RMaxV2 retrofit question

  • Just got my Duet Wifi and had a quick wiring question. I'm going to build a new printer, but i want to install the duet in my RMaxV2 and use it to print those parts. right now I have the yellow jacket board on my hotend and it pulls in a single positive 12v and sends back a ground wire for heater, fan, led etc. Can I run these to the duet as i did my rambo, allowing all the power to draw from the heater positive and running the grounds to their respective pins on the duet?

  • My understanding is that you can, as long as you not exceed max rated power for hotend heater channel, that is 5 amps.

  • OK, so a few days later i can say it definitely worked. Now im curious about exploring this further. I don't want to start another thread so ill just dump any new ideas into this one.

    Since all the devices are apparently switched on the low side, I'm considering two more options.

    Option 1 - connect both Vin terminals from the two hot end wires into one line, giving me a 10 amp rated +12v to the hot end. from this I would then simply run a ground wire back for each device. Does anyone know if there would be any load issues from running the two Vin lines as one bus line? I would be running back grounds for a single heater, cooling fan, part fan, and LED ring. obviously if i had a dual extrusion machine i would ground the second heater to its appropriate port, assuming i could still keep the single positive line?

    Option 2 - skip the middle man and bring in a +12v line directly from the power supply. I would still send back grounds to their appropriate connectors on the duet. I guess i would need to fuse the positive line? Or would i still have protection from the onboard fuses?

    The main goal of this is to reduce and simplify wiring to the effector, as the yellowjacket board on the hotend was designed to take all its Vin from the Rambo heater port positive, and switch all the devices to ground at the board. Since it apears i can do the same here I want to run 3 large wires (positive, Heater 1, Heater 2) and up to seven small wires (fans, leds, thermistor) In the form of two separate multi core coiled cables so they stay tidy and self retract.

    i guess I'm just hoping someone will jump in and tell me no before i do something stupid.

    I appreciate any advice you guys have.

  • administrators

    1. Yes you can do that. The recommended maximum current per terminal from the extruder heater output terminal blocks is 6A, but it's probably OK to go a little higher.

    2. Yes, you ought to fuse a positive wire run directly from the PSU to the hot end, because the onboard fuse would not be in the circuit.

  • Thank you. Would a 10 amp in line fuse be acceptable? if any of the components like the heater failed closed or shorted, would the fuse pop before the full current damaged any of the ground ports? I know you said the heater ports can only take around 6, and I assume the others less.

  • administrators

    Unless your hot end heaters are unusually powerful, I suggest a 7.5A fuse rather than 10A. It certainly won't protect the fan mosfets if you get a shorted fan, but it might protect the heater mosfets.

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