use the following search parameters to narrow your results:
e.g. subreddit:aww site:imgur.com dog
subreddit:aww site:imgur.com dog
see the search faq for details.
advanced search: by author, subreddit...
20,107 users here now
Request an explanation
Have an idea to improve ELI5? r/IdeasForELI5
Make sure to read the rules!
This subreddit is for asking for objective explanations. It is not a repository for any question you may have.
E is for Explain - merely answering a question is not enough.
LI5 means friendly, simplified and layperson-accessible explanations - not responses aimed at literal five-year-olds.
Perform a keyword search, you may find good explanations in past threads. You should also consider looking for your question in the FAQ.
Don't post to argue a point of view.
Flair your question after you've submitted it.
the front page of the internet.
and join one of thousands of communities.
EngineeringELI5 how a smoke detectors test function works, does it just test the battery and beeper? Or does it test the sensor too?
submitted 5 hours ago by SavingsTask
Post a comment!
[–]Icy-James [score hidden] 5 hours ago (6 children)
I’m assuming it just tests if there’s enough juice in the battery to make the beeper ring. As far as I’m aware, most smoke detectors use a tiny radioactive source that emits alpha particles (which can be absorbed by a few metres of air or a thick sheet of paper) and a detector to detect those alpha particles. When smoke gets in the gap, it blocks the alpha particles from reaching the detector and that’s what sets off the alarm. That’s why I don’t think the the test button tests whether the sensor works or not - only the battery, but I could be wrong. I guess if you want to test the sensor then get a candle underneath
[–]Gnomio1 [score hidden] 4 hours ago (1 child)
Broadly correct but it’s slightly simpler than that.
They don’t actually detect the alpha particles (from the 241Am source). The alpha particles ionise the air in a gap between two plates, a very small voltage thus exists between the two. As you said, smoke stops the alpha particles, so the voltage changes, the alarm goes off.
[–]Icy-James [score hidden] 4 hours ago (0 children)
Ahhh I see, very cool! thank you so much!
[–]ItsLikeRay-ee-ain [score hidden] 4 hours ago (3 children)
Do not put a candle underneath a smoke detector. Large fires have started that way when they set the smoke detector on fire.
[–]Icy-James [score hidden] 4 hours ago (2 children)
Im hoping they would have enough sense to not literally put the flame so close as to burn the smoke detector lmao
[–]we_need2talk [score hidden] 4 hours ago (1 child)
Also, if you want to test it, you would blow the candle out first and then let the smoke waft up.
I was hoping that was implied too but maybe not lmao sorry
reddit and the ALIEN Logo are registered trademarks of reddit inc.
Advertise - lifestyles
π Rendered by PID 22955 on r2-app-0455a2cc00fe93812 at 2021-01-11 07:09:28.251131+00:00 running d8cca48 country code: JP.