Timer limit

[Guest TheDOG]

The timer has a very limited number of minutes (999 seconds = about 16 minutes). I need timers that require duration of hours. How can I do it? Thanks for help.

[PdL]

Use the system minute clock pulse flag that drives a counter with a preset value of 60, when the counter counts down use the completion flag to drive another counter or an integer increment that represents the hours to count. A compare instruction that compares the counter value or the integer with a preset target can be used for your logic.

[jacekd]

Which flavour of Siemens do you use ?

[Groo]

yes, is it a S7-200 or S7-300/400 your talking about. If you talking about S7-300/400 look to the standard block libraries for the Timer blocks. If its S7-200, I'm not sure there as I haven't used one.

[Rod_Hackney]

Cascading timers - counters as suggested above usually solves the problem

[Guest TheDOG]

Thanks. Have a good weekend. Edited December 14, 2007 by TheDOG

[Groo]

You never did reply on which PLC type. Just to re-iterate, if your talking S7-300/400 you do not need cascading timers. SFB4 = IEC Timer, On Delay with the timer preset in TIME format to a maximum of 24Days 20Hours and 30Minutes (or just over) C'e la vie

[Guest TheDOG]

Thanks. We use both S7-200 and 300/400. In fact we use AB, Siemens, Modicon, and AutomationDirect. Long timers only be used occasionally for a piece of equipment. We have used AB, DL205, and Modicon on this equipment with long timers. We have not used Siemens on this piece of equipment. I just want to know and be prepared in case if a customer want it. Thanks for the help.