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BITS N BYTES

Replacing External PID Controllers with Internal PID on CP1L

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We have an upcoming project where our customer is utilizing external Partlow 1800 series controllers. These are externally tuned and setups to simply send ON/OFF input signals to the PLC to turn ON/OFF pumps, valves etc.. Would like to remove these external controllers and include them in a CP1L using Analog I/O expansion modules and use and HMI [Probably a NB Series] to set/tune the PID loops. Am a total newbie to PID control and would like some pointers/ideas as to whether this approach is viable AND if so how best to implement!! Thnx for any feedback. Edited by BITS N BYTES

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The PIDAT function in the CP1L is a very good algorithm.It is heat or cool only, so if you need heat / cool, you need to use 2 loops.Just like many Omron functions, there are a series of memory locations that you allocate for PIDAT.Some are for the parameters, some are for background memory for the internal calculations.The setup is fairly simple, and the auto tuning typically works very well.Biggest thing to know is that you need to clear the background memory (c+10 to c+40, or something close to that) every time you start the loop, or it is starting with stale history data.You should not be afraid of using the PIDAT in CP1L, and we will help you with the details when you are ready.

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Use the TPO instruction too if you need to translate your PID output to ON-OFF signal.

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HI, Can you give an example to use TPO for a heat valve control? Thanks in advance. Melin

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Does your valve need ON-OFF signal or proportionnal signal? If it expect proportionnal signal you only need PID (or PIDAT) instruction. If it expect a ON-OFF signal, you input in the TPO instruction the result word of the PID instruction. The output of the TPO instruction is an ON-OFF signal, and the cycle period depend on the parameters you put in it. It is very well documented in the Instruction Manual of your PLC, and examples are included.

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Hi, Our valve is an OPEN-CLOSE signal; we need a tmp. control of air. I will read the Instruction Manual of CJ2M. Thanks

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