INTRODUCING: the "Roto Damper"


 
I have finished assembling my RDTC. It seems to be working fine.

I did have to carve the case a little near the pin header for the servo and blower. I think I discovered that the servo worked intermittently if its connector is a little crooked.

Tomorrow I will attach it to my UDS. I think I notice that the servo works differently, depending on orientation of the RDTC.

Has anyone noticed if it works better when its servo axis it vertical (vs horizontal)? Intuitively, I might expect that there is less stress on the servo if its axis is vertical.
 
Tomorrow is the inaugural cook on my UDS - using the HM4.2 with RDTC.

I am going to configure it to use the blower only when the damper is at 100%

What PID settings should I start with?

What max blower % should I use with the stock HM blower?

How should I use the "start-up" part of the blower % config?

Any advice is appreciated.

Thanks.
 
The settings are based on your setup and smoker/BBQ. PID settings, should be stock until you are sure they need to be changed. Blower settings are a depended on your smokers overall size. Start your smoker without the blower and RD attached and get a stable temperature, then add the RD and blower(100%) and check to see if it controls the temperature. if you are getting overshoots then lower the blowers percentage, to see if that helps. If the blower cant control temperature then maybe the blower is a tad to small. If the blower and RD are controlling the blower pretty good but you start to see a Sin wave that may get bigger over time then PID adjustments maybe needed.

The best advice though is to play with it and don't be afraid to make a change. Keep track of the changes, so if they don't work then you can revert them back and try again. There is still a lot of trial and error, but gradually you have a good understanding of what works and what doesn't.
 
I would start with the default PID settings, Startup set to 100%. If you are doing low and slow I would set the blower on at MAX only and set the MAX to somthing like 25%, so if/when you pop the lid the blower doesnt go crazy pumping air at 100%. From there you need to tune to your own grill...
On the RD rotation, make sure the servo isnt FORCED into the RD barrel, if it is too tight the servo will bind and rotation will be erratic, also make sure you dont tighten the servo screw so much that the RD becomes stiff, back off on that screw until the RD rotates as easy as it did before you tightened the screw...
 
Here is information about my inaugural HM RDTC run. The meat I am cooking seems like an afterthought today. This is fun.

I followed the advice I got here. I setup the UDS and manually got it up to my target temp - 225. The cool part about the RDTC was that I detached the electronics module and used the HM to monitor the temp while I let it climb to the target. Then I mounted the RDTC, and connected it to the electronics module.

150321%20-%20RDTC%20on%20UDS%20-%20Small_zps2xumpnia.jpg


I left the PID settings alone. I set the blower to run at max only - at 25% max. I found that the temp would drop even when the blower was on. Could it be that the 6.5 blower at 25% actually feeds less air than the damper open 100% without the blower on? I adjusted the max to 75%. As you can see by the chart, the damper is usually close to 100% with the blower on. However, I am very pleased with how it is maintaining the target - consistent. I used one of my iGrill probes to monitor the cooker temp - as a double-check of the T/C pit probe. With the offsets entered, they have tracked together pretty well. I actually reduced the pit t/c offset by 5 deg, and then again by 4 more during the cook - when the probes did not agree.
The big overshoot was when I pulled the butt and wrapped it in foil. I opened the lid to remover the meat, and then opened it again to put the foiled meat back in the cooker. That really freaked out the HM. When it reacted to the large overshoot, it drifted low enough to trigger the lid open mode. There is definitely some learning and tweaking. But great performance so far.

HM-RDTC%20Cook%20Chart%20-%20150321%20-%207%20lb%20Pork%20Shoulder_zpsgrybrozd.jpg


When I checked the probes in boiling water, I did it with the probes connected to the RDTC at the end of a 15 ft CAT-5 cable. The T/C pit probe was 27 deg low. It was 20 deg low when connected directly to the HM. Any ideas about that?

In conclusion, I am extremely pleased with the operation of the HM and RDTC. I am editing this post - instead of staring at my iGrill app and making frrequent trips out to tweak the inlet valve.
 
This is awesome! Read through the whole thread today and sent an email to Ralph to see about getting a RotoDamper & sliding back case.
 
The chart in my previous post shows that the damper was open all the way (100%) most of the time. Of course this turned on the blower. Soon after, when the temperature started increasing, the damper backed off (and shut off the blower).

My thought process right now is that my RD was not able to supply enough air with just the damper. Using the blower only at 100% damper ("On at max only") effectively caused the air supply to be "pulsed" - heavy when the blower was on, and much less when the damper output was less than 100%.

Even though I am ecstatic with how well it maintained the target temperature, I think consistent air flow is probably better for cooking.

I am now thinking that my UDS may operate better with the blower speed controlled at the same percentage as the damper position.

Further, would it be even better if I ran the servo (damper) in the "fully open or fully closed" mode, and let the blower speed maintain the proper air flow? If so, does that mean my UDS needs a bigger damper, or just use a blower with no damper?

Intuitively, I prefer the concept of controlling convective air flow instead of forced air (blower).

Perhaps I need an inlet bigger than 1 inch? Also, do larger exhaust ports 'encourage' better convective flow - due to better draft? My current exhaust is 4 1" elbows on the lid.
 
Looks to me like you need more fire, and or need to deliver the air more directly to the fire? I've never run a UDS so it's tough for me to say what the requirements are. I know the settings I recommended to you are pretty ideal for a Kamado, but you are right, you're HM shouldn't be running anywhere near 100% all the time.
So I would either get a bigger fire going and/or set the HM to run BOTH the RD and the blower I (turn off the "On at Max Only" option) and see how it goes. The fully open/closed option should also work well, but I tend to prefer full action on the RD unless I am doing high heat cooks like Pizza. Also make sure the ball valve you got there is wide open...
 
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From my experience of using a blower on my UDS for 4 years or so...

Do you need a damper/blower? Nope, the UDS will hold temperature perfectly flat +-1 degree for many hours with just using the ball valve.

Can you use just a blower? Yep, I did this way, 3 years or so.


Further, would it be even better if I ran the servo (damper) in the "fully open or fully closed" mode, and let the blower speed maintain the proper air flow?
Yep, this is the way I run mine on the UDS, and it will hold awesome temperature.

If so, does that mean my UDS needs a bigger damper, or just use a blower with no damper?
If not using a damper or blower, having more or a bigger air inlets would be just as good as have a 1 inch(same as mine) and a blower(with or without a Rotodamper). If properly setup using the ball valve and a blower, you don't need to use a Rotodamper on a UDS, in fact I just use mine as a way to mount the blower to the smoker.

Intuitively, I prefer the concept of controlling convective air flow instead of forced air (blower).

Then you would most defiantly, would need more air inlets around the bottom of the UDS, the Rotodamper wont by its self control the UDS, as the half moon shaped air inlet restricts some air and a 1 inch inlet would not be enough. I originally has 4 3/4inch holes for inlets and would control the UDS with the ball valve, but I usually had one of the other holes cracked open or fully open to get the temperature to stay at setpoint. The problem with that, if using a RD in the mix would be getting everything set correctly and that can be a big hassle, trying to figure out exactly how much to open other air inlets to help the RD maintain a steady temperature, if the wind picks up be prepared to manually change the air inlets not being controlled be the RD.

Perhaps I need an inlet bigger than 1 inch? Also, do larger exhaust ports 'encourage' better convective flow - due to better draft? My current exhaust is 4 1" elbows on the lid.

Yes, bigger inlets would help. I use a Weber top on my UDS and it only has the 4 outlet holes on the lid, so the 4-1 inch outlet hole should be ok.

Next, weekend, I am going to be testing a new HM for somebody I just built for them. I will be using a 25CFM blower and a RD. I will post the link on the thread for your live cooks, and if you get a chance to take a look, you will see the benefits of using a bigger blower. The UDS needs a minimum of at least a 8.4 cfm regardless of using anything between .5 or 1 inch pipes on the air inlet I have used both without much difference. Although, If you plan on higher heat during colder months, then having extra inlets would help. Temps above 40 the 1 inch, should be fine for UDS cooks.

Most people would agree that the UDS runs perfect without any blowers and Servo dampers, Its a set it and forget it smoker, and I agree with that. Mine would stay at 230 for hours and hours sometimes. But, using a blower, you need to restrict air flow, so that the blower controls the smoker and that's the whole idea of using a servo controller, to restrict the air flow, so that the blower can do the work quickly and then the servo closes the air inlet. If you look at your graph above, The blower is continuously running at 100% for the most part, is not really controlling the smoker. Its not able to push in enough air into the smoker. 6.5 cfm on the UDS is just way to small. I can start my UDS charcoal basket and then set the setpoint on the HM and walk away, knowing that the Temp will be at setpoint within a few minutes, unless its running hot then it could take a bit of time to settle down first.

Here is a pic of my setup
1f75y.png
 
Thanks for the feedback guys. The reason I ended up with an HM and an RDTC, is because I was not ever able to get my UDS to be "set and forget". I have tried many methods. I took great care when I built it - to prevent air leaks. It runs well, but its temperature is always climbing or falling.

I do recall now that many people have figured out how to fit a Weber lid onto their UDS, and they have just the one pinwheel exhaust vent. My 1" ports should OK.

I guess I have to disagree somewhat with John. You wrote:
"If you look at your graph above, The blower is continuously running at 100% for the most part, is not really controlling the smoker. Its not able to push in enough air into the smoker. 6.5 cfm on the UDS is just way to small".​

When I look at the graph, I see that the blower ran, and then shut off when the output (servo position) dropped below 100% (I also saw that visually. Since it was my first HM / RDTC cook, I spent many hours just watching. It was fun.) I was running like Ralph suggested - with the blower "on at max only". In addition, I set the blower max to 75%. Therefore, the 6.5 cfm blower at 75% (~ 4.9 cfm) pushed enough air to cause the temperature to climb above the target.

So what I am concluding based on your advice, and my own limited experience is this:

  • The "On at Max Only" option should not be used if the damper can fully control the temps all by itself. The blower will then be used only for quick target increases (incl startup), and maintaining higher temps when more air is required.
  • If I want to use only convective airflow (no blower under stead-state conditions), I need to increase the damper size. I don't want to open other ports. I prefer that all input air is controlled by the HM.

During my next cook, I will configure the HM to run the damper and the blower at the same output %. I could then just change the max % of the blower to "shift" the output range required for the target temperature, and how much meat is in the cooker. This is something I can do with just a configuration change. That would verify if the blower can provide enough air, and controlling the blower speed would at least make the airflow more consistent over time.
 
In the middle of my first cook with my HeaterMeter & RotoDamper. Having some problems maintaining temp. Cooker is a WSM 18.5". RD is attached via dog dish over one of the bottom vents, other two bottom vents are closed. Top vent started fully open. At 6:30 I had set my alarm and woke up, while not perfect, it looked good and I went back to sleep. At 8:30, woke up to 245 deg pit temp. Maybe it got windy? Not sure. I peeked once to make sure my pit TC hadn't come loose and fallen or something. It kept creeping up so I peeked again and put in another probe with a different thermometer system to make sure the pit TC was reading correct. So at the high temp around 8:45, I shut the top vent 50%. Then pit temp fell but overshot bad when the fan ramped back up, so I shut the top vent a little more. Left it alone since, now it's bouncing up and down between 210-235. When the fan kicks in (I have it set to fan on at max only) it cools the cooker off quite a bit before the temps pick back up. Not sure what to do now.

VCfqyXJ.png
 
First thing to do is make sure the RD barrel is still hugging the body closely, some MG90s servo's will let the shaft pull out of the body which will let the RD valve loosen up. If this is the case then use the shims to tighten it back up. Next, you can leave the startup max set at 100% but might be better to have the regular max set way lower, like 20% or so.... Can give you more advice later, but just got a call and have to run....
 
I am about to try wiring my HM 4.2.4 for the RDTCv6. Since I use a Thermoworks 72" 113-041 alligator probe I have no problem reaching my HeaterMeter with it which is in a Rubbermaid chest next to my Green Egg. Therefore I plan to wire the incoming CAT5 RDTC probes (pins 1, 2) to HeaterMeter food probe jacks 1 and 2 and the RDTC probe ground (pin 8) to the ground at one of the HeaterMeter probe jacks. Lastly I will wire the incoming CAT5 RDTC TC output (pin 7) to the disconnected end of the 100Kohm RC filter resistor that feeds the AtMega for food probe 3. Does that sound right? Thanks Web
 
Peachy. The wiring seems to all work, but today it has decided that the root password is not what it was yesterday. Is there any simple way to reset the root password?
 
Web Dove said:
Therefore I plan to wire the incoming CAT5 RDTC probes (pins 1, 2) to HeaterMeter food probe jacks 1 and 2 and the RDTC probe ground (pin 8) to the ground at one of the HeaterMeter probe jacks. Lastly I will wire the incoming CAT5 RDTC TC output (pin 7) to the disconnected end of the 100Kohm RC filter resistor that feeds the AtMega for food probe 3. Does that sound right? Thanks Web
Click to expand...

That sounds right, the only thing I might add is you can use a SPDT switch between the HM TC amp and the RDTC amp so you can use either as your pit probe at the flip of the switch. Just wire the common leg of the switch to the resistor end you have lifted, and put a wire between the hole you lifted the resistor out of and one leg of the switch, and the jumper wire from your CAT5 jack pin 7 to the other leg of the switch.
 
Actually I want to be able to use my thermoworks meat probes so I need both thermocouple amps at the same time. That was why I connected the RD TC amp to probe 3 on the HM
 
Ah.... yah, you can do that, but you would need to remove the 10K pullup resistor for that probe, or put it on a switch so you can use the standard probe or the TC probe there.
 
RalphTrimble said:
Here is a graph of the first test burn...
RotoDamperGraph.jpg



I started the pit with an alcohol soaked cotton ball and lump coal, the HM was set in damper mode (with fan assist at 100% only) and a setpoint of 175 degrees. There was a short 5 degree overshoot then she settled right in on 175 degrees and held steady. Then I upped the temp to 225, the pit responded quickly due to the fan assist, then I bumped it to 250, then bumped back down to 225 to test the rise and fall with the valve. Finally I set the pit to jump way up to 375, the blower kicked on and you can see the super fast rise up to 375 on the graph, most excellent!
Click to expand...

Ralph,

Thanks for all of your work and advice on the Roto-Damper and the Fauxmodo.

For the benefit of the class, what were your settings like in this test?
BPID? Fan Min/Max?

Looking forward to firing up the redhead tonight with its new roto-damper.
 
I stick pretty close to the (old) stock PID values... For low and slow I set the fan on at Max Only, for medium temps I let the fan run all the while but set the blower Max at about 20%, for high heat pizza cooks I set both blower Max values to 100%. I always leave the blower startup max at 100%.
 
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