Is using just servo control enough?


 
D

DavidNP

TVWBB Member
for my kamado, I usually smoke around 220-340 (don't do any high-temp cooking with HM).....

I think it's been said that for low-slow that the fan is hardly used to maintain temps, so would I be missing anything/control with just a servo controlled damper (no fan at all?)....other than getting to a setpoint would take longer....

I'm working on a mini-all-in one and trying to make it with as little components as possible.....(and battery operated would be great with no fan)...

which damper design would allow the for the most air-flow control using just a single servo?....
 
I do all my low and slow cooking with the damper only, though I do stoke the pit to temp with the blower. You shouldn't have any problem achieving/holding that temp range in a kamado without a fan, though it may take more time to heat things up, but if you master the timing of closing the lid you could leave it open longer to stoke in the open air and make the initial warm up go quicker...
As for which damper, you would want a damper with a large opening, my RD3 damper has a large opening but it is designed to house the blower inside it. I haven't printed a micro damper, but the damper portion is very similar to the RD3, if you truly plan to run with no fan at all the micro damper might be the best choice due to it's smaller size.
 
DavidNP said:
which damper design would allow the for the most air-flow control using just a single servo?....
Click to expand...

The most airflow is with nothing other than the built in damper on the smoker itself. I have mine set up to just directly open and close the damper on the grill itself, works perfectly
 
Thanks for the plug Ralph. In the end all that matters is which portion of the damper has the smallest cross sectional area. It don't matter if the intake is gigantic, flow will be restricted if the exhaust is the size of a pea. With that said, I don't have a RD3 anymore so I'm not sure what the size of the exhaust is, but it's certainly smaller than the intake. The MicroDamper has a near equal size intake and exhaust (I increased the size of the intake slightly to offset for drag), equivalent to the area of a 1" diam tube. I sized it based on the fact that I can run my UDS with a single 1" ball valve once it is up to temperature - so you should have no problem running it on a Kamado. Someone on this forum has said they are using it on their kamado just as you are looking to do. I don't remember who, perhaps they posted in the MD thread, not sure.
 
Here's a cook that I am just wrapping up which uses a microdamper on the large Big Green Egg. I have it set to fan on above 50% damper fully open at 50%. I didn't to such a good job of putting it together, so there's some gap between the damper wheel and the face so it doesn't make a great seal, in fact I just noticed it doesn't even have a screw in it. That's why when it goes over setpoint it can take a little longer to come back down. Still, the peak temperature was 255.8F on a 250F setpoint. It does sometimes go over 50% speed which means the fan is kicking on though.
o67AeK4.png
 
Bryan Mayland said:
Here's a cook that I am just wrapping up which uses a microdamper on the large Big Green Egg. I have it set to fan on above 50% damper fully open at 50%. I didn't to such a good job of putting it together, so there's some gap between the damper wheel and the face so it doesn't make a great seal, in fact I just noticed it doesn't even have a screw in it. That's why when it goes over setpoint it can take a little longer to come back down. Still, the peak temperature was 255.8F on a 250F setpoint. It does sometimes go over 50% speed which means the fan is kicking on though.
o67AeK4.png
Click to expand...

Bryan what pid did you use?
 
Wait did I just delete my post by mistake?

P=5 I=0.01 D=10
Although I would probably up the I back up to I=0.02 or I=0.015 because you can see how long it takes to unwind the I-sum after the pit crosses the setpoint. Upping the P a bit (maybe 6 or 7?) could help as well. Either way, a 2-3F swing every 2 hours ain't too shabby.
 
Bryan Mayland said:
Wait did I just delete my post by mistake?

P=5 I=0.01 D=10
Although I would probably up the I back up to I=0.02 or I=0.015 because you can see how long it takes to unwind the I-sum after the pit crosses the setpoint. Upping the P a bit (maybe 6 or 7?) could help as well. Either way, a 2-3F swing every 2 hours ain't too shabby.
Click to expand...

Thank you! I will be trying to run my kamado same way and this will definitely help me!
 
Bryan Mayland said:
I didn't to such a good job of putting it together, so there's some gap between the damper wheel and the face so it doesn't make a great seal, in fact I just noticed it doesn't even have a screw in it.
Click to expand...

I'm going to guess you're using the SG90 model? Even though I find the SG90 to be far superior to the MG90 (simply because of better manufacturing), the one downside is the screw that is used on the servo horn can be stripped if messed around with too much. Always good to screw in with firm pressure as it cut's it's own threads
 
I think it is an SG90 but the little gear bit that sticks out is too long by about a millimeter so the horn can't push all the way down to the damper face. It could easily be fixed by shimming either side with a piece of single ply cardboard or some foam but it works well enough that I don't mess with it. All the wires just come out the side and have alligator clips on them too because I never finished building it. It also is still screwed into the wind tunnel test rig so you can see where we are here. I got more important things to work on!
 
Hmm, I wonder if you printed the wrong version. The two servos share a similar shape, only real difference is the height of the nose on the servo (that part that secures to the servo body housing). Off hand I don't remember how much anymore but it's right around 1-2mm. I know how it is, if it works fine and you're too busy some things just will never get "fixed".
 
Bryan Mayland said:
Here's a cook that I am just wrapping up which uses a microdamper on the large Big Green Egg. I have it set to fan on above 50% damper fully open at 50%. I didn't to such a good job of putting it together, so there's some gap between the damper wheel and the face so it doesn't make a great seal, in fact I just noticed it doesn't even have a screw in it. That's why when it goes over setpoint it can take a little longer to come back down. Still, the peak temperature was 255.8F on a 250F setpoint. It does sometimes go over 50% speed which means the fan is kicking on though.
o67AeK4.png
Click to expand...

The question is to see how much more time it would take (assuming it would be enough air) with the damper fully open (without any fan) to get your temperature back up when it started to fall (did the fan 'boost' cause the overshoot at first 50%?)....

Considering what SteveCK said, I guess I should look to have larger than a 1" diameter area for better range? ....if you're using just a damper, would opening the top vent a little more mean you could get away with having a larger opening on the bottom (within reason)....I'll try and test it out once I get my 3d printer up and running again...

now if we have stepper support, then an attachment to the kamado's physical damper would work as well...
 
DavidNP said:
Considering what SteveCK said, I guess I should look to have larger than a 1" diameter area for better range? ....if you're using just a damper, would opening the top vent a little more mean you could get away with having a larger opening on the bottom (within reason)....I'll try and test it out once I get my 3d printer up and running again...

now if we have stepper support, then an attachment to the kamado's physical damper would work as well...
Click to expand...

I'm not sure I follow your logic. The more you open the bottom vent, the more you should be opening the top vent as well. If you're looking for maximum range without using a fan/blower, rig up your own servo to the exhaust built into your pit. I think you're best off using a damper with a fan/blower and if you want to run natural airflow then set your fan/blower to turn on at a high percentage. Also keep in mind that the graph you provided above will cook food just fine, just because the line isn't dead flat doesn't mean you're getting flawed bbq.
 
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