question about powering a relay

I am using an arduino to power Keyes SR1y Relay module circuit | Techydiy

Can I use an external power source to power this relay?

Hi, and welcome to the forum.

Basically, yes.

Connect + of the external 5volt supply to + of the relay module.
Connect - of the external supply to - of the relay module.
Connect - of the relay module also to Arduino ground.
Signal (s) goes to an output pin.

Why do you want to do this.
Most Arduinos can power one or two of those relay coils (<= 80mA each when active).
Post a list of the hardware you have and the supply you’re using.

This Keyes relay board has no opto couplers (extra/optional isolation), and I think this board also has very little creepage distance between Arduino and relay contacts (seen it before).
Highly dangerous if this board is used for mains voltage switching.