Time Proportional Control Example?

[brooksware2000]

Hello Curtis

Welcome to the forum.

Your problem can be broken down into 2 parts
1 - caluclate the value of output power via your PI routine
2 - convert this power to a time value

From your question, I guess, you have no issues with point 1

Assume you have power going from 0 to 100% corresponding from full off to full on. This can be converted to time thus

If the cycle time Tcyc you specified for your controller is - let us say - 10 seconds

On time will be
Ton = (Tcyc * Power) / 100

With this, you will get a Ton ranging from 0 - 10 seconds

Now, to control the duty cycle of your heater using this value, you can do this
Tvar var word

Tvar is a variable that runs from 0 to 10 seconds.


Tvar = Tvar + 1
if Tvar >= 10 then Tvar = 0 ' roll over

if Tvar < Ton then
gosub HeaterOn
else
gosub HeaterOff
endif

I hope this will help you


Oh, I forgot to add that you need to have the code above run at a fixed 1 second rate to get correct results

Very good! You made it look so simple. I'll be sure to post the code once it is all worked out.

Thanks,
Curtis

[cncmachineguy]

Yup, as I said, my lack of understanding. Thank you for the links Curtis. It may just be time for me to start playing with PID. Good luck with your project