The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

BLDC Fan RPM vs. PWM Duty Cycle

A simpleminded MOSFET circuit provides PWM drive for the BLDC blower:

BLDC Fan PWM Test Fixture - schematic
BLDC Fan PWM Test Fixture – schematic

The Tek P6302 current probe looms much larger in real life than in the schematic:

BLDC fan PWM Test Fixture
BLDC fan PWM Test Fixture

A quick dataset shows the RPM variation against PWM duty cycle:

BLDC Blower - RPM vs PWM - doodles
BLDC Blower – RPM vs PWM – doodles

Unsurprisingly, the RPM curve resembles the earlier results against a variable DC supply voltage:

BLDC Blower - RPM I P vs V
BLDC Blower – RPM I P vs V

Capturing the current waveform is stalled behind another project, but it has exactly the voltage spikes you’d expect from forcibly switching an inductive load.

Comments

One response to “BLDC Fan RPM vs. PWM Duty Cycle”

  1. BLDC Fan vs. PWM: Inductive Spike | The Smell of Molten Projects in the Morning Avatar

    […] 50% PWM at 1 kHz into the simpleminded 24 V BLDC driver produces the results you’d […]