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Topic: Arduino Uno Rev3 onboard voltage regulator (Read 252 times) previous topic - next topic

brice3010

When applying 15VDC via the DC connector for external supply the onboard regulator starts of with 4.90V but gradually over a period of about quarter to half an hour climbs to 5.5V, measured at the exit of the voltage regulator on the board.

The voltage regulator is an AMS1117 5.0V SMD device.

The spec sheet shows it can be powerd with up to 18V.

I never applied more then 15V, and the load current of the Arduino has never been more then about 200mA.
This is without the USB connected.

Is it bust?


bwxd

Cool. Until now I just know that this board can apply a voltage more than 5VDC. If knowing that earlier, it would save lot of time for making a voltage converter from a 12VDC power supplier to my UNO board. Haiz

CrossRoads

Any voltage into the barrel jack above 7.5V is just wasted as heat by the regulator. 9V, 12V, 15V, all are way more than you need. The heat generated will be approximately P = (Voltage - 5.7V) x current.


So with 12V, 200mA current, P = (12 - 5.7) x 0.2 = 1.26W. The poor little regulator has not in the way of a heatsink, just a little bit of copper on the board, so it's gonna be pretty warm. And when it gets too warm it will go into thermal shutdown. If it gets too warm too fast, it can fail and need replacing.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

deligence

due to overheat this is happing try to lower your input or else try some cooling method to reduce heating. that will stable your voltage.
Sanjay Kumar

brice3010

due to overheat this is happing try to lower your input or else try some cooling method to reduce heating. that will stable your voltage.
It looks like I have been walking the line with the specifications: both the input voltage (absolute maximum voltage = 15V) and the generated heat (1W without heatsink, although it never was so warm you could not touch it) have been too high for the regulator.

Right now when I apply 9V it outputs 4.84V, not quite right for this device; probably better replace it?


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