So doing quite a project here and I think I've destroyed my brand new Mega. If you power it the TX & RX LEDS constantly burn, and it's not visible on the computer also not when I connect the USB while holding the reset button.
The Atmega chip is however still doing it's work, the program that's on it still runs. At least the bit I was able to test.
The situation: - I have 16 sensors (very simple +5v - 1k[ch937] - output - sensor - GND, where the sensor is a resistor that changes value) - And I have 48 outputs, these are 6 LED's per output powered on 12v through 3 TLC5940NT's
I got the 12V for the LEDs by connecting a 12v DC (which actually outputs 12.76V) to the Arduino and then taking 12V again from the Vin of the Arduino.
This worked fine last friday, but today one of the sensors kept outputting HIGH (4.8V) while it's state should normally be low. Turned out a wire was broken which meant the 1k[ch937] resistor wasn't connected anymore. Which is odd I think because the 5V needs to go through the resistor to ever make it to the output. :-?
After this the Arduino became hot (touching the Atmega 2560 chip hurt) and stopped working. Now when I put the 12V adapter in the little metal-plate+chip richt next to the socket becomes very hot (as in: don't touch!) and after a while the USB-socket starts heating up as well, although the Atmega 2560 in the middle stays cool.
I've tried to connect one of the working sensors and output again and that worked (haven't tried with 16 again though). But still the Arduino won't communicate anymore with the computer and the RX and TX lights stay on forever.
Anyone here who can tell me what's exactly broken, can it be fixed, what caused it, etc?
The Mega2560 is quite expensive so I wouldn't like ruining another one. My first step would be to just power the Arduino from USB and connect the 12V directly to the LED's rather than connecting the power to the Arduino and using the Vin port. But I'm not sure this would solve everything, I've tried and there was no point where a connection to sensor or TLC was over 5V.
The strange thing is that it worked for hours on friday and now broke within half an hour, is that because of the malfunctioning sensor drawing more current perhaps than a properly functioning one meaning that the Arduino overheats with the 12V supply?