Power On LED starts blinking


we´re using an Arduino Mega 2560 board with Ethernet Shield and external 12V DC power supply. After turning on the power, the uploaded sketch works just fine and does what it´s supposed to. After an undefined time (sometimes just 1 minute, sometimes about 30 minutes) the programm seems to get stuck. The strange thing is, that the "on" LED on both, the Arduino Mega board and the Ethernet shield starts blinking (at a rate of about 0,5 Hz). I haven´t found any information yet, what the blinking means.

Does anyone have an idea?

Thanks in advance.

My guess would be that the 5V voltage regulator is shutting down due to excess heat. Ideally you would use a 7V supply. 9V would be an improvement. At 12V more than half the power going into the Arduino is being turned into heat in the regulator.

Heat problems was also one of my concerns. We use the Arduino as a part of an elerictric cabinet. The board itself is placed in a housing. I measured the temperature inside and it didnt exceed 32 °C. After opening the housing, the whole board was feeling fairly warm, thuogh. After further testing with no lid on the housing the error still randomly occured. Im still wondering what the blinking power LED means. It definetely want's to tell us something. ;)

We are using the 12V power supply, because it was the "smallest" one we found, which is suitable for mounting in the electric cabinet.

Perhaps you could find a small-enough regulated 5V supply. Then you can connect that to the +5V pin and bypass the regulator.

Or you could use a USB Charger and USB cable to power the Arduino.

Or you could add an intermediate regulator after your 12V supply to bring the voltage down to 7 or 8.

Ok, thanks for the advice! I think we can still fit an intermediate regulator in the circuit.

So you think, the problem is definetely heat related?