Yet another Weintek question (#5)

Thanks for the help so far guys. I have my screens made, login setup, and now I'm looking at trends. I want to trend a tank temperature, and I do have the trend set up, but I do have a couple questions. I have it set up to log data to an external USB drive.

I'm trending this data. Will this data always trend, or is there a way to set it up so that I can have it trend only when a boolean value is true. This way, when a station is not in use, the data is not being logged.

Does the screen with the trend need to always be on in order for the data to log? I currently am closing the screen on exit to prevent there from being a ton of different screens open and slowing down the HMI. The trend is set up to use history.

Ideally, I would like the boolean value to determine whether or not the data is being logged, and have the trend load that data when you go to the screen containing the trend.

Thanks again.

The data will only be logged to the file when "Triggered" the trigger could be preset by the HMI to be (Example: every 1 minute or up to 2 hours) or you could setup a "Boolean" trigger in the Plc that gets triggered by a timer set to what ever you want.

So you could setup a button on hmi that would start a timer in plc that triggers the boolean trigger ever 3 minutes and then press a stop button to stop the data logging.

Please Note: when you trigger a boolean from the plc you will have to hold the "Boolean" on longer than a single scan otherwise Hmi may not see the trigger.

I make all of my Plc triggers to be active for 8 seconds, and this has always worked for me, however you could test shorter if you need.

Thanks again for the info.

damica1 said:

I make all of my Plc triggers to be active for 8 seconds, and this has always worked for me, however you could test shorter if you need.

Click to expand...

The shortest time could be 2x the HMI update rate.
So, if the HMI updates the screen data every 1 second then the PLC needs to hold the trigger for 2 seconds.
Longer is okay.

So your 8 seconds means that the HMI could update once every 4 seconds and the data log should still trigger. But I'm pretty sure the Weintek/Maple Systems updates much faster than that.

Each station's task only runs when power is on to the station. So I set up a timer with a value held in a tag, which the user can change in the HMI. When the timer times out, the trigger bit is latched. This trigger bit then opens the timer enable rung.

Once the trigger bit is set, the HMI resets the trigger bit. If at some point the HMI goes not, it won't be an issue because the HMI won't be recording. If the power goes off at the station, my main routine sets that bit back to zero, so that it being stuck on will never be an issue. Once the trigger bit reset, the timer begins timing again. Works pretty well.

sparkie said:

Each station's task only runs when power is on to the station. So I set up a timer with a value held in a tag, which the user can change in the HMI. When the timer times out, the trigger bit is latched. This trigger bit then opens the timer enable rung.

Once the trigger bit is set, the HMI resets the trigger bit. If at some point the HMI goes not, it won't be an issue because the HMI won't be recording. If the power goes off at the station, my main routine sets that bit back to zero, so that it being stuck on will never be an issue. Once the trigger bit reset, the timer begins timing again. Works pretty well.

Click to expand...

That works too; like a SYNchronize and ACKnowledge.
I do like that better than just timing.

It also gives you a status of the HMI. If the HMI does not clear the trigger bit then you (the PLC) know something is wrong; or the station power is off.