Question for Polyfuse

Hello everyone.
I was reading the specifications of the pins of the Arduino and found that USB can only draw 500mA and I went to the schematic of the Arduino to find out that there is a Polyfuse rated at 500mA and after a small research I found out to be for just safety.
So hypothetically speaking. If I have a project drawing more than 500mA could I just remove or replace the Polyfuse with one with bigger value if I am sure that there won't go anything wrong?
I am repeating that it's a hypothetic question. Not a project question.

The fuse is there to also protect the PC/laptop.
Devices that require more current should be powered directly, not through the Arduino.
5volt Arduinos can also be powered directly on the 5volt pin.
Leo..

Also know the polyfuses are not precision devices and are really meant to save things from shorts not from overloading.

Thank you both for the answers.

Wawa:
The fuse is there to also protect the PC/laptop.
Devices that require more current should be powered directly, not through the Arduino.
5volt Arduinos can also be powered directly on the 5volt pin.
Leo…

By project i meant something permanent. For example and arduino that does a specific job and wont be ever put again to another project and wont be programmed again.

So if you are using a 1 or 2.1 Amp "Phone charger" as the power supply and not connecting to a PC, then it would be convenient to use a USB cable (short, and of the variety that uses decent wire) to connect it to the Arduino and bypass both the polyfuse and the FET.

But it is just as sensible and easy to wire direct to the 5V pin (and ground).

Paul__B:
So if you are using a 1 or 2.1 Amp "Phone charger" as the power supply and not connecting to a PC, then it would be convenient to use a USB cable (short, and of the variety that uses decent wire) to connect it to the Arduino and bypass both the polyfuse and the FET.

But it is just as sensible and easy to wire direct to the 5V pin (and ground).

Ooohh.. So the fuse is only "active" if it is connected to a pc?? Because at the Schematic the XUSB (which I guess is the 5V) goes straight to that fuse.

The fuse is in the USB connector circuit together with a FET to switch off this supply if there is power on "Vin". It does not matter whether the USB is plugged into a PC for communication or just a power supply.

Paul__B:
[...] use a USB cable (short, and of the variety that uses decent wire) to connect it to the Arduino and bypass both the polyfuse and the FET.

How do you bypass them? I must have missed something

Piece of wire and solder. Wire-wrap wire and the stripper tool would be good; this takes some experience and skill I hesitate to say! :grinning:

So hypothetically speaking. If I have a project drawing more than 500mA could I just remove or replace the Polyfuse with one with bigger value if I am sure that there won't go anything wrong?

Factually speaking, if you have an Arduino board drawing more than 500mA, you’re doing it wrong.

Regardless the source of the power, whether it’s from the USB port, Vin or the +5 pin, the only place for that current to go is through the voltage regulators and/or the processor pins. The typical Arduino atMega processors are limited to a total current consumption of 200mA from all pins combined and the voltage regulators aren’t good for more than 500mA output under the best of conditions. Sure, you can control devices that consume more than 500mA but that current must be passed through wires off the Arduino board.

It’s a fair question and it shows you’re thinking things through but replacing the poly fuse with a higher rating is a solution to a problem that you should never create - as you don’t want high levels of current passing through the Arduino board, the devices on the pc board or the pc board traces themselves.

Most USB ports will only supply 500mA, drawing may cause a port failure, or on a decent a port shutdown with some Error message on the PC. Mine declares "Surge current" and shuts down the port, requiring a PC Reboot to get it back.

Thank you all for your answers. They really helped me undestand things. :smiley: