Uno r4 minima rx LED is always on

Hello.

There is a malfunction in my minima.

The day before it broke, it worked very well, no problem. But, the next day I plugged it back in and the rx LED was still on. And when I touched the board, what looked like a resistance near the microcontroller was very hot. Here's the photo at the bottom.

The sensor values were received from A0 and A1, but the change in the value was well detected. Literally, the sensor value increased and decreased. However, the previously output value was output about 25% lower.

It is less hot when given by USB power, and it becomes very hot when external power is added.
I use a 12V external power source connected to a power jack. I run two Arduinoes with the same auxiliary power source, one of which works strangely. There is no problem with a normal-looking Arduino being hot or getting the value strangely.

I'm upset that the board is broken, but the most important thing is that this should not happen again. I control my EV car with this because if it breaks down in the middle of running, it will be a big deal.

It works when you run these Blink examples. They turn off completely and turn on.
It works even if I passively turn off LED_RX and leave it, but after a while, the RX pin suddenly turns on.

// // the setup function runs once when you press reset or power the board
void setup() {
// // initialize digital pin LED_BUILTIN as an output.
pinMode(LED_RX, OUTPUT);
}

// // the loop function runs over and over again forever
void loop() {
digitalWrite(LED_RX, HIGH); // turn the LED on (HIGH is the voltage level)
delay(1000); // wait for a second
digitalWrite(LED_RX, LOW); // turn the LED off by making the voltage LOW
delay(1000); // wait for a second
}

There doesn't seem to be a problem with the coding itself. This is because RX pins are turned on even for completely empty sketches.

My guess is that the board is definitely in trouble. But, I want to know the cause for sure because this shouldn't happen again.

In summary, I connected the same external power source and only one of them broke down. It worked well the day before and suddenly broke down the next day.

Please tell me the cause

Yep that is how faults show up. Did you think if you left it a month before trying it again it would be more understandable?

Why is the ON LED circled on the picture it is not the one giving you problems?

The Arduino is not a automobile part so you shouldn't be doing this, there are legal reasons why this is not a good idea as well.

It failed because you did not construct your circuit correctly. However, what you did wrong is hard to tell because you provide very little detail about what you actually did. All we got was a rather rambling narrative.

A car is a hostile environment for electronics, there are voltage spikes produced from it and unless you take precautions to suppress them this is the sort of thing that can happen.

Also what precautions did you take to protect your input sensors exceeding the 5V maximum signal you could get? Abuse of electronic components don't always show up as an immediate failure, but if a system is not designed correctly it will have a short lifetime.

There is no reason why an Arduino should get hot if everything is designed correctly. If it is getting hot then I suggest it has not been designed correctly. But as you have provided no details, like a schematic and how it is wired to the card we can't yet offer any useful advice.

You might want to look at this How to get the best out of this forum before you proceed any further. It tells you how to ask a question here.

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