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Topic: Adding ON/OFF control & temp display to PID SCRIPT (Read 2 times) previous topic - next topic

retrolefty

#15
Jul 02, 2009, 02:20 am Last Edit: Jul 02, 2009, 02:30 am by retrolefty Reason: 1
In the PID controllers I have worked with the auto/manual mode selector, when in manual mode the setpoint value (as a percentage of range) is sent directly to the output (as a percentage of range). This gives the user the ablitly to manually place the output value anywhere from fully off to fully on and allows for a 'bumpless transfer' when setting the mode back to automatic.

Lefty

br3ttb

Quote
MANUAL mode is OFF?


When I was first starting with pid, the way I used to keep track was by thinking of it as "Manual Override."

in manual mode, you get to set the output to whatever you want.  in automatic, the pid controller does the work.  automatically.

I'm open to changing this.  Any suggestions on a better naming convention?  Something that's easier for the beginners, but is still understood by the old salts?

retrolefty

I may have over simplified somewhat in my explanation of manual mode. It does indeed turn off PID calculation and 'freezes' the output value at it's last updated value. However if one wishes to manipulate the output directly while in manual mode and 'setpoint tracking' is implemented, the setpoint changes as manual changes are made to the output. This allows for the 'bumbless transfer' I mentioned and also usually allows the same up/down users controls to be used no matter which mode on has placed the controller in. It may sound somewhat confusing to a newcomer to PID control but is intuitive once one has to 'operate' a controller.

Lefty



Coding Badly

Quote
when in manual mode the setpoint value (as a percentage of range) is sent directly to the output (as a percentage of range)


Yikes!  I can see where someone like me might be confused by that and do the wrong thing.  (changing the OUTPUT but thinking I was changing the SETPOINT).

The algorithms I've seen have an OUTPUT that is read-only when the loop is AUTO and read-write when the loop is MANUAL.

- Brian

Coding Badly

#19
Jul 02, 2009, 02:54 am Last Edit: Jul 02, 2009, 02:55 am by bcook Reason: 1
Quote
I'm open to changing this


Please don't. ¬†AUTOMATIC / MANUAL are the (very) commonly used terms.  I suspect using different terms will create considerably more confusion.

- Brian

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