PID Tuning for Primo XL


 
C

Chris Peisher

New member
Here is a screenshot of my test cook.
https://imgur.com/gallery/VfEz7

From the graph it's apparent that the fan PID settings are causing oscillations, and possibly a positive feedback situation. I'd like to see if anyone could recommend some PID settings to keep it a little more controlled on a ceramic cooker like my primo. Is there a script our something i should load that would enable damper only control until it really needs the fan?. If there is could you please tell me exactly how to enable that control process?

Thanks for your help.
 
Looks to me you should try another cook but dial down your fan speed. Then we'll be able to see how it's performing a bit better. What do you have your min and max fan speed set at?

No need to write a script for running damper only. Look at your settings it says "Fan on above XXX% min YYY% max ZZZ%". Change the XXX to be the value at which your fan turns on.
 
You should also keep in mind that the cook you just did outperforms a typical home oven, so there's no need to get hung up on some oscillation.
 
I assume you're using a blower, and not an axial fan like the MicroDamper uses. That being the case you probably want something like 40-50%. You should want to see more fan usage, right now you have too many coals lit up. Even though you are maintaining temperature well you have little airflow which can translate to stagnant air, and stagnant air can mean creosote build up. I would also guess your I is too high, try lowering it. For reference on my akorn I use 0.0035 for my 'I' value running with a MicroDamper.

I'll try to check in a few more times tonight to see how things are going, but I can't make any promises!
 
From your settings, it looks like you're running Fan Only, as you have your damper open full at 1%.

If you want to run damper until fan is needed, try "fan on above" = 99%, and Servo fully open at 100%. This will the Damper to do most of the work, until the fan is needed.

Leave fan min at 0%, but set max to 40-50% as SteveCK mentioned.
 
I'm using the roto damper assembly. Here are my current settings i just changed at 21:10 EST

https://imgur.com/a/otA73

And here is the current graph

https://imgur.com/a/ixubL

At 18:15 i fished the fan min to 70%. That didn't really fix the "problem".

At 1945ish i opened the lid and changed some probes around. I also edited the servo pulse settings as the damper was binding on full close and not opening all the way.

And as i said above i just 10 minutes ago changed to the pid settings above. I'll post another graph in 30 mins or so.
 
SteveCK said:
You should also keep in mind that the cook you just did outperforms a typical home oven, so there's no need to get hung up on some oscillation.
Click to expand...


Your not kidding,

I did some turkey pho stock in the oven last night and the oven temperature looked like a sawtooth, it sometimes varied 80°f or more, up and down. More up then down though. It seemed when it dropped to 180°(set at 200°), it would then rise to 250 or so and then drop back below setpoint.
 
Chris Peisher said:
I'm using the roto damper assembly. Here are my current settings i just changed at 21:10 EST

https://imgur.com/a/otA73

And here is the current graph

https://imgur.com/a/ixubL

At 18:15 i fished the fan min to 70%. That didn't really fix the "problem".

At 1945ish i opened the lid and changed some probes around. I also edited the servo pulse settings as the damper was binding on full close and not opening all the way.

And as i said above i just 10 minutes ago changed to the pid settings above. I'll post another graph in 30 mins or so.
Click to expand...

I would lower the blower speed. Put the blower into manual and let the temperature drop below set point, atleast 20° and then slowly raise the blower speed until you start to see the temperature rise. That would be your max blower speed, with maybe another 5% or so. That would help with over shoots, and oscillation
 
When you're on the main screen press 'P' on your keyboard and a little table will show up on the left hand side (if it doesn't show, try clicking anywhere on that screen and try again) that shows you the live PID values. It comes in handy when you want to tune your PID, also helps us help you.

What fan % are you using now, looks like you need to increase it a little bit. Also, what settings are you using now?
 
Here is the Image showing the full ~13 hour cook

https://imgur.com/a/xgAS7

And here are the current settings.

https://imgur.com/a/dVD4U

I have to say that I'm extremely pleased with the performance over the first 10 hours. And again, this us with only a half load of charcoal. I really can't say that I'm disappointed with the last hour or so either. +/-10° is pretty good, right?. If it can be better I'm all ears though!

Edit: i changed the live link to an image of the graph.
 
Last edited:
A straight line, with a few degrees variance.up and down. After a while you will see and learn the tendencies that your smoker likes and you will gradually get better results. Some smokers are just more easier to control then others. My UDS is happy at low temps and it can run very stable(1° up and down) for a long time, without using a blower, just knowing how to adjust the air inlet using my ball valve.

If you have issues with over shooting the setpoint, maybe start with less lite charcoal or lowering the maximum that the blower works and making sure the smoker is air tight as possible will help.
 
John Bostwick said:
Your not kidding,

I did some turkey pho stock in the oven last night and the oven temperature looked like a sawtooth, it sometimes varied 80°f or more, up and down. More up then down though. It seemed when it dropped to 180°(set at 200°), it would then rise to 250 or so and then drop back below setpoint.
Click to expand...

Stuck my HM probe in my oven once to see how it did. Set at 350 if fluctuated +-25 from like 325 to 350 in pretty my an exact repeating pattern. My parents have the same oven and it was even worse.. With my heatermeter on my WSM or Kamado Joe I get temps that are +-5 at 350...much more stable.
 
Yeah, home ovens aren't very efficient. Here's an example. Oven set to 250. Turns out, the low is 250, and the high is upwards of 280.

AcURAMF.jpg
 
I should use my HeaterMeter on my Breville Smart Oven and see how it performs. It's one hell of a "toaster oven", I use it on 90% of all the items I cook in an oven.
 
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