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

  • CNC 3018-Pro: CAMTool V3.3 USB Power Diode

    The CAMTool V3.3 board dispenses with fancy USB power switching circuitry:

    CAMTOOL CNC-V3.3 schematic - USB Power Entry
    CAMTOOL CNC-V3.3 schematic – USB Power Entry

    The NUP2201 is an ESD clamp diode / suppressor IC, which is a nice touch, but FU1, a simple 300 mA polyfuse, is the only thing standing between the USB cable and the on-board +5 V regulator. In real life, it looks like this:

    CAMTool V3.3 - USB power fuse
    CAMTool V3.3 – USB power fuse

    It’s the little black rectangle between the USB jack and the CH340 USB-to-serial chip. The

    The far end of the USB cable plugs into a Raspberry Pi, a device known for unseemly fussiness about USB power, so I unsoldered the fuse and installed a diode:

    CAMTool V3.3 - USB power diode
    CAMTool V3.3 – USB power diode

    It’s a BAT54 Schottky diode, pointed toward the right to prevent current from the board getting to the Pi. Pin 2 (toward the bottom) isn’t connected to anything inside the package, either, so it’s all good.

    I suppose if one were a stickler for detail, one could gimmick the diode in series with the fuse, but I figured that’s a solution for a problem well down on the probability list …