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Chargriller....basic questions

post #1 of 27
Thread Starter 
So, I'm new here (well, I've been spectating for a bit). I've had a Chargriller pro with the SFB for about a year now. I haven't done any of the mods I've read so much about. I'll probably get to dropping the chimney first, but until then, what about the coal grate in the smoke box? When you guys are smoking, do you leave that in? I guess it doesn't hurt anything, but I didn't know if the heat would circulate differently without it.

Thanks for the advice. You guys have really helped a rookie become an adict really fast! One of these days I'll post some pictures of my servo actuated, computer controlled damper. I read the temperature from one of my wireless probes into my computer, then update the damper position as needed to maintain temp. Yes....my name is Josh....and I have a problem!


AKA: Geek with fire
post #2 of 27
I want to see a pic of that damper mod. That's a first. I use my CG with the the grate flipped upside down to allow air to continue to flow after some ash built up.

Hope this helps!

Take care, have fun, and do good!


post #3 of 27
welcome Josh, you computerized your smoker?????????????? wow.

leave the lower grate in,and place your wood / charcoal on that,also turn it
so that the ends point up and catch the charcoal that will roll off the ends other wise.
also if you open the chimney flap all the way and your damper vent 1/3 you
should maintain 225 degrees without trying.

good luck

post #4 of 27
Got a pic of that, I'm trying to understand, but cornfused. I get that way all to easily anymore.

My son has a CG. He turns the grate in the main part upside down, and uses it as a baffle. We have found that the SFB works best for us when we build the fire on the cast iron grate that sits about the middle of the box. When we tried building the fire on the bottom grate, we couldn't get up to temp no matter what we did.

He has yet to do the stack mod, but he usually cooks so much that the pipe would get in the way.
post #5 of 27
Thread Starter 
Thanks for the suggestions. Although, I must be doing something wrong, 'cause If I leave the damper alone, the temperature will change as the fuel burns down. With the laptop rig, I add sticks and lumps about every hour on a long smoke and maintain an average of 225 the whole time.

I don't have any pictures of the rig here at work, but here's a picture of the temp chart of one my early tests of the rig. Since I'm reading the temperature, I thought, why not log it. So, every 20 seconds, I save the temperature and the damper percentage to a database.

AKA: Geek with Fire
post #6 of 27
Way toooooo high tech.PDT_Armataz_01_23.gif
post #7 of 27
Oh a geeker after my own heart! Tell us more about the servo system?
post #8 of 27
Thread Starter 
No problem. I take the probe from my Maverick BBQ wireless thingy and run it to a digital I/O card that plugs into my laptop. I wrote a Visual Basic program that reads the temperature and runs a PID Loop (for all of you Engineering geeks out there) to calculate what percentage the damper should be set to; which updates every second (yeah overkill, but what the heck). The computer then takes this value and sends it out to the output of the I/O card and updates the servo position. The servo is connected to the thigh bone......no wait, I got distracted there.....the servo is connected to a pushrod, which in turn is connected to the damper. This keeps the servo away from the fire box and from getting crispy.

AKA: Geek with Fire
post #9 of 27
Welcome to the forum, Josh. It's great to have you here!

I'll be anxious to see pics of your current mods, as well as your future mods. The only thing I've done, so far, to my CG is to add the chimney downcomer. As soon as I get some high temp gasket from the warehouse, I'll add that too.

When you let the computer control your damper position, do you find that you get a consistent temp throughout your cooking chamber?
post #10 of 27


I have no clue what your talking about,but it sounds cool!
post #11 of 27
Thread Starter 
Well, that's a good question. I usually put the probe right in the middle of the smoke chamber. I haven't really made any attempts to tune the smoker so right side is hot, left side is cooler. I guess what I'm saying is, the temperature I'm reading is the average temperature. With the average temperature maintained, I focus more on the temperature of the meat with a separate probe.

AKA: Geek with Fire
post #12 of 27
I am interested in how you are reading the probe. I too am a VB programmer and was considering doing something similar. I have a dataq and was considering hooking it up to an air intake tempature sensor off a car since I know the voltage map for it. I also have a maverick therm, so if that is easier to read, I'd like to try it.

post #13 of 27
Thread Starter 
Most meat temperature probes are based on NTC Thermistors. As the heat increases, with an NTC Thermistor, the resistance decreases. However, this relationship isn't linear; meaning doubling the temperature isn't half the resistance. There's a fairly simple calculation to get around this:
T = 1 / ( a + b.ln(R) + c.ln(R)3)
With that said.......I cheated. I didn't want to have to pull out the ohm meter to setup my rig. Better yet, if some day I choose to market this (which I doubt), I didn't want someone else to have to have a special tool like a multimeter. So, I added a process in the program to calibrate the probe based on a scale of 5 degree increments. I just took relative measurements on the probe every 5 degrees and stored this in the database. When a reading is taken on the probe, it looks up the appropriate values in the database and calculates the temperature.

AKA: Geek with Fire
post #14 of 27

Holy Crap!

Just when I think I have done all I can do to improve the performance of my CG, along comes this...

I have been in the electronics industry for better than 37 years (I design printed circuit boards) and I never in my lifetime would have thought to hook my laptop up to my smoker. PDT_Armataz_01_23.gif I am afraid that if I did that mod to my smoker, my wife would REALLY think I lost it. PDT_Armataz_01_11.gif

Sounds interesting though... got pics?

Oh, and welcome aboard! PDT_Armataz_01_34.gif
post #15 of 27
Thread Starter 
Thanks. You know what's really funny? You guys are actually intrigued.....my family thinks I'm a nut. It's so nice to finally fit in somewhere (I'm not sure what that says about you though! PDT_Armataz_01_12.gif )

I still don't have any pictures (which is shameful, because I'm also a professional photographer...go figure!). I do have a really....and I mean really terrible video of my indoor prototype. This was an electric skillet with water in it. The water was intended to simulate the heated air in a smoker, and to calculate the response of how long it would take for an adjustment to effect the temp. Water doesn't have quite the same thermal properties as smokey air, but close enough for what I was trying to accomplish. Anyhow, here's the video:

AKA: Geek with Fire
post #16 of 27
Must see pic of the rig on the smoker!!!

Take care, have fun, and do good!


post #17 of 27
This is similar to what I was thinking about with the AIT sensor, except I was planning on reading the voltage after suppling a 5v source. I got the idea, because I datalog the sensors on my supercharged mustang when I am tuning it.

What IO card are you using to read the resistance? The IO devices I've seen that work directly with thermocouplers are in the $400 range which would make it too expensive for me to play around with.

post #18 of 27
My family thinks I'm a nut too but they let me chatter away about something I'm working on and then I say "Did you understand a word of that?" They always say "No, but you were so excited we didn't have the heart to stop you." rolleyes.gif
post #19 of 27
Why that thing'll be the ruination of good old fashioned hand cooked BBQ if you ask me.icon_evil.gificon_evil.gificon_evil.gifbiggrin.gif
post #20 of 27
Welcome josh...................And just think, all I thought I had to do was to light some charcoal and wood, throw meat on the smoker, and wait. PDT_Armataz_01_05.gif
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