Running 120v LED lights on 12v

Discussion in 'Technical Repair' started by chuco61, Mar 21, 2018.

  1. chuco61

    Thread Starter Member

    Jan 21, 2015
    45
    2
    Hi,

    I am working on retrofitting a wall light art piece from the 1970s. Currently in the art, there is a fluorescent bulb and a motor that spins a colored psychedelic disc.Upon opening, both the motor and light are running off the same module.

    Im looking for direction on the following.
    Thoughts?
     
  2. chuco61

    Thread Starter Member

    Jan 21, 2015
    45
    2
    Or is something like this safer, running ac to ac for the light and then a transformer for the motor?
    [​IMG]
     
  3. chuco61

    Thread Starter Member

    Jan 21, 2015
    45
    2
    or perhaps a third option would be to run a power outlet into the unit
    Splice a 2 prong terminal onto the LED light transformer > plug into the outlet
    Use a 12v DC wall wart for the motor > plug in

    This seems a little more straight forward and safer, maybe?
     
  4. chuco61

    Thread Starter Member

    Jan 21, 2015
    45
    2
  5. ebp

    Well-Known Member

    Feb 8, 2018
    2,243
    784
    The photos of the lamp are not good enough to reveal anything useful. About all that can be said is that the driver is a constant current type (evidence is lack of resistors on the LED boards).

    It is hard to guess how the LEDs are configured. The inner board has two rings of 15, the outer of 18, and the boards appear to be simply connected in parallel. The implication of the parallel connection is that each board is actually some number of substrings connected in parallel. The highest common denominator for 15 and 18 is 3. Viewed another way, the outer board is 36 LEDs and the inner 30, which gives a highest common denominator of 6. The latter seems more likely to me - paralleled groups of 6 LEDs in series. 6 LEDs in series requires about 18 volts, which would mean they would have to be reconfigured to run on 12 volts - groups of three, each with a current-limiting resistor. When LEDs are connected directly in parallel there are current sharing issues due to variations in forward voltage. Strings of 6 in series would be much more likely to share nicely than strings of 3.

    The circuit board is almost certainly made on an aluminum substrate. Trying to cut traces and solder to the ends, after removing the solder mask, would not be easy. The aluminum would conduct heat away very quickly. It isn't impossible, just somewhat difficult.

    If the spec's are to be believed, that lamp will produce almost double what a 9" circline fluorescent tube would. Since reconfig to 12 volts would require series resistors you could reduce the LED current if you wanted to.

    Depending on how much work you are willing to expend, I would suggest considering some of the LED "tapes" that are available. The white ones are almost all intended to run on 12 volts and are arranged in groups of 3 LEDs with the required resistor. Most are designed so they can be cut apart between each group of 3. You might arrange them in angled radial fashion. Some come with adhesive backing for convenient mounting.
     
  6. chuco61

    Thread Starter Member

    Jan 21, 2015
    45
    2
    Thanks for the reply. I am trying to recreate the attached image.

    Its a psychedelic light with what looks to be a circline lamp connected to some kind of converter (a ballast??) ALSO running a motor.

    Is there any way to decipher or even recreate (with a modern module) this exact setup?
    Circline lamps are easy to find, however, I am worried about the ballast not being grounded.

    Any thoughts?

    [​IMG]
     
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