LED flood light fixtures

What are dimmable light bulbs?

Dimmable bulbs are specifically manufactured for dimmable fittings (i.e. when you have a dimmer switch on the wall). They’re popular due to their aesthetic and energy-saving potential: the ability to lower the lighting can completely change a room’s ambience while using less energy. Most modern light bulbs, such as LEDs and halogen, are available in dimmable versions but fluorescent tubes need to be fitted with a dimmable ballast.

Why do I need to install a dimmable ballast to dim fluorescent tubes?

Just like any dimmable bulb, fluorescent tubes need to have the right control gear in it to be dimmable. Without a dimmable ballast, fluorescent tubes can’t be dimmed.

What are the best dimmable light bulbs?

This will depend on what type of fitting you have but if it’s for downlight LEDs then the All In One LED dimmable downlight 10w (known as the SOLO) is an ideal choice as the colour temperature can be adjusted from warm white, cool light to daylight and comes with a number of different fascias.   For a cheaper option for a downlight try one of the 8w downlight range, these bulbs have weatherproof fascias, are dimmable and are fire-rated to comply with building regulations.

Are dimmable light bulbs available for outdoor use?

Yes, dimmable outside lights are possible but need to be fitted with a dimmer switch, ideally this should be a trailing edge dimmer for use with LEDs or a basic leading edge dimmer for halogen lights or similar. Fluorescent bulbs also need the right control gear to enable them to be dimmed, whether it’s fitted indoors or out. Any outdoor light fittings will need to be IP rated so they aren’t affected by water.

If you are wanting to dim an outdoor light such, as a downlight in a garage soffit for example, you need IP65 rated downlight fittings and an appropriate dimmer switch, ideally controlled within the house.

How do dimmable LEDs work?

Dimmable LEDs offer longevity PLUS superior energy efficiency — but how?

The benefits of dimmable incandescent and compact fluorescent light bulbs, that is, the ability to easily adjust the intensity of overhead lighting, improved energy efficiency, etc., are all greatly enhanced when dimmable LEDs are used instead.

Dimmable LED light bulb by Philips. (Credit: lightbulbmarket.blogspot.com)

But how, exactly, does this particular type of LED technology work? This has become a common question to ask as today’s consumer becomes more aware and thus more curious about the benefits of LED technology.


First and foremost, LEDs are not dimmed based on an increase or decrease of voltage (as is the case with their incandescent counterparts.) Light gets emitted from a semiconductor chip, so it’s either on or off, and the LED will maintain its operation at the same voltage and current level as if it were operating at full light output.

Instead, what the LED does is it creates a “dimming effect.” There are two ways to do this: pulse-width-modulation (PWM LED) and analog dimming (sans cool-sounding acronym.)

Pulse-width-modulation LEDs

With pulse-width-modulation, the LED is wirelessly programmed to split its “on” time cycles, measured in milliseconds or thousands of a second, into intervals where the light is “on” and “off.” Take a look at the chart below.

Pulse-width-modulation is one way to dim LEDs.

For a low-lit light effect of just 10% brightness, the LED is “on” 10% of the cycle and “off” for the other 90%. For an LED light dimmed to 50% brightness, the light is turned “on” for half the cycle. Basically, the longer the “on” periods are relative to the “off” periods, the brighter the LED looks.

This, of course, begs the obvious question — why doesn’t it look like the light is blinking?

PWM LEDs rely upon the human eye’s ability to assimilate the average amount of light out of the pulses. As long as the rate is high enough, the eye won’t perceive any pulsing. Instead, it’ll recognize the overall average. To ensure the flickering is not noticed, the frequency of today’s PWM LEDs range from a few hundred to hundreds of thousands of pulses per second.

Analog dimming

Analog dimming is another way to dim an LED. In this scenario, the analog dimming supply controls the forward current being fed to the LEDs; its electronics linearly reduce the current so as to dim the LEDs.

While this technique is pretty simple to implement, and the efficiency of the LED is increased when run at a lower current (dimming reduces operating temperatures inside the light source), this particular type of LED doesn’t necessarily offer the best performance. That’s because it can turn out an inconsistent color as a result of the lower drive currents. This is particularly noticeable if different colored LEDs are used in a variety setting to produce white light. The amount of shift in current, particularly with red and yellow LEDs, can end up producing a low-quality white light.

Why’s it taking so long for dimmable LEDs to catch on?

The challenge for LED manufacturers is to design an affordable LED that can be retrofitted into existing installations, with the capability of being able to work with a variety of established dimming-control technologies as well as any emerging wireless-network-control scenarios. This is a tall order, to say the least. And while there are dimmable LEDS already available on the market, it still is a developing technology. 

As it continues to advance, prices will become more consumer-friendly, at which point we will likely begin to see a broader adoption of LED technology in more and more homes. ■

Related Products: LEDs and LED Lighting

LED light bulbs unlike incandescent or halogen have the option to come in both dimmable and non-dimmable versions. This is because when LED light bulbs were first released, it was uncommon for them to be dimmable. As LED bulb internal electronics became more advanced, dimming became possible and ultimately we are at the point today where dimming is essentially a no-cost or low cost adder to most LED bulb types. Because of this, many manufacturers no longer offer a non-dimming option outside vendors who are pursing the lowest retail cost point possible. 

This leads to a question however, if you do not have a dimming switch installed, does installing dimmable LEDs cause any issues?

The answer is absolutely not, dimmable LEDs when installed in a non-dimming switch will operate at 100% output and will run just as well as if they were installed with a dimming switch. Sure, there may be a non-dimming option available for a fractionally lower cost but generally speaking, if you plan on keeping your LED bulbs for a long time, it makes sense to choose the dimmable option.

What about installing LED bulbs that are non-dimmable with a dimming switch?

If you install a non-dimming LED bulb in a circuit with a dimming switch, it will likely operate normally if the dimmer is at its 100% or fully on. Dimming the bulb, will likely cause erratic behavior such as flickering or buzzing and ultimately may cause damage to the bulb. If you have to do this, we suggest keeping the bulb at full power. Again, as mentioned above, dimmable LED bulbs are overall a better investment. 

Resources: https://www.earthled.com/blogs/led-lighting-faq-frequently-asked-questions/can-i-use-a-dimmable-led-light-bulb-with-a-regular-non-dimmable-light-switch


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