High current extruder heater

  • Hello,

    I'm new in this forum and I can't find information about my problem.

    I would like connect two extruder heater (230V, 280W of each). How I can connect it to Duet 3?

    It is possible to connect one heater to OUT1 and OUT2 to get 10A current?

    I have power supply: 24V 350 W (3 pieces)

  • administrators

    We don't (yet) support connecting multiple OUT ports in parallel. Also the maximum VIN current (excluding bed heater, which has its own terminals) is 15A.

    I suggest you use a mosfet switch to drive each heater. If you are not using the bed heater output to drive a heated bed directly, then you could use the bed heater output to drive one of the extruder heaters directly.

  • @Kevvv if the heaters are 230VAC, then you'll definitely need something external to drive them as the board is only rated up to 36Vdc (I think). Either a mains rated Mosfet or an SSR. You'd then control the Mosfet/SSR using the output from the board (though it will only be a low voltage, low current signal so could use any output channel to suit)

    Out of interest, what kind of extruder are you using that needs a 280W mains powered heater!?

  • Ok, so if I connect heater via SSR to OUT1 it will be okay? Will heater be heat up slower becouse max current out is 5A?

    I use one screw (d25 mm) extruder to large print, but now I have other problem becouse if I command G1 H0 E200 F1000 all it's okay, but if I command G1 H0 E500 F1000 occurs error (phase B may be disconnect). Any idea?

  • what extruder motor are you using ?
    if you run your extruder heater from ssr then your max current will be the max current of the ssr , you can use 40A ssr if you want to.
    note that typical ssr's are slow . you'll need to lower your PWM frequency .check ssr datasheet for max freq.
    better solution is a mosfet switch .

  • It's my extruder motor:
    SM 110/150-6504A - 22Nm

  • @Kevvv said in High current extruder heater:

    SM 110/150-6504A

    holy cow , thats an 8kg motor ! 🙄
    22Nm holding torque ... even if duet can power it , i think it is a bit too much for onboard drivers .

    what voltage / stem mm are you running ?

  • M906 X6200 Y6200 Z5500 E6300 I30
    Screw is 25 mm diameter and 600 mm lenght.

  • with 24v supply your max speed will be (without starting to loose torque)
    revs_per_second = (2 * supply_voltage)/(steps_per_rev * pi * inductance * current)

    = 48/(200 * 3.14 * 0.0159 * 6.3)= 0.76 rev per sec

    your back EMF due to inductance at that sped is approx 22V

    add to that rotational back EMF voltage and you quickly realize that supply voltage is not enough .

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