I am using an Arduino Mega to control a few devices, most of them using reles.
My arduino board restarts every X time once a few of the reles are activated and I suspect it is a power issue. Reles are powered with an external power supply, witch also provide power to the board.
So once 11 of the reles are activated, the board is restarted after a while.
Why could it be? Maybe the board is not able to provide enough power to activate the reles?
It is rare that an Arduino can supply enough current to drive a relay. You need some sort of driver.
There could be many reasons for your problems, a schematic Would help us rule out 90% of them or even pin point your mistake.
But if you tell us nothing about what you have we can tell you nothing about what you have done wrong.
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
Then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?