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.

The New Hotness

  • 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.