Uno R3 voltage regulator

are there 2 voltage regulators on the Uno? One for USB and one for the 2.1mm input jack? I have a project ( xmas lights of course ) where I can power it fine from the USB but anything I put on the 2.1mm power jack doesn't quite drive the relays enough....the lights will come on but they won't always trip. It's fairly consistent..and if I tap the relay that doesn't trip it will trip. After a few tries with different power inputs, I decided to try another board and it works fine. Could it be a bad regulator?

Thanks,
Dale

The USB does not go through a regulator as it is regulated by the source.
If you put 5v into the power jack, it passes through a regulator that drops voltage. This socket is meant for 7v or more to allow for the regulator loss.

Weedpharma

Thanks for the info...I actually saw that the regulator was only for the jack after I posted. I tried 12v 1.5a all the way to 20v 1.5a wall warts....with the same result. Would it be worth replacing the regulator? Or for the cost...should I just replace the unit?

Thanks,
Dale

Try a 9 volt 1A wall wart. That will reduce the heat on the regulator. I use a 7.5v 1A wall wart on my Mega/ethernet shield.

Can you measure the voltage at the output of the regulator with the 12v supply?

Weedpharma

There are 2 regulators - 5V,800mA, and a 3.3V 150(?)mA, that is fed from 5V.

7.5V DC input on the barrel jack works great. With 9V, 12V, the 5V regulator can get quite hot if driving a lot of LEDs or using 5V off the power header to provide current to offboard components.
http://www.dipmicro.com/store/DCA-07510

I personally use 5V wallwart and skip using a regulator in a lot of my projects.
Need to have a wallwart no matter what, why complicate things with a linear regulator?
http://www.dipmicro.com/store/DCA-0520
http://www.mpja.com/5-Volt-DC-Plug-Power-Supply-4A-Regulated/productinfo/18520%20PS

If you need 12V for an LED strip, okay, then a 5V linear regulator to power the uC makes sense, & control some MOSFETs to switch the strips on & off. But that only needs some 10's of mA of 5V current.