Heater catridge voltage

  • Is there a way to safely drive 12v heater cartilages on a 24v system? I know in Smoothie I could cut the PWM in half and it would work fine. The reason for asking is I have about 10 of these from my last printer that was a 12v, and the new one is running on 24v. I hate to waste things. I measured the resistance and they were definitely different, but so much so that I think I may have just been a bad unit. 3.4 vs 14 and change in Ohms. I skimmed through the RepRap G-code page but nothing jumped out at me.

  • administrators

    Those resistances sound about right.

    P=V^2/R so

    P=12^2/3.4. =~42W
    P=24^2/14 =~41W

    However running a 12V rated heater cartridge at 24V and relying on the PWM to limit the power is asking for trouble. A failure of the MOSFET on, frozen firmware etc could cause:
    P=24^2/3.4 =~170W through the hotend.
    This is a recipie for a fire.

    Even 40W is higher than necessary for a normal hotend.

  • Thanks, I'll order some of the right thing since I like having spares on hand.

  • You can use a voltage converter there are a lot of threads about how to wire one so that you still have pwm control.

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