Mega with RAMPS 1.4 not powering up without USB

Hi Guys and Gals,

Well, the header says it all, I’ve built a 3D printer using a RAMPS 1.4 and Arduino Mega setup and it’s been working great. Recently I’ve wanted to be able to disconnect it from USB but I’m finding that nothing happens when I try and use any other power source.

From what I understand the RAMPS board should power the Arduino via the Vin pin, which does have 12V on it but nothing powers up, not even the ON led, zero! I’ve also tried removing the RAMPS shield and plugging 12V into the power jack and switching on but again, still bupkis! The only time anything comes to life is when the USB cable is plugged in, and as soon as it’s removed the whole system instantly switches off even though the 12V supply to the RAMPS or the jack is still on.

What am I missing???



Right, well thank you for your insightful comment there spycatcher. If you'd bother to actual read my question you'd realize it has nothing to do with the RAMPS, it's an Arduino issue.

If I wanted sarcasm and people being rude for no reason I'd have posted this on Facebook!

Go home young man, it's past your bedtime!


Then why didn't you just say that? Instead of being a smart-arse about it?? Better still, post a link to it, there are dozens of forums (that I know of) for RAMPS related stuff splattered across the internet, which one in particular are you referring to?

Besides, as I said, the RAMPS board seems to be behaving as expected, it's the Arduino that's not accepting external power, even WITHOUT the RAMPS shield on it, which is why I'm here, in an Arduino forum... I've spent many hours on this, I don't like to ask questions lightly, everything I've read so far does and tested does not explain my issue. Do the posts you speak of address this? If so I'd read them with renewed gusto and vigor! Please point the way!

P.S. I do apologize for referring to you as "young man", from the (assumed) attitude of your post I pictured a 15 year old boy...