How to wire dual PSUs with a Duet WiFi 2?

  • What is the safest way to wire two power supplies to power the Duet and a heatbed, including fuses and switches? Is an external MOSFET required on the bed?

    I have a 24V coreXY printer with LEDs, a single hotend, and a 300mm bed. I noticed the fan for the 350W Meanwell PSU kicks on often and seems to struggle with bed temps over 100C. It looks like PSUs over 350W jump to the $100-150 range. Instead, I bought a second smaller 24V/150W to power the Duet, LEDs, motors, and hotend for $15.

    Originally I was going to purchase an external MOSFET for the bed but I believe there is a way to directly connect the larger PSU ground to the Duet heatbed output ground, and the heat bed in between the Duet and PSU since I think the Duet does the PWM control on the positive heatbed positive output.

    Also, I would like to use one switch to turn both PSUs on if possible. I don’t think it is safe to use one of the standard “plug, fuse, switch” combos most printers use since it would be one fuse for two PSUs. I believe the correct way would be to use a plug with a switch then make three Y cables with their own fuse to split the incoming power between the two PSUs.

    I’d like to verify the correct wiring before making a house fire though 🙂 are there any schematics available? Thanks!

  • have you measured the resistance of your bed and calculated the power draw?

    if the bed can not reach over 100C its not necessarily a problem with power supply, but rather that the bed can not reach temperatures above that easily.

    i would go with the mosfet, because that will allow you to increase the voltage to the bed.
    the max voltage to the duet wifi is 25V. however with the mosfet you could run the bed at something like 28V by turning the Potentiometer on the psu. this will increase the power usage by the bed and will allow you to reach higher temperatures.

  • @whiteglint143 The Duet PWM switches the ground or negative of the bed, not the positive.

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