3.3V pin, Arduino UNO R3, doesn't work!

[miladbagheri]

Hello everyone,

My Arduino UNO (R3) doesn't have voltage on the 3.3V pin, while it has power on the 5V pin.
How can I fix it? Should I replace the on-board regulator?

I search for it and I found that there is just one regulator. Is it related to regulator because I have 5V and I don't have 3.3V?

Thanks,
Milad

[CrossRoads]

Can you post a picture of it? Is it an Arduino Uno, or some knock off clone?

[system]

Did you check voltage on the regulator's tab is 3.3V?

If exist, then some trace to the pin is broken.

[pert]

Which USB to TTL serial chip does your Uno have? On some of the Uno derivatives, they used a pin on the CH340 to provide 3.3 V to the 3.3V pin.

From my reading of the CH340 datasheet, that seems to be not a usage intended by the designers of the chip. It's possible that pin is not as well protected as a dedicated voltage regulator would be and it could have been damaged by you subjecting that pin to conditions outside its rated specs. Of course it's also possible the board is defective and the 3.3V pin never worked.

If you have an official Uno or a faithful clone then there is a dedicated 3.3 V regulator (LP2985-33DBVR), which is shown on the schematics and Eagle files available from the "Documentation" tab of the product page:

Arduino Uno Rev3

[miladbagheri]

Thanks @CrossRoads

I have attached the pictures of it.

CrossRoads:
Can you post a picture of it? Is it an Arduino Uno, or some knock off clone?

[miladbagheri]

pert:
Which USB to TTL serial chip does your Uno have? On some of the Uno derivatives, they used a pin on the CH340 to provide 3.3 V to the 3.3V pin.

From my reading of the CH340 datasheet, that seems to be not a usage intended by the designers of the chip. It's possible that pin is not as well protected as a dedicated voltage regulator would be and it could have been damaged by you subjecting that pin to conditions outside its rated specs. Of course it's also possible the board is defective and the 3.3V pin never worked.

If you have an official Uno or a faithful clone then there is a dedicated 3.3 V regulator (LP2985-33DBVR), which is shown on the schematics and Eagle files available from the "Documentation" tab of the product page:
Arduino Uno Rev3 — Arduino Official Store

Thanks

[pert]

That looks like an official Uno. It does have a dedicated 3.3 V regulator. It's the part circled in red:

[miladbagheri]

noob314:
Did you check voltage on the regulator's tab is 3.3V?

If exist, then some trace to the pin is broken.

Thanks,
I didn't check it out,
I will do.

[miladbagheri]

pert:
That looks like an official Uno. It does have a dedicated 3.3 V regulator. It's the part circled in red:

Thank you so much for your help.