Arduino nano crashes - please advise

[jhinshel]

@wildbill

If you're pulling a lot of current to drive whatever the relay's switch, be careful to keep the power wires away from the Nano.

I'd be inclined to have those relays switching LEDs with a separate power supply to start isolating the problem.

The relays are powered via a separate 12v power supply and switched via an optocoupler.