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Need a dummy load

Discussion in 'General Electronics Discussion' started by parallon, Oct 26, 2016.

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  1. parallon

    parallon

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    Oct 26, 2016
    Hello all. I have some LED lights that don't quite turn off when dimmed completely because apparently the dimmer I used has a constant leakage to power it's internal circuitry. I know that if I put a regular 10w light bulb in any of the sockets, it is enough to make the other lights go out. So, I am wanting to make a dummy load to insert in parallel to the circuit, but I am not sure how to calculate the proper resistance and wattage I would need. Can anyone help?

    Thanks,

    Mike
     
  2. Audioguru

    Audioguru

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    Sep 24, 2016
    The resistance of the 10W light bulb is easily calculated. If the voltage is 120V then a resistor value of 1440 ohms draws 10W, because P= 120V squared divided by the resistance.

    A 10W resistor will be very hot so use a 20W resistor. Paying for 10W of electricity for a year will cost more than replacing the dimmer with one designed to drive LED lights.
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I'd ensure there is an on/off switch. The dimmer not reducing the brightness to zero is a good indication that the lights are on.

    If the dimmest setting is too bright, get a better dimmer.

    Placing a resistor across a LED is an option for a single low current device, not for a mains operated appliance.
     
  4. parallon

    parallon

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    Oct 26, 2016
    @ *steve*
    Well, the dimmer is a highly rated Lutron MACL-153M. I have read that because this type of dimmer is a "digital" dimmer, that it requires constant power for some of it's features to work, and therefore some of that power is leaking to the lights. And since LEDs are so efficient, the little bit of voltage across the line is enough to turn them on.

    @Audioguru
    Thank you for your reply. Actually, this dimmer is designed for LED/CFL/Incondescent bulbs. I know that the LEDs aren't on the dimmer's certified list, but at this point, I have 17 bulbs between 2 switches, so that is way too much to replace. I have (9) 5000k leds that do the same thing, but they eventually shut off, but my (8) 2700k leds are the problem child right now.

    Thanks,

    Mike
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Just to be sure we're talking about the same thing... They are mains voltage LED bulbs, not individual LEDs, right?
     
  6. parallon

    parallon

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    Oct 26, 2016
    That is correct. They are 5" LED lights for recessed lighting.

    Mike
     
  7. Audioguru

    Audioguru

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    Sep 24, 2016
    The Lutron datasheet for the dimmer shows that it is used for approved bulbs (yours are not approved) or a minimum 10W load.
     
  8. parallon

    parallon

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    Oct 26, 2016
    Correct. I know that they are 13W lights, but not sure of the draw when turned off.
     
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