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Are LED Lights Dimmable?

Summary

Are LED lights dimmable? The short answer is that it depends. You see, some bulbs are designed to be dimmable whereas others are not. Luckily for us though, manufacturers are pretty good about indicating this on their packaging. Another factor that plays into dimmability is dimmer switches. Older switches were designed to handle the high wattage requirements of incandescent and halogen bulbs. This worked great until the invention of LED technology, which uses about 60% less energy than their older generation counterparts. What often happens today is switching out old incandescents with LEDs but keeping the dimmer switch the same. As a result, flickering, buzzing, or incompatibility often results. Not because of the bulb but because the dimmer switch is designed for older lighting technologies. To address this problem, the industry created “Trailing Edge” dimmers that are designed for the low wattage requirements of LED technology. In the end, any area can have dimmable lighting but a couple of requirements must be meant first.

Introduction

In a little more than a decade, LED lights have become very popular, more popular than their older fluorescent counterparts. This is due to their longer life span, energy efficiency, environmental friendliness, safety, and health benefits. But one question that is often asked about LED lights is “Are LED lights dimmable?”

The answer to this often asked question is, it depends. LED lights may be dimmable or non-dimmable. So if you’re looking to buy a dimmable LED light, simply check the product description or product listing if you’re shopping online. Manufacturers are encouraged to place this information prominently on their products as more customers are requesting this functionality. Yet, just because a bulb is dimmable does not mean that it is compatible with your dimmer switch. Read on to learn more about bulb dimmability and compatibility with your current lighting system.

Leading Edge Dimmers and Trailing Edge Dimmers

Leading-edge dimmers, also known as 2-wire forward phase dimmers, incandescent dimmers, or TRIAC dimmers, are designed for older bulbs such as incandescents and halogens that have high wattages. Using a high-speed bidirectional thyristor device, which could be either a Triode for Alternating Current (TRIAC) or Silicon Controlled Rectifier (SCR), these dimmers cut out the ascending or leading edge of each “half-sine wave”. Since LED lights use much less energy than other types of light, they may not be able to trigger the TRIAC or SCR, resulting in flickering and buzzing.

Leading-edge dimmers are made to use up a high volume of energy. So using an LED light with a leading-edge dimmer is not going to give you the best results since LED lights operate on low wattages. This type of dimmer is still common in houses and establishments since this has been around for quite a long time already. If your space has been around for 15 or more years, then you most likely have a leading-edge dimmer. 

On the other hand, trailing edge dimmers also called 2-wire reverse phase dimmers, utilize a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) or Insulated-gate bipolar transistor (IGBT) device to chop a voltage signal waveform at the descending or trailing edge of a sine wave. These dimmers are specifically designed for low-wattage bulbs such as LED lights. They can easily and effectively gauge the energy levels required for LED lights, giving you the best chance for dimming.

Leading-edge and trailing edge dimmers are referred to as phase control dimmers since both chop a portion of voltage signal waveform at certain areas of a sine wave to supply the needed amount of voltage and current to lamps for dimming purposes. 

A note about sine waves

A sine wave is a geometric waveform that oscillates (moves up, down, or side-to-side) periodically. This waveform is represented by an s-shaped, smooth wave that rises above and below the horizontal line represented on a graph. It’s nothing to be concerned about for most lighting purposes as the technicality of the sine wave is outside most lighting considerations. Nonetheless, it’s a part of lighting that is used for technical analysis.

Can I use my current dimmer switch with LED lights?

Another question that is frequently asked is if an existing dimmer switch may be used with an LED light. The first thing to do is to identify your dimmer switch. In many cases, what people have in their homes is commonly referred to as traditional dimmers known as leading-edge dimmers. Chances are if you have been using your current dimmer with incandescent bulbs, then you have a traditional dimmer. Below is a simple test that you can do to identify your dimmer switch. Still, it pays to give your contractor or installer a call to correctly identify your dimmer switch.

Try this simple test:

  1. Install your dimmable LED light(s) with your existing dimmer as normal.
  2. Check if the following problems occur. 

• Flickering – the light(s) pulses unsteadily and rapidly.  

• Strobing – the light flashes unsteadily, but less frequently than a flicker.

• Flashing – the light turns on and off randomly.

• Drop out – the light goes out upon reaching the bottom of the range. 

• Pop on – the light unexpectedly becomes brighter at a certain point when increasing light levels.

• Unresponsive – the light is not responding properly, staying at the same level of brightness for some or all of the dimming scale.

  1. If the above problems occur, change to a new dimmer switch that is compatible with your LED light(s).

Encountering these issues could mean that your dimmer is a leading-edge dimmer, hence the issue. But also keep in mind that these issues may still arise even when you have an LED dimmer. That’s why it’s important to check your dimmers manufacturer’s specifications to determine which specific dimmer may suit your bulb(s) requirements well.

How low can a dimming bulb go?

Now, how far can you dim your LED light? Traditionally, LED lights can dim up to 10%. But with the advancements in LED technology, some LED lights can now dim down to 1%. This just gets better since the lower the dimming range the longer the life of a LED bulb. Additionally, high-end LED bulbs now offer a smooth transition of light for a better effect rather than an abrupt change.

Other Dimmer Options

As times progress so does technology. Nowadays, aside from leading and trailing edge dimmers, there are other types of dimmers that you can have as options such as 0-10v, Digital Addressable Lighting Interface (DALI), and Digital Multiplex (DMX). Choosing one depends on your lighting layout, system configuration and control, and the LED bulb(s) characteristics.

0-10V 

Originally, 0-10V or 4-wire dimming was used to dim fluorescent lights with the use of dimming ballasts. Over the years, this dimming method has evolved to become a reliable LED light dimmer. It adjusts the output by using an analog low-voltage signal. In the LED driver, when a low-voltage pair of grey and purple wires are open, the driver outputs 100% from a 10V signal. But when the two paired wires are shorted together (touching each other), the driver is set at the minimum since it receives a 0 dimming signal. The LED light turns off into sleep mode when the dimming is at 0V. 0-10V dimming may be used with any dimmable LED light and 0-10V LED driver. It also has wide applications such as retail, office buildings, theaters, and even outdoor commercial places. 

NOTE: LED lights require LED drivers to operate. We will discuss this in the next part.   

DALI

DALI is a digital dimmer in the form of a controller, designed to dim various light sources independently from one place. It is an interface that has a master-servant structure. The controller, which acts as a master, sends signals to the driver that works like a servant, following instructions to dim the lights as requested. With DALI, you can dim various lights at different levels. For example, in a living room, if you have 5 lights, you can dim 1 at 100% and the others at another percentage. Compared to other dimmers, in one place, you can only dim all your lights at either full or a certain percentage. DALI is certainly more complex and so more costly than the others, but also more powerful.

DMX

DMX was originally for drama and stage lighting needs. But it is now being utilized to bring the drama of theatrical lighting into interior and exterior spaces, mostly architectural areas. DMX transforms data into bits through a shielded cable. DMX is used with RGB LED. 

What is an LED driver? 

LED drivers, also known as LED power supplies, are devices used to provide electricity to LED lights to function successfully. They are like the ballasts to fluorescent lights or transformers to low-voltage bulbs. 

Why is an LED driver needed?

Since many places run on a high voltage, alternating current electricity and LEDs operate on a low voltage direct current, a driver is needed to convert the energy. Having an LED driver also protects the LED light from damages caused by fluctuating voltage or current. LED lights need to operate on a certain current range, so too little or too much will damage the bulbs. So an LED driver is also important to keep the LED light at its rated level.

Basic Guidelines for Dimmable LEDs

1.1  Check the bulb.

If you want a dimming effect, choose an LED bulb that is dimmable. Look for the following image that manufacturers prominently display on product packing and online listings.

1.2  Use a compatible dimmer.

As I have mentioned earlier, you may use a traditional dimmer with an LED bulb. You can even try to use a non-dimmable LED bulb to a traditional or even a trailing edge dimmer. But doing so will not let you achieve the best dimming experience. The dimming effect will not be as great or desired, flickering and buzzing problems will appear and both the bulb and dimmer will get damaged. The best choice is to use a compatible dimmer such as a trailing edge dimmer.

Tip: Check the compatibility charts from manufacturers. Manufacturers have embraced the practice of testing their bulbs with a variety of dimmers to see which ones are compatible with their bulbs. After testing, they use the data collected during their test to compile their compatibility charts. Checking the manufacturer’s compatibility charts can ensure you get the correct dimmer switch the first time. Below is an example of a compatibility chart from Leviton.

LEVITON's Compatibility Chart
https://www.leviton.com/fr/docs/Dimmer_Bulb_Compatibility_Chart.pdf

1.3  Select proven and tested ones.

As the LED market booms, many manufacturers have grabbed ahold of the opportunity to reap the revenue benefits. However, some manufacturers have created LED bulbs using inferior materials. As a result, the market is flooded with inferior LED products that don’t perform as expected, burn out quickly, and even catch fire. Save yourself the frustration and order your bulbs with a trusted supplier that can guarantee safety and performance. 

1.4  Do a mockup.

Once you have a bulb, try to install it on your dimmer. Make sure that you’ve got at least a matching bulb and dimmer. Observe if there will be issues like flickering, buzzing, strobing, etc. Once these problems occur, then you most likely need to get another bulb or dimmer. On the other hand, if there are no issues, then you’re good to go. You can now enjoy a dimming experience. See what works well for your space. Other than that, you may approach a lumen master at goodbulb.com to help and guide you through.

How many LED lights can I use with my dimmer?

One common mistake is to overload dimmers. Doing so may cause the same problems that using incompatible dimmers with LED bulbs causes such as flickering, buzzing, strobing, and many others. How do we know how many bulbs we can use with our dimmer? 

Follow the simple formula below:

  1. Take the minimum load of the dimmer / 10.
  2. Take the maximum load of the dimmer / 10.

Example:

Dimmer is rated 100W-400W
Dimmer Minimum load is 100W / 10 = 10W
Dimmer Maximum load is 400W / 10 = 40W

This means that the dimmer can carry 10W-40W of LED bulbs.       

Next:

         Count the total wattages of the LED bulbs.

         Example

         4 x 5W = 20W

Since the combined wattage of the 4 bulbs is 20 and within the calculated 10W-40W range, the dimming will work fine.

Tips: (1.) The total wattage must exceed the minimum calculated load of the dimmer, but not the maximum, or else it won’t work properly. (2.) Use bulbs of the same type and manufacturers for the reason that having different types of manufacturers may result in bulbs that have different circuitry components that may result in dimming issues arising.  

So, are LED lights dimmable? It depends. Some LED lights are non-dimmable. But having dimmable LED lighting shouldn’t be complicated. If you have the right number of dimmable LED bulbs and a compatible dimmer switch that are all proven and tested, carry on. Not only will you save on your energy bills with safer and more long-lasting bulbs, but you will also achieve that dimming effect you’ve been dreaming of for your space.


Author: Jayk Guylaine Magistrado
Editor: Preston Gilmore