LED Dimmer or Lamp Dimmer?

Problems and Solutions

LED dimmer or lamp dimmer is about risks using an external lamp dimmer with a LED - in this case LED rope - but the problem relates to other LED lights as well as using a proper LED controller.

Recently had an enquiry from Jared about the suitability of external LED dimmers, which I promised to post here with my answer and other thoughts you will find interesting. And in case you were wondering, he has a 5mth follow up after my reply too.

So this is how it started:

Jared wanted to use a Lutron dimmer that he already bought for his LED rope light. Because his problem relates to the use of other third party lamp dimmers with a LED light in general I post it right here. Read the thread below.

Taking care of strange technical words in the post, like "PWM"

Jump to the FAQ page for other useful technical wording. >>

For those of you who don't know what PWM is: it is just short for Pulse Width Modulation. Behind the fancy name is a digitally encoded light output control. It regulates the cyclical peaks and lows of power - called duty cycle - released to your LEDs via a special program often hard-coded in a device called controller.

More precise definition of PWM and other good resources at the bottom of this page

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Using a lamp dimmer with your LED light - possible risks

I've hooked up a Lutron lamp dimmer to my LED rope light and all seems to be fine (I tested one for awhile before attaching the entire series).  The Lutron dimmer uses PWM technology and the rope light plugs into a standard AC wall outlet (as does the lamp dimmer which is why I selected that particular model -- to avoid hard wiring).

The light rope manufacturer had nothing about dimming on their packaging or instructions ... 

... but did not recommend using a dimmer with the LED light rope when I called customer service.  Since I assume some of their recommendation has to do with liability, I would like to ask you, a neutral party: what are my risks and if I reduce the life of my LED rope lights by doing this, how much will it really affect them?

(will they work 9000 hours instead of 10,000 or more like 1000 instead of 10,000)?

Any other risks?  Thanks in advance -- I appreciate your feedback and will let you know how things go should I choose to continue my experiment (at most I'm out about $150 but I prefer running 45w LED to 450w incandescent which is why I'm doing this).

I wouldn't use a dimmer at all but I'm running the perimeter of my new deck and without it the neighbors think I've opened a DISCO so I needed to tone things down. (Jared)

Hi Jared,

As much as I want to help, I have to qualify my answer because I am not a properly licensed electrical engineer. Problem of course that even they don't know much about the 'fine print' on LED yet.  And If you are a frequent at FLL you probably know that besides running this site I am a building information modeller and developer. So sorry to disappoint, but I cannot confirm any wiring or electrical issues or give such proper advice.

That said, I find that there are many hidden issues with LED dimmers. So let's see a controller dimming first. This is what manufacturers recommend simply because they work on known operating points of the LED. (Still, each LED has individually different ones as one crystal has slightly different hole mobility than the other.)

But the controller still needs voltage to go through to read the knob setting so there is a limit as to how low the dimming can go. You cannot dim too low with a controller.

The other issue is with selective LED dimming. Primary colors usually dim best that's the idea of RGB (Red-Green-Blue) color mixing. So if you get a good controller that dims and your rope is RGB, you should be able to not just dim but also color mix. This could be some good fun, if not especially for a disco lighting as you say then for a wild enough home party, which I highly recommend to spruce up with all kinds of LEDs - in your case LED ropes.

The problem with external or third party controllers, especially buying them online, is that vendors prefer the ones packaged with the product they have. (Guess there are obvious issues with customer service as LED quality differs from model to model and where they source it from.) So it may be harder for you to find a third party controller to use as a LED dimmer. Let us know if you have this problem.)

That said, there are good folks who do recommend external LED dimming because it's proven practical for them. So I will not confirm or counter their experiences, just list them.

Bottom Line?
When all done and dusted, your LUTRON with PWM could be a good solution for what you seek. I doubt that anyone will be willing to bet how shorter if any your LED will last. My hunch is that it will depend on the differing quilities of LEDs in the string which is usually the case anyway. But for the reasons mentioned I cannot confirm.



Just wanted to follow up and say I've been using this dimmer for 5 months without any problems (also uing in conjunction with a timer that turns on at dusk and off at dawn so there are many hours logged already).  It uses a slider switch which is a bit touchy but otherwise not bad at all.  Not a bad option for anyone wanting to dim rope light from an AC outlet.  Last time I was at Home Depot this dimmer was only about $10.

Take care,



Great input Jared, glad to have helped and thanks for the feedback --- L.

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Related Articles, Resources, Products:
The FAQ page has many of the other terms explained.

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The LED rope light mini site map

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