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Topic: Arduino UNO R3 stopped working (Read 2 times) previous topic - next topic



My Arduino UNO R3 stopped working. The power and the yellow led light remain on. Pressing the reset button has no effect. When I plug it in via USB it does not appear and if it's powered via an external adapter and I plug the USB in, my macbook shuts down.

Does anyone know what the problem could be and what could have happened?


A capacitor is bad or the voltage regulator has shortcut or something like that.

On the Uno are two chips. One for the USB-to-serial and the main microcontroller (ATmega328P) which runs your sketch. If the yellow led stays on, the main microcontroller is not working. If the board is not recognized by the computer, the USB-to-serial part is not working. If both are not working, it could be a voltage problem.

Don't connect it to a computer anymore, but use an adapter for the tests.
Can you measure the voltages on the board with a multimeter ?


Jan 26, 2013, 11:41 am Last Edit: Jan 26, 2013, 01:01 pm by mishari Reason: 1

Could you tell me where you'd like me put the probes? The power supply is from a decommissioned linksys WAP54G. The reading I'm getting in the power supply is 18 volts even tho it's rated 12. The board also seems to get very hot.


First of all, use a power supply with a lower voltage, say 9V (7...12V).
Measure the pins "5V" and "3V3"
If they are okay, measure the pins of the voltage regulator.
If that is all okay, you could try to write a sketch to the ATmega328P (the main microcontroller) with a programmer and the ISCP header (the 2x3 pins near the ATmega328P). But you need a programmer for that.


I attached a 5V power source via a USB cable to a phone charger, I get 3.29V and 4.95V respectively which seems ok. The input regulator I'm not sure how it works (yes, I'm a n00b), I attach the positive probe to the pin closest to the round adapter socket and the negative probe to the other end and I'm also getting 4.95V. Does this mean that the board is salvageable?

I've placed an order for another arduino board to be the programmer. Is that you mean?

What do I use as a stable power supply to get the rated voltage? Battery is not feasible as I'll also be using a GSM shield which will drain it out in no time.

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