Damage possibility

Other Hardware General Electronics
1

Hi All,
Is it valid to connect a 9V DC to the arduino Jack and in same time connect the USB cable to the computer to use its serial connection ?
And in this case will 9V DC supplied on the arduino Jack be the supply or the USB will be the supply

THANKS

2

Yes you can have both connected, if you have an early board there will be a jumper to select where the supply comes from.
I'd say you have a later board, selection is automatic, with both connected the 9V jack is used.

Tom.... :slight_smile:

3

When a high enough voltage (6.6V) is present on Vin a p-channel MOSFET switches off
the USB 5V supply (from Uno rev 3 schematic). In the absence of Vin the MOSFET is
switched on connecting the 5V rail to USB 5V.

4

MarkT:
When a high enough voltage (6.6V) is present on Vin a p-channel MOSFET switches off
the USB 5V supply (from Uno rev 3 schematic). In the absence of Vin the MOSFET is
switched on connecting the 5V rail to USB 5V.

But the serial interface through USB will still be working right ?

5

Hi, yes...

Tom.... :slight_smile:

6

TomGeorge:
Hi, yes...

Tom.... :slight_smile:

Thanks TOM :slight_smile:

7

When a high enough voltage (6.6V) is present on Vin

Note that Vin is after the reverse polarity protection diode, so the barrel jack voltage must be a little higher to allow Vin/2 to be >3.3V and select the 5V regulator output as the source.