Solarbird 5d ago

Okay so let's write this down to think it though.

The latest smoke detector to howl pointlessly into the night sends out 11.3V DC onto the signal pin when triggered but running off batteries. I suspect that's 12V nominal, and it probably delivers 12V when operating on AC power.

Most importantly, it's not like... 500mv. Or AC. Or complicated. It's simple DC.

When acting as a non-reporting _satellite_ node, it triggers when _receiving_ 4V DC on the signal pin (4.0 exactly), and that voltage is polarity sensitive. -4V doesn't trigger the alarm.

(1/n)

#electronics #SmokeDetectors #why

Show threadRue Mohr5d ago

@moira "from the neutral line to the signal line"

right?

Show threadSolarbird 5d ago
@RueNahcMohr Yeah? I mean, you're not gonna use AC mains hot as a reference xD
Show threadRue Mohr5d ago
@moira actaully, there were old detectors that did!!!
Show threadSolarbird 5d ago

@RueNahcMohr for a third-wire fire signal? holy shit okay

i guess thinking about it... if you're talking retrofit on two-wire electrical systems i guess you better be ready to work either way... but wait no you still need the signal wire so you're rewiring anyway so you should fix that shit. unless you want to piggyback the fire signal directly onto hot. is that what they were doing?

Show threadRue Mohr5d ago
@moira 3 wire, old as hell model detector, but when you connected a neutral-ref detector (first alert) to the network it would trigger them all. "sorry, I know you only had one detector technically fail (of your ion detectors made by Davinci himself, and should have been changed millennia ago) but we have to change ALL your detectors."
I'd like to hear the 'stand alone' results! I bet between the detectors the ref line has a bad splice, 4V diff is a lot!
Show threadSolarbird 

@RueNahcMohr You'd be waiting a while for a "stand alone" result because this is like five months between problems.

Also, these are detectors which identify who set the network off, and for what reason. And in all cases, the guilty party claims responsibility, and the other units agree.

Current units are FirstAlert, after trying two kinds of Kidde first.

Also something I didn't say is that I noticed the when-we-bought-the-house Kiddes were 20 years old the first time it happened, after 10 years in the house. I replaced them all for age. Since then, it's been 2-4 times a year.

I have also checked _all_ the accessible connections and updated _all_ the harnesses. No change.

Mar 26 at 2:43amWeb
Show threadRue Mohr5d ago

@moira oh, sorry, I got brands mixed up, it was kidde I was referring to in the neutral ref units.

hmm

Show threadSolarbird 5d ago

@RueNahcMohr Well, foo.

I'll still check it just to see, but after dinner.