Please apologize my english. I am working in a project using an original arduino uno, one generic servo (no factory marks) and one HC-SR04 sensor.

I make a circuit like the one here: http://s24.postimg.org/43jra5l9h/mycircuit_bb.png ([url=http://postimg.org/image/lgu1p0gkh/][img]http://s24.postimg.org/lgu1p0gkh/mycircuit_bb.jpg[/img][/url], sorry, upload of image not allowed due reputation)

As you can see from the picture I accidentally connected green into Vin instead of GND. (If the image won't load, that means that my positive is connected to arduino 5V and the ground of the circuit is connected to arduino Vin)

Now my board turn on the lights but I am unable to execute the program already in the microcontroller as aslo I cannot upload a new program to it. (It gives some error message of failed to connect).

I think I burned the microcontroller(mc) by short circuiting 5V and Vin.

That said, I have three questions:

1 - Is there any way to find out if I really burned my board using just a low budget multimeter? And if I did, which parts I need to replace? I have access to some spare ATMEL mc and I think I could replace and reprogram them by using another arduino board. However, I am affraid that I may have burned few other items and just by replacing the mc will not give me back all the funcionallities of a new board.

2 - I have basic knowledge of electronics, could someone explain to a beginner like me which impact did that mistake could/have make in all components of the circuit? (Arduino board, the servo and the sensor)

3 - Even before the accident, the circuit just work well for few minutes. I read tons of pages and tried a lot of suggestions, most of them related with power supply (capacitors to avoid flutuations, One battery just for the servo, one battery just for the sensor...) and none gave me good results. I am wondering what are the alternatives to power up this simply circuit, in particular I am looking for this possibilities: Complete external power supply (by using AC to DC adapters), Complete internal power supply (Using just batteries) and a mix of those two (Using AC to DC and batteries). I have no access to a external DC power supply generator other than batteries.

  • How was your Arduino powered when this accident happened? USB or power plug? Mar 16, 2015 at 13:04

1 Answer 1


If you have another Uno then your best bet is either:

1) Swap the suspect processor into the known good board, test it.

2) to buy a replacement chip (ATMega 328-PU), use this link to flash it, if it works you win, if not you can at least use the new processor again.

I have done this myself & it worked well, it isn't easy to be sure any other way as the chip needn't fail in a predictable manner. The chances are it will take a large current if it's dead, until it burns out & goes open circuit. Once the magic smoke has come out you know it's dead... the Arduino power supply is reasonably capable of looking after itself so your chances are good.

  • 1
    Before replacing the target processor, it's also important to verify that the USB-serial chip still works - can the computer recognize the device as connected? Can the serial port be opened without error (even though no data will be received in return). If not, the interface chip (FTDI, ATmega6u2 or whatever) may be dead, and while replaceable it is a bit more tricky to do so. Jun 14, 2015 at 14:44

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