Heater 3 ON at startup

  • I'm using the HEATER3 (pin 8 on the extension connector) to drive a CNC motor controller via PWM, and so far, it works. I need to use this pin (or a similar pin) instead of the heater or fan connectors on the board because I need a PWM signal relative to GND.

    One slight issue: During startup, the pin goes briefly to HIGH, which makes the spindle turn on for a moment. I've already managed to fling my Z probe connector across the room in this fashion and decided I didn't like that... Is there a way to prevent this, or is there another pin available that I could use that does not default to HIGH during startup?

  • administrators

    @vwegert without checking the datasheet i guess that pin defaults to high and the firmware enables an internal pull down. If you want to prevent it going high then try an external pull down resistor. 4K7-10K should do it.

    (please test without Z probe in position to be flung)!

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