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Joining battery operated led fairy lights to mains source

Discussion in 'LEDs and Optoelectronics' started by Chris S, Dec 3, 2019.

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  1. Chris S

    Chris S

    Jan 20, 2018
    I wish to join 3 sets of fairy lights (50 bulbs per set) together and have them powered by a mains power source.
    Each set is currently powered by 3 x 1.5V AA batteries. They are connected to a circuit board as they offer a flashing function, but I do not need that so I am prepared to cut the cables and discard the battery holder.
    I would like to know how to join the three sets of lights together and connect them to a mains powered source.
    I attach a picture of one of the light sets but other than that I’ve no further information.
    I would be grateful if someone could tell me the simplest and best way to do this.
    Many thanks in advance. 1C72450F-F364-4B50-9088-6589A78C3663.jpeg
  2. bertus

    bertus Moderator

    Nov 8, 2019

    Is it possible to open the box and post a picture of the inside?
    That way we can see where to connect the external power.
    The external power would be an 4.5 Volts adapter.

  3. Bluejets


    Oct 5, 2014
    5V 1A plug pack should be sufficient.

    You will need to trace the wiring of each set of lights into the battery box and find which is positive and which is negative.

    The positives from each set are connected together along with the negatives and then to the new plug pack supply.(i.e. loads in parallel)
    Negative on these is usually the outer conductor on the barrel jack. You need to determine which one this is and possibly mark it.
    You can simply cut this off and twist the appropriate wiring together.
  4. Martaine2005


    May 12, 2015
    As already stated above, a 5v DC plug pack will be fine.
    Any usb plug pack will work. 90% of homes have a mobile phone charger or digital camera charger that uses a 5V adapter / plug pack. I still use the old Nokia phone chargers for projects I give to family members.
    Never throw away old / unused chargers. They still have a purpose in life!.

    Harald Kapp likes this.
  5. Chris S

    Chris S

    Jan 20, 2018
    @bertus @Bluejets @Martaine2005 - thank you so much for your replies.
    It all makes perfect sense and I will give it a go later today.
    I wish you all the best.
    PS - would 2.1A 5V supply be too much for the set?
    Last edited: Dec 4, 2019
  6. Bluejets


    Oct 5, 2014
    The load will only draw what current is required.
    Your stated current is the maximum the unit is designed to supply.
  7. Chris S

    Chris S

    Jan 20, 2018
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