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Topic: UNO Rev. 3: What is the LM358 for ? (Read 3 times) previous topic - next topic

AlxDroidDev

What is the purpose of the LM385 in the Arduino UNO Rev. 3 ?

I see one of its output simply feeds a MOSFET (?) while the other lights a LED.

Thanks.
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CrossRoads

1/2 is used as a voltage comparator, to select whether the board is powered from USB or from Vin.
The other buffers D13, removing the load created by the L LED and its current limiting resistor.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

AlxDroidDev


1/2 is used as a voltage comparator, to select whether the board is powered from USB or from Vin.


Thanks, CrossRoads!

So, the 1st half of the LM358 works like an electronic jumper, automatically switching between different power sources ?

If that is so, what happens when both inputs (USB & jack) are powered?
Learn to live: Live to learn.
Showing off my work: http://arduino.cc/forum/index.php/topic,126197.0.html

CrossRoads

Yes, auto power selection.

If Vin/2 is greater than 3.3V, Vin is used for the power source.
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17.
Arduino for Teens available at Amazon.com.

AlxDroidDev

The schematics won't show the other pins for the LM358. What powers the IC? Since power source hasn't been selected yet, where does it get its power (5V, I guess) from?
Learn to live: Live to learn.
Showing off my work: http://arduino.cc/forum/index.php/topic,126197.0.html

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