How to Dim LED Strip Lights

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How to Dim LED Strip Lights 1
LED strip lights are great lighting tools for any project. But sometimes, you will want to have some level of dynamic control over the brightness of an LED strip.

For example, you might want to use them at full brightness while reading a book, but then dim them down later for mood lighting.

If you are confused about how to get it done, read on to familiarize yourself with LED strip dimming methods!

 

First, to clarify: Virtually ALL LED strips are dimmable

When you shop for common household LED lights like A-style bulbs, you may oftentimes see NOT DIMMABLE listed under the product description. The reason that some LED bulbs are not dimmable is due to the fact that the electrical circuitry inside the LED bulb is not designed to be able to interpret the dimming signal of a wall dimmer, which, in turn, is/was designed for a traditional incandescent bulb.

On the other hand, LED strips are not designed to be connected directly to line voltage (e.g. a 120V AC wall socket), and require a power supply to convert the higher voltage AC into a lower 12V or 24V DC voltage.

 

 

Therefore, if a wall dimmer is involved, it must first “talk” to the power supply before any dimming can happen at the LED strip. Therefore, the dimmable/not dimmable question depends on the power supply unit, and whether it can interpret the dimming signal produced by the wall-dimmer.

On the other hand, virtually all LED strips (as in, the strip itself) are dimmable. Given the appropriate DC electrical signal (typically PWM), any LED strip’s brightness can be freely adjusted.

How do we make sure the LED strip receives the correct DC electrical signal to dim properly? Below, we’ll go over the two most common options.

 

Option 1: Using a Traditional TRIAC Wall Dimmer + TRIAC Dimmable Power Supply

If you like the availability and style of traditional wall dimmers and are looking for an elegant, permanent LED strip installation (e.g. under cabinet lighting), this is most likely your best bet.

Most wall dimmers that are available today use the TRIAC dimming signal, and as such, you will first and foremost need to find a TRIAC dimmable power supply.

The TRIAC dimmable power supply has a dual function here –

1) reduce and rectify the 120V AC signal to a 12/24V DC signal compatible with the LED strip, and

2) interpret any TRIAC dimming signals produced by the wall dimmer, and then translate that into the corresponding LED strip light output.

The TRIAC dimmable power supply connects directly to the TRIAC wall dimmer, and the output end of the power supply connects to the LED strip. Since we are working with internal wiring in the walls, these components will likely not have any plugs or connectors you are accustomed to, and the power supply will likely also be concealed or hidden inside the wall or an electrical box.

Furthermore, to mitigate the effect of voltage drop, the power supply unit should be located as close to the LED strip as possible.

Keep in mind that any solution that involves a wall dimmer, including this one, involves hard-wiring connections to mains electricity and should be only performed only by qualified and licensed individuals.  Always follow safety precautions when performing electrical work!

 

Option 2: Use a Low-Voltage DC PWM Dimmer 

Intimidated by the prospect of messing up the wiring in your walls? No problem – another option allows you to use components that only draw power from a regular wall output.

A DC PWM LED strip dimmer can be installed between a standard, non-TRIAC dimamble power supply, and the LED strip. It usually consists of a turn dial (potentiometer) that adjusts the LED strip brightness.

The power supply can be any standard DC power supply and does not need to be TRIAC dimmable. These power supplies are generally lower cost and readily available, compared to TRIAC dimmable power supplies.

This is a very simple circuit design that will work well for smaller or portable installations where the dimmer does not need to be built into the wall. Unlike TRIAC dimamble power supplies, these standard power supplies will typically include standard 2-prong plugs that plug into any wall outlet.

DC PWM dimmers are typically very simple to assemble and connect to the power supply and LED strip. Waveform Lighting’s FilmGrade LED Dimmer, for example, includes DC plugs on both ends, allowing you to assemble everything in a matter of seconds without any tools.

 

Simply connect the two output wires from the power supply to the dimmer unit, and then the two input wires from the LED strip. The dimmer simply acts like a valve, and the power supply unit will automatically provide the rated current and voltage to depending on the dimmer’s knob position.

This is convenient if you plan on frequently moving the LED strip installation, but perhaps an issue if you are looking for something more permanent or less “cluttered.”

Also, another significant disadvantage of this approach is that the PWM dimmer must be placed relatively close to the LED strip. This is due to a phenomenon called voltage drop that is primarily an issue with low voltage DC applications only. A wall dimmer approach (Option 1) would allow you to avoid this.

Final considerations

LED strip installations and dimming can be made tricky by the fact that we currently straddle the latest in DC electronics and legacy TRIAC dimming systems that continue to be popular in existing and new homes.

With many variable components and combination, we strongly recommend testing for compatibility prior to any permanent or large scale build. Sometimes, unexpected issues like non-linear dimming or flickering can occur, and it is best to catch these issues as early as possible.

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