MEGA 2560: GND jumper, I want NO USB power

Development Tools IDE 1.x
1

Hi Guys!
I want to power the Arduino through VIN and NOT via the USB power.
Is it therefore enough to cut the little bridge on the Arduino?
And does the USB connection still work then (if powered via VIN)?

Thank you very much :wink:

2

You are putting >= ~7.5V on Vin? Why do you need to anything with USB power? The Pfet in the autoswitching circuit already provides separation.
Vin is only 1 diode away from powering via barrel jack, you don't cut any jumpers for that, do you?

3

The little jumper is most likely the DTR/Reset Enable jumper from the 16U2 to connect to the Reset line.

4

Well, it's an commercial system (the Ultimaker board).
The Arduino is powered via VIN from the Ultimaker shield or, if there is no power on the shield, powered via the USB connector. The problem is the following: VCC from the arduino is also available on the shield and poweres it (or at least tries to). Since the necessary power on the shield is 12V and not 5V, the fan is running and the LCD is very very dark.

I want to stop powering the ARDUINO via USB therefore.
So, if i cut the little jumper (which is connected to GND from the USB), will it work?
Does the USB still work - can i still transmit data? Because GND is the the GND of the power supply and not the one from USB.

Thanks :wink:

5

I don't know what the purpose of that cuttable trace is on the Mega and Uno board bottom by the USB port, but I would like to know. On the schematic it shows it providing ability to cut the ground pad "pin 33" of the ATmega16U2. I don't think it has anything to do with cutting power.

I think you should remove the polyfuse to cut USB power.

6

I think it's better to desolder the MOSFET FDN340P, since otherwise you have to power the ATMEGA16 through a jumperwire or sth. else. What do you think?

But even if that would work, i'm still interested if the other solution also works (at least in theory) ;D

7

Update: I tried it! But UGND and GND are also connected internally (inside the ATMEL), cutting the bridge doesnt work therefore (what's the bridge good for then?). Furthermore: Removing the MOSFET works like a charm :wink: