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Disabling USB Power because my memory is CRAP!

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You may have noticed especially if you have the ulticontroller that the electronics will be powered by the USB cable if you switch the primary power off.

The problem is that I believe the ulticontroller draws more current than the arduino's USB power source can supply. This causes the resettable fuse on the arduino to kick in and cut the current only to reset and kick in again over and over.

I see this as the ulticontroller to pulse or blink.

As I'm old and my memory is crap this was a regular occurrence.


******** DO THIS MOD AT YOUR OWN RISK *******


After doing this, turning off the UM1 with the power switch causes everything to power off and the COM port disappears on the PC.

Here is how to PERMANENTLY prevent the arduino mega 2560 R3 from drawing power from the USB connector.

disable Usb power notes

Unmodified vs. modified:


First pic without annotations.



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That mod disconnects the 5v line in the USB cable from the arduino so it is actually less likely to damage your computer. All the other protections built into the arduino still work and protect your PC.

The jumper is required to take the onboard 5V to the ATMEGA16. I checked the ATMEGA's datasheet and this is how self powered (as opposed to USB powered) .configurations are done.

I'm fairly sure that this mod won't hurt your PC but ANYTHING you do with respect to this type of mod has RISK So don't do it if you don't understand it.


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I know this thread is old but I'm trying to solve the same problem a.t.m.

My question is: Why have you chosen that way?

Woudn't it be more easy to just desolder the MOSFET that is between the USBVCC and the +5V on the board?


It will still power the ATMEGA16 this way but not the remaining board.


And VIN does still power the board as before:


Can anyone confirm my thoughts? (maybe @anon4321)

Thanks ;)




Edited by Guest

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