PSU Help?

Hey Guys,

I'm building either a Rostock or a PM i2, and using RAMPS

I haven't actually bought the electronics yet, but I know I'm going to want a heated bed, and lcd panel, and all of that good stuff.
Eventually, I hope to have a dual extruder setup.

My question is, how do I determine the amperage I need.
I've looked at this with this.
The other one I looked at was this with this.

Also, I plan to have an extruder fan cooling the print, and if I go with a Prusa, a fan cooling the Pololu z-axis stepper driver, because I read that that gets hot driving two steppers.

I already have a PSU, meant for a computer build. It is 12V, 550W. When I did the math, that came out to about 46 Amperes. Can too many amperes damage my system? Is it okay for me to use that?
I'd prefer to go with a system meant for a printer, because the supply I already have has a bunch of wires sticking out (meant for attaching to hard drives, fans, etc., etc. in a computer), and I would have no idea where to start conencting that to the Arduino, and would probably fry my electronics.

Please help me figure out what kind of power supply I should get!

PS the other reason I kind of don't want to use the computer PSU is that it's relatively big and ugly-looking...it's ATX size.


Thanks!

Amps represent the capacity of your power supply. The situation you want to avoid is to have your electronics draw more amps than your power supply can provide. A power supply that is rated for higher amperage is not an issue.

I actually have a power supply similar to your second link, but I got mine on ebay and it's rated for 30 amps.

Basically your RAMPs has two power rails, one for the heated bed that is rated for 11 amps. The other for hot end(s) and motors is rated for 5 amps.
So that all totals 16 amps. If you tried to draw more amperage than that through the RAMPS board, you'd probably start tripping your fuses.

Generally speaking, unless you go overboard, the amperage drawn by LCD's, fans and such is inconsequential. I guess you can get into higher drawing fans, but if you're talking about small PC types fans, the 20 amp power should be more than enough.

The only thing that i hesitate with is the current drawn by a second extruder, but I guess the RAMPs is engineered for it, so I guess it would fit into the overall 5 amps on that rail.

Thanks for the info and the quick response. I think I'll go with the 20A. Do you think that's a good price, or would it be better to go with something from ebay, like you did?

The lulzbot price is in line with what I paid, and I have since made purchases from them. They're a fine vendor.

why not for the time being use your e1 for one of your z dives until you get the second extruder

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Check my rubbish blog for my prusa i3

up and running
[3dimetech.blogspot.co.uk]

you could get this i buyed it and work great with a graphic lcd, Sd card, an encoder, heatbed, a fans (1 for print and 1 to cool the ramps) so this work great for what yout want and the price is great

12V 30Amp Regulated power switching PSU