First rPi+HM4 smoke experience questions/comments


 
B

Burt H

New member
Hello - first, thanks to Bryan and all involved with HM. Awesome project! :)

So I am running my first smoke with my unit, I am about 3 hours in. It started very stable for about 2 hours. Then it started to dip and overshoot a few times. HM detected/assumed the lid was open on several occasions. The last dip got down to ~200 degrees at which time I checked the coals and stoked them a bit to get the ash dust to fall through. So far it looks better but only time will tell. Is this pretty typical of other people's experiences? I have had to do that with conventional smokes as well, but usually not this early in the cooking time.

Also I was looking to start a thread dedicated to plots/screen shots of people's full cooks. I couldn't find one, does one exist? I think it would be useful to show typical experiences, trends, problem points, etc.

 
That behavior is not common, at least how my HM works with my cheapo water smoker. When the fan starts to ramp up and blow more like that for me it generally means the smoker is low of fuel, so perhaps add some more coals? Also, you can set the threshold on how low the temp has to dip before the lid open mode is triggered in the config, you might want to increase that percentage if you are having false triggering.
 
Yeah that's not typical of my experience either. Your smoker changes temperature a lot faster than mine does so you may need to play with the PID values a bit.
 
Ok so I reloaded more charcoal and it's holding well now. I am surprised I needed to add so early, but I am using the Target brand charcoal, maybe it burnt off faster. Here is the current data, it's been steady for an hour since adding more charcoal. I also tweaked the open lid trigger point to -10 for now. I'll have to read up on the PID tuning pointers.

For those using WSM do you leave the top vent on the lid wide open? I do, but curious if others do.

 
I leave my top vent wide open (on a UDS).

Did you really lift the lid that many times or did it just go off? Going into lid mode when you aren't supposed to really messes things up as well. You may want to increase the lid detection. I currently run mine at 10%, don't know what the default is, but I'm pretty sure it is less than that. My UDS does not hold heat well so I could get false triggers at a lower setting.

As a reference, here is my current cook. I changed the I pid value at 11:40 from 0.05 to 0.005 and it flattened out better. I also run a higher D=20 than default.

RibsJune9th_zpsca4d5c92.jpg


dave
 
Nope I didn't really open the lid during those first few triggers. I too changed mine to 10% and refueled. With a combination of the 2 it seems stable now.

Loving this HM so far!
 
Burt, a couple of questions, for science, regarding your first run:

How did you layout / start your coals? You mentioned a specific brand, did you light them all or were you doing a Minionesque burn?
Where did you have your dampers set?
How did you connect your blower to the WSM?
Did you put water in the pan?
Where did your PID / other settings settle down at?

Where did you put your pit probe and how did you string it out of the WSM?

Thanks! I have my first run tomorrow.
 
Sorry I didn't see this sooner, you are probably on your way at this point.

- Yup, Minionesque. I filled the ring with unlit briquettes and some peach wood scattered throughout. I then put about a dozen lit briquettes in the center (Started in a chimney).
- 2 of the dampers were closed, the third (which had the blower covering it) was wide open. Top lid vent was wide open too.
- Blower attachment method:
Stainless steel mixing bowl with a ~3/4 inch hole drilled. Copper plumbing parts. Threaded rod bent into a hook on one side which I hooked into 2 of the vent holes and used a wing nut and washer on the other side. I 'shaped' the 3/4" copper pipe to fit into the blower and drilled a small hole through the pipe and blower and put some small wire through that to ensure it wouldn't call off. I used some silicon caulk to seal it all up. It made a nice fit against the WSM.





- Water bowl was full
- PID settings left at the defaults (I am not smart enough on how to productively change them yet)
- Pit probe was sitting on the rack above the water bowl, same rack the 8lb Butt was on. I ran this probe through the lower access door. The meat probes I ran through the top between the middle section and the lid.

And finally here is my overall cook data. I had a bunch of false lid openings until I added charcoal and lowered the detection point to 10%. I wrapped the butts at around 1530 but canceled the 'lid open mode' by accident causing the spike. Around 1700 the temperature became steady but below the set point, the HM ramped to 100% and the set point was unattainable. It ran at 100% until I finished the cook, it was maintaining and I didn't want to add charcoal yet again. I did change the setpoint to 235 midcook, just as an experiment really, then later to 230. It had some false lid open detections then too until I changed the lid open settings. Lots to learn still, but so far I love my Heater Meter!

 
Oh, I forgot to mention. The 3 lb bone in butt read > 190 around 1630. I removed it, took it inside and checked it out. It didn't pull so I put it back in the smoker with the probe inserted somewhere else. You can see that the temp dropped, then followed the 8 lb butt's curve. Very odd, I don't know how I had such a hot spot in the meat yet the majority was about 10 to 15 degrees below that, I assume it must have been due to probe location.
 
I'm guessing your probe on the one butt was more on the edge than the center of the meat, or in a thin spot. When you are not able to hit the set point and the fan is running 100% that indicates you are low on coals, or don't have enough coals lit. When you were done with the cook did you have any coals left?
 
I also use a WSM and had the top vent opened the whole time for my last pulled pork. It was working not bad but I think it could work better. So does anyone have some good PID values? At the moment I work with the default ones and my last cook was for 19 hours without filling briquettes in again and the temp was allways at 115°C +- about 7-8°C.
 
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Did they burn off after the food came off or were they pretty much gone by the end if the cook? Reason I ask is because when the temp goes low and the fan ramps up high but the temp does not recover that usually means you are low on coals, either not enough in general or not enough coals that are lit....
 
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