer as an instruction destination, it may write to this timer, intentionally or by erroneous program operation. - If there is an HMI connected to the PLC, check it for possibilty to affect this timer setting or accumulated value.

[panic mode 246]

We still don't even know what PLC we are talking about. I'm suspecting that either: a) timer logic is not scanned or b) you have double (multiple) coils scenario. c) preset is not what you think it is Don't make us guess, try to describe it better or just post the code. I'm sure we'll come up with solution.

[jerrycat 0]

The timers Used in the PLC are software timers, It is very difficult to imagine that a timer program the right way wouldn,t work. If you thing your timer doesn,t work then you have a software problem. sinds your PLC is functioning correctly , this is clearly not the case. i can agree with the others that you post part of the code so we can help you to solution