Power supply and circuit boards?

Hi, I am kinda new to Reprap. Been researching it for the past month or so and bought a partly build one yesterday, just waiting for it in the post now.
One question I have about the power supply that I can't seem to find anywhere.
The electronics all take like 5v - 12v at about 10 or less amps. I have seen that a ATX supply is recommend but these run at about 300 - 600 Watts.
Since W = V*A that would make the 300w supply give 25A at 12 volts! Or is this just the maximum that the supply can supply. Will the circuit board draw the current it needs.

Another question, which circuit board is best? The one I have bought has Gen 3 but there is something wrong with it and the seller doesn't have time to find out what has gone wrong with it. I was thinking about getting this one from ebay is it any good? looks all right but am I right in saying it is Gen 6? and there is a Gen 7 out but I can't find it on ebay or on any other website. Is it only available for building it yourself? Because I don't trust my soldering skills.

Thanks

mapexmbirch Wrote:
-------------------------------------------------------
> Hi, I am kinda new to Reprap. Been researching it
> for the past month or so and bought a partly build
> one yesterday, just waiting for it in the post
> now.
> One question I have about the power supply that I
> can't seem to find anywhere.
> The electronics all take like 5v - 12v at about 10
> or less amps. I have seen that a ATX supply is
> recommend but these run at about 300 - 600 Watts.
> Since W = V*A that would make the 300w supply give
> 25A at 12 volts! Or is this just the maximum that
> the supply can supply. Will the circuit board draw
> the current it needs.

Many reprappers reuse an old ATX supply to run their printer, but making sure you have the right one can be a bit tricky. That 300 watt value you quoted was the total wattage used by the PSU, on all voltage rails - you have to consider the 12v rail by itself.

For the printer itself, 5 amps at 12v is plenty, but if you're running a heated printbed, you'll want at least another 11 amps available, so you're looking for a PSU that can provide at least 16 amps on its 12v rail.

Then, there are issues just getting an ATX supply to work outside of a computer - this instructable comes in handy for that.

If you want something a bit less "hackish", Ebay has these.

> Another question, which circuit board is best? The
> one I have bought has Gen 3 but there is something
> wrong with it and the seller doesn't have time to
> find out what has gone wrong with it. I was
> thinking about getting this one from ebay is it
> any good? looks all right but am I right in saying
> it is Gen 6? and there is a Gen 7 out but I can't
> find it on ebay or on any other website. Is it
> only available for building it yourself? Because I
> don't trust my soldering skills.
>
> Thanks

Asking what electronics are best is kind of like asking what cereal is best - if you want something that's easy to solder, you're looking for Sanguinololu, RAMPS or Gen 7. If you want something prebuilt, Gen 6 would probably be easiest to find.

Thanks for the help.

So that 12V 20A 240W supply would be enough for just the circuit board and the heated print bed if I wanted to add that at some point?
How can I get 5A and 12V to the circuit board and 11A to the print bed. Does the power supply have a 5A connection and a 11A connection?
Sorry I'm not very good with electronics.
Do I need to use a resistor to get less current to the circuit board?

Could I use this? Or is the connector wrong?

Edited 1 time(s). Last edit at 09/01/2011 05:19AM by mapexmbirch.

A power supply supplies a defined voltage across two wires. How much current flows depends on the load and each load takes the current it wants. As long as the power supply had a rating higher than the total load and the wires are thick enough to handle the current, you don't have to worry about it.

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[www.hydraraptor.blogspot.com]

Thank you nophead that helped a lot.

Arduino circuit are using in power supply because it has ability to control the voltage of supply as well as with digital display.
Jaycon