Hey!
The power LED of my Arduino UNO R3 blinks and turn off As soon as I connect board to USB of my PC . The IDE does not recognize it too.
Please guide me.
Is there anything connected to the Arduino?
Did it ever work and has now just got this new behavior?
It sounds like your Arduino is broken.
It was working. No thing is connected to it.
Therefore it looks like you broke it. It would be difficult to try and fix it yourself, you are better off getting a new one. Let's hope you haven't blown your USB port, can you try it on another computer?
How can i test it?
What is about trying to feed the board via 5 V pin?
It used to be that if you had a regulated 5V source it could be applied to the 5V pin but that's not true for all. Uno R3 should be safe for that but a newer Uno with some tricky-dicky circuit may not.
On Uno R3 and earlier the socketed chip can be replaced but in your case, there's no telling. I might guess that you have a short that blows the USB fuse right away and does the same after the fuse cools down.
Uno is a development board, it is far more expensive than a little plain Nano that can plug into a breadboard and do much the same.
It does sound as if its broken.
Can you measure the voltage on the 5V and 3V3 pins with respect to ground?
Have you tried a different USB port? a different cable?
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If your USB connection is disconnecting as soon as you plug it in you are not going to be able to program it, so there is no point trying to feed it with an external supply voltage.
I guess you are right. How can I find the short? I've checked back four pins of the USB, the voltage between last two pins was 5 V.
My UNO is CH340 ( a Chinese version).
they are Zero when the board is connected. I've checked back four pins of the USB, the voltage between last two pins was 5 V.
I've checked a different PC.
The "traditional" way, is to feed power into it and look at the board with a thermal camera for hot spots.
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Post-mortem or pre-op?
Why do you think there's a short? Sounds more to me like the regulator has failed/shut down, hence output is zero.
Maybe. How can I test it?
USB power passes through a regulator on an Uno?
And all this time I thought that was for 7+VIN since USB power is regulated by the source.
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You means powerup+USB simultaneously?
I plug the USB cable into my Uno and it powers up. I check 5V to GND and I read 5V. The USB link shuts down when > 500 mA is drawn.
What were you doing just before the board got flaky?
UNo+L298N which was powered by external motor power in. The L298N was burnt by a mistake.
I've checked and no potential has been seen. How to check the regulators?
Pre-op.
Do you know exactly the mistake you made?
If the motor power voltage got onto the Arduino lines then, given what you have said before, the Arduino is toast.
As @GoForSmoke said, the current from the USB does not pass through a regulator.
I connected the Power in to Power out, No thing about 5 V or other Arduino pins.
How can I check the regulator?