So I just had Integrated LED Recessed Retrofit Ceiling Light Fixtures installed on a Lutron Toggler 150-watt Double Pole 3-way White Toggle Indoor Dimmer (rated for LED lights).

When the dimmer is set to a certain lever on low, to turn off while the remaining 6 are dim but they're still on.

Any idea what the issue is? Thanks guys!


closed as off-topic by Andy aka, Dmitry Grigoryev, Maple, Sparky256, Finbarr Sep 13 '18 at 17:12

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  • \$\begingroup\$ Sounds like production tolerances. \$\endgroup\$ – winny Sep 9 '18 at 9:00
  • \$\begingroup\$ Poor design. Inappropriate use of a dimmer. Voting to close as you should read the data sheets and confirm whether this is a problem and buy from reputable sources that provide good data. \$\endgroup\$ – Andy aka Sep 9 '18 at 9:14
  • 1
    \$\begingroup\$ Welcome to EE.SE, Jay, but you're on an Engineering forum so you need to be precise with your details. Please edit your question to explain what a "can light" is and supply a link to a datasheet. (2) Similarly, we would need to know at a minimum what type of dimmer it is. (3) Can you provide any voltage measurements? \$\endgroup\$ – Transistor Sep 9 '18 at 9:14
  • \$\begingroup\$ Here are the lights i'm using. homedepot.com/p/… And here is the dimmer, hope this helps! lowes.com/pd/… \$\endgroup\$ – Jay Ely Sep 9 '18 at 9:25
  • \$\begingroup\$ Hi, Jay. This information belongs in the question so that it's all in one place. Highlight the word you want to link and press the 'link' button to enter the URL. \$\endgroup\$ – Transistor Sep 9 '18 at 14:10

Dimmers work by varying the trigger angle of the mains.

enter image description here

Figure 1. Phase or trigger angle control of AC mains. Source: Dimmers for LEDs.

How the bulb responds to this depends on its internal circuitry. The incandescent lamps were simply a hot resistance wire and they worked fine. LED mains lamps have a wide variety of circuit configurations - some of which work well with dimmers and some that don't.

enter image description here

Figure 2. Some of the cheap LED mains lamps use a capacative voltage dropper to reduce the voltage and limit the current to the lamps. These generally work OK on a standard dimmer.

enter image description here

Figure 3. A slightly more complex version has a smoothing capacitor, C2, added.

If a smooting capacitor such as C2 is included after the rectifier then the dimmer won’t appear to do anything until the control is adjusted below 50%. This is because the capacitor charges up fully at peak mains even if it hasn’t been on up to 90° into the half-cycle. (See Figure 1.) From 90° to 180° the peak voltage drops so the lamp will dim in proportion.

Any idea what the issue is?

It is most likely a minor difference in components due to production spread in the various components of the lamps. Unfortunately the subject of dimming has got a lot more complex since the conversion from incandescent to LED lamps. Unless you can source lamps designed to work with a specific dimmer the results will be a bit hit and miss.

I have written a little more on the topic in the article linked in Figure 1.

  • \$\begingroup\$ Oh yeah, now he'll know which dimmer to buy. ☺ \$\endgroup\$ – Misunderstood Sep 9 '18 at 18:55
  • \$\begingroup\$ I don't understand your comment and don't want you to be Misunderstood. Can you clarify? \$\endgroup\$ – Transistor Sep 9 '18 at 19:09
  • \$\begingroup\$ And I even added the smiley face so I would not be misunderstood (oh lord, please don't let me be...). I think you may be way over this guy's head. I don't think he wants to know how a dimmer works and likely would not understand if he did. And I have a warped sense of humor. And I have been drinking today.☺☺ Your answer is good. +1 \$\endgroup\$ – Misunderstood Sep 9 '18 at 19:13

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