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pid controller problem

post #1 of 14
Thread Starter 
Can anyone tell me how to fix my problem
I am using a pid to control a Lp control valve that runs my burner for my smokehouse.the pid cycles constant trying to keep the temp..is there a way to widen the cycle times so let's say it lights burner then shuts off till the temp dropped like 5 degrees then turns on and heats till temp is reached again?
post #2 of 14

Hi Smokingbk, can you tell me which PID you have. If I have the spec sheet or can get it I can probably help you get it going.

I have used a lot of the PID's befoer I retired and for sous vide since. There is a term for how long the cycle period is and what portion of the cycle will be on.

 

GeneK

post #3 of 14
Thread Starter 
All Ic for a name is dh/rex-c....I don't c a brand any where
post #4 of 14

Smoking, I have fond a site for the Rex c series PID controllers. which number do you have?

 

GeneK

post #5 of 14
Thread Starter 
Ic a Rex 100....is that what u need?
post #6 of 14

Smoking, do you have the setup sheet for the C-100?  If you do, there is a term near the bottom of the chart that says CYCLE  or Heating CYCLE.

That is the setting for the cycle length, it has a symbol that looks like a backwards 7. Sorry I can't figure how to send the symbols from a seven segment display in this message.

 

GeneK

post #7 of 14
Thread Starter 
Yes Ic the symbol they call it work period...time scale period is 1-100s....factory default says*3 relay connection output20s,voltage impulse/set on control thyratron output trigger is in need/control thyratron output 2s.....that's what *3 says
post #8 of 14

Smoking, that is the term we're interested in changing. I found at least two different data sheets on the C-100 and the extra things they say on that line is just covering the bases for the engineering types who may be doing who know what. Yeah I can pick on engineers, I'm a retired EE)

if you increase the setting, I would go for 10 or 15 to start and see how it esponds and then go from there.

I hope I'm being clear, if not let me know.

 

GeneK

post #9 of 14
Thread Starter 
Yea I gotcha....I will try it and get back to ya....thanks a bunch I really appreciate ur time and ur brains!! Thank you!!
post #10 of 14

Smoking, my pleasure, knowledge is made to be shared.

 

GeneK

post #11 of 14
Thread Starter 
OK so I raised that setting and it worked fine holds right at The temp I wanted,....but is there a setting that will let the pid swing say 5 degree either way?
Edited by smokingbk - 5/17/14 at 7:47am
post #12 of 14

Smoking, Morning to you. Had to get a Greek loaf of bread set up to bake later today.

There is a setting that displays as Lbd labeled dead band, which is what engineering types call what you are asking for. Try setting that to half the span you want and see what happens.

At Electro Scientific we had a heating/cooling system that used the alarm high and alarm low to maintain a range of temps. But that had a slew of external relays to steer the current in the right direction.

 

GeneK

post #13 of 14
Thread Starter 
OK I will try it when I get back home.....well now I have ur brain rolling I'm gonna ask another question about a different controller it is a mypin ta6...I think maybe it went to hell but what happened is it always puts out 24volts even after it goes by the set temp...it worked fine a week ago but now it doesn't is there a setting that could be messed up? Or maybe just shorted out idk......anyway hope the bread was good!!
post #14 of 14

Smoking, on that mypin controller I would just check the wiring and step through the program and see if anything has changed. Usually there's a light on the front panel the turns on when the output  is enabled. Also on the SSR there's a similar light, they should be in sync if the SSR is always on and the controller is off it is being enabled by something else.

 

The bread is in the second rise, my wife and I went out for lunch and I just punched it down and shaped it when we got back. About another half hour or so it goes in for the baking.

 

GeneK

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