Wrong connection to the relay, power supplier died!

Forgive me for this question, but I was testing a 12V relay and I supplied both 12V and 5V as VCC (you know, you have JD-VCC and VCC: it seems I burned the power supplied doing this.

Can you explain me "why" this happened?

I don't understand what you connected where.

Are you saying that you connected 12v onto the Arduino Vcc?


Sorry for my bad explanation: I was playing with a Relay Board 12V like the one you can see here

You see there is JD-VCC in the picture jumped with VCC for the board. At the right, again, VCC.
I had VCC (to the right) connected to 5V and VCC (in the left) connected to 12V...

For clarification,

There is no involvement with Arduino, and the connections were only power supplies to the relay board.

It was the external power supply that was destroyed. (Not on the board.)

I assume the damage was to the 5v supply. The supply would have been damaged by having too higher voltage applied across the regulator output.


Again sorry.
I've got a custom board, that I supply with a 12V power supplied (fried), a regulator (7805), an ATMEGA328 (fried), a display and so on.

From the board I took the 12V and the 5V and connected as above explained.

The power supplier died: means that 17 volts (I read somewhere that power supplier can be putted in series) came back to the supplier and burn it?

Hi again.

You can add up 2 sources to become a new source.
So if you have a 12 volt source, and a 5 volt source, you can add them up to become a 17 volt source.
But you do not have that.
The voltages are derived from that single 12 volt source, if i understood what you did correctly.

Connecting the 5 volt wire with the 12 volt wire will not do this.
You need to connect the GND wire of the 5 volt source to the positive wire of the 12volt source.
If you would do that with a setup where the 5 volts is derived from the 12 volts, you would create a full short on the 12 volt power supply.

As you might have noticed, i am speaking of sources.
Read that as separate batteries.
You have just one “battery”, you can’t tap 5 volts off of it and then add it up to its own positive wire.

You should make a sketch/diagram of what you did, how you had things arranged.
That's how we do things in the electronics world.
These prosaic accounts of this and that are seldom if ever productive.
Put pencil to paper, take a picture of that and then post it.