Arduino Mega 2560 clone USB chip up in smoke...

Hello all, I'm new to the forum and new to building/using 3d printers.

Quick background, I'm no stranger to electronics and have been a CNC machinist for 15 years. Currently the Engineer for an Firearm/Aerospace company.

I recently purchased the FolgerTech 2020 prusa i3 kit. The kit went together very easily and straight forward. All parts and pieces were included.

I followed the build guide, scoured the internet for problems that other people had, and Saturday night I finished the kit completely (triple checked the wiring)



Here is when the trouble started, and thusly ended in about 2 seconds.

I had the Ramps board attached to the Mega clone, everything wired up. (again, triple checked Everything was proper, especially the endstops as that seems to be an Instant failure point if wired up wrong)

I downloaded the Arduino software, opened the Marlin sketch and plugged in the USB cable to my laptop. LCD screen lit up, end stop LED's came on when triggered. My computer would not recognize the arduino. I thought 'Oh, maybe the PSU needs to be On in order for the there to be enough power for everything.' I plugged in the power cord for the printer PSU and PUFF! Smoke poured off the Arduino.

Instantly annoyed after spending Hours triple checking the wiring, etc I disconnected Everything from the Ramps/Mega and took it off its acrylic mount. I assumed the Vreg on the Mega had popped (as this seems to be the most common electrical failure) Upon separating the Ramps board from the Arduino, It was the USB IC that was fried.

I have SCOURED the interned for instances of this same problem and have only found ONE instance of this happening (on this very forum). Although the solution was not very clear to me after reading that particular thread multiple times. I did check the resistance between the PSU ground and the Ramps V- as suggested, and it is most certainly 0 ohms...

I'm at a loss and I don't want to burn up multiple Arduino boards trying to find what the issue is. (even though the clones we typically use are ultra cheap)




Anyone out there have Any idea as to a simple way to ensure this doesn't happen again? I'm anxious and excited to get the printer going asap.

Thank you in advance and thank you all for the wealth of knowledge this forum has already provided me as I lurked around building my own knowledge base.

Nathan.

I´ve read a few stories of USB cables melting from bad ground loops. The key is to use the same wall outlet for PC/Laptop and PSU for the Ramps.

And of course the arduino FETs switching between USB and external power have to be functional. This might have been the failure for your Arduino ?!
-Olaf

Thanks for the response.

Both were plugged into the same outlet at the time of the failure.

Is there anyway I can check the functionality of the FET's without plugging in the USB?

Or Just plug Only USB in, see check the FET and then switch to PSU power Only, and check it again? (If so, how would I go about this lol)

Thanks again in advance.

Nathan

Sounds like you might be the type of guy who can follow a schematic so checkout the schematic on the RAMPS page page. The whole board is really just a bunch of individual circuits all lumped together on one board. I'm almost a supporter of separating them just for the very issue you are having. That said, with the cost of a new RAMPS and Arduino being so cheap and the risk to other things I would advise just ordering a new pair. Use a meter on the ends of the wires for your heated bed and hot end heater to make sure neither one of them are shorted. I saw a guy once who didn't have any insulator on his hot end resistor leads and both of them were shorted to the metal of the hot end. Keep in mind both of these do have a very low resistance, but they should read some resistance with your meter on the lowest setting.

Quote
appdev007
Sounds like you might be the type of guy who can follow a schematic so checkout the schematic on the RAMPS page page. The whole board is really just a bunch of individual circuits all lumped together on one board. I'm almost a supporter of separating them just for the very issue you are having. That said, with the cost of a new RAMPS and Arduino being so cheap and the risk to other things I would advise just ordering a new pair. Use a meter on the ends of the wires for your heated bed and hot end heater to make sure neither one of them are shorted. I saw a guy once who didn't have any insulator on his hot end resistor leads and both of them were shorted to the metal of the hot end. Keep in mind both of these do have a very low resistance, but they should read some resistance with your meter on the lowest setting.

You are correct, a schematic will be no trouble. Thank you much, I will double check the hot end/heat bed as well, although I never got to send Marlin to the mega so I would assume that the hot bed/hot end wouldn't have had power applied to them yet but I will check to be sure.

Thanks much, I appreciate all assistance/information.

Nathan.

Oh, well then no, they probably weren't the problem. I would take the Ramps off of the arduino, unplug all wires and the stepper drivers, and pin out what you can without power. After that plug up power to it and use some resistors and switches that aren't connected to your printer to test the rest of the board.

I like to hear you triple checked wiring. Could have not been your fault at all. One of your components could have been bad, even a stepper driver. You can find a schematic for those too. Put meter probes in the end of all those connectors to make sure none if the motors, thermistor, or such are shorted.

Edited 1 time(s). Last edit at 07/06/2015 01:41PM by appdev007.

This is probably a stupid question, but am I correct in assuming that Any Arduino Mega 2560 will work with the Ramps 1.4 board? (is there a better option?)


Thanks again,
Nathan

Well, I can't promise someone hasn't put the chip on a different form factor, but I would say if it looks like yours all except in color, your probably good. I've used the cheap Chinese ones and they work fine. If it would make you more comfortable find one that has arduino compatible in its description.

Btw,if you are desperate (willing to pay) and still have a RadioShack, they have them at full full retail price.

Quote
EnigmaticEngineer
This is probably a stupid question, but am I correct in assuming that Any Arduino Mega 2560 will work with the Ramps 1.4 board? (is there a better option?)


Thanks again,
Nathan

Edited 1 time(s). Last edit at 07/06/2015 02:28PM by appdev007.

Well, I broke down and purchased a (retail, but internet price matched) 2560 clone from a local retailer.

I installed it Exactly the same way as before. (Wiring in exactly the same places) Plugged in the USB and it worked. Uploaded Merlin after configuring the .h's and...


Its alive!!! (I still have an error on my X axis, the motor doesn't stop after hitting the endstop when Homing) But Y and Z axis's stop where they are supposed to.

I won't be home till this weekend to continue configuring/setting up the Printer to make my first print.




Now if Dan will get back to me over at FolgerTech so we can discuss Why, when 100% properly wired, the USB chip fried on the Mega he sent me.

Thanks for the tips, I'm sure I'll have more questions soon.

Nathan

I externally power my drivers to avoid putting too much current.