1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

LED "fairy" lights transformers

Discussion in 'General Electronics Chat' started by denno, Dec 9, 2008.

  1. denno

    denno Member

    Joined:
    Aug 30, 2008
    Messages:
    52
    Likes:
    0
    Hi all,

    I have got myself a few sets of LED fairy lights, and I am putting them up, as it is christmas time. They are all exactly the same, they're the same brand, have the same transformer to plug into the wall socket and power them, and are literally all 100% the same. What I would like to know is:

    Is there a way that I can eliminate a few of the transformers, and only have maybe one of them connect to the power switch in the house, thus removing all the power boards and extra double adapters needed to allow the transformers to actually fit, but still being able to power multiple strands of the LED lights.

    I basically want to know how people who have lots of christmas lights up manage to power them all, because I'm sure they don't have a transformer for EVERY lighting application on their house.

    Thanks in advance for any help :).
     
  2. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

    Joined:
    Jan 4, 2007
    Messages:
    21,240
    Likes:
    645
    Location:
    Ex Yorks' Hants UK
    ONLINE
    hi,
    The wall adaptor should have the current rating printed on it.

    If you want to drive five sets of lights from one adaptor, you need one wall adaptor rated at five times the original one.

    Dont try to run all the 5 from one original transformer, you could have a burn out and a fire.
     
  3. JKF1000

    JKF1000 New Member

    Joined:
    Nov 26, 2008
    Messages:
    96
    Likes:
    0
    Location:
    South Yorkshire, United Kingdom
    A lot of lights are supplied with a transformer which is selected by cost and avaliability, and as such may be rated at many times the actual required load, you may be able to calculate the total load of each set of lights, and from that, compare what is supplied by a single transformer, it may be that the supplied transformer may be able to supply 2 or more of you light displays at once.

    All I advise is not to run the transformer at its maximum loading, as this will inevitably create heat, and very few transformers built today have ventilation holes or similar!!, Karl.
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. denno

    denno Member

    Joined:
    Aug 30, 2008
    Messages:
    52
    Likes:
    0

    How would I do about working out how much current the lights actually need? The transformer says its output is 24V~18VA.

    Any other ides on how I can power these lights without multiple bulky transformers?
     
  6. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

    Joined:
    Jan 4, 2007
    Messages:
    21,240
    Likes:
    645
    Location:
    Ex Yorks' Hants UK
    ONLINE
    hi,
    For the transformer you have, 24V ~18VA,,, thats 18VA/24 ~ 0.75Amps

    If you have a multi meter you could measure the current in the 24V lead.
    Unplug,, make a cut in one of the wires ,insert the meter set to 'amps' and measure the actual current taken by one set of lights.

    You dont say if the 24V is 'ac' or 'dc' so select the meter to suit.

    OK.?:)
     
    Last edited: Dec 10, 2008
  7. denno

    denno Member

    Joined:
    Aug 30, 2008
    Messages:
    52
    Likes:
    0
    alriiight.. I think I understand that. The adaptor is an AC-AC one, so I guess the 24V is AC?
    I'm not too sure I want to go cutting the wire though, in case I stuff up that set of light completely somehow... If, however, there is a way that I can connect the lights all up and that required cutting them, then I would do it, but seeing as though it's just to measure the amperage, I would thought it's a big of a waste to cut the power to one strand of LED's...

    Oh, I forgot to as that I would like to connect each of the light to one 'function select' box. Each of the lights have their own 8-function select module thing (all combinations, steady on, chase, flash etc etc), but the problem is, when I turn on the lights, even thought they're all getting power at pretty much exactly the same time, they're doing different functions! This is pretty irritating, and I would like the lights to all do the same thing at the same time, is this possible too?

    Thanks for your help so far :)
     
  8. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

    Joined:
    Jan 4, 2007
    Messages:
    21,240
    Likes:
    645
    Location:
    Ex Yorks' Hants UK
    ONLINE
    The cut wire would be reconnected after the current test, so there would be no waste.??

    I would think the chances of synchronising the 5 light controllers is virtually zero.
    I expect the internal timing circuits will very simple and run at their own rates.
     
  9. JKF1000

    JKF1000 New Member

    Joined:
    Nov 26, 2008
    Messages:
    96
    Likes:
    0
    Location:
    South Yorkshire, United Kingdom
    you would need to measure current drain before control box as this itself will draw a few milliamps, you wont be able to sync. all the sets of lights,

    One other thing to mention is that when taking any current measurements, make sure that you are on a pattern when all, or the maximum amount of lights are illuminated.
     
  10. denno

    denno Member

    Joined:
    Aug 30, 2008
    Messages:
    52
    Likes:
    0
    what's the best and safest way to re-connect them then?

    Oh and also, with the synchronising, I was thinking that maybe I could connect several of the lights together BEFORE the 8-function selector, therefore the two (or more) lights would run off the one function module... Or would this not be recommended?
     
    Last edited: Dec 10, 2008
  11. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

    Joined:
    Jan 4, 2007
    Messages:
    21,240
    Likes:
    645
    Location:
    Ex Yorks' Hants UK
    ONLINE
    hi,
    I would not recommend connecting extra lights to the output of the controller, you could blow the switching circuits.

    For reconnecting a 'cut' wire, use a piece of 3amp connector strip.
    The type made of plastic with two small screws to clamp the wire ends.
     
  12. JKF1000

    JKF1000 New Member

    Joined:
    Nov 26, 2008
    Messages:
    96
    Likes:
    0
    Location:
    South Yorkshire, United Kingdom
    So you are wanting to use more than just the one controller, measure the current drawn as eric suggested from the feed line from the transformer to the controller module on a static light display, we have already established that you have 0.75amp avaliable from your transformer.

    If the current required for each set of lights and a controller unit is around 350mA/0.35A (or less) you will have no problem connecting 2 sets to a single transformer,
     

Share This Page