Need Help Question for circuit and relay

[banetooo]

My question is about diagram of the image.

Can anybody tell what exactly is the relay of the picture and
which cable and where to contact pins.
Understand where to connect + 12V and Ground but can not figure out which of the other three
is common / normally closed / normally open
Please help.
How to find relay model
How to connect the pins
1-?
2-?
3-?

[pebe]

The image is much too small to read the numbers on the contacts. And they would also be clearer if you posted the file as a .gif file rather than a .jpg file

[Relayer]

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

[banetooo]

thanks for the detailed answer. It was very useful
But I wonder if you connect directly to 1-3 without relay. Is it possible to be without 2
the whole thing is to activate ON/OFF the audio signal of an original car radio navigation to be able to play music in 3.5 mm audio jack

[Relayer]

thanks for the detailed answer. It was very useful

You're welcome

Pin 2 is permanently connected to the Common pin (Pin 3) up until the relay is energized then switched over to pin 1. Pin 1 will then be the connection to the Common pin (Pin 3) until the relay is de-energized.
If the signal going into Pin 2 is not significant, then you can bypass it by shorting Pin 1 and Common (Pin 3) together. But you MUST break the track going into Pin 2. Otherwise it will connect all 3 pins together at the same time.
I'm not sure if that is your intention, as I'm unaware of what the signals are going into Pin 2 and Pin 3.
If I'm incorrect in my assumptions, then please let me know.
Take care.
Regards,
Relayer