Help needed, problem with connection.

Hi everyone, i'm going straight to the problem.
I have a Prusa i2 with Pronterface (not important), with an arduino mega and ramps 1.4 .
It seems that everytime i turn off the computer and connect my electronics via usb, arduino doesn't respond.

An example.
Yesterday, i connected my ramps with arduino and everything to my laptop, but the mega didn't light up and the laptop didn't make the classic sound of device connected, nonetheless arduino ide didn't see the mega connected. I then disconnected everything from the Mega and connected only the Mega to the laptop, everything ok, then i connected ramps and my printer worked just fine.

For some reason it seems that everytime i have to unplug ramps and replug it to turn on the Mega.

Any ideas of the problem ? It's very annoying

Maybe your USB on the laptop doesn't have enough current or voltage to for the mega. Do you have an LCD screen on your build? That would be powered off the USB power as well. If it doesn't light up there is no/not enough USB power.

Have you tried powering it with an A/C to usb wall charger? Does it light up this way? An Apple USB wall charger will power my Arduino/Ramps1.4 + LCD display just fine.

Yep. USB probably can't power the whole RAMPS, including the LCD (if applicable), fans if they're on, etc.
Make sure that the RAMPS is running on the power supply before you do any flashing- you wouldn't want it to be interrupted.

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Master Tinkerer