Relay Shield and a hot 7805

Hello to everyone.
In my actual project (an Arduino Standalone with some peripherals) I’m going to attach a relay board, I can say quite exactly like this one

It’s an octocoupled 2 channels relay that work at 12V.
Like quite all these kind of boards, it turns on with a LOW signal.

When the relay is connected to the board, even if it’s not working (and I do not understand what’s up with it - using it with an Arduino UNO it works - !!!) the 7805 that I’m using to power all the shield is running really hot. Should I reduce the current from pin to Relay Input? The board should have all the necessary resistors and do the regulation autonomously, am I wrong?

I’m setting up the pin like output

[…]
pinMode(LIGHT, OUTPUT);
digitalWrite(LIGHT, HIGH);
[…]

and when expected, moving it to LOW to turn the light on

[…]
digitalWrite(LIGHT, LOW);
[…]

Attached a Fritzing image (sorry, I realyzed it in a quick way, just to explain, it’s not complete) to better explain how I’m attaching the realy.
Without the relay, the 7805 is just a bit warm…

To become so hot, I think the circuit is going to charge an high amount of current. Otherwise, I’m thinking to a kind of short… but I cannot understand what it could be.

I also made another test, unplugging the GND from the 12 power source and leaving just one GND (it should be a common ground module…). The shield is not working and the 7805 isn’t getting hot.

Should I use resistor between the ATMEGA and the the shield?
Do you have any other suggestion?

Sorry, I maybe solved the issue after a few minutes... writing or speaking about smth sometimes helps!
Removing one GND the relay is working and the 7805 is not getting hot: WHY was this happening?

If you have a 12volt relay module (printed on the relays), remove the jumper.

Connect 12volt to the JVCC pin.
Supply ground to any of the two ground pins.

5volt to VCC (the VCC next to IN2).
And the Arduino output pins to IN1 and/or IN2.

Leaving the jumper on will send 12volt to the Armega chip, and will fry it.
You’re lucky if it hasn’t happened yet.

The 7805 needs capacitors on in and out pins.
It could oscillate without them, and send more than 5volt to the chip.
See the 7805 datasheet for the right values.
Leo…

I already fried one, but in another way ))
The issue is GND: why 7805 become hot if both GND are connected?

Better post a real picture of your setup.
The 7805's input and output are shorted on the fritzing diagram.
I also hope you're not using the Atmega chip without supporting parts.
Leo..