HeaterMeter and Kamado Joe Classic II


 
PShin said:
Could you please attach a screen shot of your configuration? I have inverted the servo but not the fan. When I change the set temp to a negative value, the fans and servo kick in but any positive value, it turns off and there is no movement in the fan or damper. When I invert the fan, the fan is on constantly. Thank you.
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I wish I could offer help troubleshooting your problems, but I really don't understand how these things work. All I did is follow the recipe for building the Heatermeter and Adapt-a-damper. Then I set the fan to come on at 50%. That's about all I know. Sorry.
 
Could anyone with a Joe classic II post their lid open setting? Finally put mine together and set the temp to 225 but it shot up to 240 and the dampers still remained fully open. Trying to understand if that has some role in the overshoot and damper being fully opened.
yzV81Fz
https://imgur.com/yzV81Fz
 
I did a cook did other day with set point of 350 and held very tightly with the settings:

P:2.5
I: 0.0035
D: 6

Fan on above 25, min 10, max 40, start up 100.

Today, I try to do a slow cook with 225 set temp. I climbed to 255 and stayed there consistently. Both the previous cooks and the current cook with 225 set temp had top vent open the first mark. For the attached picture setting, I had to close the vent to 1/2 of the first mark on the classic 2.

Could this be a PID setting issue or do I need to close the top vent more for lower cooks? Attached is the PID output which I have no idea what it means. ANy feed back would be greatly appreciated!
n1Diqf9
https://imgur.com/a/n1Diqf9
 
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first question is which damper are you using. Next where are you placing the pit probe in the grill and is it a thermocouple or rtd. What brand of device is the pit probe. Last, where are you place the pit probe. I do not mount mine to the grill, instead mine is real close to the grills mechanical thermometer. On my grill there is a small hole in the cast iron damper assembly which is there to fasten the damper to the grill. I just removed the screw and fished a thermocouple through and down into the grill. This works great for me and my thermometer reads the same as my heater grill once everything is up and stable. I also just crack my damper open about the diameter of a 1/8" drill bit for 225 degrees. As I go up in temp I open it a little more. Even at 350 degree I never need to open more than 1/4". One other thing is the lump charcoal. They are not all the same. Go to the NakedWhiz website and check out the lump charcoal database.
 
PShin said:
Could this be a PID setting issue or do I need to close the top vent more for lower cooks? Attached is the PID output which I have no idea what it means. ANy feed back would be greatly appreciated!
n1Diqf9
https://imgur.com/a/n1Diqf9
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What I can see in that image is Rule #1 of tuning: If HeaterMeter's output is 0, then the temperature should go down. If it just overshoots and stays there with 0 input from HeaterMeter, then it isn't controlling anything. This is caused by the smoker being able to pull in enough air on its own to burn indefinitely, so either the damper isn't closing or you've got too many other vents open / lid gaps letting air in.

No configuration settings are going to change anything until HeaterMeter is actually able to control your smoker. When it is at 100% output, the temperature has to go up, and when it is at 0% output the temperature has to go down. The "down" can take 5-10 minutes or so, depending on how big the overshoot is.
 
Gary V said:
first question is which damper are you using. Next where are you placing the pit probe in the grill and is it a thermocouple or rtd. What brand of device is the pit probe. Last, where are you place the pit probe. I do not mount mine to the grill, instead mine is real close to the grills mechanical thermometer. On my grill there is a small hole in the cast iron damper assembly which is there to fasten the damper to the grill. I just removed the screw and fished a thermocouple through and down into the grill. This works great for me and my thermometer reads the same as my heater grill once everything is up and stable. I also just crack my damper open about the diameter of a 1/8" drill bit for 225 degrees. As I go up in temp I open it a little more. Even at 350 degree I never need to open more than 1/4". One other thing is the lump charcoal. They are not all the same. Go to the NakedWhiz website and check out the lump charcoal database.
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Thank you for the info. I am using the adapt a damper using a thermocouple from amazon with a aligator clip. What I am understanding is that for low cooks like 225, the top vent opening is going to be smaller opening compared to say a 350 degree cook. It held 350 with top vent open to the 1st mark. For 225, I'll try half of the first mark or smaller opening next time.
 
Bryan Mayland said:
What I can see in that image is Rule #1 of tuning: If HeaterMeter's output is 0, then the temperature should go down. If it just overshoots and stays there with 0 input from HeaterMeter, then it isn't controlling anything. This is caused by the smoker being able to pull in enough air on its own to burn indefinitely, so either the damper isn't closing or you've got too many other vents open / lid gaps letting air in.

No configuration settings are going to change anything until HeaterMeter is actually able to control your smoker. When it is at 100% output, the temperature has to go up, and when it is at 0% output the temperature has to go down. The "down" can take 5-10 minutes or so, depending on how big the overshoot is.
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Thank you Bryan. I just tried a low grill. 225 set point. I only opened the top vent by a tooth pick width and it seemed to hold the temperature after messing with the on above fan setting to 25%. Attached is my output. Could you tell if its doing good? Thank you. https://imgur.com/a/llwnADB
 
PShin said:
Thank you Bryan. I just tried a low grill. 225 set point. I only opened the top vent by a tooth pick width and it seemed to hold the temperature after messing with the on above fan setting to 25%. Attached is my output. Could you tell if its doing good? Thank you. https://imgur.com/a/llwnADB
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Yeah see that looks good! You want to see HeaterMeter in control so it is able to affect the outcome. Sitting at 100% or 0% for a long time would mean we're just getting lucky, since it's like we turned off the lightswitch and the light isn't going out.

The overshoot doesn't look too terrible, but if you want to lower that, there are two options:
  • 1 - Lower your Fan Startup Max. This will stoke the fire less on startup so there's less momentum as we approach the setpoint. Downside: it takes longer to start. Possible side effect: It slowly still overshoots and takes a long time to slowly come back down to temp.
  • 2 - Increase the PID "D" value. See how before the pit reaches the setpoint, the HeaterMeter output is already throttling back to try to prevent overshoot? We track that momentum of the temperature rise, how fast it is coming up to temperature. The faster it comes up, the faster our output drops off. The rate at which we do that is "D". Increasing your D to 8 or maybe 10 would make the output drop off more sharply, hopefully cutting it early enough to reduce or eliminate the overshoot. Downside: This just doesn't affect startup, so setting it too high means that in normal operation your output might go between 0% and 100% every few seconds. We want a smoother control hovering around, not full on/off all the time. That won't happen at 8-10 but it does set a practical upper limit how how D can be raised.
  • 3 - You can increase your "Fan on above" and/or lower your "Servo fully open at". Both of these reduce the actual air output for a given HeaterMeter output percentage, and adjusting them could create a more linear actual air flow curve.

EDIT: I should say that if your damper isn't operating properly, it isn't at the openness that HeaterMeter is requesting, then neither of these could apply because the damper helps to prevent overshoot too, so fix that first.
 
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Hi Bryan. Been meaning to thank you earlier for the awesome info. This is exactly what I needed to figure this out. Very practical and informative.

I just finished an overnight cook and came out perfect and stayed very tight to the set temperature for most of the cook.

I did want to ask you how I can better diagnose my graph. If I have a high "I" value but pretty neutral P and I values, what can I discern from that? My overnight cook stayed the course but noticed the fan output was close to 40 almost the whole time. Is this something that is good, bad, or indifferent, in your opinion? Thanks again.
bFNsbj7
https://imgur.com/gallery/bFNsbj7
 
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Wow that graph looks great! I mean your output is like rock stable and not oscillating on its own at all. The I value is exactly where it should be. It is like when you're driving down the highway at a constant speed and you're just holding your foot in the exact same position, that position is your I sum. Your temperature is close to right on, so 0 error means 0 P value. The temperature isn't changing, so 0 change means 0 D value. The I has "figured out" exactly how much it needs to run the output to keep the temperature stable and is just holding its foot there. When you'd need to be concerned is if your I value is bouncing all over the place.

As far as the output being 40% all the time, that means you could probably open your grill's top damper just a bit more and that would lower the average output. That might save you some charcoal on a longer cook at the cost of very slightly lowering your insurance against any flare up that might raise the temperature.
 
Phil,
Nice looking graph. What did you end up with for final settings? Also do you use any type of isolation plates between food and flame.
 
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