Is this an AC/DC converter circuit?

[Curiousphy]

I found this circuit (attached images) in an insulated pouch inside my basement's smoke detector compartment. It gets power from the hot line that feeds my smoke detector, and outputs power to a mystery load through a second outgoing romex wire (no idea where it goes). All my smoke detectors work without this outgoing feed, so I removed it and left the second romex unconnected at the moment. Is this an AC/DC converter circuit or some kind of filter? The blue part has a eec1.OK Mer-S250V part number. What could this mystery device be doing? I was thinking security alarm related, the house has ADT hookup. thanks!

 

[davenn]

Is this an AC/DC converter circuit or some kind of filter?

looks like the typical and nasty transformerless AC to DC power supply

here is a typical circuit similar to your one

and I have no idea what your "romex wire" is ??

the cables on that board don't really look like what "romex wire" looks like on the net
Dave

 

[Curiousphy]

Thanks. The wires soldered to this board are screwed onto the 14/2 and 14/3 romex cables, the 14/3 feeds the 120V to it and the smoke detector, and this board feeds the 14/2 romex whatever the transformed voltage is. The capacitor says 16V on it, so it probably outputs 16V DC? Is the blue part also a capacitor? I agree it's nasty and looks rigged by a previous homeowner rather than professionally done. Do you know why these are nasty as an AC-to-DC?

 

[rbelli1]

so it probably outputs 16V DC?

The orange part under the loop of black wire appears to say "240" on it. My best guess is that it is a 1N5240 which will make the output 10V. This is equivalent to D3 in the schematic that davenn posted.

Do you know why these are nasty as an AC-to-DC?

You are relying on the integrity of the capacitor (C1) and resistor (R2) to isolate protect you from mains voltage. These types of supply are only allowed to be used where the output is permanently isolated from any external contact. If you do find out what this is for and want to keep using it then treat those wires outputting from the supply the same as you would treat the mains wires.

BoB

Edit: Per Averagesupernova's #9 post below, protect is the correct word in this context rather than isolate.
2nd Edit: You also relying on everything being perfect with the neutral so still not a safe voltage.

 

[Curiousphy]

Thank you both, you confirmed what I suspected that it was an AC/DC converter circuit. I can't think of anything other than the security alarm system where this DC voltage would be needed on a permanently (and dangerously) connected basis (hidden inside a smoke detector compartment too!)... I think I will just keep it removed.

Side note, there's also a mystery circuit breaker in the breaker panel that does not seem to turn on/off anything in the house... full of mysteries -- is it better to leave such things on or off...

 

[rbelli1]

is it better to leave such things on or off...

It probably powers the government brain transmitters. Leave it off. If you see lots of black helicopters over your house turn it back on real quick.

BoB

 

[Curiousphy]

 

[anorlunda]

Side note, there's also a mystery circuit breaker in the breaker panel that does not seem to turn on/off anything in the house... full of mysteries -- is it better to leave such things on or off...

Steven Wright said: I have a light switch in my house that doesn't seem to do anything. I flip it every time I walk past. Last night, I got a call from Germany. A woman's voice said, "Cut it out."

 

[Averagesupernova]

Without seeing more of this setup I am not willing to say if it is 'rigged' or not. There are requirements by the NEC to provide AC power to smoke detectors nowadays. I don't recall just how this is done.
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Was in on a wiring job on a new house back in 2014-2015 and I know we ran romex to at least one of the detectors but I can't recall if it was just one or all of them. My hunch is that it is likely that ALL detectors in your house have this board and various connections are made based on which detector is the 'master'. Chances are by removing this you have defeated the AC powered reliability of the smoke detection in your house. Not a smart move. The mystery breaker most likely feeds the detectors. I know we needed a dedicated circuit for the smoke detector(s) on the new house.
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ADT security systems usually use a wall transformer. I assume you are correct in that it is in no way related to the security system. The ADT detectors I have been around detect heat, not sure about smoke, but I know for sure they detect heat.
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Describing it as a nasty circuit is a bit of a stretch. Saying it relies on several components to isolate from mains voltages isn't really correct. It is not isolated at all, and it need not be. Why should it be isolated when it is feeding wiring that is intended to be at mains voltage in the first place?

 

[Curiousphy]

I am positive and verified the smoke detectors in the house are fed by the living room circuit, not connected to the mystery breaker. The Kidde combination smoke and co detectors get 120VAC power directly from the 14/3 romex cables. So this AC to DC conversion circuit does not seem related and is just leeching off of the 14/3 romex and feeds a secondary 14/2 romex that routes to a mystery place...

The main ADT box does have a wall transformer, there's a smaller white box next to it though... maybe I will try to remove it and look at the back wiring...

 

[rbelli1]

Saying it relies on several components to isolate from mains voltages isn't really correct.

I amended my post.

BoB