Do you have 12V relay if the LED supply is 12V.

 

Yes. I have a 12V relay.
So The relay will act as a driver and I will not need a separate driver for the LEDs right?

 

If your led strip works without a problem when you apply 12V to it then, yes.
What is relay model no.
We need to know the relay operating current.

 

It does. Ok. Thank you.

 

The transistor driving the relay should have a base resistor or you might destroy the uC port

 

yes. you are right. I forgot to draw it in the schematic.i will put it

 

i am putting 2K resistor at base and a 1K resisitor at collector

 

Draw up ur diagram and post it to confirm

 

The formula I use for calculating base resistor is:

Rb = ( Base signal Voltage - Vbe(sat) ) / ( Ic/hfe )

Base signal voltage = voltage from MCU = 3.2V
Vbe(sat) = 0.65 (from datasheet of 2N3904)
Ic = Current that needs to be switched (12V Relay Coil Rated Current ) = 33.3mA
hfe = Minimum gain of the transistor = 0.65

Therefore,
Rb = 0.051231 ohm

 

Wrong !
Just put between 1K to 2K as base resistor and you will be good.
Make sure the Relay coil current does not exceed the Tr Ic

 

Wrong !
Just put between 1K to 2K as base resistor and you will be good.
Make sure the Relay coil current does not exceed the Tr Ic

OK...I am sure you are right about me being wrong. But can you tell me why? So that I dont make the same mistake again...

 

Build it.
Measure the base voltage and current first during relay on and off.

 

is a LED Driver cumpolsary in this arrangement?

nothing is "cumpolsary",

the mosfet you have in abundance can handle > 1amp at 3v Vgs and 15v Vds. I would simply try it directly as a relay, switching the leds to 12v. much simpler than that you have now.