PROMOTIC FORUM

I have a binary variable PHC_AGRO_IN3 defined. The value changes with the change at the PLC input. I want to generate an alarm when it changes to true. I created a new variable related to PHC_AGRO_IN3 and assigned it a binary alarm. Unfortunately, the alarm does not activate. In the INFO system I see how the Value changes, but nothing happens in the ValueBeforeChange field. How to generate an alarm in this case?
Thank you for your help.
Pawel

Hello, unfortunately you are right.
This is the scenario when an ExtAlarmBinary dosn't work. The problem is that you have 2 variables (Data var and Comm var) and you connected them with dbind PP. You defined dbind PP as dbind from from Data var to Comm var. This is good for output value from promotic to plc. Dbind means that in the var in which is defined (data var) is not real value. Instead of value there is a connection or dbind to another var. If you read from that data var, the value is read from dbind instead. If you write to data var, the value is written to dbind instead.
The key point here is that the value in data var doesn't exist. ExtAlarmBinary is driven by change (write) to var. It doesn't read value itself, it is similar to script event onChange.
In your case the real value exists only on comm var not on data var so that no onChange internal event is invoked and no alarm is then activated on data var (but on comm var it is invoked).
You can either move the ExtAlarmBinary to comm var from data var.
Or you can try to move the dbind PP from data var to comm var. The value would then exists in data var and the comm var would write any new value thoroug dbind to data var.

Dbind PP in application tree (Var in PmData) is a little bit tricky and we plan in the future to replace this concept with a new better one.

Great information it was very useful for me in my project.