KRAK LLC

Sous-Vide 1.1 | October 12, 2014

Small update.

Testing showed that the PID tuning was quite finicky. Even with the Auto tuning feature I had enabled, I was having issues with overshoot on the ramp up cycle. I also found that the PID control, by it’s very nature, caused the relay to chatter a lot when the crockpot temperature is near the set point temperature. I attempted to re-tune the PID several times but did not come up with a parameter set that I found to be acceptable.

A step back in controls:

I had previously, in a different project, used a more simple temperature control system. That system simply turned a heater on when the current temperature is low, off when the current temperature is high. It was a very simple method and worked well for a test chamber that was used in testing scenarios that required temperature stabilization over a 30 minute period prior to test execution. With a little bit of modification, the same concept has worked for the Sous-vide too. I added a little bit of logic to help prevent over-shoot. The relay no longer chatters, and the crockpot comes up to and maintains the setpoint temperature.

A step forward in progress:

Now that I have the temperature control segment of the program working well for this application, I can proceed to the next phase. With this new approach to the control, I have been able to remove the PID code. That freed up a large portion of the program memory that I plan on using for other features of the controller. Having free space in the program memory means I can add the profiles, delay timers, a selection of notification sounds, and logging. I’ve already started cooking with the unit, but I can’t wait to get the next set of features added to the program.

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Posted in Arduino, Controls

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