Folgertech Prusa i3 - PC doesn't see the Arduino if Ramps connected

I have a Folgertech Prusa i3. I've done the construction and started the configuration. The Arduino is flashed with the Marlin firmware. But when I plug the Ramps board into the Arduino and turn on power the Arduino is not seen by the PC. The error message in Repetier was something like "there is no port".

So I ran the Arduino software that I used to flash the firmware. It also does not see the Arduino. If I remove the Ramps board from the Arduino the Arduino software sees the Arduino on the USB port just fine. Plug the Ramps board back on and the Arduino can't be seen on the USB again. I also noticed that with the Ramps board plugged in, the LED on the Arduino does not light up where it is lit without the Ramps board. The wiring on the Ramps board all look good.

Any ideas on fixing or troubleshooting the problem?

Steve

Edited 2 time(s). Last edit at 11/03/2015 08:52PM by SteveSimpson.

Your Ramps board or the drivers or endstops create a shortcut in 5V rail.
Don't use it, until you've found the cause!
-Olaf

I agree with o_lampe, unplug everything and plug in just the ramps board. Start adding wires to it one by one confirming it's still connecting properly. Make sure to power off the board before making any changes, you can damage the arduino or stepsticks.

I unplugged everything and it worked. Bit by bit I plugged everything back in. It is the Z stop switch that kills it. If it is plugged in the LED on the Ramps board does not flash and the Arduino LED does not light up and the software cannot see the Arduino. Unplug the Z stop switch and the software can see the Arduino. There was a spare switch in the parts so I tried that. Not surprisingly it still didn't work with a different switch.

So, now what?

Check if the end stop switches for the z axis are not soldered wrong, ie check if they are normally open instead of normally closed with a volt meter in resistance or continuity mode.

Also check if you're not shorting +5V and GND, as the endstop connectors have 3 pins, signal, GND and +5V. The end stop switches need to go on the signal and GND. On the PCB you see S, - and + which is Signal, GND and +5V respectively. Why they've chosen a non standard notation is beyond me.

See the PCB diagram:


Edited 1 time(s). Last edit at 11/05/2015 08:09AM by imqqmi.

When using the spare switch and cable didn't help, then compare wiring order and colors with the working switches.
Also check the Ramps board for solder bridges below the endstop headers.
-Olaf

Aha! I found it. The switch end itself was wired up correctly. But the connector that plugged into the Ramps was not. The wires should be red, black, green and itstead it was red, green, black. At least now the Ramps LED flashes once on power up. This weekend I'll continue from there.

Thank you everyone for your help.
- Steve

Good to know you've found the problem!