Author Topic: Understanding PID Parameters for the Auber (WSD-1500GPH)  (Read 2677 times)

FunkedOut

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Understanding PID Parameters for the Auber (WSD-1500GPH)
« on: August 20, 2015, 08:06:48 AM »
With a less than stellar explanation of the PID parameters in the manual, and the differences in PID parameter nomenclature and definition across PID controllers, I felt a little clarity on the subject was warranted.
While much (if not all) of the following will apply to any of the Auber PID's used for electric smokers, I included the model number in the subject I am referencing, as I have seen other Auber controllers with differing definitions.
(YMMV)

Real Basic PID Explanation (geared towards this forum)

A PID controller will monitor the box temp via the temp probe, compare that reading with the set temperature, and control the power applied to the heating element in a way that brings the box temp in line with the set temp.
The total power applied to the heating element is comprised of three components; P, I and D.
Most of the tutorials you will find readily available online will discuss tuning of PID controllers by manipulating the gain factor for each component.  The gain factor is multiplied by each component directly.  This results in a simple relationship where doubling the P parameter, doubles the P contribution to the total power applied.  Halving the I parameter halves the I contribution.  Same for D.  While that is a straight forward way of describing the concepts of PID control, they do not apply directly to the parameters utilized by the Auber.
Below I will attempt to explain what the Auber is asking for in the 166 menu:


Auber Specific

P - Proportional contribution to the total power applied at any given moment is based on the difference between the set temp and the box temp at that exact moment.
The P parameter for the Auber is given in 0.1 degrees.  The factory setting of P = 70 means that the proportional band is 7 degrees.  When you first fire up your smoker with a box temp of 80F and a set temp of 200F, the P contribution will be 100%.  That means if I and D stay out of the way, the heating element will receive full power from the Auber, just like if you had plugged your smoker right into the wall outlet.
P contribution will continue to be 100% until the box temp reaches the proportional band.  In this example, the proportional band is the range from 193F to 200F (200F - 7F = 193F).
At a box temp of 193F, proportional contribution is still 100%.
At a box temp of 200F, proportional contribution will be 0%.
Simple math can be used to figure out the contributions for temperatures in between those two end points.  It is a linear relationship.

I - Integral contribution to the total power applied at any given time is based on the history of the difference between the set temp and the box temp up until and including that exact moment.
The I parameter for the Auber is given in seconds.  The factory setting of 600 means that it will take 600 seconds for the I contribution to ramp up until it equals the P contribution at this time (assuming nothing changes between now and 600 seconds from now).
This I contribution can be positive or negative, depending on whether the box temp is below or above, respectively, the set temp.  This contribution is added to the P contribution (and D, of course) to determine the power required to apply to the heating element.

D - Derivative contribution to the total power applied at any given time is based on the rate at which the box temp is changing at that exact moment. 
The D parameter for the Auber is given in seconds.  The factory setting of 150 means that the Auber will assume the current rate of change will remain constant for the next 150 seconds, calculate what the box temp will be 150 seconds from now and compare that temp with the set temp to determine its contribution, just like it did for the P contribution. 
Example: The box temp is rising at a steady rate of 0.1F every second.  The box temp is currently 175F.  The set temp is 200F.  150 seconds from now, the box should be at 15F higher (0.1F x 150), or 190F.  190F is still outside of the proportional band, so the D contribution will be 100%.
The D contribution can be positive or negative as well.
« Last Edit: August 21, 2015, 12:50:50 AM by FunkedOut »
Joe, in FL
Smoking It #3, Auber PID WSD-1500GPH, 23cfm of boost

elkins20

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Re: Understanding PID Parameters for the Auber (WSD-1500GPH)
« Reply #1 on: August 22, 2015, 12:03:51 PM »
Hey Funk, thanks for the info
Bill SI#1, SI#3, 2 Auber Pids, Cold Smoke Plate for the #3, Large Weber kettle, Smoky Joe Weber, and 2006 Harley softail deuce for stress relief,  from Kansas City, Missouri