Tag update on Red Lion DSP

I have a Red Lion DSPSX set up to read native L5K tags over Ethernet to populate tags in the DSP. I then send these tags out over RS-485 to Modbus Addresses. It was working fine but timed out and quit pushing the values (tank level %) so I changed the update policy from automatic to continuous and it seemed to keep pushing the value. Well 5 days later and it has quit pushing the values into the modbus addresses again. Any idea what might be causing the data to quit sending? I'm new to Red Lion so I would really appreciate any help you can give me.

Thanks,

Kraken Fan #69

I would recommend adding one tag from the Modbus side and one tag from the AB side to the watch window. See if you are communicating to both devices. If you aren't this will let you know which direction to start troubleshooting.

Thanks
Jeremy

Thanks for the reply,

I had set up a web server and was monitoring the G3 tags being pushed to the Modbus address and they (everything) was working fine. At some point however the modbus address began seeing 0's and triggered an alarm. I have created a new web server that will monitor the tags being read from the native Compact logix and the modbus values separately and will see how that goes. I hope to be on site tomorrow to look into it.

The values from the native l5k tags are being red in through a wireless Ethernet system. If we lost comms and that internal G3 was no longer being updated would it retain its last value or would it go to zero?

Thanks again for the help and I'll post the results (most likely a setting on my end) when I can.

Kraken Fan #69

Experiencing possibly similar issue with DSPLE

Kraken and Jeremy,

I'm jumping in on this post because I'm hoping what Kraken finds may help me resolve an issue I recently experienced with a DSPLE. In my setup, I've got two way communications between a CompactLogix (using L5K tags v1 driver) and a Johnson control system which uses the BACNet UDP driver. I have two of these installed at the site...both ran fine for about 2 weeks...then one day, the Johnson system started getting oscillating values from the Red Lion even though the values in the Compact PLC were steady. I'm reading/writing alarm enable/alarm status bits back and forth, and the enables were steady in the PLC but were changing in the Red Lion back and forth every few minutes.

I did a re-send of the configuration to the Red Lion and that cleared it up.

Needless to say, the client is very concerned as it seemed random and was not triggered by any particular event. Any tips on what to try or how to troubleshoot would be appreciated. If Jeremy can explain the Automatic vs. Continuous setting, I'm not familiar with that...not sure if that might help in my case.

-Greg

krakenfan69 said:

Thanks for the reply,

I had set up a web server and was monitoring the G3 tags being pushed to the Modbus address and they (everything) was working fine. At some point however the modbus address began seeing 0's and triggered an alarm. I have created a new web server that will monitor the tags being read from the native Compact logix and the modbus values separately and will see how that goes. I hope to be on site tomorrow to look into it.

The values from the native l5k tags are being red in through a wireless Ethernet system. If we lost comms and that internal G3 was no longer being updated would it retain its last value or would it go to zero?

Thanks again for the help and I'll post the results (most likely a setting on my end) when I can.

Kraken Fan #69

Click to expand...

If the source drops out and we are a modbus slave we will respond to the modbus master with a zero.

With the automatic setting only when the data in the source changes do we write to the destination. This is the best for most applications. The continuous setting transmits data to the destination regardless of what is happening on the source side.

Thanks
Jeremy

Hi Jeremy,

My DSP is the Modbus Master in the setup. The Wireless Ethernet had dropped out and caused the RS-485 to quit sending. When the Ethernet connection was restored the RS-485 did not go back to sending data. I had to cycle power to the unit to get it talking again. I have added tags to the web server that show the value being read into the unit from the Control Logix and the Modbus address to help isolate issues if it drops out again. I also added a button that will reset the unit so operations can log in to the webserver and reset it without having to actually mess with the wiring. Not ideal but for now will get them up faster than me driving 2 hours to get there.

My values going out RS-485 are set to continuous because when they were set to automatic they went to zero after an hour or so. Continuous seems to be working better although if I remove the Ethernet connection the value remains as you say but I have SD's from the plant PLC that are not routed through the Red Lion so if the tank does go hi level (even if the Red Lion value doesn't) the unit will get shut down.

What will the DSP modbus master do if the source drops out?

Thanks so much for responding in the forum you are a great asset to the site!!

Kraken Fan #69

If the source drops out our Master driver will continue to send the last known value.

Thanks
Jeremy

That's looks like what I see while on site but I can't seem to determine why the values went to zero. Is there any way to force the RS-485 driver to reinitialize once the Ethernet comes back online?

Thanks,

Kraken Fan #69