Experience needed

Hello all I am new to the reprap community and have just finished building a Mendel Prusa with ramps 1.4 electronics. I am definitely an amateur when it comes to electronics, I know just enough to get myself in trouble, so I was hoping that I could find someone who would be kind enough to help me with my lack of experience so I don't fry any of my electronics. Please excuse my lack of knowledge and thank you in advance for any insight or help you may be able to provide.

I built my power supply with an ATX PC power supply that says it provides 380 watts with 18 amps on +12v1 and 16 amps on +12v2. I tested the output of each terminal with my multimeter and all my readings seem to be good, I think, I get 12.23 on the +12v terminal, -11.54 on the -12v terminal and 5.15 on the +5v terminal. My supply did not have a -5 supply.
My questions are:

1) Is this sufficient power for a MK 2 heat bed, 5 nema 17 stepper motors as well as the other components of the machine, hot end, thermistors, etc.

2) I don't understand the positive and negative terminals of the DC power supply, do I connect two leads from the +12v terminal to the positive sides of both the 11a and 5a terminal on the ramps board or is the -12v terminal on the power supply supposed to provide the other power to either the 11a or 5a terminal.

3) As far as the 3 pins next to the reset button the ramps board go does the +5v lead from the power supply go to the vcc pin and the ground terminal lead go to the 5v pin next to it or is it opposite that.

4) Can I hook up a 12v cooling fan too the D2 12v AUX pins on the ramps board, is this the purpose of the pins and does polarity matter.

Ramps just takes 12V. You can ignore the 5V and the -12V.
18A should be fine.
You run 12V to the positive sides of both terminals and ground the the otherside, make sue you get it the right way round.
If your PSU has multiple rails, you can run the 5A and 11A inputs form different rails, but you shouldn't need to.

A word of warning, you should measure the voltage under load, some ATX power supplies need a load on the 5V line or the voltage on the 12 V line will drop under load.

Thanks, that makes me feel better about hooking up the power, any insight on three pins at D1, the vcc and the 5v, I know that by hooking these up to a 5v power sourse that I can then use G code to turn on and off the power supply but the ramps wiki is kind of hard to understand about exactly how to hook it up as far as polarity and such, is it 5v supply to 5v pin and ground to vcc or the other pin?

All mine have D1 installed, and I don't connect anything to those pins.
Reading the wiki, it looks like you can input 5V to it and the pins can be used to connect the On/off wires from the ATX PSU, to allow M80 to turn the PSU on.
I'm not convinced there is any real value to it, but I'm interested in what others have to say.

I've got an ATX power supply with the ATX 5V SBY wired to VCC and ATX ON wired to PS_ON, and it works very nicely. I just add "M80" to my Slic3r start_gcode and "M81" to the end_gcode, so unattended prints can start and stop the power supply to the motors and heaters as-needed. The Arduino/RAMPS is powered by the 5V SBY when nothing else is attached, including the LCD panel, so the ATX doesn't need to run its fan until printing starts. The only way to completely shut down RAMPS in this setup is to power down the PSU and disconnect the USB cable. I can't see any disadvantages to this setup at all.

Edited 1 time(s). Last edit at 02/21/2013 07:00AM by Thinkyhead.

Polygonhell Wrote:
-------------------------------------------------------
> All mine have D1 installed, and I don't connect
> anything to those pins.
> Reading the wiki, it looks like you can input 5V
> to it and the pins can be used to connect the
> On/off wires from the ATX PSU, to allow M80 to
> turn the PSU on.
> I'm not convinced there is any real value to it,
> but I'm interested in what others have to say.

I do this polygon. It also allows the ramps to have it's 5v power while the PSU is off.

But, after having some experience with my machine now, I realize the simple easy way is to just hook up the 12v, and jump the atx-on wire right on the PSU. Then it's just switched on or off, simple and sweet.



I am still curious about the diode, if I remove the diode this will totally isolate my PC-USB5v power from the RAMPS shield, but NOT the Arduino, correct?

And The Ramps/Arduino 5v and 12v will function just fine with JUST a 12v hookup and no USB5v, right?

Edited 1 time(s). Last edit at 02/21/2013 02:14PM by xclusive585.