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kecyesterday at 5:42 PM1 replyview on HN

PID loops work best when you have active control for both heating and cooling. PIDs are also best when you have a single optimal point you’re aiming at, there’s a kind of fundamental mismatch here in that there isn’t really a “too cold” for your system, you’re just aiming to keep the system below an upper limit while hopefully keeping fan noise to a minimum (otherwise you’d just send it and run at max 24/7).


Replies

Espressosaurusyesterday at 5:54 PM

A simple PID wants to keep it at a setpoint, but it’s easy enough to layer a target change on top of it, some hysteresis so it’s not pulsing on and off, perhaps with control authority depending on the the target, etc. but then that gets complicated and usually manufacturers aren’t going to expose those sorts of tunings to the user.

For most people a fan curve is more obvious to work with and it’s largely good enough without the irritating behaviors insufficiently tuned control loops can exhibit.