Bryan Mayland
TVWBB Hall of Fame
I think that has a lot to do with it, the fact that I have a BGE. I've also had like 4 years to dial in my PID values. The new PID info dialog (press P on the home page when logged in) helped a lot this time.
Post your HeaterMeter graphs
- Thread starter Bryan Mayland
- Start date
RalphTrimble
TVWBB Diamond Member
John, Nice to see you built the "air burner" and it is working out for you. It's really a very simple concept, but getting the air distributed more evenly under the coals is a big help in getting your coals to burn eventy.
If I had built your unit I would have gone a bit bigger (if it will fit) and added a cross member in the middle. I would have also gone with the holes on the top instead of bottom. I have the holes on top on mine and have never had any problem with ash or anything, the air will push it out if any gets in there. The thing I like about the holes on top is the little jets of air blow directly on the coals and this stokes them better, specially during the initial fire up. I can start my fire with just a little piece of paper set ablaze with a lighter, the jets of air assure the fire wont go out even if it just starts out smoldering.....
At any rate, it's awesome to see you build one of these, makes me feel like I contributed something to the community..... Happy Smoking!
If I had built your unit I would have gone a bit bigger (if it will fit) and added a cross member in the middle. I would have also gone with the holes on the top instead of bottom. I have the holes on top on mine and have never had any problem with ash or anything, the air will push it out if any gets in there. The thing I like about the holes on top is the little jets of air blow directly on the coals and this stokes them better, specially during the initial fire up. I can start my fire with just a little piece of paper set ablaze with a lighter, the jets of air assure the fire wont go out even if it just starts out smoldering.....
At any rate, it's awesome to see you build one of these, makes me feel like I contributed something to the community..... Happy Smoking!
RalphTrimble
TVWBB Diamond Member
Bryan, that graph looks awesome! Did I read it right, that you were running both the fan and servo and let the fan blow all the time? I guess your BGE must need a lot more air flow than my Fauxmado if that is the case.... At any rate, that looks like about as perfect as it gets. I know when I got my first graph that looked like that I was really "stoked"....
Thanks for the tip about hitting P to get the PID info dialog display, I had done that by accident one time and wondered what the hell I had done! LOL I still find PID tuning to be very mysterious and haven't quite got a feel for it yet. Could you possibly give an estimate of the operating range for each parameter? I have a hard time deciding how much I should alter the numbers, and it takes so much time to let the pit react and figure out what your change has done... My cheapo smoker works like magic with the default PID settings, but this Fauxmado is really tricky, I would really like to learn to dial in the PID settings for this thing cause I know it needs a lot of tweaking....
Thanks for the tip about hitting P to get the PID info dialog display, I had done that by accident one time and wondered what the hell I had done! LOL I still find PID tuning to be very mysterious and haven't quite got a feel for it yet. Could you possibly give an estimate of the operating range for each parameter? I have a hard time deciding how much I should alter the numbers, and it takes so much time to let the pit react and figure out what your change has done... My cheapo smoker works like magic with the default PID settings, but this Fauxmado is really tricky, I would really like to learn to dial in the PID settings for this thing cause I know it needs a lot of tweaking....
Bryan Mayland
TVWBB Hall of Fame
Yeah both at the same time. My fan has gotten somewhat gunky inside over the years I guess so my min fan speed is 25% to make sure it turns on. With your fan installed on the servo but off you can maintain 250F? I was worried about it needing >80% servo just to keep the temperature up. My fan is duct taped on for now though so maybe that causes extra restriction or something.
As for the PID value ranges, you definitely don't want anything close to 100 as that would mean the output would be pretty much on/off all the time.
P - Here's the easiest place to start. Think about what the acceptable temperature range is for operation. At what point of the pit temperature dropping do you want BWOOP BWOOP giver 'er all she's got, Captain! Divide 100 by that number. That's going to set the lower limit on the P value. For a setpoint 225F with a lower temperature limit of 215, P = 100/(225-215) = 10. That's your ballpark. The faster your grill can change temperatures by changing the output value, the smaller this number should be. In my graph the P was 3 because the blower can really turn things around quickly in there. With just the servo, if I opened it fully it would still take a long time before anything actually happened. Fast response, low P. Slow response, high P.
I - This is where the PID status window on the home screen can really help. Subtract your setpoint from the current temperature, multiply by that by your I constant and that is added to the I value on the pid status window every second. If you have a I of 1 and the temperature is off by 5 degrees, it will add 5% output every second. Because this can compound so fast, you want a pretty small number. The value again depends on the response time of your grill, faster response, lower I (I think, not 100% sure on this one). The easiest thing to do is watch the I value i the PID status as the temperature swings back and forth across the setpoint. It shouldn't have wild swings from like -25% to 25%. The I term's job is to figure out exactly how much output it takes to maintain your setpoint. The value should roughly be the same as the yellow "average blower speed" pip on the blower speed bar on the home screen. Your P value needs to be set at least close before you can tune this, and the value I think should be 0.1 or less always.
D - Again the PID status will help here. Your D constant is multiplied by the value dT shows on the status window. dT is the change in temperature over the last minute or so. You want to set your D high enough that you can see the output reversing as your temperature is changing. If you're at the bottom of a temperature swing and the temperature is starting to rise, you should see dT getting larger and the D status subtracting % from the output trying to prevent overshoot. If you set it too high you'll see the output stop before it gets to the setpoint, or the fan turn too early and prevent the grill from cooling to the setpoint. The way to logically think of a good value for this is to ask "If I'm at 223F, setpoint 225F, ad the temperature has come up 1 degree in the past minute, how much do I want to throttle back the output to prevent overshoot?". Like the I constant, this number is proportional to the P constant. Probably best to keep this under 20 unless you're having serious overshoot problems, and that's probably created by the P or I constants being too high.
As for the PID value ranges, you definitely don't want anything close to 100 as that would mean the output would be pretty much on/off all the time.
P - Here's the easiest place to start. Think about what the acceptable temperature range is for operation. At what point of the pit temperature dropping do you want BWOOP BWOOP giver 'er all she's got, Captain! Divide 100 by that number. That's going to set the lower limit on the P value. For a setpoint 225F with a lower temperature limit of 215, P = 100/(225-215) = 10. That's your ballpark. The faster your grill can change temperatures by changing the output value, the smaller this number should be. In my graph the P was 3 because the blower can really turn things around quickly in there. With just the servo, if I opened it fully it would still take a long time before anything actually happened. Fast response, low P. Slow response, high P.
I - This is where the PID status window on the home screen can really help. Subtract your setpoint from the current temperature, multiply by that by your I constant and that is added to the I value on the pid status window every second. If you have a I of 1 and the temperature is off by 5 degrees, it will add 5% output every second. Because this can compound so fast, you want a pretty small number. The value again depends on the response time of your grill, faster response, lower I (I think, not 100% sure on this one). The easiest thing to do is watch the I value i the PID status as the temperature swings back and forth across the setpoint. It shouldn't have wild swings from like -25% to 25%. The I term's job is to figure out exactly how much output it takes to maintain your setpoint. The value should roughly be the same as the yellow "average blower speed" pip on the blower speed bar on the home screen. Your P value needs to be set at least close before you can tune this, and the value I think should be 0.1 or less always.
D - Again the PID status will help here. Your D constant is multiplied by the value dT shows on the status window. dT is the change in temperature over the last minute or so. You want to set your D high enough that you can see the output reversing as your temperature is changing. If you're at the bottom of a temperature swing and the temperature is starting to rise, you should see dT getting larger and the D status subtracting % from the output trying to prevent overshoot. If you set it too high you'll see the output stop before it gets to the setpoint, or the fan turn too early and prevent the grill from cooling to the setpoint. The way to logically think of a good value for this is to ask "If I'm at 223F, setpoint 225F, ad the temperature has come up 1 degree in the past minute, how much do I want to throttle back the output to prevent overshoot?". Like the I constant, this number is proportional to the P constant. Probably best to keep this under 20 unless you're having serious overshoot problems, and that's probably created by the P or I constants being too high.
Ralph, thanks! I can always flip it over!
RalphTrimble
TVWBB Diamond Member
Thanks a bunch for taking the time to post that Bryan, I think I have a much better idea how to go about PID tuning now. I'm sure I will read it a dozen times over before it has all sunk into my (semi) thick skull...
So far I've not been altering the PID values in much smaller amounts than your post suggests may be appropriate, and haven't had the PID display onscreen to help me figure this out. I was gonna take a day off from the Fauxmado but I just got another blower I want to try out (15CFM) and want to experiment with this new information at hand, so I think I'll go and pick up a chicken or something that doesn't need to cook forever (cause I got a late start here today) and give her a go...
I did pizza's the last couple days with a new 25CFM fan, it did a lot better than the stock blower getting up to pizza oven temperatures, but at this point the 3/4" copper tube is limiting the flow a bit much so the fan whistles like crazy and still isn't quite delivering the air I need. I'm hoping this 15CFM fan is a bit quieter and plan on adding a second 3/4" tube to my grill adapter to double the air delivery volume for high heat pizza cooks.
On my Fauxmado grill with an undampered 3/4" input tube attached to the stock HM fan the pit will overshoot set points below 300 degrees reliably (LOL), it tends to want to settle in the upper 300's, so I have to damper down the input to keep the temps in check. The volume of the 3/4" copper is roughly equal to the opening of the stock HM fan, I have to reduce that down quite a bit to hold temps in the low 200's. That is why I was surprised you weren't getting enough draft through the fan on your BGE. Not sure if it's because your fan is gunked up and restricting flow, or my FauxMado is leaking somewhere and stoking a bit on it's own... prob my grill leaking... I haven't inspected it in a while and have done a lot of super hot pizza cooks, since its pretty new still it may have opened up somewhere from all that heat, I'll have to give it a once over (and cleaning) and make sure things are still nice and tight...
Thanks again for the very helpful info above, and all your work on the Heater Meter....
So far I've not been altering the PID values in much smaller amounts than your post suggests may be appropriate, and haven't had the PID display onscreen to help me figure this out. I was gonna take a day off from the Fauxmado but I just got another blower I want to try out (15CFM) and want to experiment with this new information at hand, so I think I'll go and pick up a chicken or something that doesn't need to cook forever (cause I got a late start here today) and give her a go...
I did pizza's the last couple days with a new 25CFM fan, it did a lot better than the stock blower getting up to pizza oven temperatures, but at this point the 3/4" copper tube is limiting the flow a bit much so the fan whistles like crazy and still isn't quite delivering the air I need. I'm hoping this 15CFM fan is a bit quieter and plan on adding a second 3/4" tube to my grill adapter to double the air delivery volume for high heat pizza cooks.
On my Fauxmado grill with an undampered 3/4" input tube attached to the stock HM fan the pit will overshoot set points below 300 degrees reliably (LOL), it tends to want to settle in the upper 300's, so I have to damper down the input to keep the temps in check. The volume of the 3/4" copper is roughly equal to the opening of the stock HM fan, I have to reduce that down quite a bit to hold temps in the low 200's. That is why I was surprised you weren't getting enough draft through the fan on your BGE. Not sure if it's because your fan is gunked up and restricting flow, or my FauxMado is leaking somewhere and stoking a bit on it's own... prob my grill leaking... I haven't inspected it in a while and have done a lot of super hot pizza cooks, since its pretty new still it may have opened up somewhere from all that heat, I'll have to give it a once over (and cleaning) and make sure things are still nice and tight...
Thanks again for the very helpful info above, and all your work on the Heater Meter....
Bryan Mayland
TVWBB Hall of Fame
The HeaterMeter defaults (BPID): 4, 3, 0.005, 5.
Steve_M
TVWBB Guru
Not a great start to the first non test use of the HM on the Kamado Joe.
Used 1 weber lighter cube, placed on the indirect plate, closed the lid and let the HM go to town.
BPID are defaults ( 4, 3, 0.005, 5 )
Fan is set to defaults ( Min 10, Max 100 )
I've got the top daisy wheel just open a crack, just enough to ensure that smoke doesn't get trapped inside.
I'm limiting the natural convection via the fan with some tape, but it's only marginally helping.
I can see myself being a good candidate for the servo driven damper.
Used 1 weber lighter cube, placed on the indirect plate, closed the lid and let the HM go to town.
BPID are defaults ( 4, 3, 0.005, 5 )
Fan is set to defaults ( Min 10, Max 100 )
I've got the top daisy wheel just open a crack, just enough to ensure that smoke doesn't get trapped inside.
I'm limiting the natural convection via the fan with some tape, but it's only marginally helping.
I can see myself being a good candidate for the servo driven damper.
Steve_M
TVWBB Guru
It took about 45 minutes for the overshoot in temperature to come back down to 225. The HM has been holding a pretty steady 225 for about 3 hours now. I opted to let this be a dry run rather instead of an actual cook. Pretty pleased with the way it's holding temps and I'll let it chug away overnight.
Steve_M
TVWBB Guru
Looks like there was quite the early morning party in the cooker. The first 3 hours were tame, followed by a roller coaster ride for another few hours and then things seemed to stabilize and kept on trucking. I didn't make any adjustments to the HM config or at the cooker from the time I started this as I didn't want to mess with any variables.
Also, unless a raccoon came by and managed to pop the lid open for a quick check, the open lid activation blip was a result of the temp dropping on its own.
Also, unless a raccoon came by and managed to pop the lid open for a quick check, the open lid activation blip was a result of the temp dropping on its own.
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Bryan Mayland
TVWBB Hall of Fame
Those varmints! Yeah it looks like the temperature took a nose dive faster than the I constant could compensate and the Lid Detect kicked off and then things got a little out of control. The fan had only ramped up to 20% during the dive and with a P of 3 and Lid % of 6, that should mean that the blower output should have been 39% based on the P alone, with the I adding another % every 15 seconds. Did a block of ice fall into the grill or something?
Steve_M
TVWBB Guru
I'm wondering if maybe the wind kicked up a bit outside during that early morning spike and was forcing fresh air into the cooker via the fan opening. Other than the ceramic heat deflector shield, there's nothing else in the cooker other than lump coal and the steel grate which sites about 4" above the shield. Maybe the heat deflector shield cracked in half and fell on top of the coals, who know. I actually haven't lifted the lid on the cooker and wont be able to do so for another 8 hours or so.
Right now it's going through some pretty wide temperature swings. I think I'm probably getting close to the end of the lump coal in the cooker. What looks to be happening right now is that the fan is blowing on the coals but the oxygen levels are too great for the level of combustible coals and when the set temp is reached and the fan finally shuts down, the coal temps surge since the fan isn't effectively trying to snuff them out and the cycle repeats.
This adds further weight to the idea that the servo controlled damper would lend itself to a much more even, controlled burn as you aren't forcing any air into the cooker, you are simply limiting the oxygen supply via the damper.
Here's a 12, 6, and 1 hour graph snapshot.
12 hours:
6 hours:
1 hour:
Right now it's going through some pretty wide temperature swings. I think I'm probably getting close to the end of the lump coal in the cooker. What looks to be happening right now is that the fan is blowing on the coals but the oxygen levels are too great for the level of combustible coals and when the set temp is reached and the fan finally shuts down, the coal temps surge since the fan isn't effectively trying to snuff them out and the cycle repeats.
This adds further weight to the idea that the servo controlled damper would lend itself to a much more even, controlled burn as you aren't forcing any air into the cooker, you are simply limiting the oxygen supply via the damper.
Here's a 12, 6, and 1 hour graph snapshot.
12 hours:
6 hours:
1 hour:
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Steve_M
TVWBB Guru
Did a pork butt yesterday and decided to try out the servo damper, and here's what happened.
02:00: Charcoal lit
03:00: Cooker at temp and meat goes on - set point of 230
08:00: Receive email and sms notifications that pit temp above 250
08:00 - 08:45: Realize I have some draft problems on my servo shroud and try to fix them
11:30: Temps take a big dive even with the damper wide open
12:00: Replace the servo + damper with the fan.
12:10: Fan was blowing full speed and overshot the set temp
13:30: Realize temps aren't coming back down so I close the top vent of the cooker some more
14:00: Temps drop and fan can start working again
15:00: Ramp up pit temp a couple of times till it hit 265 ***
20:00: 5 hours of solid pit temp control. Wish I had that for the previous 12 hours!
The cook result - happy, happy, happy!
*** Setting a high temp alarm on the meat probe really saved this cook for me. With the high-temp alarm set, the HM web screen would show a constant update on when it thought it would hit 195F based on the degrees per hour that the meat probe would rise. This is why I ended up kicking the temps up to 265 in hopes that I could get the internal meat temp to rise a little faster and it worked great. It pretty much hit 195F at 20:00 on the dot.
02:00: Charcoal lit
03:00: Cooker at temp and meat goes on - set point of 230
08:00: Receive email and sms notifications that pit temp above 250
08:00 - 08:45: Realize I have some draft problems on my servo shroud and try to fix them
11:30: Temps take a big dive even with the damper wide open
12:00: Replace the servo + damper with the fan.
12:10: Fan was blowing full speed and overshot the set temp
13:30: Realize temps aren't coming back down so I close the top vent of the cooker some more
14:00: Temps drop and fan can start working again
15:00: Ramp up pit temp a couple of times till it hit 265 ***
20:00: 5 hours of solid pit temp control. Wish I had that for the previous 12 hours!
The cook result - happy, happy, happy!
*** Setting a high temp alarm on the meat probe really saved this cook for me. With the high-temp alarm set, the HM web screen would show a constant update on when it thought it would hit 195F based on the degrees per hour that the meat probe would rise. This is why I ended up kicking the temps up to 265 in hopes that I could get the internal meat temp to rise a little faster and it worked great. It pretty much hit 195F at 20:00 on the dot.
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Latest cook 13 pound brisket, on my big steel keg. Cooking for late evening party so cooking during the day for one of the first times.Great time to tune my PID, I'm using servo without fan. I want to make removable fan mount so I can go fan and servo or just servo with no restrictions from the fan.
PID B 0 P 10 I .002 D9.78
PID B 0 P 10 I .002 D9.78
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Ralph,
This is my first smoke since I posted my first graph. I have switched my strategy. This time, I attempted to get my vents closed just below stable with the natural convection only and rely on the fan to keep the air flow at stable. It's working so much better. It probably took about 4 or 5 adjustments to get the vents where I wanted them. But, I haven't adjusted them in probably more than 2 hrs. I'm still using the default bpids. And, I'm still fan only. But, the HM is doing an outstanding job. I think Bryan should rename it from Heatermeter to Heatermeater.
Here's my graph after about 3 hrs. I will edit this post later with a final graph.
First brisket smoke on HeaterMeter w/ WSM 18.5
First brisket smoke with my HeaterMeter. A 10.5 pound packer that took 20 hours to pass the fork test in the flat. When it was done, the point was OK but the flat was dry. It was labeled choice but I think it was more toward select. Oh well, I'll just have to make chopped brisket in BBQ sauce sandwiches. I used the BBQ Guru Pit Viper 10 CFM blower and WSM Adapter.
I started my WSM with the meat probe in a water filled tin can and the pit probe on the grill. During that time the WSM ran hot probably because I have a leaky door. Once the meat goes on it places a large thermal load on the smoker and things settle out very nicely. I used the stock PIDs with min fan percentage at 10% and max fan percentage at 30%. I did not see where the max fan being set to 30% made any difference.
You will notice that the ambient temperature goes up to 120 degrees F. The outside temperature peaked at about 85 degrees F. I have a black HeaterMeter case and I guess it was in the sun. Should I worry about frying the electronics?
-- Mache
First brisket smoke with my HeaterMeter. A 10.5 pound packer that took 20 hours to pass the fork test in the flat. When it was done, the point was OK but the flat was dry. It was labeled choice but I think it was more toward select. Oh well, I'll just have to make chopped brisket in BBQ sauce sandwiches. I used the BBQ Guru Pit Viper 10 CFM blower and WSM Adapter.
I started my WSM with the meat probe in a water filled tin can and the pit probe on the grill. During that time the WSM ran hot probably because I have a leaky door. Once the meat goes on it places a large thermal load on the smoker and things settle out very nicely. I used the stock PIDs with min fan percentage at 10% and max fan percentage at 30%. I did not see where the max fan being set to 30% made any difference.
You will notice that the ambient temperature goes up to 120 degrees F. The outside temperature peaked at about 85 degrees F. I have a black HeaterMeter case and I guess it was in the sun. Should I worry about frying the electronics?
-- Mache
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Alan Erickson
TVWBB Fan
Mache, that's a pretty nice looking graph. Capping the max at 30 percent keeps things from getting out of control, but your cook went so well it was never an issue. What can happen some times is that you move a lot more air than you can heat and the controller just keeps ramping the fan so you move even more air when in fact you should be cutting it back. By setting a max, which from looking at your graph the most you need is 30 percent, that keeps that from happening. That's pretty amazing that you got 20 hours burn on one load of charcoal. Were you using lump or briquettes? Also, where were your top and other bottom vents set at?
Thanks
Thanks
Thanks for the comments Alan.
On my old BBQ Guru Competitor I have gone as long as 25 hours on a full ring of Kingsford Original briquettes.
For this cook, I used a full ring of Kingsford Original briquettes and started it off with the Minion Method using between 15 and 20 lit coals. Two out of the three bottom vents are fully closed and taped with metal HVAC tape and the third bottom vent is fully open with all but one of the vent holes taped shut with metal HVAC tape. The remaining open hole has BBQ Guru's Small Universal / Weber Adapter attached and their Pit Viper (a 10 CFM blower) inserted. The top vent was open about 1/8.
I let the blower try to stabilize for around 90 minutes before putting on the brisket but as you can see the temperature never did stabilize and started to rise. Using my old Competitor rig, I have always been able to stabilize empty before putting the meat on so this behavior is new. I can only assume my door has become more leaky (perhaps its time for me to get a Cajun Bandit aftermarket door). I believe that once the brisket went on, the rather large cooler thermal load overcame the air leaks and things settled out very nicely.
Sadly, however, while I have done many briskets with my Competitor, this brisket did not turn out as well. I usually do 14-15 pound choice packers but was only able to find a 10.5 choice packer this time. By the time the fork test seemed reasonable, it was close to 20 hours. The point was fine but the flat was very dry and coming apart. Either I missed an earlier successful fork test at a much lower temperature or this brisket was just a dud as far as fat and connective tissue content.
-- Mache
On my old BBQ Guru Competitor I have gone as long as 25 hours on a full ring of Kingsford Original briquettes.
For this cook, I used a full ring of Kingsford Original briquettes and started it off with the Minion Method using between 15 and 20 lit coals. Two out of the three bottom vents are fully closed and taped with metal HVAC tape and the third bottom vent is fully open with all but one of the vent holes taped shut with metal HVAC tape. The remaining open hole has BBQ Guru's Small Universal / Weber Adapter attached and their Pit Viper (a 10 CFM blower) inserted. The top vent was open about 1/8.
I let the blower try to stabilize for around 90 minutes before putting on the brisket but as you can see the temperature never did stabilize and started to rise. Using my old Competitor rig, I have always been able to stabilize empty before putting the meat on so this behavior is new. I can only assume my door has become more leaky (perhaps its time for me to get a Cajun Bandit aftermarket door). I believe that once the brisket went on, the rather large cooler thermal load overcame the air leaks and things settled out very nicely.
Sadly, however, while I have done many briskets with my Competitor, this brisket did not turn out as well. I usually do 14-15 pound choice packers but was only able to find a 10.5 choice packer this time. By the time the fork test seemed reasonable, it was close to 20 hours. The point was fine but the flat was very dry and coming apart. Either I missed an earlier successful fork test at a much lower temperature or this brisket was just a dud as far as fat and connective tissue content.
-- Mache
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