Most of the LED light strips I see are either 12V or 24V, which require a driver to step down the power from 120v at the wall (thus the little black transformers that come with them). However... I only recently discovered they come in 120V with a small in-line rectifier, AND they can be run over 150ft without a voltage drop in a single strip.

Aside from cost, why bother with the 12V and 24V route with the wiring when you can simply hook up the 120V directly to a dimmer switch in the wall (with a built in rectifier of course)?

I'm new to the LED light strip world, but am I missing something when it comes to why most people go with the 12V and 24V version?

Minor clarification edit for my application: I'm looking to use a long run LED lighting setup in crown molding around a living room, and it greatly simplifies things with a single run as opposed to several power supplies to driving about 100 feet of lighting. But I'm new to this kind of lighting, so willing to learn something new)

  • \$\begingroup\$ Safety and safety again. \$\endgroup\$
    – Andy aka
    Feb 17, 2020 at 17:15
  • \$\begingroup\$ And auto, boat, motorhome, off grid, for all of which 12V makes more sense. \$\endgroup\$ Feb 17, 2020 at 17:20
  • 1
    \$\begingroup\$ I doubt that 120V LED strip will respond well to a dimmer switch. \$\endgroup\$
    – Hearth
    Feb 17, 2020 at 17:21
  • \$\begingroup\$ @Hearth I was thinking about this switch, which is rated for 450 Watts LED. Knowing that particular light strip in my post is drawing a max 387W (8.5W/m for 45m), which should be about 3.25 Amps. Can you tell me why you don't think a dimmer would work with that light strip? Link: smile.amazon.com/gp/product/B01MS6JDUW/… \$\endgroup\$
    – v15
    Feb 17, 2020 at 17:25
  • \$\begingroup\$ Your linked product does not appear to meet UL or any other safety standards. If the specs don't explicitly say that the lamp is dimmable then I would assume that it is not. But, hey, it's your life. \$\endgroup\$ Feb 17, 2020 at 17:42

1 Answer 1

  1. Safety. Low voltage won't kill someone that comes in contact with the wiring.
  2. Insulation. Related to (1), the higher voltage strips will require better insulation.
  3. Cut-to-length. Figure 1 and 2 show the typical setup for a 12 V strip. They can be cut to length at any of the scissors points without any dark LEDs. The higher the strip voltage the more LEDs per section and the longer the sections. This affects their usefulness in many applicatons.

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Figure 1. Typical flexible striplight. Images: Flexible LED strip light

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Figure 2. Schematic diagram for Figure 1.

  1. The mains powered strips are likely to have forty or so LEDs in series. If any one goes open circuit the whole strip will fail.
  • \$\begingroup\$ Thanks @Transistor, I did update my question regarding my specific use for the lighting, crown molding. I can see the safety aspect of it, and makes sense if it's somewhere people may come across it easily. Since it's going up high, I wasn't sure if there was another reason not to run it because it's essentially the same as ceiling lights (only wiring at the wall switch). With the waterproof casing around the strip itself acting as a conduit so the wires are not contacted at all. \$\endgroup\$
    – v15
    Feb 17, 2020 at 17:30

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