PLC5 analog transfer with slew rate

[servant 0]

How can I design a analog transfer with slew rate for a PLC5?? If criteria is met, I want to transfer to input one at specified slew rate; however, if criteria is not met, I want to transfer to input two at specified slew rate.

[Keith Menges 0]

Can you provide a few more details? What are you trying to transfer? You say you want to transfer to an input. Do you really mean output? I have a few different ways you can slew values in a PLC5. We just need a better idea of what you want to do. Keith

[servant 0]

When ramp up mode is pressed I want to pulse a setpoint to a PID controller to 600gpm( which is slewed over 15 seconds). Once the ramp setpoint reaches the HMI setpoint, the SP will be released so that the operator could make an adjustment. When ramp down mode is pressed, I want to take the current PID setpoint and ramp/slew it to zero over a 10 second duration.

[BobLfoot 302]

So if I get this right you have an analog output driving a pump motor for speed. When the Ramp Up button is pressed it goes from 0 to 600 GPM in 15 seconds and holds there. The operator cannot change the gpm during the 15 second ramp up. Once "at speed" the operator can tweak the GPM as desired. If the Operato then presses the Ramp Down button you want the output to go from wherever it is to 0 GPM in 10 seconds. Again prohibiting operator changes during the down ramp.

[servant 0]

Yes. Your description of the desired strategy is exactly right. Do you have a solution?? Does anyone have any ideas on a AB PLC5 solution for this??? Edited 6 Apr 2006 by servant

[BobLfoot 302]

I did not have a solution at the time I wrote the question and I am not sure if the following will avhieve what you are looking for or not. The general idea of the program is as follows: 1. A PID Loop Exists which Updates every 100 ms. 2. In Slew Up the Setpoint Changes from 0 to 600 in steps of 20 over a 15 second period changing once per second. 3. In Slew Down the Setpoint Changes from Where it is to 0 in steps of 1/10 over a 10 second period changing once per second. I have not tested this and am not a PID Guru. It is just a thought kernel. Slew_Rate.zip Edited 8 Apr 2006 by BobLfoot

[BobLfoot 302]

Couple of weeks since I posted the slew rate program -- how did it check out.