Gradual step-up of fan speed based on temperature

[patschi]

I just received the board today and planning to use it for cooling of my network rack. The fans an ramp up to 2000 RPM. I'm wondering if it's possible to control the fan speed based on the difference of current and target temperature? For example when I enable PID Control, set target to 23.0 and current temperature is 31.1, it spins up the fan to 100%.

Am I doing something wrong? Ramping up the fan slowly would be better from noise perspective and most likely enough to bring down the temperature.

[zeroflow]

Hi! Thanks for picking up the board.

What you're seeing is normal PID behavior. A typical PID controller is trying to reach it's setpoint as fast as possible with as little overshoot as possible. With an 8°C gap between current (31.1°C) and target (23.0°C), the controller immediately outputs 100% to reach the setpoint as fast as possible. It's not a bug, it's just aggressive tuning for your use case.

Quick refresher on how PID works:

P = error * kp
I += error * ki
D = (error - error_old) * kd
Output = P + I + D

In your case with default values, the error would be 8.1°C => P = 8.1 * 0.395 = 3.2 = 320% which gets clamped to 100% PWM
You can observe these values live in Home Assistant via the debug sensors (error value, p term, i term, d term, output value).

Depending on your goal, there are two approaches:

Option A: Use a simpler module
If you just want "hotter = faster fans" without the complexity of PID tuning, the temperature_linear or temperature_curve modules map temperature directly to fan speed. Easier to reason about and likely a better fit for rack cooling.

Option B: Tune the PID for gentle control
Two things to adjust:

1. Set a realistic target. 23°C is very ambitious - the PID will always push to 100% trying to get there. For reference, my workshop rack sits at 24°C with fans at 20% while the room is at 18°C. Something like 27–28°C is a more achievable target.

2. Reduce the PID gains. With a 28°C setpoint and your rack at 31°C, that's a 3°C error. Try:

   • kp: 0.08 -> P = 24% (gentle start)
   • ki: 0.001 -> fans slowly creep up if temperature doesn't drop
   • kd: 0

   You can adjust all of these live via the Number entities in Home Assistant - no reflashing needed.

I'd suggest starting with Option A if you want something simple, or Option B if you like fine-grained control.

Let me know if you have any questions!

[patschi]

Thanks for the detailed explanation!

I think I might have messed up a bit: I meant 23.1 and 23.0 (or 31.0 and 31.1, not sure) - so only 0.1C difference. But I think I had "Manual Fan Override" active, which just bumps the fan speed to 100%.

But adding to this, a question in regards to the values... I copied the example config and hence have this:

  temperature_pid:
    url: https://github.com/zeroflow/esphome-fancontroller
    files:
      - path: modules/temperature_pid.yaml
        vars:
          friendly_name: "Server Rack"
          kp: "0.39509"
          ki: "0.00470"
          kd: "20.74267"

When I change the values in HomeAssistant directly, which values are used?

Also, I find the values a bit difficult to understand it first. I would find an "Online Calculator" (e.g. on your website) very useful, to show example temperatures, show tables, graphs, etc.

[zeroflow]

You're welcome.

For the first topic:
The vars: passed in the config are the default values on first boot. as soon as you set other values via the sliders, the module will internally keep track of the last change.

Regarding the explaination, I let claude write up a PID simulator and validated it against my network rack at home.
https://fancontroller.arthofer.dev/pid-simulator

I've also reworked the PID module to have easier-to-use variables and some internal fixes.
There have been small edge cases - e.g. if manual override is active, the I-Term can accumulate a lot of error ("wind up") - so as soon as manual override was disabled, the output could have jumped to 100% due to the accumulated error.

Settings:

• kp = 3.0
• ki = 0.005
• kd = 0

Test was from ~28°C to a Setpoint of 24°C

Simulator output:

Real-world behavior:

[patschi]

Very helpful - thank you very much!

the output could have jumped to 100%

I actually think this has caused me confusion and why I raised this issue here. I played around with the toggle, but somehow it stuck to 100% even with just a 0.1C difference (due to testing).

[patschi]

Some nitpicking about the PID-Simulator (thanks again for this!): It would be handy to have the values and the first diagram side-by-side (in 2 columns). So it would be easier to see any updates on any changes of the values. Instead of scrolling up and down.

[patschi]

Also two feedback things:

1. It looks like the number fields are gone? I find it easier copy-pasting the numbers from the PID-Tuning-Simulator than carefully selecting it.
   
2. There are multiple "PID Deadband" entries I don't really understand honestly, and also are not present in the PID-Tuning-Simulator.