by Relayer » Mon Oct 05, 2015 10:59 am
Hello Banetooo,
The relay in question is a SPDT (Single Pole Double Throw) type.
Pin 1 is the NO (Normally Open) contact, Pin 2 is the NC (Normally Closed) contact, and Pin 3 is Common.
The other 2 pins are for the relay coil which MUST have an external diode attached between +12V and ground, with the cathode connected to +12V as shown in the diagram. Failure to do this may cause damage to the rest of the circuit. A 1N4004 diode would suffice.
Unfortunately there is a myriad amount of different types of relays available out there and you need to choose the correct one for your application. Actual pin configurations can vary as well, so you really need to get a datasheet on the relay you decide to get.
One main factor with relays is the switching current contact rating and voltage. Its really going to depend on what currents and voltages you need to switch. A relay designed for DC switching in most cases cannot be used in AC switching as an example.
Going by the diagram, it seems its there to ground whatever pin 3 is connected to when the relay is energized.
Is this relay intended to be used in a project of your making, either on veroboard or a PCB made for it?
If you can give us an idea on what you're intending to do, it will make it so much easier pointing you in the right direction in regards to the best suited relay for your application.
Take care.
Regards,
Relayer