Heatermeter on UDS, my PID settings


 
M

Marlin Schrock

New member
I might be the ugly duckling here, but I have been fiddling with the heatermeter on my ugly drum smoker. Like others I've struggled with temperature stability with the default PID settings. I've also bludgeoned my head against the wall fiddling with said PID settings.

Tonight I drunkenly stumbled onto:

Bias: 0
P: 30
I: 100
D: 60
Fan Max 60%

It isn't 100% perfect but it is far and away better than any settings that I have tried so far, so I thought I'd share.

I have:

55gal drum, with the digikey blower (one in parts list) connected with a 1/2 ball valve to the drum. Output is snuffed down to comparable area. No damper on blower, just the 1/2 valve fully open.

Blower Attachment:
qIR0Vlo.jpg


Flue:
okPWZ6N.jpg


Stability:
X2u5O58.jpg


Closeup 225F - 229F:
UMlnz6y.png
 
Well, as the smoker got going and the fat started dripping into the fire, things got less stable.

I should have called this the "quest for pid settings for UDS."

The thing that is different in a UDS is that the charcoal, air inlet, and meat in is a common cavity. Most smokers, the air intake is under the charcoal, where the air must go through the fire to get to the food area.

Seems to me that with the UDS arrangement, when the fan kicks in, there is a longer lag to create heat than in a "typical" smoker. This lead to overshooting with the default heatermeter PID values.

I finally switched back to the default pid values, and started tinkering.

Currently running with:

Bias:4
P: 1
I: 0.005
D: 5

here is my reasoning for it. Low P value as oscillations are very easy to make. Hight D value as it really needs to read those temp fluctuations to kick the fan up.

I'll update the thread until i find something that works reliably. I wonder how the bbqguru and the like handle the differences of smoker types.

If all of this looks horribly wrong: Feel free to chime in and set me in the right direction!!
 
I use mine on my UDS successfully all the time. I use the default P and I settings, and bump the D to 50-100 range. The higher D makes the fan respond quicker, not sure why it makes a difference, but I can hold really good temps. But PID settings are only part of the solution.

My air intake is a 2" ball valve (yeah it is HUGE), that I almost completely close. I leave the top all the way open. I set the fan to a max speed of 50%, but I'm not sure that even matters since I close the valve so much. When I say almost completely closes, I can't fit a #2 pencil in there, it is about have as think as a pencil. Since it is a 2" valve that is still quite a lot of area compared to your 1/2" valve. Basically you want the valve opened such that without a fan, you would get a temp 25-50F cooler than your target temp. Then the fan will make up the difference.

Charcoal. I have a brick in my charcoal basket radially from the outside to the center. I then fill the basket with charcoal and light it next to the brick. The brick acts as a fire block so the fire only spreads in one direction (clockwise for me) instead of in all directions. This tends to help slow down the amount of charcoal active at one time and gives me a more stable burn. I light my charcoal using a home made lighter (dryer lint covered in wax in paper egg carton). I just set it on the charcoal and light it.

I do have temp spikes anytime I open the smoker. This is caused by the inrush of oxygen when taking the lid off. One way to counter act it is to turn the valve off all the way and let the temp drop a little before opening, and when opening keep the lid off a little as possible. I typically only open the smoker once, to wrap the meat, per smoke so it isn't too bad.

From the looks of your graphs, I think increasing D will help as mine looked very similar to yours prior to setting D so high. I've a post somewhere on the board where Bryan was helping me get it under control. I remember him being surprised that the D being set so high worked so well.

Hopefully this helps,
dave
 
Just pulled the butt off the smoker. Dave, I'll give those settings a go, as well as the brick "divider". What size charcoal basket are you using?
 
My charcoal basket is a re-purposed 22.5" $30 grill from Big Lots. I used the lid as my smoker lid and the bottom grill part as my charcoal basket. It pretty much fills up the entire bottom of the smoker.

dave
 
Thanks for the contributors to this thread.
Currently have this on my UDS, and was happy with the results. Was doing a lot of playing with probes and settings during the last cook, so, I'll have a "clean" run in a few days with HM only.

Bias: 4
Prop: 1
Integral: .005
Deriv: 20
100% max fan speed
 
Last edited:
Well, went to bed, woke up to this. I have some work to do it seems and have to hit the wiki :) sometimes I miss the auto-tune on my crap JLD612 but not going back !

uds.png
 
Seth, what were your settings in the last graph. Curious to compare.

Currently, I am trying the fanless heatermeter controlled damper approach...
 
I'll get them to you later, Marlin. They did get a little worse for me and I ended up changing them slightly.

I need to do a test cook when home to nail down the settings. I was putting ribs/burnt ends in/out when I was awake so my data isn't great as far as PID tuning... going to try to do a tuning session tomorrow
 
Looks like I need a damper. It's really windy out and I never have problems with temps staying above 225 but I seem to be today.. Temp floating around 230F with no fan on for almost 2 hours.

Still doing a trial run but closed up the ball valve and lid vent a little to choke it up and get the HM working... will see how that works up.
 
Closing the lid will keep more heat in for a bit,

I have never had the need to close the lid. I will have the ball valve closed to a crack, regardless of the wind, when temp is 230 or below and is pretty stable without the him. Its harder to get temps down on a UDS, then to slowly bring the temps up to the set point.
 
John Bostwick said:
Closing the lid will keep more heat in for a bit,

I have never had the need to close the lid. I will have the ball valve closed to a crack, regardless of the wind, when temp is 230 or below and is pretty stable without the him. Its harder to get temps down on a UDS, then to slowly bring the temps up to the set point.
Click to expand...

I've never had the ball valve or lid vent closed either - just doing a test run with an empty smoker so I assume that plays a role. No big cold food to suck up some heat..
 
Seth R C said:
I've never had the ball valve or lid vent closed either - just doing a test run with an empty smoker so I assume that plays a role. No big cold food to suck up some heat..
Click to expand...

Actually, the one thing I hate about the UDS is when you think you have a stable temp at start up, with nothing in it and then you have to lift the lid and put a couple of pork shoulders in and then the temp drops or if you leave the lid off to long, it then raises way above your set point. I still after 5 years with my uds, have not learned a good technique of closing the inlet and removing the lid and not screwing up the temperature.
 
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