8. Auto-Tune
This section can be ignored if you are using the controller to control the Bradley Smoker
because the controller is already set for it.
The controller's most powerful feature is its ability to regulate virtually any cooker with
stable temperature control. For stable temperature control the controller requires two
things; (1) the controller must be set to the correct power level and, (2) it must be tuned
to the cooker being used. Tuning is the process that matches the control characteristics
of the controller to the heating characteristics of the cooker. The controller is said to be
tuned to the cooker when its memory is programmed with values telling it how fast the
cooker warms up, cools off, and how efficiently it transfers heat. For example, consider
the difference between a heat lamp and a hot plate. When electricity is applied to a heat
lamp it begins to heat instantaneously, and when it's turned off it stops heating
instantaneously. In contrast, a hot plate may take several minutes to begin heating when
electricity is applied and even longer to start cooling when electricity is turned off. But, to
do this it must be programmed with the time constants. Describing how fast the heater
heats when electricity is turned on and how fast it begins to cool when it's turned off.
These time constants are called the tuning parameters.
Every type of cooker has its own unique set of tuning parameters. For the controller to
heat with stability, it must be programmed with the tuning parameters for the cooker
currently being used.
When Should the Controller be Tuned?
If the PID parameters we provided are not working for your likings, you can use the
auto-tuning function to let the controller to determine the PID parameters automatically.
The auto-tuning function (it’s often known as self-tuning) can automatically optimize the
PID parameters for your chosen cooking system. The auto-tuning function will heat up
your cooker then let it cool down. It will repeat this heat/cool cycle several times. Based
on the response time of the whole cooking system, the controller will calculate and set
the PID parameters for your cooker.
Figure 92. Auto-tune
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