INTRODUCING: the "Roto Damper"


 
Bob Ivey said:
Just wanted to thank Ralph for the new case and the new RD3. They look great and work great.

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Nice design. I really like the switch on the case.
 
Hi Ralph,

Wondering if you are able to sell this already assembled or in a kit?

I am a bit intimidated by the aux board you have created, would it be possible for a layman to assemble one of these?
 
Hello, for the record, John Bostwick and I collaborated on building the Aux TC board. It is all SMD so if you are not up to doing SMD soldering then I guess building it is beyond your ability. SMD soldering seems impossible, but with a magnifier and a thin tipped soldering iron (and thin solder) it's pretty doable. However, there is also a hand wired version of the RD3 which requires no SMD soldering at all. (but does not have a TC pit probe that you can connect through the CAT5 cable)
As for the RD3, I don't sell them or sell kits, I do occasionally print the parts for people that don't have 3D printers but lately I haven't had time for doing much of that either...
 
Ralph, Thanks for the awesome design.

I'd love to replace my ping-pong damper with a real servo damper. How do I go about doing that?

I just got a 3d printer a week or so ago, as soon as I sort out the MAXTEMP error I saw last night, I want to print out a RotoDamper.

When I read all the stuff on this a few months ago, there wasn't a place to download the STL files.

Thanks,
-Mark
 
I've had good luck with the stock PID settings, lately I've been watching the HM system log after the pits held temp a while and using the auto-tune PID settings that are suggested in the log.
 
The fan settings have a lot to do with it, what are you running for fan and servo settings? How well sealed is your grill? Where are you running the top vent?
 
I used the settings you recommended. The grill is sealed tight enough that if I leave the servo closed, it snuffs out the fire. During startup with the fan running, I had the top vent opened just past the dimple. Once it went to damper control, I opened it up some more.

I've tried plenty of different fan and servo settings. I'm mostly interested in the PID settings folks are using. I have run the grill manually enough to know that the controller isn't responding optimally and the PID settings need tweaking.
 
You could always read over the PID tuning section of the HM wiki to get a better grasp on what each setting does. Sounds to me like the fire is building up too large at startup creating a long period of overshoot during which the damper chokes out the fire. I would suggest you start a smaller fire with perhaps less coals or less starting fuel, or lower startup max setting for the blower... it only takes a tiny bit of burning coals to hold 225F in a kamado.
Right now my PID settings are 1.4, .012, 1.4 as suggested by the HM auto tune log, though I have had them all over the spectrum and gotten decent results.
 
Yes, startup max at 100% (as was recommended) is way too high. I dropped it to 50% and it was better, but still too much. I will lower it some more.
 
I use startup max 100% and it works fine for me, the key is starting a small fire. What are you using for starting fuel? I use 1/2 of a weber starting cube...
That said, whatever works for you go with it, the HM has plenty of flexibility to run things whatever way suits your fancy....
 
Cotton ball with alcohol. Same as I've always used. It doesn't light too big of a fire without the fan. I've started dozens of cooks with the cotton balls both with manual vent adjustment and with the Auber and never had a problem. I really think the easiest thing to do will be to bring it up manually, either with the regular vents or by slowly walking the setpoint up, and then putting it in auto. Always worked great with my Auber.
 
How long are you burning the fire with the lid open after you light it? It seems like your fire is building up too large from the start for some reason...

As for PID tuning...

Look at the Manual PID tuning section on the HM wiki here

You can alter the PID settings to make the HM faster to respond (cut off earlier as the temp approaches the setpoint), or set the startup max setting lower, but to me it seems like you are lighting too many coals at startup since you are getting so much overshoot...
 
How long are you burning the fire with the lid open after you light it?
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maybe 5 minutes. not much longer than it takes to stick my diffuser in, put the cooking grate in, and clip my thermocouple to the grate.

It seems like your fire is building up too large from the start for some reason...
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yeah, exactly. seems to me it's because of the blower blowing so hard. no way I can get away with 100% startup max. not even 50% startup max. the high startup max seems to contribute doubly. it gets too many coals burning, but it also introduces so much cool air that it produces the cooling effect so that the temp i'm reading isn't a very good indication of how big my fire really is. so when i finally get close to the setpoint, the fire is way too big.

do you run an airburner on your akorn? perhaps an airburner chokes the air flow back enough that you can get away with a 100% startup max.
 
Nope, no air burner on the fauxmado...
It's been a while since I used the cotton ball start method, can't recall how long/hot they burn. I know with 1/2 or a whole weber starting cube I have no problems landing on 225 with the startup max set to 100%. Since the fire is choking out we know the grill is sealed up and the damper is working, you just need to get the initial stoking under control and you should be set...
How long is it taking to reach the setpoint after you light it?
 
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