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dahnuguy

Bi-directional PID with a V350

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Using the latest version of Visilogics, and a V350.

How do I use a PID to control motor speed?

How do I control anything with PID that requires an up and a down control?

How do I heat to some setpoint and hold it there and keep the temperature from climbing? 

Can I use 2 PIDs and have one oppose the other? I had this thought, but it may not work.

Is the Visilogics PID one way only? Is that the end of it?

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Never tried it, but I'd start two PID blocks acting on the same SP and PV with proportional only control, and some logic to map the output value of each block to the actual control word. Keep your hand on the power switch.

Joe T.

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The answer strongly depends on the specific system.

Motor speed driving:

What is the interface? Analog input? If so:

You set the inpout of PID the frequency from encoder 9there is a special mocule in VisiLogic, which measures frequency very precise with resoluiotn of 0.01 Hz!)

The output to analog signal.

As result, PID will change CV, linked ot AOand this way will change - increase or decrease - the speed of thhe motor!

No "two way PID" needed at all!

Heating to temperature and then holding it is a classic PID application. In this case PID regulates the output energy (usually PWM) to the supply the energy needed to keep the system in stable state (compensate energy losts) and thhis way to keep the temperature stable.

Onece again - no "two way PID" needed - at all!

If you have specific system, please give more info about it and we will find the way to control it.

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I have an application with two PIDs for Temperature: The Climatic Chamber.

One PT100 input but two outputs, one for heating and other for cooling.

The application works fine with 2 PID but the Auto-tune don't get the parameters.

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