Fan Compatibility
Connector Compatibility
Section titled “Connector Compatibility”The controller uses standard 4-pin PWM fan headers. Fan type determines what is possible before any speed control is considered:
| Fan type | Speed control | RPM sensing |
|---|---|---|
| 4-pin PWM | Full range | Yes (tachometer wire) |
| 3-pin DC (with tach) | None — runs at full speed | Yes |
| 3-pin DC (no tach) | None — runs at full speed | No |
| 2-pin | None — runs at full speed | No |
3-pin fans are physically compatible with 4-pin headers (the PWM pin simply has no contact), but the controller cannot slow them down. All speed control, temperature curves, and RPM-PI modules require a 4-pin PWM fan.
PWM Spin-Down Behavior
Section titled “PWM Spin-Down Behavior”The Intel 4-Wire PWM Fan Specification (Chapter 3.3) defines fan behavior at 100% duty cycle, but leaves behavior below approximately 20% duty cycle undefined. Individual fan manufacturers implement this range differently: some fans have a hard minimum PWM threshold below which they stop responding and continue spinning at their minimum speed, while others can spin all the way down to 0 RPM at sufficiently low PWM values. Some fans in the latter group also exhibit hysteresis - they spin down to 0 RPM but will not restart until PWM rises above a higher threshold than the one that stopped them.
This matters for any control module that sweeps the full 0-100% output range. If a fan cannot spin down to 0 RPM, it will continue running at its minimum speed even when the controller output is 0%.
Community-Reported Fans
Section titled “Community-Reported Fans”This table reflects user-reported observations. PWM behavior can vary between firmware revisions of the same fan model.
| Fan | RPM Range (per spec) | Spins down to 0 RPM |
|---|---|---|
| Arctic P12 Max | 400-3300 RPM | Yes (user reported) |
| Noctua NF-A14 Industrial PPC PWM 3000RPM | 0-3000 RPM | Yes (user reported) |
| Noctua NF-A12x25 120mm PWM | 0-2000 RPM | Yes (user reported) |
| Noctua NF-A20 PWM | 350-800 RPM | No (user reported) |
| Thermaltake CT200 | 500-900 RPM | No (user reported) |
What “Spins down to 0 RPM” Means in Practice
Section titled “What “Spins down to 0 RPM” Means in Practice”Fans that do NOT spin down to 0 RPM: When the controller output drops below the fan’s minimum PWM threshold, the fan continues spinning at its minimum speed. The RPM sensor will still report a non-zero value and the fan will remain audible. For use cases where fans must fully stop (e.g., silence during idle), these fans are not suitable without additional hardware.
Fans that DO spin down to 0 RPM: The fan will stop when PWM drops low enough. If the fan also exhibits hysteresis, it may require a higher PWM value to restart than the value that stopped it. This can cause brief delays when the controller ramps up from 0%.
Adding Your Fan
Section titled “Adding Your Fan”This list is community-reported. If you have tested a fan not listed here, please open a GitHub issue with the fan model, observed RPM range, and whether it spins down to 0 RPM.