Power clarification

I have been referencing this drawing for my wiring [reprap.org] and were the power in connectors are there is only 5A and 11A marked with no voltage. I am using a server power supply with 3.3, 5 and 12 volts but I have see no reference for the voltage requirement on the Ramps board? I know at least one of the connectors is for 12v but do I also feed a 5v connection? Also in terms of the 11A and 5A markings and I am assuming that this is for amperes how can I regulate that with this server supply? Thanks, I don't want to cook my board on first startup.

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Both connectors are for +12V, as denoted by the yellow wires in the diagram you're referencing. The 5A rail is for the stepper motors and hotend, and the 11A rail is dedicated to the heated bed. (They split it up into two power rails so that you have the option of running the heated bed from +24V if you want.) The RAMPS board has the circuitry to derive +5V from the 5A rail, or it can pull the +5V from the USB cable. You don't need to feed +5V or +3.3V to the board. I seem to recall something about a diode needing to be installed or removed if you wanted it to self-power +5V, but you can search the wiki and archives for that.

Let me throw in a disclaimer that my primary board is a Megatronics 2.0 (single-board RAMPS/2560 clone), and I have not tried to power my backup RAMPS setup from anything but the USB port so far.....

Thanks!

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roontoon
Also in terms of the 11A and 5A markings and I am assuming that this is for amperes how can I regulate that with this server supply?

You don't need to regulate the power supply. It will supply only what is needed by RAMPS up to the capacity of the power supply. So if RAMPS is idling, your power supply may only be supplying a fraction of an amp but if it's printing with the heated bed warming up (maximum draw) it may be producing 16 amps or more depending on how things are wired.

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vreihen
You don't need to feed +5V or +3.3V to the board.

It's not needed for basic operation, but many people have found that the 5v regulator built in to the Mega isn't enough to power a servo reliably while having enough for normal operation. If you plan on going down a route that uses a servo say for a auto z-axis probing then that +5v from the power supply may be useful.