Hey All,
Relatively new to electronics and managed to get the 5V relay working with Arduino which is fantastic.
However I'm wondering why I can't get my 5V relay to work direct from power source.
The voltage drop across the Input is 5V, similar to Arduino output, yet the relay won't engage and I can't figure out why.
I've attached a diagram which shows how I've wired it up.
Here's OP's pic:
Looks like you have a relay module (ie relay on a board) not a bare relay? Most of those are active low, gnd to in.
(But that wouldn't explain how your code's working, unless you're digitalWrite()-ing a low there too.)
Hey,
Yes you're correct, it's a module - not just the relay itself.
There's no code - I'd just like to wire it up directly to the power supply and a reed switch.
I'll try using ground....
ltsmash:
There's no code
I saw this:
ltsmash:
managed to get the 5V relay working with Arduino
... and took that to mean a code solution.
Yep that worked, thank-you so much.
So I need to use GROUND instead of the 5V supply to activate the relay module.
Thank-you!
Keen Nosey to know why you have an Arduino in the mix if it's not for its program...
I did post it in "General Electronics" 
I'm just wanting to use a simple Reed Switch to activate a relay - not really arduino related.
Thank-you for your assistance.
Arduino-as-power-supply 