I am using Fire on Change on a Digital Input variable to fire an event. I only want the event to fire when the particular variable has changed to 0 so in the event condition I am putting IO_DI1_FlowPulse = 0

This is not working as I am expecting as the Event fires every time the variable changes i.e falling and rising edge.

Am I correct in thinking this is how the Event Condition works i.e if the condition is satisfied then the event will fire?

Just altered my program and I guess I am not correct, as in the activity program that this Event runs I added a decision to do the above and it works fine now.

I would be grateful if someone could explain how Event Conditions work.

Hi,

Which event are you using? "Flow Pulse Fire on Change" or "Flow Pulse Fire on Change Condition". I Think the later one would be correct.

Just my 5 cents. :)

Hi Joakim,
Thanks for your reply,
Ahhh! I see what you mean now, I was using the "Flow Pulse Fire on Change" event but having looked again I see that I can select the "Flow Pulse Fire on Change Condition" event as well to run the activity program! I didn't realise that the conditions created a new event! (to be fair though I haven't been on a training course - I'm entirely self taught).

Just tried using the "Flow Pulse Fire on Change Condition" to run the activity program though and the activity program never runs......

Am I understanding the above correctly though as in the Programming manual there is the following section regarding Events,

>>>>
• Event Conditions: Created to conditionally fire its parent event based on the result of an expression. For example, an event condition called Shutdown if Temperature > 250 degrees can be created that fires another event called Shutdown if the temperature gets too hot.
<<<<
This would indicate too me that it is the parent event i.e. in my case "Flow Pulse Fire on Change" that should be fired?

On your digital input variable IO_DI1_FlowPulse do you have it's Fire on Change event selecting the condition event "Flow Pulse Fire on Change Condition"?

Hi Boyce,
Yes, I tried that

Just tried using the "Flow Pulse Fire on Change Condition" to run the activity program though and the activity program never runs......

and it didn't work. The only way I could get it to work was to have the activity program run on every fire on change and then use a decision block within the activity program. I assume that using the above should work though?

Am I right in what I am thinking though with the Event Condition?

Also Can Event Conditions be nested several levels deep (if desired)?

Checking for a condition in an Activity Program is probably the easiest way to do it.

Event conditions can be nested.

Thanks Boyce,