Trying to develop an easy way to run a vent from fully open to fully closed and all positions in between using a PIDD block. The opening/closing is done to maintain a temperature in a room (set point 75F). Fully closed-open takes 60 seconds. Iv'e set the full and zero at -50 and +50. Each output controls independent relays (1 open and 1 close). Is there a way to use PIDD for this purpose? I'm obviously missing something because i can't get it to work like i want it.
This should certainly be possible to manage with PIDD. You'll need a temperature input to the RTU as your Process Value, and two digital outputs. One will pulse to increase temperature, and the other will pulse to decrease temperature. That's probably the most challenging part of this, getting those digital outputs properly wired to your vent control motor. We can't really help you much with that, as it's so specific to your application.
Not knowing whether you've taken a Telepace course or not, I can certainly recommend you sign up for one if not, and if there's one available in your area. However, I'm attaching a few pages from the training manual, covering the PIDA exercise. Unfortunately there's no PIDD exercise, but they operate in a generally similar way. The Help documentation for PIDD is pretty good, though.
Thanks for the fast response. I have the input temperature coming into the PIDD and the outputs wired correctly. I guess the issue is understanding the cycle time vs other tuning inputs to allow the vents to open/close a certain distance (time)/ distance the temp is away from set point
Probably the most challenging aspect of PID control is tuning of the parameters. The exercise I attached does include some pointers about initial settings of the Proportional and Integral parameters. (Derivative is rarely used in cases such as this) Also, any scaling in logic can dramatically impact the results if done incorrectly.
If after working through the exercise and Help documentation for PIDD you're still having issues, please feel free to contact our Tech Support team. They'll want to see a copy of your logic as well as a drawing of the wiring you've implemented.
Are you able to break the problem into two parts (i.e. do you have any positional feedback from the vent?)?
If you were in the RemoteConnect / Unity world, then there is a SERVO function block that would allow for the Vent position control, and then it should be a relatively straight forward approach to wrap the commanded position with a PIDFF to perform the Temperature -> Vent position control.
Or as Joel suggested, you could tailor the scale to a timeduration, and every X seconds (or minutes) trigger the valve movement for Y seconds (based upon the value of the control output from the PIDD).
I'm not familiar with the Telepace platform, but sometimes there is already a split range controller. There's nothing like that there?
Thanks for the help. I have not configured a PIDD. So here is the issue. The total open-close time is approximately 60 seconds. I'm having trouble with the min/max where the pulse output isn't consistent. Like you, I'd like to have it open/close for say 10 seconds to increase or decrease temperature. Thanks again.
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