How a Dimmer works
How do dimmers work and which lamps are dimmable?

Especially in the winter, you like it really cozy in the living room, but often the living room lighting is too bright for a homey atmosphere. A few candles? Too dark. The mood just doesn’t want to adjust. A dimmer is often the right solution. But how do dimmers work and is every lamp dimmable?

What is a dimmer and how does it work?

A dimmer is an electronic device which has the ability to switch electrical currents. In Germany the voltage in the power supply is 230V and works with alternating current. This means that the voltage changes its polarity per hundredth of a second, and always takes the value zero (sinusoidal curve). Via the rotary knob of a dimmer, we set when the dimmer should ignite in the course of a sinusoidal half wave. This control principle in electrical engineering is referred to as a phase-cut control. Some lamps also require dimmers that operate with the phase-section principle. This then works just the opposite way.

Since both the phase control principle and the reverse phase control principle cause switching to take place very fast, a halogen lamp often cannot follow due to the inertia and therefore the light does not flicker either. Common dimmers are, for example, the rotary knob, or the touch dimmer, which, in addition to turning the lighting on and off, also allows the brightness to be adjusted. Examples of other dimmers in the household are vacuum cleaners, which dimming the suction power with a rotary knob.

Dimmers in lighting technology create pleasantly comfortable light. However, they also help save energy and can extend the service life of the lamps used.
Christine HillerLighting expert at Houzz & HQ Designs

As simple as replacing incandescent or halogen lamps with LED bulbs or energy-saving bulbs is, there is a big difference in dimming. Since these types of lamps are often used with integrated control devices, they must also be designed for dimming. And even then the right dimmer has to be selected exactly according to lighting technology and switchgear / transformer used.

3 things to consider when buying a dimmer

  • null
    Is the lamp dimmable and which bulbs are being used?

There are different dimmer models, as well as load types, which make it necessary to select the right device. The dimmer is selected according to the load type. This means for you: Which lamps are used and is a transformer in the lamp or does the lamp work normally via the 230V power supply? This information can be found on the packaging of the manufacturer, but also on the lamp. If in doubt, ask the electrician. There are a lot of different dimmable bulbs on the market which require special dimmers. But all in all, they can be classified according to their technology.

The following are the most popular lamps and also the most common:

  • 230V high-voltage halogen (socket G9 or GU10)
  • Low voltage 12V with electronic (Tronic-) transformer (socket G4, GU5,3, GY6,35)
  • Low voltage 12V with conventional transformer (socket G4, GU5,3, GY6,35)
  • LED lamps (many types of sockets possible)
  • Energy saving lamps (many types of sockets possible) dimming is only possible to a limited extent. Check manufacturer’s data!

Make a note of the total number of watts and see if the dimming principle can be found on the bulb or the lamps. Each dimmer has a minimum and maximum connection power (from-to … watts). Thus, only lamps or lamp groups with a total power between this range of the connection power of the dimmer can be connected without problems.

The industrial marking for dimmers: the letters R, L or C can be seen on the lamps, usually together with a “rising” toolbar. But there are others (see below). For the correct selection of the dimmer, the letters on the lamp and the future dimming device must match.

The following table shows which lamps can normally be used with which dim technology:

Comparison of luminaires and dimmability

1) Dimmable energy saving lamps (ESL)
Only when energy saving lamps are explicitly dimmable, they can be dimmed with conventionally operated dimmers (rotary or sliding controllers) or especially electronically controlled dimmers of the dimming method indicated at the lamp (phase control / reverse phase control). However, this has to be mentioned in the description of the dimming device. In principle, dimmers designed for incandescent / halogen lamps are not considered suitable for energy saving models. Even if the combination works, it can possibly lead to strong radio interference due to the emission of increased glitches on the mains cable.

2) a. LED lamps
230 V LED lamps and high-voltage LED lamps must be marked as dimmable. If the LED lamp is marked as dimmable, check whether a phase-control or reverse-phase-control dimmer has to be used. This is usually put on the packaging from the manufacturer.

12 V AC and 12 V AC / DC LED lamps must also be marked as dimmable. Care must also be taken to ensure that the transformer used is dimmable. Which dimmer can be used, is shown in the manual of the respective transformer. Many transformers designed for low-voltage transformers also require a basic load (minimum load), which must be loaded by the LED lamps, since the transformer does not even “start”.

b. LED stripes and single LEDs (DC)
LED PWM dimmers (PWM = pulse-width modulation) are used for LED lamps which do not work directly with 230V (typically 12V or 24V DC)! Either an additional LED ballast (driver) is required or this is already integrated into the PWM dimmer. Dimmable LED drivers are also available for various control types.

3) Fluorescent tubes
Fluorescent tubes can only be dimmed with the special electronic ballasts (ECG with 0 – 10V interface) meant for this purpose and dimmer.

  • null
    Choose your switch program

To find out which dimmer you need, you first have to specify a switch program, or find out which program is installed in the room that is to be equipped with a dimmer. Then select a touch / turn or other dimmer.

Universal dimmer

Universal dimmer
The universal dimmer is the simplest option for dimmer installation. It can dimm almost all types of load and thus makes the selection of the suitable lamp considerably easier. It is available for turning as well as for pushing. Advantage: Even if you later get a new lamp and new load type, no new dimmer is required (except for LED dimmers).


LED dimmer LEDOTRON – standard
These dimmers have some important points to consider. When dimming LED lights, use only branded lamps, which can also be dimmed according to the manufacturer! Many switch manufacturers have entered cooperations with major brand manufacturers and have developed standards that ensure easy dimming of the offered LED lamps. This standard was called LEDOTRON.

Dimmer for electronic transformers

Dimmer for electronic transformers (reverse phase control dimmer)
Reverse phase control dimmers are suitable for dimming electronic transformers, e.g. lamps with low-voltage halogen bulbs. These transformers are often cleverly integrated into the lamp housing, so that you can only know from the operating manual what kind of transformer is installed.

Dimmer for conventional transformers

Dimmer for conventional transformers (phase control dimmer)
Inductive loads can be dimmed with phase control dimmers. These are, as already mentioned, less and less built-in and are mainly found in old buildings, where they already supply existing low-voltage installations, such as recessed luminaires.

  • null
    Select the appropriate dimmer type and model

The most common dimmers are as follows:

  • Rotating dimmer: the classic with rotary knob
  • Tap dimmer: simple control by finger tapping
  • Foot dimmer: comfortable control by foot, e.g. with floor lamps
  • Touchdimmer: direct selection of the brightness level via LEDs
  • Serial dimmer: control of several lamps or lighting groups

Have the device installed by an electrician / specialist, so that you also get any guarantee claims in case of a defect.

Tips & hints for the use of dimmers

  • With a dimmer, you can save energy, because depending on the dimmer setting power is saved.
  • If your lamp or transformer is humming, it can help to loosen the screws on the transformer and tighten them again. Alternatively, rubber material between the transformer and the ceiling can be a solution. The cause of the humming is often the abrupt magnetic field changes, which can cause the transformer to vibrate when the lamp is switched on or off.
  • If you dimm your lamp frequently, you should switch it to full power from time to time, so that the halogen circuit in the lamps is used again and the lifetime is maintained.
  • In the case of permanent dimming operation, you should consider whether it would not be better to install lamps with less light output for energy-efficient reasons.
  • If the search for the right dimmer is too much of a hassle for you, you can get lights with LED technology and the included remote control for the dimming function like Philips LivingColors. With this, the corresponding light can then be dimmed usually in 2-10 steps. Some models also offer the option of using the remote control to control light colors from warm white to cool white. But this is only possible for the lamps that are equipped with the remote control.

Share this with a friend