New Toy - Ebay PID controller

[bubbonehead]

OK, ever since building my smoker I've been looking a these temperature controllers. They're pretty much all not in my budget if I want to keep the peace on the home front. Then I saw this one on Ebay selling out of China. The first thing that caught my attention was obviously the price of $99. Then as I read the item description I learned that I could upgrade to a 50cfm fan for just $10 more! 

I could not pass this up.

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• bubbonehead
• Mar 18, 2013

The seller goes by trustedinventer and said to allow 3 weeks for delivery. I got it in 10 days! I used it for the first time Saturday and am very happy with the way it performed! The preset settings seemed to be designed for a smoker that is not as indirect heat as my reverse flow. Once I changed the P value to 002, it kept my temp +/- one degree!

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• bubbonehead
• Mar 18, 2013

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• bubbonehead
• Mar 18, 2013

My only complaint if you want to call it that is the little light weight plastic box. The weight of just the wires made it difficult to keep it where I wanted it.

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• bubbonehead
• Mar 18, 2013

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• bubbonehead
• Mar 18, 2013

So Sunday I made this stand out of some scrap. Problem solved!

 

[DanMcG]

Kool stand

 

[michael ark]

Sweet .I have been looking for one.

 

[dennis waters]

Is this the one they show for the Green egg? Did you have to do any conversion for your smoker?

 

[bubbonehead]

Actually, I just looked and he's either out of this model or discontinued it. Seems I bought the last one.

He has other versions on ebay now. Might be worth contacting him and asking. The model I have is called Golden Dog.

Here is a link to what he is currently offering. http://www.ebay.com/sch/trustedinve...h=item20ced544ef&rt=nc&_trksid=p2047675.l2562

I did modify the adapter it came with a little.

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• bubbonehead
• Mar 19, 2013

I had to extend the flange on one side. Otherwise this handle would hit the fan before my vent closed to the original flange.

The mount for the fan has two heavy duty springs that snap into the opening similar to that of the auberins product.

Instead of extending the flange, I could have repositioned the handle on my vent slide.

 

[bubbonehead]

Looks like he has restocked this unit!

http://www.ebay.com/itm/Programmabl...925?pt=LH_DefaultDomain_2&hash=item20d08bc74d

 

[bigtexun]

That looks like a pretty sweet PID rig...

I just assembled my own PID rig for my Char-Griller Kamado Kooker.  I used a $23 PID off of Amazon, added a $12 thermocouple, an $8 SSR and a $46 smoker fan from auberins.com.  So it came out to a similar cost to the one I see selling on ebay.

The downside to my rig is the documentation for the PID is awful, so learning PID theory from the documentation isn't going to happen.

My smoker is an insulated unit that is very efficient, it can burn a day and a half on a single load of lump charcoal.  So doing a low and slow cook of something like a brisket doesn't require adding fuel.  But that efficiency can bite back, if you overshoot the desired temperature, it is difficult to get the temperature back down to where you want it, without causing the fire to go out.  So the secret is to not let the temp overshoot.

I started down the path to my PID rig after deciding I wanted to build a network connected controller, similar to a stoker.  I figured I would start with a standard PID, then work on designing my own linux based PID that I could put on the Internet for control from work.

In general, it is difficult to maintain a temperature lower than 230 just by adjusting the vents alone, it requires the vents to be nearly closed, and for there to be no wind.  If the wind changes during the cook, the temperature overshoots.  I figured that a good controller would allow me to achieve lower temperatures by pulsing the fan with a duty cycle that is used to steer the temperature.

The first test run with the PID has demonstrated that the PID is having similar trouble, and the autotune mode didn't really find a good set of settings.  The pid is overshooting, and failing to get a low enough pulse cycle to bring the temperature down after an overshoot.  It is tending to keep the temp in the 150 to 160 range.  But the good news is it isn't causing the fire to go out, it is still cycling on enough to keep the fire lit.  But clearly I need to learn PID theory, so that I can manually select the values I need.  I wish I had seen the unit that you purchased, for just a few dollars more I could have had someone to give me tech support that probably speaks English.

On the bench, the pid seemed to work pretty good.  I had expected some overshoot in the initial trial, but I was hoping that autotune would correct it, but it has become clear that I probably need to learn to manually tune the system if I'm going to achieve success. But it could also be that the PID is simply not set-up correctly.  Any advice for me?
 

 

[bigtexun]

Update...  I noticed that after running for a while, the PID turned off autotune, and tended to hover within one degree of 250 when set to 220.  So I decided to try turning it down to 190, and see what happens...  Sure enough, it went down to 220.

So the temperature is under control, I just have something configured wrong, or the PID is off by 30 degrees.

 

[bubbonehead]

I don't know how universal these settings are from one controller to another, but this unit came preset at:

P = 0030

I = 0240

D = 0060

P  depends on the present  error, I  on the accumulation of past  errors, and D  is a prediction of future  errors, based on current rate of change.

Because my smoker is a large indirect reverse flow, I ended up with P set at 0002 because I'm reading temp so far away from were I'm causing change. Yours wouldn't have that issue so the orginal setting of 0030 probably would work well. 

Sounds like you need to calibrate your [color= rgb(24, 24, 24)]thermocouple. On my unit that is done by adjusting the value of Pb. Ice water should be around 32F, and boiling water 212F.[/color]

[color= rgb(24, 24, 24)]Hope this helps a little.[/color]

 

[bigtexun]

Yeah, what I discovered is that my PID seems to be getting glitched by something...  When I reboot it, it behaves better.  But the alarms seem to still work correctly.

I just need to stop futzing with the PID, and get a linux PID library and build my own controller.  The one I have now works good enough to get me by until my linux based controller is ready.
 

 

[bigtexun]

So I did my first smoke with my new PID set-up.  I purchased a small brisket consisting of the point end only.   I put it on at midnight, and the only problem was I was very low on charcoal, so I only loaded 1/3rd of the normal load, so I wasn't sure if it was enough or if it would stay lit.  Near the end of the cook, the temperature started dropping off because the fuel was out, but other than that it was a perfect brisket.

Previously I have had some good briskets, but I also had some that were over cooked.  Adjusting the temperature by adjusting the vents sounds easy, but with every change in the wind, temperature control would be lost.  Now with my cheap PID solution, I'm seeing effortless temperature control.

I found some example PID software on the net, so the next step is to see if I can build my own PID based on a small linux system.  Once that is working, I'll be able to put up a bbq web server that I can check with a smartphone, the TV in the living room or from my desk at work.