How to connect LEDs in series

Discussion in 'Circuit Help' started by NewEET, Aug 6, 2012.

  1. NewEET

    NewEET

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    I have a question if anyone can help me out . I want to connect 7 3 volt leds in series each one will be separated about a couple of centimeters apart. When I'm done i will basically have 5 plates with 7 leds on each plate. I am basically building a led light in my house to cut down on some power. So I'm thinking with about 120 volts which is about 20 amps. So I'm looking at trying to power each led with 1 amp a piece but this is where i am having a hard time trying to figure out the proper way of doing this without blowing anything up. Some one Please help?????
    NewEET, Aug 6, 2012
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  2. NewEET

    CocaCola VIP Member

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    Slow down... Where are you getting this 1 amp number? Most LEDs are mA not A rated...

    You should give us more info, as much as you can and than we might be able to offer up some suggestions...
    CocaCola, Aug 6, 2012
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  3. NewEET

    NewEET

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    Sorry about that, I meant to say mA. Like I was saying I'm creating a light fixture and I have flat leds on each plate which is 5 plates in all 7 leds on each connected in series. Currently I am using a driver to power them but making it useful in a house is where I am losing focus. I am asking for advice on how i can use resistors and capacitors of sort to power the fixture. I also want to be able to find out what i could use to put in like a heat sink that would shut down part of the leds when they are too hot.
    NewEET, Aug 6, 2012
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  4. NewEET

    CocaCola VIP Member

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    For most newbies, running off a wall wart is a safer bet, but not as efficient... Resistors waste energy again not efficient...

    LEDs should never be 'too hot' normal LEDs run at a very low temp, high flux ones run much hotter but with proper heat sinking they should never get 'too hot' either...

    Again I'm going to ask for more info, LEDs? What kind, brand, specifications? Why have you wired 7 in series?

    IMO the absolute best way to do this off the mains is using this technique, mind you this is mains voltage and thus potentially lethal...

    http://www.marcspages.co.uk/tech/6103.htm
    CocaCola, Aug 6, 2012
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  5. NewEET

    CDRIVE VIP Member

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    It would be nice to make this a sticky, though I'm bewildered as to why he put the fuse in the neutral leg. ;)

    Chris
    CDRIVE, Aug 7, 2012
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  6. NewEET

    NewEET

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    I can do all of this but my problem is how to power these leds using capacitors and resistors.
    NewEET, Aug 7, 2012
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  7. NewEET

    CocaCola VIP Member

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    The page I linked pretty much explains it all, you just need to work the math for your application...
    CocaCola, Aug 7, 2012
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  8. NewEET

    NewEET

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    Thanks
    NewEET, Aug 7, 2012
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  9. NewEET

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Two answers.

    1) I'm reluctant to put the mains wiring stuff into the LED intro.

    2) It's 120V and L/N don't mean much when you can place the plug around either way. (although I agree with you)
    (*steve*), Aug 7, 2012
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  10. NewEET

    CDRIVE VIP Member

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    Though it's an interesting approach (for the experienced) I totally understand your reluctance,

    Good point about the plug but there are the polarized 2 blade versions. ;)
    CDRIVE, Aug 7, 2012
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  11. NewEET

    CocaCola VIP Member

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    I have to agree there, best for the newbies to use wall warts and resistors... Once they get that understood they can move up when they are ready...

    In the US plugs are supposed to be polarized and you can only plug them in one way, problem is many remodelers and home owners over the years didn't/don't follow the polarization when wiring the house or hooking up the duplex leaving it as an unreliable standard to assume is correct...

    Also you generally don't see inline fuses on household items anyway ;) And as the guy suggest the resistor will also act as a fuse the minute anything goes wrong...
    CocaCola, Aug 7, 2012
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  12. NewEET

    CDRIVE VIP Member

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    I had no idea that large blade = neutral small blade = hot was such a tuffy to remember. :rolleyes:

    Damn, the population has become even dumber than I thought! :D

    Chris
    CDRIVE, Aug 7, 2012
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  13. NewEET

    CocaCola VIP Member

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    Worse they color code the screws 99% of the time and that goes right over many heads... But, I regress even the screws are too hard for many to figure out (aka wrap the wire so it tightens with the screw) and now they have moved to cheap stab locks, and now we see how many people fail at stripping wire correclty...
    Last edited: Aug 7, 2012
    CocaCola, Aug 7, 2012
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  14. NewEET

    CDRIVE VIP Member

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    I replaced all the outlets and switches in my shop with hospital grade 20A Hubble's and Leviton's. Whenever we did a remodel at the hospital they would replace all the receptacles and switches but they never found there way to the dumpster. :D The kick is we would do a room remodel every year or two so these things are like new. Come to think of it, all the fluorescents in my shop came from the hospital.
    CDRIVE, Aug 7, 2012
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  15. NewEET

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    What about the bazzilions of US style power leads I've seen with equal sized blades?

    I'm not sure I've ever seen a polarised one.
    (*steve*), Aug 7, 2012
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  16. NewEET

    CocaCola VIP Member

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    Those are devices where polarity does not matter to the design ;) The polarization of the plug was supposed to be a safety feature so that designs could exploit the neutral leg as a 'ground' (neutral and ground should be bound at the service location, usually to a ground rod or the metal water supply pipe coming to the house that is buried) but as evidenced it failed miserably as a 'standard' thus the implementation of the proper ground terminal...
    CocaCola, Aug 7, 2012
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