25V inputted to Vin. Is my board fried?

Hardware
1

I have been powering my Arduino board (the CH340 clone version) through the 5mm barrel jack with a 12V wall adapter. It worked fine. My current project requires 3 Arduinos, so I wired their Vin pins together thinking that I could still use 1 wall adapter to power all 3 arduinos. My logic was that the Vin from the wall adapter would be split into the 3 sepparate arduino PCBs.

Unfortunately, my wall adapter burnt out (i confirmed this later with an oscilloscope and a different load) and started outputting 25V AC into the Vin pins. There were no flames or any heating (yes i touched the boards to see if they were hot before disconnecting). When using a different external power supply connected to Vin, the 5V pin on the Arduino is now actually 4Volts, which I think means the linear regulators have been broken.

I am still able to upload code to the boards. And no errors show up even when verbose output and code verification after upload is done.

I also checked to see if a simple 'blink LED' program worked. Yes, it worked on every single IO pin. All of this was checked while powering the board via USB port.

However, none of the code I wrote for my project works. For example, I'm not able to transmit anything on I2C or the serial port.

My questions is: should I just assume the boards are beyond repair, or is there some other option (such as replacing the 5V linear regulators)????

2

Are all 3 boards doing the same thing?

3

If the blink sketch works, try an I2C scanner (put one or more I2C devices on the bus). If that works the board is probably ok. Your code is a different matter.

4

Vin must be 7-12V DC. If your adapter gave 25V AC, the board is damaged for sure.

5

The onboard 5V regulator has been destroyed, it is not used when powered by USB.

You could forget about a 12v Supply and use a 5V supply connected to the 5V pins of the UNO's.
Is there a reason you need to use 12V?

Tom.. :smiley: :+1: :coffee: :australia:

6

I tried the I2C scanner by Luis LLamas. It didn't find any devices. Unfortunately, they might be damaged as well, since they were connected when my power supply failled.

7

Nope there is no need to use 12V.

8

Yes.

9

It looks like I might need to replace all the parts connected to my 3 arduinos(bunch of LCDs and a real time clock). Can anyone recommend a robust way of powering them next time I build this setup? I don't want a damaging voltage to be output by the power supply if it gets overloaded. Or, at least somekind of power supply that is more difficult to overload.

10

That is a bad sign. I would not waste any more time on that board, and there is a chance the board could damage other components. Time to move on

11

Of course. What I meant was how should I power the replacement boards so that this problem doesn't happen again?

12

I just completed a project and it is powered by a wall plug USB C charger. I got mine on Amazon.ca, you may need to change the URL for your local Amazon
https://amz.run/9TzE

13

I have been using these power supplies for a while and have not had any problems. 5 amps should cover just about anything you are doing.

https://www.amazon.com/gp/product/B01NBRTCIT/

They also make 3.3v and 12v versions.

14

Old original Samsung phone charger is one of the most reliable 5V supply.

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