Power Supply question (new user)

  • I have a makerfarm pegasus 12, a Cartesian printer with 2 Z-axis motors and a 12v 12x12" heated bed

    I have read over the motor selection and power supply documentation and did not.. achieve an understanding.

    My question is whether this power supply and motor combination will work and what I should know about my setup. Additionally, I am currently using a RAMPS 1.4 controller. Is there any mapping between the motor wiring on the RAMPS to the DUET WIFI?
    Will this setup work 'as is'? Do I need to upgrade the power? Upgrade the motors? I am willing to accept less than ideal performance (speed) to save a few $.

    . The power supply is
    Meanwell MODEL LRS-350-12
    DC VOLTAGE 12v
    RATED CURRENT 29 amps
    CURRENT RANGE 0 – 29 amps
    RATED POWER 348 watts
    And the motors specification is


    Thank you

  • 1.5A * 3 ohm * 2 phases = 9W per motor peak * 4 motors = 36W / 12V = 3A.
    40W extruder / 12V = ~3.5A
    ~150W usual heatbed/12V = 12.5A

    That is a total of 19A. Your 29A power supply will be just fine.

  • I don't know if you want to print ABS, but a 300x300 mm bed is probably going to need much more power than a 12V supply can practically deliver. A 300x300mm 12V heated bed is almost always a PCB type that will not be flat and will require some additional layer of glass or cast aluminum to provide a flat enough surface to print on. You might be able to get it to work with flatness compensation built into RRF if you put the right sensor on the extruder carriage.

    I have a printer that has a 300x300x6.35 mmm bed and a 450W 24V heater (big mistake, made about 6 years ago, to be corrected later today) and it takes about 10 minutes to get up to 100C to print ABS. Of course, if you're only going to print PLA, it will take less time to heat up because it doesn't need to get above 70C. This web site will give you a pretty accurate estimate of the heat-up time for your bed/heater/target temperature combo.

    As an additional point of reference, I have another printer with a 300x300x8mm aluminum bed plate that gets to 100C in 4.5 minutes using a 750W line powered heater.

    If you use a higher power, line powered heater, you can use an SSR without a heatsink or minimally heatsinked by bolting the SSR to any handy piece of metal such as the printer's frame (if it is aluminum). A line powered bed heater will allow a smaller, cheaper, quieter power supply to power the rest of the printer. Consider using 24V instead of 12V.

  • administrators

    Yes the Duet WiFi can drive those motors.

    A 12x12" bed heater is likely to draw a lot of current, possibly more than the 18A rating of the Duet or the 15A rating of the default bed heater fuse. Unless you already have an external SSR or mosfet switch for the bed heater, I suggest you measure its resistance and work out the current draw @12V. It's easier to use 24V power or mains power for bed heaters larger than about 220mm square because it keeps the bed heater current in a more sensible range.

  • Thank you for all that responded. The heated bed is on a relay, however I have ordered a separate but identical power supply to dedicate to the bed.

    On to assembling the plugs with my crimper and those dang tiny pins.

  • Oops, missed the 12x12" bed size. Sorry.

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