Arduino Mega 2560 R3 power supply

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Arduino Mega 2560 R3 power supply

Postby Alen.ATLow » Wed Nov 14, 2012 10:37 pm

Can we connect the USB cable and and External 12V supply to the main board together? It seems shorting my USB when I connect it in such a way.
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Re: Arduino Mega 2560 R3 power supply

Postby robosang » Thu Nov 15, 2012 9:23 am

I don have Mega, but I have UNO, get it during crazy sales :)

Anyway I never experience shorting the USB even with or without the power from adapter. Try putting the adapter only, and try with USB only.

What is the condition when you say it is shorted?
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Re: Arduino Mega 2560 R3 power supply

Postby zhenning » Thu Nov 15, 2012 12:32 pm

Alen.ATLow WROTE:Can we connect the USB cable and and External 12V supply to the main board together? It seems shorting my USB when I connect it in such a way.


So far, if you put external power supply of < 6.6V then you have some problem. Take a look here:

http://arduino.cc/forum/index.php/topic,82046.0.html
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Re: Arduino Mega 2560 R3 power supply

Postby Alen.ATLow » Thu Nov 15, 2012 3:45 pm

My laptop output device blink when my USB cable touching my USB port. this is weird.
Any way, it work fine with either external power supply or USB port.
Notice that USBVCC from the circuits connected to UVCC of ATMEGA 16U2 IC. may be this is the cause of this problem.
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Re: Arduino Mega 2560 R3 power supply

Postby Alen.ATLow » Thu Nov 15, 2012 3:49 pm

I wonder can we improve this by applying forward bias diode to prevent the voltage flow from higher potential to lower potential source of both USB and External Power supply.

Bricking up Mega is not a big pain compare to having out USB port burn up. haha
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Re: Arduino Mega 2560 R3 power supply

Postby zhenning » Thu Nov 15, 2012 3:51 pm

So, I guess its safer to go with either external or internal supply :)
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Re: Arduino Mega 2560 R3 power supply

Postby zhenning » Thu Nov 15, 2012 3:53 pm

]
Alen.ATLow WROTE:I wonder can we improve this by applying forward bias diode to prevent the voltage flow from higher potential to lower potential source of both USB and External Power supply.

Bricking up Mega is not a big pain compare to having out USB port burn up. haha


Its there already :) If you see the section after the DC Jack in the sch . There is a diode ^^

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Re: Arduino Mega 2560 R3 power supply

Postby Alen.ATLow » Fri Nov 16, 2012 1:08 am

what about USB VCC ?
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Re: Arduino Mega 2560 R3 power supply

Postby robosang » Fri Nov 16, 2012 10:08 am

I guess putting a diode will lower the voltage from USB by 0.3V, though is not much but for ADC application might affect a lot.

I don have the Mega, so can only study schematic :)
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