PLCprogrammer
2020-04-30T19:58:54Z
I have a GE 90-30 CPU 374 PLUS. The program currently has a PID controller that controls a valve. I would like to add a second PID controller to control fans. However I am having a problem implementing the 2nd PID controller. When I upload the program and run it, all the parameters are constantly changing. The P,I and D gains fluctuate, upper/lower clamps, etc are changing. The original controller still functions properly. Moreover, if I remove the old controller (mixing valve) and run it, the new fan controller now runs fine. I ensured that the controllers each have enough reserved memory (40 words). Has anyone had any similar problem?
Guest
2020-04-30T20:00:16Z
Sounds like something is being overwritten. Are you sure the new PID addresses are not used elswhere? Have you done an implicit search?
Zackbo
2020-04-30T20:01:25Z
Are you using Proficy ME to program? The 374's are known to be a little flaky, even though they are the highest-end CPU you can get for a 90-30 platform. Are you using PID in ladder, or in a FBD?
PLCprogrammer
2020-04-30T20:07:44Z
turns out i did have something that was overwriting the PID registers
RSLogix500 Introduction
RSLogix500 Inserting Instructions
RSLogix500 Opening a File
RSLogix500 Creating a Project
RSLogix500 Instruction Comments
RSLogix500 Rung Comments Page Titles
RSLogix500 Inserting Branches
RSLogix500 Program Organization, Part 1 - Overview
RSLogix500 Program Organization, Part 2 - Examples
RSLogix500 Using Symbols
RSLogix500 View Properties
RSLinx
RSLogix500 Online Offline
RSLogix500 Dowloading and Uploading
RSLogix500 Processor Modes
RSLogix500 Processor and Cards
RSLogix500 Introduction to Faults
RSLogix500 Indirect Addressing
RSLogix500 Indirect Addressing Faults
RSLogix500 Handling Faults
RSLogix500 Forcing I/O
RSLogix500  Custom Data Monitor
RSLogix500 I/O Configuration
RSLogix500 Advanced Diagnostics
RSLogix500 Instructions OTL OTU, Part 1
RSLogix500 Instructions OTL OTU, Part 2
RSLogix500 Instructions OTL OTU, Part 3
RSLogix500 Instructions, OTE
RSLogix500 Instructions, XIC XIO
RSLogix500 Instructions, ADD
RSLogix500 Instructions, COP
RSLogix500 Instructions, CPT - Part 2
RSLogix500 Instructions, CTU CTD - Part 1
RSLogix500 Instructions, CTU CTD - Part 2
RSLogix500 Instructions, CTU CTD - Part 3
RSLogix500 Instructions, CPT - Part 1
RSLogix500 - Comparison - Part1
RSLogix500 - Comparison - Part 2
RSLogix500 Instructions, DIV
RSLogix500 - FIFO - FFL and FFU - Part 1
RSLogix500 - FIFO - FFL and FFU - Part 2
RSLogix500 Instructions, FLL
RSLogix500 Instructions, JMP and LBL
RSLogix500 Instructions, Masking and MEQ
RSLogix500 Instructions, MUL
RSLogix500 Instructions, MOV
RSLogix500 Instructions, LIM
RSLogix500 Instructions, NEG
RSLogix500 Instructions, OSR
RSLogix500 Instructions, RTO
RSLogix500 Instructions, SQO sequencer - Part 1 of 3
RSLogix500 Instructions, SQO sequencer - Part 2 of 3
RSLogix500 Instructions, SQO sequencer - Part 3 of 3
RSLogix500 Instructions, SUB
RSLogix500 Instructions, TOF
RSLogix500 Instructions, JSR and RET
RSLogix500 Shift registers
RSLogix500 Instructions, SQR
RSLogix500 Instructions, TON - Part 1
RSLogix500 Instructions, TON - Part 2
RSLogix500 Instructions, TON - Part 3
Introduction to Ladder Logic