Arduino with Solenoid

[Mad Cows]

What if I put it in reverse (5v to 12v)

[protoserge]

Originally Posted by Mad Cows

What if I put it in reverse (5v to 12v)

It's a step-down regulator meant to convert the 12V to 5V, not the other way around.

It sounds like you have everything you need if the relay can be triggered by a 5V source.

Here is an example schematic. Scroll down to the Arduino + 24V on relay.