Whenever I connect the board using a USB it heats up real hot (sometimes shuts itself off. When if doesn't shut itself off I smell some burning smell and pull the cable out). The part circled in red below is where the heat builds up.
Initially it was connected to a CNC shield, which I was trying to use to control a stepper motor when this problem started occurring, even after removing the shield this still occurs.
At that time were you using another power source, and then plugged in the USB while the Arduino was still running?
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Welcome!
Did you have problems with the motors? How were they and the Arduino powered? Can you get a clear view of the hot part or post its number? I think it is a 3V3 regulator but I cannot be sure.
After trying for a while, I was busy for 10-20 searching the internet for a solution (also wrote this post) after that is works again. I would still like to know the issue so that I can avoid it in the future.
Yes, it was connected to an external (24V 20A, Kind of overpowered, but that the only thing I had in hand and it shouldn't be a issue).
I turned the power supply on then connected the USB, nothing ran. I turned off the external power supply and unplugged the Arduino. I plugged the Arduino again to check if there was something wrong is the code and try again but I faced the issue described above.
Edit: Clarification, the Arduino was not connected to the 24V. The 24V power was connect to the CNC shield, and from documentation for the sheild it can handle 12-36V. The only power to the Arduino was through the USB connected to my laptop so 5V.
After trying for a while, I was busy for 10-20 searching the internet for a solution (also wrote this post) after that is works again. I would still like to know the issue so that I can avoid it in the future.
Since it worked again later, I know the motors, the motor controller and the CNC board works. The Arduino was powered using the USB cable connected to my laptop.
I left the Arduino at the campus, I'll provide a more clear picture tomorrow.
24v is indeed out of spec.
Look at this documentation on powering the UNO.
https://learn.adafruit.com/ladyadas-learn-arduino-lesson-number-0/power-jack-and-supply
The max voltage on the power jack is 20v but it is stressful on the board. 9 to 12v is much better.
Ye, it is the 3.3volt regulator. The Uno only uses it as a reference to turn off USB suppy when the Uno is powered externally.
Show us how what and where you connected this stepper.
Maybe you powered the stepper throough the Uno, which cold explain things.
Leo..
Unless electronic devices are designed specifically to allow multiple power sources, then problems are inevitable. Such designs specify the order of power application. Much better design is to use buck regulators to reduce the single higher voltage to the lower, if possible.
Otherwise there are ICs the can sequence the power application to avoid problems.
I do not know the actual cause of your problem and you likely don't want to experiment!
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The likely scenario is that that took out the 5volt regulator, which then fried the micro and the 3.3volt regulator which is powered from the 5volt regulator.
Bye bye Uno.
Leo..
Clarification: The Arduino was not connected to 24V. The 24V was connected to the CNC shield (which is rated for 12-36V). Arduino is only connected to 5V through the UBS cable. Even after I remove the shield and the 24V power (only running on 5V through the USB cable), it still heats up
I know these are not the best images, this is from a video I took. (I left the UNO in the campus for the night). Let me know if you want explanation in any connection.
Remove the shield and see if the Blink sketch still works.
If so, then the Uno is still OK, except for the 3.3volt output.
That 3.3volt chip is not used for anything when the Uno is powered via USB.
You could swipe that 5-pin chip off the board with a soldering iron.
Leo..
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