# Filtering 230 V

#### ssd_9

Joined Sep 2, 2020
17
Hello Everyone,

Can someone suggest a circuit wherein I can filter out 230VAC and allow only 3.3VDC to pass-through it?

#### Ramussons

Joined May 3, 2013
916
Can someone suggest a circuit wherein I can filter out 230VAC and allow only 3.3VDC to pass-through it?
What is " it " ? Pass-through What?

If the 230 VAC is level shifted by 3.3 V DC, it should be possible ti use a RC filter with a large Time Constant to remove the "ripple".

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#### DickCappels

Joined Aug 21, 2008
7,147
Not really until you explain what you want, to what it connects, and how much filtering you desire.

#### gerty

Joined Aug 30, 2007
1,298
How much current do you need ? A simple walwart will give you 3.3 volts dc

#### MisterBill2

Joined Jan 23, 2018
8,199
REally, it is not reasonable to "filter out" what seems like the 230 volt mains power.
So the TS needs to describe in a lot ore detail what the results of whatever they want to do are, or would be. Otherwise the responses will be a mass of guesses.

Joined Feb 20, 2016
3,781
I think the TS may actually want a 230V to 3.3V power supply.

#### andrewmm

Joined Feb 25, 2011
1,125
This is a mains power supply ?

if its for real use, just purchase one ,
it will be cheaper than the parts you can purchase,

If its an academic exercise
then

isolated or none isolated
current out require ?
ripple allowed ?
over current limiting ?
no load voltage out ?

#### ssd_9

Joined Sep 2, 2020
17
Hello Everyone,

Can someone suggest a circuit wherein I can filter out 230VAC and allow only 3.3VDC to pass-through it?
Actually I am trying to pass 3.3V through a manual switch to nodemcu and operate a relay based on the input received from the manual switch but In case of some failure in NodeMCU manual switch cannot be operated so in such scenario I want to give 230 V to the same point of the manual switch so that appliance can be operated in case of NodeMCU failure. But there is a high risk of 230 V flowing to the input of NodeMCU and damaging the circuit. Can anyone help me resolve this issue?

#### BobTPH

Joined Jun 5, 2013
2,981
Sorry, but that description does not tell me much. How about a schematic. It sounds to me like you need a 230V relay.

Bob

#### andrewmm

Joined Feb 25, 2011
1,125
Thats very confusing, but does not sound at all like you first described,
can I suggest that you draw a picture / diagram of what your after

#### MisterBill2

Joined Jan 23, 2018
8,199
What it sounds like to me is that the TS needs a physically separate switch to bypass some sort of controller that operates some sort of appliance. If it is some sort of internet connection then the TS is probably out of luck. AND, an additional warning is that working with 230 volt mains power is dangerous to those without adequate experience and skills, and knowledge, with hazards including shocks and death, in addition to other injuries.

#### Tonyr1084

Joined Sep 24, 2015
5,802
an additional warning is that working with 230 volt mains power is dangerous to those without adequate experience and skills, and knowledge, with hazards including shocks and death, in addition to other injuries.
And it seems like the TS doesn't have the necessary experience, skills, and knowledge.

I recall back in high school the teacher demonstrated a way to use ONE of the two AC lines to conduct DC. And it wasn't with such a high potential difference between the two. I'm being purposefully vague because I don't want to be the one who sends the TS off trying experiments with 230 VAC. And I suspect we may be skirting the fringes of the guidelines to not discuss working with mains voltages. I may be wrong. Nevertheless, I don't want to be the one responsible for saying something that someone misunderstands and goes off and doesn't come home again.