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Author Topic: Mega 2560 works just with external power  (Read 443 times)
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Budapest, HUNGARY
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Hi all! I have a brand new Mega 2560 board but when I plug it into the pc's usb port it remains total blind. Nothing happens smiley-sad I've an 6V DC external adater and when I plug it in it, the board starts to work. I've tried many PCs, different usb port, different cables, same result. Does someone have the same problem? Or any idea to work just with usb? Thank you!!
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hello
lets go step by step
If you just connect it via USB does it work?
Can you upload sketchs?
Does the leds turn on?
If not you probably have some damage on a dc regulator onboard
when conected via USB all the board is powered from the 5 volts on the usb port.

« Last Edit: August 16, 2011, 08:24:00 am by hugo007 » Logged

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Budapest, HUNGARY
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"If you just connect it via USB does it work?"

No. It remains black smiley-sad Nothing happens.

"Can you upload sketchs?"

No. Just in case if I plug in an external supplier. (6V)

"If not you probably have some damage on a dc regulator onboard"

smiley-sad can I fix it somehow or do I have to forget it and use it with external power?

Thank you!


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Left Coast, CA (USA)
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The failure is that the board is not getting regulated +5vdc from the USB cable, so there is nothing wrong with the on-board +5 vdc regulator, as the board works if powered from the external power connector. So that failure is with something in the following, USB connector power pin, USB thermofuse, auto-voltage selector circuit, etc.

 It's obviously a hardware problem on the board, so if you can't get the supplier to exchange it, you should get a voltmeter and try and see where the USB power is being lost, start at the +5vdc power pin of the USB connector on the board, when it's plugged into the PC and with no external power.
Lefty
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Budapest, HUNGARY
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Thank you for your advice!

I've made some picture:

1. As you can see there is no lifesign when I connect the board with usb.


2. Follow your advice I tried to find where stops the current. At the bottom of the board there still the 5V smiley


3. Suddenly I found that if I wire these two pins together, the BOARD STARTS TO LIVE just width the usb without external power!!
What do you think shall I solder these two pins together???


THANK YOU AGAIN!!
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