I am trying to replace 12V MR16 halogen spotlights in the ceiling with dimmable MR16 LEDs. The existing halogens do not have a dimmer driver, and each has its own transformer (I'm 90% sure of this). I have a few questions:

  • Will the MR16 LEDs work just plugging it into the existing transformers?
  • What sort of a dimmer driver would I need to get to dim the LEDs?

I hope I've explained the scenario sufficiently.

  • 1
    Are the transformers big heavy lumps of iron and copper, or electronic featherweights? Jul 25, 2018 at 11:42
  • yes, you can use the old psu. you want a PWM-based dimmer, which goes between the lamp and driver. or replace the driver with a PWM-capable driver, and drive all those drivers at once from the same input.
    – dandavis
    Jul 25, 2018 at 18:49

1 Answer 1


You would be better off getting a 12V DC driver/power supply, and then using a DC 12V PWM dimmer between the power supply and LEDs.

The obvious thing to do is use a 120VAC dimmer driving the 120V->12V power supply. To begin with, AC dimmers use one of several rather awkward schemes. But even more is "lost in translation" in any 120V-12V power supply. You are simply better off making 12VDC, and then dimming that.

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