So I have this whole system which has a noise of 2V, I have a PCB board which has got some LEDs which are lighting up because of this noise, how do i implement a simple circuit that restricts the 2V noise signal but enables when the power supply of 12V is applied. The PCB board consists of only LEDs for further clarification, the power is supplied when my microcontroller (on a different PCB) closes the mosfet which lets the power to be supplied

 

Chances are you could solve the problem by placing some resistors across the LEDs, but with no schematic, I can only guess.

 

2V is a lot of noise. Perhaps the first thing to think about would be reducing the noise, but with no schematic, I can only guess.

 

An added capacitor from the noise line to ground could also help.

 

You might solve this with a simple SPST 12 V relay, or 1 transistor plus a diode, or a TL431, but without a schematic of the board it is impossible to say.

ak

 

What is the source of the noisy signal?

 

To understand this.
You have two voltage sources, you apply different voltage sources to a bank of leds. Consisting of leds and no resistors.
The current, the number of leds and the frequency of the noise was not specified. Some LED projects use HF?
The 2 voltage sources are:
1. 2V AC noise.
2. 12VDC regulated
You want to select either source 1 or source 2 but not both ?
You would like to use a microcontroller and mosfet to switch between sources ?
The uC software program possibly uses an if- then loop. ?
When an event becomes positive the uC issues an unlatch of source 1 and issues a latch to apply only source 2
also assume that it will switch back to the 2V noise source when another event is indicated on software secondary nested decision loop.

 

post schematic or at least photo of the board.

 

What is the source of the noisy signal?

i think the source is a motor controller which is causing the noise

 

So I have this whole system which has a noise of 2V, I have a PCB board which has got some LEDs which are lighting up because of this noise, how do i implement a simple circuit that restricts the 2V noise signal but enables when the power supply of 12V is applied. The PCB board consists of only LEDs for further clarification, the power is supplied when my microcontroller (on a different PCB) closes the mosfet which lets the power to be supplied

also due to some reasons i cannot provide the schematics, my apologies

 

Without any more information the very best you will get is random guesses, even from the best experts. To avoid the noise effect it will be best to remove the two volt signal.
BUT to avoid the effect of the noise, you could offset the common side of the affected circuit two volts positive. that would put the noise just below zero, where it might not have any effect.
This is not a fix, it is a "work around" trick.