Dimming of LEDs can be confusing because there are several ways to dim and many different products for each method. Using the wrong products together can cause many issues.

When you think of dimming you probably think of slider-type controls mounted in the wall, like those by Lutron or Leviton, found in most homes and offices. But it’s not the only way.

They are “triac-based” dimmers, though you won’t see those words on the package. They work by chopping the 120 volt AC power signal, which basically reduces the amount of power getting to the light.
Traditional incandescent bulbs with tungsten filaments dimmed very easily by this method. However, LED lights are electronic devices, more complex than an incandescent bulb.

LED lights can come in different forms. They might be bulb-shaped with a screw base, designed to replace traditional bulbs in lamps and light fixtures. They might be linear flexible strips that are used for under-cabinet and cove lighting and many other effects. They might be “LED bars” which are similar to LED strips but in a rigid form. They could also be “LED panel” lights designed to replace fluorescent fixtures in offices.

LED screw-in bulbs are generally designed to work with wall-slider dimmers. However because the electronics inside each company’s bulb are a bit different, they may work better with some dimmers than others.

That’s a subject for another article.

Each bulb has a built-in power supply (“driver”) that converts the 120 volt AC wall power into a lower-voltage DC power to power the LEDs. That built-in driver is also responsible for converting the “chopped” AC power from the wall dimmer into a lower light output.

LED flexible strips generally rely on a separate power supply / driver to convert the 120 V AC wall power into the lower voltage suitable for LEDs. Can these be dimmed the same way, with a common wall-dimmer?

The answer is, it depends. If you use a “triac dimmable” power supply (driver), the answer is yes.

But is it the only way? No. You can use a non-dimmable power supply, and add a separate low-voltage dimming module to the 12 v or 24 V DC output to dim the output side, often using a PWM (pulse width modulation) technology.

These dimmers may include a knob, buttons or slider to set the dimming level. Some are available with a remote control so you can put the control on the wall or carry it with you, within a certain distance range. They can communicate with the dimming module by infrared (IR) light similar to a TV remote, or by radio-frequency (RF) signal.

But wait, there’s more!

There are drivers (power supplies) on the market that support 0-10 volt dimming, and other methods. What’s that?

For 0-10 volt dimming, a separate pair of low-voltage wires must be run from a special 0-10 volt dimmer to the LED driver. That seems like a lot of extra work, and it is. Why does this even exist? Basically it wasn’t that easy to design a high-power “triac” type driver, so this system was developed. It’s commonly found on drivers for LED panel lights, warehouse-type high-bay lights, but other lights might use it too. Note: some automation systems such as Lutron RA2, Vantage etc. offer modules that support 0-10 volt dimmable power supplies. However, they also offer modules for “normal” incandescent or LED screw-base bulbs – those are the modules sthat hould be used for “triac (AC) dimmable” LED power supplies (drivers).

You can buy drivers that support 0-10 volt control signals, and connect them to power LED flexible strips and bars. BUT be careful: The connections on those drivers are often just marked “DIM”.

Do not connect a 120 volt AC wall dimmer to those inputs. It won’t dim, and may even damage the driver or dimmer. Why do they just put “DIM” then? Because some of these drivers can also accept a varying resistance as a dimming control on the DIM input. That’s normally supplied by a “potentiometer” (POT) which is like a knob on a stereo system, also found on things like electric guitars. So, technically this is a “dimmable” driver, but it’s not dimmable by the common wall sliders, only by more esoteric methods!

Seems weird? Maybe it’s weird for lighting, but these power supplies are also designed for industrial applications, not just residential lighting. And they may be used all over the world, where different types of controls may be more commonly used. There are even different control protocols such as DALI, Zigbee, Zwave and more that can be used to achieve dimming and other effects.

Having read this far, you might be more confused than ever.

Don’t worry, we’re here for you. Call us, or use the contact form on the website and ask us your specific lighting and dimming questions!

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