BBQ Engineer: PID Controllers

Have you ever wondered how your grill is able to maintain temperature throughout an entire cook? It’s slightly more complicated than just the thermometer. Put on your nerdy glasses and head to BBQ Engineering school to find out!

What does PID mean?

PID simply stands for Proportional-Integral-Derivative. If that sounds like a lot of math mambo jumbo that’s because it is! (Math is awesome.) And PID controllers are great for your pellet grill. PID controllers allow for greater temperature stability which leads to more consistent cooks. PID controlled pellet grills are also more fuel efficient due to fewer temperature swings.

PID vs. non-PID

A PID controller uses an algorithm and feedback loops to hit and maintain the temperatures you set on your controller. In comparison, non-PID controllers are either time based (feeding pellets into the firepot at a set rate or set intervals) or they do monitor the temperature of the grill, but don’t make any adjustments to fan speed or auger feed rate. If the grill temp is too high: don’t feed any pellets; if the grill temp is too low: feed pellets. It’s either all or nothing. This leads to significant temperature swings (that are even more exaggerated by weather conditions) and can lead to “dirty” smoke which generally isn’t very tasty.

I’m intrigued, give me the details

PID controllers provide greater temperature stability which helps you to achieve more consistent results despite weather or temperature fluctuations. If you’re interested here is a bit more about how PID controllers work:

Error Signal: The error signal is simply the difference between the set temperature and the actual temperature.

PID: The proportional, integral, and derivative are all working to drive the error signal to zero (set temperature = actual temperature).

  • Proportional: The proportional creates an output signal that is proportional to the error signal. If the error is small the proportional output will be small. If the error is large the proportional output will be large. The proportional signal alone is not sufficient to bring the error to zero.
  • Integral: The integral creates an output signal that is proportional to the magnitude and duration of the error. The integral portion of the PID controller will continue to adjust until the error goes to zero.
  • Derivative: Derivatives are used to measure the rate of change of a system. The derivative output is proportional to the rate of change of the error signal. The derivative is essentially trying to predict future error and account for it. 

In Summation…

The combination of Proportional, Integral, and Derivative outputs allows for quick, accurate temperature adjustments and more stable temperatures overall. These outputs are primarily used to drive actuation of the auger (feeding pellets into the fire pot), or fine tune the feed rate of pellets (any one or some combination of auger speed, duration of cycle time, or frequency of cycles). On some grills, the PID output may also be used to control the duty cycle of the fan that is used to aid in combustion.

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Adam Truhler

I am the resident Patio Daddy-o and outdoor chef for my wife and 5 children! I’ve been grilling for 15+ years and smoking meat for over 7 years. Grilling is a part of my family’s cooking culture. I have butchered and grilled Ribeye and New York Strip steaks and smoked brisket, ribs, pork butt, and sausage for multiple events with 70+ attendees.

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