Which component it is?

Hi, i was looking my arduino UNO board and i saw a little yellow component which i can't identify or find information about it. It's just aside the USB port, is like this one:

but mine say "505Y", googling i found some others that say "500Z", "510K" "1905", and even some green coloured, but none information about it.

Does anyone know what it's and which is it purpose?



500mA auto-reset fuse to protect the 5volt power line coming from the PC/laptop.

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Tom… :slight_smile:

I see, also known as Resettable Fuse (in case someone else want to read about it)

to protect the 5volt power line coming from the PC/laptop.

This mean if i build a circuit very badly and it turn in shorts or something the USB port will be safe right?

Interesting factoid about this part:

Here's a major fake-alert! The component 501 K located next to the voltage regulator is generally green on fake boards. The green one has similar properties as the original Arduino golden-black component and is available off the shelf.

We get it specially made for Arduino to make it look different:

Original board


I believe the gold one with the infinity symbol or 8 on it in the picture you posted is their new custom PTC and they just haven't updated that webpage accordingly.