Hello,
I'm new to arduino I have done like 3 or 4 projects. the board worked fine but now I have a problem
when I power the board using USB cable it works fine, but when powered through the battery via DC jack the green light glows little dim and the 'L' LED on the 13th pin starts blinking very fast and the voltage from 5V/any digital output pins is ~1.8V (previously ~5V).
Of course i can program the board the IDE successfully uploads the program to the board but the only problem is i can't use when i connect the battery, only when powered through USB and I have checked that the battery is fully charged (12.37V) and measured the voltage in the Input jack in the board it also measures (12.37V).
The battery is a 12V Lithium-Ion (3x4.2V, 2000mAh cells)
Dimension 15.2x10.2x8.9 cm.
yes the voltage regulator is heating and it seems burned, I have attached pics of the regulator ,also in the regulator the output pin gives 1.79V and input to the regulator is 9.08V
You have to ask yourself when and how this happened, typically they make a pop, crack or hissing sound and smell bad when they fail :(. It is possible the part was faulty but it is also possible that it has been damaged by reversed power connection at the Vin header pin.
The regulator is pretty tough and tolerates most forms of abuse but not reversed polarity. The input jack has a diode in the power line that protects against reversed connection but that may be blown to a near short circuit if you have been probing the board and accidentally shorted out something (meter on Amps range?), it is certainly suspect as 3V is getting dropped somewhere according to your measurements.
So you will have to use the board on 5V USB (check the regulator stays cool when powered from USB only). Alternatively repair the board by replacing the regulator as already suggested by INTP and replace that suspect diode too.
