adccommunitymod (AutomationDirect) asked a question.
Created Date: July 06,2015
Created By: MattPyne
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My application is a HVAC system designed to control 2 separate parts of a building, am using the DL06 PLC to do this. Each part of the build have the following PVs that am trying to control: refresh louver open percentage, re-circulation louver open percentage and fan speed. So I am in need of 6 individual PI loops but when ever I go over 4 PID loops the PLC becomes very unstable and usually crashes in min or so. I see that the CPU indicator light turns red and I get transport protocal error in Directsoft5. After this the hole system needs to power cycle. I tried increasing the Sample time to 0.5sec for all loops but no luck. All the loops work fine as long as there is less then 5 loops active. Any thoughts? :confused:
Created Date: July 06,2015
Created by: Bob S BN
In DS5, menu PLC>Set Up>PID, do you have the proper number of loops and addressing set up? Any other program areas writing to VMEM areas assigned to the PID loops?
Created Date: July 06,2015
Created by: MattPyne
I have the correct number of loops and the addressing is correct.
I am writing to the VMEM areas that contain PV and SP for each PID loop in the ladder logic. SP is just taken from V400 and put to V2042 and PV is taken from an analog card V424 and put to V2043 for example.
This happens at the start of the ladder logic and the PLC VMEM addresses are left alone afterwards.
Created Date: July 06,2015
Created by: Do-more PE
Also where is the address range of the last loop ending up? Make sure that it is within the usable memory range.
Created Date: July 06,2015
Created by: MattPyne
The last mem location for the last loop is V2300 - V2337.
Created Date: July 06,2015
Created by: MattPyne
Another thing am not sure if it matters but there is no analog inputs yet. So the PVs are all ways zero and after setting SP the loop overflow pretty quickly. Maybe having 6 loops having an overflow causes an issue?
Created Date: July 06,2015
Created by: Do-more PE
4 loops is the maximum for a DL05. I missed seeing the 6 loops in your first post.
Created Date: July 06,2015
Created by: Bob S BN
He says in the title and first post that he has an 06, which can do 8 loops according to the manual.
Created Date: July 06,2015
Created by: Do-more PE
Ok. I'm going back to bed. It's definitely Monday... :o:p:D
Created Date: July 06,2015
Created by: MattPyne
My application is a HVAC system designed to control 2 separate parts of a building, am using the DL06 PLC to do this. Each part of the build have the following PVs that am trying to control: refresh louver open percentage, re-circulation louver open percentage and fan speed. So I am in need of 6 individual PI loops but when ever I go over 4 PID loops the PLC becomes very unstable and usually crashes in min or so. I see that the CPU indicator light turns red and I get transport protocal error in Directsoft5. After this the hole system needs to power cycle.
I tried increasing the Sample time to 0.5sec for all loops but no luck.
All the loops work fine as long as there is less then 5 loops active. Any thoughts?
:confused: