minimum servo opening while running.


 
M

Marc Strickland

TVWBB Member
Is there a way to set the servo to a minimum opening while you are trying to control the grill, but still have it completely close when you want to shut the grill down? The way it is working now, if the grill over shoots, it will close the vent, sometimes for quite a while. This causes the fire to go out. Currently I need to disconnect my servo and crack the bottom vent just a hair so that the fire does not go out, then reconnect it once the grill comes down to temp.

I know I can change the pulse duration of the servo and make it think a hair open is 0%, but then I can't use the controller to close the vent completely when I want to shut down the grill.

This is on a Primo ceramic grill so.. No air leakage.. Vent close = no fire.

I guess I can set the pulse duration so that 0% = a hair open and just disconnect the servo when I want to shut the grill down, but I like everything to be automated.... LOL

Anyone have idea's?
 
I'd focus on adjusting the fan output and PID values to something that doesn't cause the grill to over shoot in such a way that basically turns the HM control off for so long.

On my Kamado Joe I set max blower output to 40%. I also try and use servo only mode while cooking, only using the blower when absolutely necessary. This technique seems to work really well on the ceramic grills.

That said, you could craft some scripts to change the servo pulse duration triggered from temp high and low actions
 
No there isn't any "Even more off" position for the servo, 0% is as 0% as it gets.

If you're getting a lot of overshoot on startup, try maybe lighting fewer coals to start? You can also increase the D term to make it throttle back sooner as it starts up.

You can do a lot of crazy stuff with Alarm Scripts too. If you want 225F actual pit temperature and it always overshoots to like 245F (which would be a ton over overshoot you should try to correct), set the setpoint for 205F and alarm for 220F. When the alarm for 220F goes off, use a script to bump the setpoint to 225F (this can also be done directly in the Alarms UI I think). You can also set the D term super high and have the script cut it down to operating levels in the Alarm Script.
 
Thank you, I'll give a few things a try. I did change the servo pulse duration so that it can not close my vent all the way, that should stop it from killing my fire. at 0%, it is now open just a crack. I didn't want to play with the PID values since it used to be dead on. After thinking about it more, I realized I did change my grill, I added a Kick Ash basket and can. I'm guessing that since the basket has room all around it, there is probably much more air/ventilation around the charcoal then there was before I put it in. It's nice for cleaning the grill, but if I can't get the control dialed back in, it will not be worth it...

I played with the grill a bit this weekend and it can hold 240 just fine, but at 225 it is all over the place. I'll play with my PID settings and see if I can get it better, if not, I'll ditch the Kick Ash basket and just run it the way it was built which used to work perfectly, the only reason I went with the basket was because my charcoal grate cracked, and I needed something to replace it.
 
Marc
I have a Primo jr and I am including my settings config page. I also use an Adapt-A-Damper. I also run my HM with a battery to reduce issues with noisy power sources. Currently using threshold method of lid control. Using lid tracker with current configuration causes control instabilities that I have not figured out yet.current HM config_010421.png
 
The times I have issues with bad cycling... overshoot....followed by fire out......followed by overshoot......cycles......is when the amount of coals burning is not enough....air is cooling the smoker until it reaches setpoint, then when air cuts back temp goes thru roof. . Very late in cook when I try to use half a basket of old used coals...or totally encapsulated in ash...etc. or trying to reach 350 without enough hot coals, etc. The fix is always stoke the coals, add more, etc. Then like magic it lines out and controls well again. Sometimes big chunks of wood catching fire cause same symptoms. Blower on, they flame up. Blower off...eventually die out.
 
I wish I could say that every situation you brought up was my issue. Been using the hm for a few years now and I have my settings dialed in and know how my grill works. I am very careful when I light my lump and in the case of my last cook, coals still had 4-5 hrs left and they burned evenly and balanced. I am including a graph of this last cook and you can see how it cycled and then at 1300, I changed back to threshold control and the process came back to what it`s been for a few years. I ran another hour and then pulled ribs. I wish this time I could agree with you, but I cannot. I will try the Lid Tracker again and see if it was a fluke. I really do not want to go through process of re-tuning HM. The config page I included earlier has worked great when using my Adapt-A-Damper for a could 2-3 years. The only thing I do is either open or closed damper a little depending on the outside temp. I live where outside temp can range between 0 and 100 degrees when grilling. I also make my own thermocouples because mine last longer and the response of my TC`s is better that what I have purchased.

LastSession.png
 
FWIW, I never use the servo to kill the smoker. My concern is heat soak with no air flowing through the plastic to cool it down. I remove the servo and cover the opening with foil. Your setup may be different though. I've considered using a pipe to get the servo further from the cooker.
 
Darren
I agree. I always remove my damper and then use the silicone plug to close off adapter that the damper connects too.
 
No heat problem here. Dog bowl and 6" pipe nipple is far enough away it's unnaffected.

I melted one adaptadamper a bit.....too close to hot chimmney
 
I hear of a few people melting their Adapt-a-Dampers. If you are printing your own, I would highly suggest printing with at least a 50% infill. I know it takes longer, but I have never had one melt or disform with those settings. Also, probably stating the obvious, but use ABS.
 
You must log in or register to reply here.

 

Back
Top