Duet3, SBC 5V, and PS_ON configuration double check

  • Hi all! I'm getting ready to flip the switch for the first time, and after searching through a bunch of posts on the subject, would really appreciate a gut check!

    My goals:

    • allow turning on/off the 24V supply via PS_ON
    • robust and safe powering of Duet3 and RPi via MeanWell 5V 30W supply

    (In case future searchers stumble across this thread, I found the discussion in this previous thread to be particularly informative!)

    My proposed setup

    • 5V MeanWell PS connected to RPi through USB-C connector
    • Jumpers on 5V->SBC and SBC->5V* per documentation. This should feed Duet3 via 5V pins on RPi GPIO.
    • Connect +5V on SSR to 5V MeanWell, connect GND on SSR to PS_ON pin.
    • I may connect RPi USB to Duet3 USB via cable with only TX and RX wires (in case I want to play around with sideloading OctoPrint) to avoid a ground loop, although I would guess the risk would be minimal given they are both powered from the same 5V supply.

    Sound plausible? I don't need to connect the 5V and GND pins on the PS_ON header, as they are redundant with the SBC ribbon connector, correct?

    Am I missing anything, or overlooking a better option?

    Thanks so much!

  • Assuming your bed is 24v then you have it nailed and you're correct about the +5V and GND pins on the PS_ON header. I'd not connect the USB power leads even with both the Duet and the SBC connected to the same power supply though. Ground loops aren't the only issue. The current capability of the two paths is different and if you have to disconnect the ribbon cable you probably don't want the USB to continue to power the Duet.

  • Awesome, thanks so much!

    My bed is 120V AC... How would that change things? I have a second SSR to control that.

  • @whopping-pochard said in Duet3, SBC 5V, and PS_ON configuration double check:

    My bed is 120V AC... How would that change things? I have a second SSR to control that.

    None at all; the AC SSR isolates the mains voltage from the Duet.

    While usb cables can be of variying quality most should handle 500ma, usb standard allows for 1a, and micro usb is frequently used for 1.5a for battery charging so on the caveat the cable is of descent quality I'd not be too concerned about having both connected at the same time even if the ribbon cable might get disconnected.

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