I'm trying to make an arduino installation.
So my plan is to turn off a 12V solenoid for 30 seconds with an Rfid card.
I already bought a 12v battery because i can't get 12v if I only use an arduino.
I am thinking on using a relay but i'm not sure what components I need to use.
Thank you for you help and sorry for my bad english.
There are plenty of schematics on the net for turning on and off relays and solenoids.
Take note of any protection parts used such as diodes etc as they will help prevent damage to your Arduino.
We don't know what you have as far as parts so it is very difficult to make specific recommendations.
Most commonly used relay modules from China would be suitable as they almost all use protections and even opto isolation.
Only the ground needs to be shared with the Arduino but in the case of using a relay even that can often be dispensed with.
Thank you for clearing things out!