Xbox PSU RAMPS wiring

Tired of ATX, I bought an Xbox psu. All the guides I have seen seem to be for powering the bed. I was wondering if and how I could use it to power my whole printer. Do I wire 2 12V wires to each 11a and 5a or do I wire 3 12V to 11a and 1 12V to 5a?

Yes you can just about run a full machine with a 10A heated bed. I have run a Mendel90 from one.

Mine has three 12V wires, but however many it has I would common them before splitting for the two RAMPs inputs for best load balancing in the cable.

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Quote
nophead
Yes you can just about run a full machine with a 10A heated bed. I have run a Mendel90 from one.

Mine has three 12V wires, but however many it has I would common them before splitting for the two RAMPs inputs for best load balancing in the cable.

I am terribly unfamilar with electrical terms. Could you please elaborate?

Say the XBOX cable has three or four 12V wires then connect them all together to make a star point and then follow that by a Y junction made with thick wire where each branch goes to one of the RAMPS inputs.

That ensures that regardless of the what split of current is on the two RAMPS inputs, all four XBOX wires will share the total current equally and give the smallest voltage drop possible. If you arbitrarily pick a split in the wires it will only be optimal if the RAMPS inputs take current in that exact ratio and since it varies massively depending on what the heaters are doing it will always be sub optimal. This is particularly relevant because the XBOX wires are long compared to say an ATX PSU.

Edited 1 time(s). Last edit at 11/03/2014 12:06PM by nophead.

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[www.hydraraptor.blogspot.com]

Quote
nophead
Say the XBOX cable has three or four 12V wires then connect them all together to make a star point and then follow that by a Y junction made with thick wire where each branch goes to one of the RAMPS inputs.

That ensures that regardless of the what split of current is on the two RAMPS inputs, all four XBOX wires will share the total current equally and give the smallest voltage drop possible. If you arbitrarily pick a split in the wires it will only be optimal if the RAMPS inputs take current in that exact ratio and since it varies massively depending on what the heaters are doing it will always be sub optimal. This is particularly relevant because the XBOX wires are long compared to say an ATX PSU.

To clarify, solder the four 12v and four ground to each other. Then for each ground and 12v, solder two higher gauge wires and have one go to 11a and one to 5a. Is this correct?

Yes for the 12V and you could treat ground the same, but the two ground inputs of the RAMPS will be connected together on the PCB, so you can just put two ground wires into each.

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[www.hydraraptor.blogspot.com]