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Chances are, you’re probably tuning it incorrectly. Tuning is not an easy thing to do, but you should get much closer if you draw out the block diagram. At a minimum, even fuzzy logic would be better than bang on/off.

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I'm familiar with algorithmic and manual tuning, and the more latency the system has, the more time consuming and harder it is to get right. Genuinely curious how a block diagram would help?

PID is the controller for a block diagram [1]. When you have the block diagram, you can predict the response graphs extremely reliably [2]. You should be extremely close to the desired coefficients and requires a little tuning. Especially for stuff like thermal and conduction that’s very well understood. You just need to draw the thermal circuit and know the spec of your hardware.

Most of the time people use PID, they use it as a black box which causes a lot of pain.

[1] https://www.tutorialspoint.com/control_systems/control_syste...

[2] https://ctms.engin.umich.edu/CTMS/index.php?example=MotorSpe...

Thanks! I wish I learnt more control theory in my education, this is helpfull.

Control system was probably one of the hardest class I took for undergraduate. Unfortunately, it really requires a college course (mine had a lab too so you can some “real life” experience) to understand the beauty of PID controllers. Highly recommend sitting in a college course if you like this stuff!

Here's the first of several open courseware on controls.

http://mocha-java.uccs.edu/ECE4510/index.html

I think you are confusing terms. You are saying latency, but I think you mean the time constant of the poles / zeros. When one speaks of latency in a control system, they general mean a real time delay, like a digital processing delay, communication delay, etc. When you speak of something having low-bandwidth, such as due to the thermal mass and heating element you are describing, then one would say it has a long time constant. I have never seen these systems any harder to implement with a PID provided you select the proper terms to keep it stable. If it is just a linear PID, it is going to need to be a slow loop in this case.

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