Author Topic: What is a PID?  (Read 3963 times)

Offline pmmpete

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What is a PID?
« on: January 06, 2012, 08:02:10 pm »
When reading posts on this forum, I keep coming across the term "PID."  It's apparently some kind of temperature controller, but I don't know what it means.  I thought it might be a term used by Bradley to describe a part or an accessory, but Bradley doesn't sell a "PID."  Then I saw a reference to an "Auber PID."  Aha, I thought, I'm finally going to find out what a PID is.  So I went to Auber's website, and it turns out that Auber sells a variety of (dramatic drumroll) "PID Controllers" (rimshot).  Dang! So I still don't know what a PID is.  What are they?

Offline mikecorn.1

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Re: What is a PID?
« Reply #1 on: January 06, 2012, 08:15:22 pm »
I found this on Wikipedia  ;D

A proportional?integral?derivative controller (PID controller) is a generic control loop feedback mechanism (controller) widely used in industrial control systems ? a PID is the most commonly used feedback controller. A PID controller calculates an "error" value as the difference between a measured process variable and a desired setpoint. The controller attempts to minimize the error by adjusting the process control inputs.

The PID controller calculation (algorithm) involves three separate constant parameters, and is accordingly sometimes called three-term control: the proportional, the integral and derivative values, denoted P, I, and D. Heuristically, these values can be interpreted in terms of time: 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.[1] The weighted sum of these three actions is used to adjust the process via a control element such as the position of a control valve, or the power supplied to a heating element.

In the absence of knowledge of the underlying process, a PID controller is the best controller.[2] By tuning the three parameters in the PID controller algorithm, the controller can provide control action designed for specific process requirements. The response of the controller can be described in terms of the responsiveness of the controller to an error, the degree to which the controller overshoots the setpoint and the degree of system oscillation. Note that the use of the PID algorithm for control does not guarantee optimal control of the system or system stability.

Some applications may require using only one or two actions to provide the appropriate system control. This is achieved by setting the other parameters to zero. A PID controller will be called a PI, PD, P or I controller in the absence of the respective control actions. PI controllers are fairly common, since derivative action is sensitive to measurement noise, whereas the absence of an integral term may prevent the system from reaching its target value due to the control action.

Mike

Offline pmmpete

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Re: What is a PID?
« Reply #2 on: January 06, 2012, 08:52:58 pm »
Whoa.  Holy cow.  It's a good thing my smoker has a digital thermostat, because I don't think I'd ever figure out how to operate a "PID."  I am neither an engineer nor a mathematition.  Heuristically speaking, I'm your basic dope.  The only thing I use my cell phone for is making telephone calls.  I haven't figured out how to set the alarm on my digital watch.  I'm kind of a stone age guy.
« Last Edit: January 06, 2012, 08:58:50 pm by pmmpete »

Offline Quarlow

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Re: What is a PID?
« Reply #3 on: January 06, 2012, 11:10:47 pm »
Actually an Auber PID is very easy to use and regardless of the fact that you have a digital, your smoker would still benefit from a PID. Your temp swings in the Bradley are from 20 to 30 degrees + or - your set point. With an Auber plug and play PID you will only see temp swings of 1 to 2 degrees + or - the set temp.
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Offline ghost9mm

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Re: What is a PID?
« Reply #4 on: January 07, 2012, 06:46:20 am »
pmmpete...First welcome to the forum, here is a link that will or should be of some help to you on understanding the PID... read down through the thread and I think it is the eight post down the thread that GusRobin explains along with illustrations on how to set up a PID with your smoker. hope this is of some help to you..
So sorry I forgot the link so her it is..

http://forum.bradleysmoker.com/index.php?topic=18346.0
« Last Edit: January 07, 2012, 08:56:15 am by ghost9mm »
Digital Bradley Smoker with Dual probe PID
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Char Broil gas grill

Offline Quarlow

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Re: What is a PID?
« Reply #5 on: January 07, 2012, 08:27:37 am »
OOps Ghost forgot the link. Nice shootin' 9mm. lol
I like to walk threw life on the path of least resistance. But sometimes the path needs a good kick in the ass.

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Offline anderson5420

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Re: What is a PID?
« Reply #6 on: January 07, 2012, 08:46:51 am »
And now...the odd man out...unless you have a pretty good skill set to build a complete unit in a project box using the $45 basic Auber controller, probe, relay, and miscellaneous other electrical components, you are going to pay quite a lot for an Auber PID.  I looked at buying a plug-and-play Auber PID and it was just a tad outside what the Chancellor of the Exchequer would allow me to spend.  I own a brewery, and we use Ranco controllers on the fermentation tanks.  Rancos are digital controllers, and can control either heating or cooling.  I got mine from Grainger Supply for $75 tagged on to a brewery order, but I see them as low as $52.99 at Amazon today.  Just add a power cord, the simple wiring diagram is here and you are ready to go. Any way you slice it, play-and-plug or home wired, the Auber is going to cost more than the (nearly) play-and-plug Ranco. The model I have is the Ranco ETC 111000-000.

Is a Ranco as good as an Auber? That is like asking if a Doge Ram is as good as a Ford F350. I don't know, my temperature is always plus or minus 5 degrees of set temperature. The Ranco is very easy to use also.  You need a computer power cord for the Bradley cabinet, that gets  plugged into the Ranco.  Then plug the Ranco into the 120 outlet. The smoke generator is plugged in and switched separately. To set the Ranco, you just use the Set button and up and down arrows to set target temp, differential temp and mode (heating or cooling). Set one more time returns to a display of the current temp in the cabinet.

Whether you get an Auber PID or a Ranco, you NEED some kind of accurate temperature controller to do the drying step, the smoking step(s) and the cooking step(s) at the desired temperatures.  The fancy Aubers can do a lot more than that, but you really need one or the other if you are going to get consistent results. It was the best investment I ever made for this hobby.

Here is what the Ranco looks like:

« Last Edit: January 07, 2012, 08:48:28 am by anderson5420 »
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Offline ghost9mm

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Re: What is a PID?
« Reply #7 on: January 07, 2012, 08:57:31 am »
Digital Bradley Smoker with Dual probe PID
The Big Easy with Srg grill
MAK 2 Star General
Char Broil gas grill

Offline anderson5420

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Re: What is a PID?
« Reply #8 on: January 07, 2012, 09:17:14 am »
As should be obvious, the Ranco does not control successive cycles - when I want to step up the temperature, I have to go out and hit the Set button and arrows.  I also have to manually control the smoke generator. I suppose there is a model of Auber that can also play Yankee Doodle Dandy, if you want and price is no object!
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Offline ghost9mm

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Re: What is a PID?
« Reply #9 on: January 07, 2012, 09:59:38 am »
Here is the link to the most used PID on this forum, was made and design for the Bradley..

http://www.auberins.com/index.php?main_page=product_info&cPath=8&products_id=151
Digital Bradley Smoker with Dual probe PID
The Big Easy with Srg grill
MAK 2 Star General
Char Broil gas grill

Offline anderson5420

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Re: What is a PID?
« Reply #10 on: January 07, 2012, 12:10:34 pm »
Yes, if you follow that link, you will see the issue here.  $185 for the Auber PID, or $52.99 for the Ranco.  Both will control the temperature in the cabinet pretty much the same.  With the Auber, you have dual probes and can set cycles at different temperatures for different times.
So many recipes, so little time!

Offline rchunter

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Re: What is a PID?
« Reply #11 on: January 08, 2012, 06:06:17 am »
I built my smoker out of an old freezer cab. and installed a bradley smoke generator, auber pid control, and use the fan side of a "milkhouse" heater to provide some convection, and an electric stove element.  Couple issues came up I can share with you all that I had to "overcome".  First, one element was not enough wattage to bring a loaded cabinet up to temp fast enough.  Second, the auber controller is great, but voltage in equals voltage out and using it to control my bradley smoke generator which is 120v. only, meant that I could only drive my element with 120v.  So here is where I got to.  I wired up a specific purpose contactor which the auber controller supplies the coil 120v. when the controller says I need heat, it closes the contactor which in turn closes the circuit on 220v. to 3 elements in cabinet.  I am still "tuning" it as the time and derivitive functions tend to cycle the contactor to often.  But I'm sure I'm on the right track.  The advantage is that I can set up the smoker and walk away, having the smoking process stepped up by the controller at each temp I want to hit.  I now can smoke up to 100lbs of sausage ( I do alot of venison for people, and some "shop" smoked items too.)  Hope this can help someone else get there faster.