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  1. #1
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    New user needs help!

    Hello,
    I am new to Makerfarm printers and this forum. I am almost done building my 12" i3v but have a few questions.

    First is the heated bed wiring. I have the bed with the built in relay, the thick black power wires I have hooked up to V+ and COM on my power supply. The thin wires are connected to D8 on the RAMPS board. However, when I plug in the power supply, the RAMPS board doesn't turn on. On my other printers I have always run wires from the power supply to the two terminal blocks on the board, but as far as I can tell, the only two connections made on the power supply are to the heated bed.

    Second is the bed reinforcements. These are only used on the 12", so the documentation on how to attach them is a bit sparse. I think they are supposed to face down towards the base of the printer when the bed is on the extrusions, but this setup limits my y axis build volume by about 8cm.

    Thanks for any advice you can give me!

  2. #2
    Staff Engineer printbus's Avatar
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    The heat bed with integrated relay is something new. First time anyone has mentioned that. I'd be curious to see a picture of the relay or MOSFET switch on the heat bed.

    For RAMPS to work, you'd still have to connect the power supply 12v to BOTH the 5A and 11A terminals on RAMPS. The 5A connections would power the electronics, the motors, and the hot end heater. The 11A connection supplies power for the D8 circuitry used with the heat bed. Since the high current switching is happening at your heat bed, you don't need dedicated or heavy gauge wiring going to the 11A terminals. The 11A connections can be made with small gauge wire just jumpered over to the 5A terminals.

    Can't help with the bed reinforcements.
    Last edited by printbus; 08-23-2015 at 11:26 AM.

  3. #3
    Student
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    Ok, I've got the power supply wired to the heatbed relay and the 5A and 11A connections on RAMPS. It turns on now.
    However, when I try to set the heatbed temp on the LCD I hear a click from the relay and the RAMPS restarts. Does this indicate a short circuit? I didn't think that heatbeds were polarity sensitive.

  4. #4
    Staff Engineer printbus's Avatar
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    Quote Originally Posted by spaceorange12 View Post
    ...However, when I try to set the heatbed temp on the LCD I hear a click from the relay and the RAMPS restarts. Does this indicate a short circuit? I didn't think that heatbeds were polarity sensitive.
    It could be a short, or it could be the heat bed is drawing more current than your power supply can handle and the power supply cuts out. Is your supply good for 30+ amps?

    You are correct that heat beds are typically not polarity sensitive, and that's why the input wires are the same color. You're hearing a relay click, so I guess that means the heat bed doesn't have a MOSFET switch, which would make the input polarity important.

  5. #5
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    Just verified that my power supply is only 20A. I'll buy a 30A and report back soon!

    Edit: I also found out that I installed the reinforcements on the wrong side of the bed, I will fix that as well.
    Last edited by spaceorange12; 08-23-2015 at 07:34 PM.

  6. #6
    Staff Engineer printbus's Avatar
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    Yeah, a 20 amp power supply wouldn't be enough for a 12-inch printer. At least you can, by leaving the heat bed off, keep checking out the rest of the printer while you wait for the other power supply to arrive.

  7. #7
    Quote Originally Posted by spaceorange12 View Post
    Just verified that my power supply is only 20A. I'll buy a 30A and report back soon!

    Edit: I also found out that I installed the reinforcements on the wrong side of the bed, I will fix that as well.
    You may want something more than 30A or use two power supplies. According to the MakerFarm website the 12" bed draws 20+ Amps at startup; it doesn't say what it draws after start up but I would say probably about 20A. If you figure the rest of your electronics is drawing at most 5A based on the 5A fuse on your RAMPS board. I would use 25A to be safe plus 5A=30Amp+ 30%(good practice)=39A. You would probably be better of with a quality(from what I have read some of the cheaper LED Chinese supplies don't always meet the specs they advertise) 40A supply. You may be better off with two supplies. My 2 cents.

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