LED light on 120VAC switch, is transforemer necessary?

Discussion in 'The Projects Forum' started by LaZyLuke, Nov 7, 2013.

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  1. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    Hi, I want to place a custom LED light indicating the switch position on a extension cord (I know some switches come with alight but I am not interested in that).

    My question is:

    Do I have to use a transformer to step down the voltage from the 120VAC line and then rectify it, or is it possible to just rectify it to 120V DC and then step it down with a 3W 6kOHm power resistor (assuming 3.3V drop and 20mA current draw of the blue LED)? Eliminating the transformer will save a lot of space which is a constrain, also I understand the LED might flicker at 60Hz rate. I was just curious if this is even possible to wire like that

    Obvious alternative would be to use a 120V conventional small size light bulb and paint it blue :)
     
  2. #12

    Expert

    Nov 30, 2010
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    It is not possible on this website.
     
  3. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    what do you mean on this website? Could you please elaborate on this a little bit?
     
  4. wayneh

    Expert

    Sep 9, 2010
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    There are green neon bulbs that would work. Not sure about blue.
     
  5. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    I understand there are alternatives, I even came up with one, I am just interested if this wiring solution is a viable one...

    so far I only found schematics with transformers... is it because they allow variable current and my solution will work fine but only for that particular current draw? (in other words I am safe by doing this, and will not die by trying it?)
     
  6. tcmtech

    Well-Known Member

    Nov 4, 2013
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    It would appear they have a primary rule about this sort of stuff being its a direct line operated device of sorts or something to that effect.

    Capacitive coupling is where you might want to look for efficiency how ever as mentioned a mini neon bulb would be the best solution and yes they do come in blue! ;)
     
  7. Georacer

    Moderator

    Nov 25, 2009
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    This thread violates the Terms of Service of the All About Circuits forum:

    This is an excerpt of our ToS:
    Terms of Service


    Are you willing to continue the discussion provided that no LEDs are used and an isolation transformer is used?
    If not, I will have to close this thread.
     
  8. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    wow so LED to mains and transformer-less power supplies are head to head with rail guns?

    if you could only explain to me as to WHY these topics are not allowed it might just answer my question...

    Is it dangerous to do it like that? because that is the only reason I see it being, and if it is dangerous can someone tell me why? I was hoping to learn something today and I was hoping this would be the place it happens...
     
  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
    6,061
    3,824
    If you are asking faceless people on a website how to connect LEDs to mains, then, yes, it is dangerous. Because of that, AAC owners do not want the liability. They do not want your next-of-kin explaining how a post from someone halfway around the world resulted in your death.

    Also see:here
     
    Last edited: Nov 8, 2013
  10. LaZyLuke

    Thread Starter Active Member

    May 10, 2009
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    sure, but honestly even if the wiring fails or blows up or whatever it might happen you really have to be special to get killed by a wall socket... i wired up stuff to the wall before that straight up blew up and filled the room with smoke and I had glare in my eyes... but using reasonable safety percussion will suffice..

    So even if the advice is horrible and will result in catastrophic failure of the components you should not get killed by it (that's why we have breakers in the house after all) if you use some reason when plugging stuff in for the first time and making sure everything is insulated/fused properly in the final design...

    my point is that with this rationale talking about pencils should not be allowed because I can technically stab someone in the eye with one...

    My question was: is it dangerous? if so.. why? I can't understand how would be hazardous ... according to theory this should work .. if I am missing something just please explain to me what it is that is so BAD about this

    P.s. directing me to 'electric shock' wiki is like telling someone buses are bad and linking them buss accidents photos...
     
  11. #12

    Expert

    Nov 30, 2010
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    I think you answered your own question.

    A bit of additional information, circuit breakers are used to prevent the wiring from bursting into flames. They do not provide anywhere enough protection to keep a person from being hurt or killed.
     
  12. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    because you could get electrocuted and die..
    Then enter the Lawyers...
     
  13. bertus

    Administrator

    Apr 5, 2008
    15,648
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    Hello,

    Clear enough?
    Discussion closed.

    Bertus
     
  14. Georacer

    Moderator

    Nov 25, 2009
    5,142
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    In case it wasn't clear, I'll try to re-phrase it.

    Those cases that are stated in the Terms of Service are exceptionally dangerous, each for its own reason.
    People more technology-savvy than me have made that decision and me, myself at the beginning didn't understand it. However, as I got to learn more about this profession, I now support their decision.

    I wish you learn enough about electronics in time to understand this decision. For now, it is not debatable, we just ask you to trust us. It is not something you learn overnight.
     
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