RAMPS not connecting, stepper drivers heating up

Hi all. I have the RAMPS1.3 boards from Ultimachine ready to go on my reprap. I have flashed the firmware and I am able to communicate with RepSnapper when there are no stepper boards installed on the shield. The moment I insert one of the stepper boards, the USB connection is apparently lost (I can't find COM3 anymore) and the inserted stepper board starts heating up. I've tested this with all 5 stepper drivers independently in all 5 positions on the board (X,Y,Z,Extruder1,Extruder2). I have made sure to turn the trimpot all the way counter clockwise before installing on the board.

Does anyone know what could be the issue? I am pretty sure I am putting the boards in the correct way according to this picture here:[reprap.org]

I have looked over my soldering job and I see no apparent issues.

Thanks in advance.

I hope you aren't inserting the stepper board while the system is on, your wording above is unclear. When you plug the mega in with no steppers you have a COM port, with one stepper you don't?

Correct. I am of course unplugging power from the board before putting on and taking off the stepper boards.

Did you check the +12V going into the RAMPS board with and without the Pololu boards plugged in? What's the rating of your +12V power supply? Do you have a diode in the RAMPS?

It might be that your USB port may not be supplying enough power to turn on the pololu, but it is enough for the mega alone. Try a different USB port, or try a powered hub or another computer if you have one.

gunadai Wrote:
-------------------------------------------------------
> It might be that your USB port may not be
> supplying enough power to turn on the pololu, but
> it is enough for the mega alone. Try a different
> USB port, or try a powered hub or another computer
> if you have one.

The Pololu boards are powered through the +12V supply to the RAMPS shield, not the USB port.

I thought the pololu boards had a 3.5-5V logic supply that comes from USB or the voltage regulator on the mega and a higher motor supply that comes from the 12V input.

You're right. The RAMPS shield doesn't have it's own 5V regulator. How about installing a diode to supply the Arduino Mega with 12V from the RAMPS?

The Pololu boards only take a few mA on the 5V rail, not enough to kill the USB supply.

Have you tried them without motors attached? They should not get hot in that state. If they do there is something horribly wrong.

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[www.hydraraptor.blogspot.com]

Hmm. Double check to make sure that they are in the correct orientation. It's easy to plug them in backwards.