Author Archives: Taru Oksala

About Taru Oksala

Taru is responsible for marketing at Arrant-Light Oy.

Dim-to-Warm – COB LED that dims like halogen


Dim-to-Warm is COB LED which works like halogen lamp when dimmed. Its specialty is that when you dim it the color temperature gets warmer. Usually dimming does not affect the color temperature of the LED. Dim-to-Warm LED imitates the effect of the halogen lamp which gets warmer by dimming. With full power you can get color temperature 3100K and at lowest 1850K.

Dim-to-Warm LED suits especially highly for decorative luminaries, for example used in restaurants, hotels, cruise cabins and home interiors. It’s perfect for space where you want to have dimmed and warm toned atmospheric lighting.

LED has great advantage compared to an incandescent lamp. Its power consumption is less than 10% of the incandescent lamp’s power consumption.

The color temperature of candlelight, incandescent and halogen lamp.

The color temperature of candlelight, incandescent and halogen lamp.


There are seven different packages from 900 to 3000 lumens. You can download more information about the product here.

Where and how to use?

Dim-to-Warm LED is great for places where you want the light that dims like halogen or incandescent lamp. You can use it for example for restaurants, hotels, cruise cabins and decorative luminaires where you have been using halogens before.

It’s easy to use. You can use Dim-to-Warm LED for all the luminaires where you have been using COB LED or you can use it to replace led modules. All optics, lenses and reflectors that are compatible with COB LED, suit also for Dim-to-Warm LED. LES area is CLC20-series for 9,8 mm and at CLC30-series for 15,2 mm.

How Dim-to-Warm works?

As we know, usually LEDs don’t change the color when you dim them. They always retain approximately the same color temperature when the brightness is reduced. LED’s brightness depends on the current; reducing the current the brightness reduces.

Dim-to-Warm LED is made from cold and warm LED areas. It has an internal control circuit which dims the cooler area first and later starts to control current of the warm one.  The color temperature gets warmer when dimmed.  This way the dimming works similarly in incandescent or halogen lamp.

The diagram below shows how the color temperature gets warmer when led is dimmed down and the current and brightness reduces (black color). You can also compare it to halogen lamp (grey color).


Dim-to-Warm is a COB LED, so you don’t need any complicated special features from the driver, like two-channeling or programming features. Ordinary triac dimmable driver is enough. We have tested ELT’s DLC-drivers with it, and they have good compatibility.

Click the button below to download the datasheets and material. You can find more information and our product codes from the presentation. If you have any questions about Dim-to-Warm, please don’t hesitate to contact us.

Download Here

Why Heat Pipe is Better than Traditional Heat Sink?

You will need a heat sink when you use a COB LED in your luminaire. The traditional way of transferring the heat away from the light source is to use a passive aluminum heat sink. In this blog post, I’ll introduce you the new way of cooling: heat pipe.

Traditional heat sinks are based on the fact that aluminum transfers heat away from the light source. The higher the power of the LED is, the more you need aluminum.

This grows the luminaire’s size and makes it more expensive. The bigger size of the luminaire makes logistics costs go up and increases the price for end user even more.

We have a better solution for cooling high power LEDs without the need for noisy fans or heavy heat sinks.

Furukawa Heat Pipe (HYC Series)

Heat pipe technology is traditionally being used in computers and for example in satellites. But now it is available in lighting.

Furukawa HYC Series uses heat pipe technology to transfer the heat and makes heat sinks more efficient in cooling the LED.

how heat pipe works

Its thermal conductivity is almost 200 times better compared to copper. This also allows the heat sink to be a lot smaller than we are used to.

Smaller heat sink reduces the weight of the luminaire dramatically. This reduces transportation costs as well as the amount of other materials needed.

The Heat Pipe effectively transfers heat from the heat source and as a result makes the cooling faster than ever.

Unlike many Chinese manufacturers, Furukawa uses oxygen-free copper in its Heat Pipes, which means that their lifetime is over 20 years.

Heat Pipe vs. No Heat Pipe

Cooling with and without the Heat pipe

Save Money and Environment with our aLED Light Engine

aLED Engine

aLED Light Engine (Furukawa Heat Pipe + Citizen COB + optics + aLED Driver)

As a great example, I want to introduce you our own aLED Light engine that uses Furukawa heat pipe with Citizen COB. aLED Light Engine produces over 40 000 lm and weights only 1kg (without driver and optics). And only 3.6kg with optics and driver.

By combining Citizen COB and heat pipe technology, you can build luminaires that:

  • Produce a lot of light
  • Are light in weight and small in size
  • Save environment
  • Are completely recyclable

Furukawa Heat Pipes are compatible with Citizen CLU04x and CLU05x COB LEDs.

Download an example of different combinations and datasheets for custom models with screw holes for Citizen COBs.

Download Here

Why Should You Choose the New aLED Module

We redesigned our aLED-modules based on customer and market feedback. Here is  a brief explanation on what is different compared to previous version. And why I think you should consider using aLED modules.


Figure 1. New aLED Modules with examples of different connector locations.

Better efficacy (159-191 lm/W)

We upgraded the SMD LEDs used in the modules to better suit our customers’ needs. aLED modules now have efficacy from 159 lm/W to 190 lm/W. Efficacy depends on the color temperature and you can see the efficacy by CCT here:

  • 2700K (174 lm/W)
  • 3000K (177 lm/W)
  • 4000K (185 lm/W)
  • 5000K (191 lm/W)

Better placement of LEDs

We have changed the design of our aLED module. LEDs are now placed on the center line of the module so the installation of optics is easier.

aLED modules dimensions have also changed. New modules are now either 279.2 mm or 558.4 mm in length and 20 mm or 40 mm in width. 

Different options for connectors

It is now possible to order aLED modules with connectors either on the frontside or on the backside. Traditionally the connectors have been on the frontside, but these new backside connectors allow you to hide the wires behind the module and inside the profile.

For longer luminaires, there is a possibility to use backline, so you won’t need long wires. Short wires to connect multiple modules together will be enough (figure 2).

Figure 2. a) How to connect modules without back line option. b) How to utilize the back line option of the aLED modules.

Long lifetime

Thanks to the upgraded LED, the lifetime of aLED modules has also increased. You can see the lifetime prediction below. But to be brief: at maximum TC temperature (85°C) the lifetime (L70B50) is over 100.000 hours (figure 3).

Fikure 3. The lifetime of aLED Module (L70B50)

Friendly to environment

On top of high efficacy and the possibility to save energy, aLED modules are also recyclable. You can recycle all parts of module, even the PCB.

In addition to all these changes aLED modules prices have also dropped to more competitive level.

You can find the technical details of 4000K modules from the table below. You can download the datasheets of these new modules by clicking here.

Product Code Color Temperature (CCT) Color Rendering (Ra) Luminous Flux (lm) Forward Current (mA) Voltage (V) Power (W) Efficacy (lm/W) Length (mm) Width (mm)
CALOSNU0405 4000 80 1182 600 11.6 7.0 170 279.2 20
CALOSNU0410 4000 80 1224 600 11.0 6.6 185 279.2 20
CALOLNU0805 4000 80 2363 600 23.2 13.9 170 558.4 20
CALOLNU0810 4000 80 2448 600 22.1 13.3 185 558.4 20
CALOLHU1610 4000 80 4895 600 44.1 26.5 185 558.4 40
CALOSND0405 4000 80 1182 600 11.6 7.0 170 279.2 20
CALOSND0410 4000 80 1224 600 11.0 6.6 185 279.2 20
CALOLND0805 4000 80 2363 600 23.2 13.9 170 558.4 20
CALOLND0810 4000 80 2448 600 22.1 13.3 185 558.4 20
CALOLHD1610 4000 80 4895 600 44.1 26.5 185 558.4 40


Download Datasheets


In addition to these new models, all our previous module models are also still available.

Thank You for Everyone at Elfack 2017

I would like to thank everyone who we met at the Elfack Exhibition in Gothenburg, Sweden.

We had some good conversations with our existing customers as well as new people. This year we tested the color quality of Citizen’s LEDs at our stand. We got many answers through our questionnaire and found out that many visitors were excited about this new way of lighting.

If you took part in the test, you will receive the test results soon. We will also share these results with the public a little later.

We had a chance to show you our new products and the feedback we got from you was very encouraging.  I went through all the products in my last blog post, and if you wish to download more information about them, you are most welcome to do so here.

The products displayed at Elfack include:

  • aLED Engine
  • Citizen Gen 6
  • AC COB
  • Citizen Vivid Series
  • Furukawa Heatpipe
  • Merrytek sensors
  • Letaron & aLED Drivers

Our personnel will contact you as agreed, if they haven’t already. In case you have anything to ask, you can contact us directly.


What We Are Presenting in Elfack?

Elfack exhibition will be held in Gothenburg, Sweden from 9th to 12th of May. As it has been with previous exhibitions, we will be releasing new products and presenting the latest technology at our stand.

This year we will introduce and present the following products at our stand F04:70.

aLED Engine

aLED Engine

aLED Light Engine

We designed aLED Engine for applications that require a lot of light. aLED Engine consists of Furukawa heat pipe and Citizen COB LED.

In addition you can also choose a suitable optics and LED driver for the light engine from our selection. Suitable drivers are available as on/off, 1-10V dimming and DALI dimming.

aLED Engine is also compatible with Merrytek sensors, which allow you to control the lighting as you wish.

The 300W engine produces 36.000 lm at 4.000K and weighs only 3,6 kg with a driver installed.

aLED Engine will be at our stand in Elfack. There you can see the engine in action and try it with a daylight sensor.

Download More Information

Furukawa HYC Series

Furukawa HYC Series uses heat pipe technology to transfer the heat and makes heat sinks more efficient in cooling the LED.

how heat pipe works

How Heat Pipe Works

Heat Pipe’s thermal conductivity is almost 200 times better compared to copper. This allows the heat sink to be a lot smaller than we are used to.

Smaller heat sink reduces the weight of the luminaire dramatically.

The heat pipes effectively transfer heat from the heat source throughout the whole heat sink cooling the heat source faster than ever.

Heat Pipe vs. No Heat Pipe

Heat Pipe vs. No Heat Pipe

Furukawa heat pipes are compatible with Citizen COBs.

Furukawa heat pipes will be at our stand so you can see and try how light they are.

Read more about Furukawa heatpipe from here.

aLED & Letaron Drivers

aLED Driver

aLED Driver

aLED and Letaron offer a versatile range of both constant current and constant voltage drivers from low to high power (from 1 W up to 600 W).

Ouw own aLED drivers are best suited for high power applications. They are all available in IP68 and can be ordered as on/off, 1-10V dimming or DALI dimming.

Letaron drivers are best suited for low power applications, although they are available up to 52W.

Letaron offers a variety of designs to suit your needs including round, rectangular and slim models.

The Letaron low power drivers are also compatible with OLED light sources.

aLED and Letaron drivers will be on at our stand so you can see and try them yourself.


Merrytek sensors

Merrytek offers a wide range of different sensors. Some sensors come with LED driver and some are independent and can be connected to LED driver.

Merreytek has products particularly designed for eg. homes, schools, stairways, warehouses, offices, parking garages and outdoor use.

Merrytek’s intelligent lighting control products include:

  • Microwave motion and daylight sensors
  • Dimmable LED drivers
  • LED drivers with intergrated sensors

There will be Merrytek products on display at our stand. We will have an aLED engine wiht Merrytek’s daylight sensor on our stand, so you can see how it functions.

Citizen Gen 6, AC COB &Vivid Series

Citizen released Gen 6 COB and AC COB earlier this year with improvements compared to the previous versions.

Thermal Resistance

Thanks to better heat resistance, you can use much smaller heat sink. Gen 4 on the left, Gen 5 on the middle and Gen 6 on the right.

For the new Vivid series we’ve prepared a demo wall at Elfack for you to examine the possibilities of color quality control in LED lighting.

Seminar about color quality

We will organize a seminar about color quality on the first day of the exhibition.

Color comparison Vivid COBColor Comparison Regular COB 3000K Ra80 vs. Vivid Brilliant

The seminar will take place on Tuesday 9th of May.
Time: 16:00-19:00
Place: Hotel Gothia Towers, Tower 1, meeting room R22-23

The program:

  • Doors open at 16:00
  • Coffee
  • Welcome / Arrant Light Oy by Janne Mäkinen, Managing Director / Arrant-Light Oy
  • Color Quality with CITIZEN by Kosuke Tsuchiya, Field Application Engineer / Citizen Electronics Co.
  • Demonstration and open discussion
  • Refreshments and snacks
  • Close at 19:00

Please sign up for the seminar as soon as possible or latest by April 30th. We have limited seats and there is room for the first 20 persons only.

Sign Up for Our Seminar

Welcome to visit our stand F04.70 at Elfack.

All datasheets and other material will be available from our website soon. If you wish to download material about these new products before the exhibition. You can do that here.

AC COB – Easier way to make a luminaire

What is AC COB?

AC COB is brand new AC LED solution from Citizen Electronics. It is available with holder which contains necessary components to connect package directly to mains voltage. So basically it is designed to make life of luminaire manufacturer easier.

AC COB With Connector

AC COB With Connector

What advantages?

AC COB has integrated circuit which allows you to control luminous flux more accurately. For all CCT and CRI versions you are able to have exactly same luminous flux from the package e.g. 750, 1000, 1500 and 2000 lumens.

5 volt output enables you to use e.g. motion sensor, so you can easily adapt external sensors to easily add features to your luminaire.

There is no additional losses from driver and so there is no problem to have good efficacy even with low powers. AC COB with new integrated circuit has good compatibility with dimmers, you are able to dim this solution with Triac (leading-edge) and Transistor (trailing-edge) dimmers.

Small form factor and no need for external driver allow even more creativity to luminaire design. There is no need to worry where to place the driver.

What you need to take to consideration?

AC COB has of course similar characteristics than normal COB meaning warmer CCTs have lower efficacy than cooler CCTs. With fixed luminous flux, that means you have difference in power. So 2700K Ra90 AC COB consumes more power than 5000K Ra80.

And of course AC is still AC. If you don’t use more complex circuitry to modify AC to DC, you will still have AC characteristics affecting luminous flux. Mainly with AC LEDs this means that you have flicker present in light source. To reduce that effect, it is good to consider e.g. secondary optics which lower this phenomenon.

AC COB In Connector

AC COB In Connector


Even though AC LED might have it’s limitations it has certainly some advantages which make it viable solution as light source. It has ENEC certified components which are easy to use to design new luminaires and you can make testing with this solution in different luminaires. Now it is time to consider where you could use AC COB to realize its advantages.

You can download datasheets and brochure from the button below.

Download Here
Citizen COB lineup

Citizen COB LEDs generation 6 – What is new?

Citizen have released generation 6 from their successful series of Citizen COB LEDs. In this post I’ll go briefly through, what is new and what advantages these COBs have compared to previous generations.

There are five main points at generation 6 from Citizen:

1. Performance increase

Performance will up to 7% depending on CRI of LEDs. There will be also slight decrease on forward voltage, which increases lm/W efficacy on LEDs.

2. MacAdam 2-step option

MacAdam 2-step binning will be an option in new generation. Although we have had very tight 3-step binning already, there is now option to order also 2-step versions of COBs. So if you desire to have 2-step SDCM COBs in your products, we have now solution for that.

3.Thermal resistance decrease

Thermal resistance is further decreased from generation 5. Decrease from generation 5 is 5% and from generation 4 even 38,5%. This allows you to minimize your need for heat dissipation. Another option is that you can create new, bigger lumen categories with your existing products.

Thermal Resistance

On the left a heat sink needed for COB Gen 4 LED. On the middle heat sink needed for gen 5 LED. On the right, heat sink needed for COB gen 6 LED. The power of the LED is same in every case.

4. Increase of maximum Tc

Maximum Tc-temperature has been set to 120 degC. Allowable Tc-temperature will rise from 105 degC to 120 degC. This will help you to maximize light output from your design, so you can use smaller heat sinks to get more light.

5. Increase of maximum Tj

You will be allowed to have higher Tj-temperature than in previous generations, so maximum Tj-temperature will be now 150 degC. This will give you wider LED driving options especially with bigger COB packages.

Citizen COB LEDs continue to increase their performance and offer amazing coverage for lumen packages. Packages range from under 100 lumens up to 60 000 lumens from single light source. If you haven’t yet tried Citizen COB LEDs, now it is good time to learn why Citizen has been top player in the industry for so long time.

You can download the whole catalogue, datasheets and simulator tool for Generation 6 COBs from our website.

Download Catalogue, Gen 6 Datasheets and Simulator Now

How to use Citizen LED simulator

Datasheets are essential part when you compare how different light sources work in your solution. Usually it can be time taking and exhausting to glance at datasheet and find values you are looking for. This gets even harder if you have multiple LEDs or different LED packages, which would mean that you have look at multiple datasheets to get different values.

This is the reason why Citizen has created a Citizen LED simulator. The simulator is very easy to use and makes comparing different LED packages a lot easier. If you haven’t yet tried it or you don’t have the simulator, you can download it for free from our website.

Citizen LED simulator basic view

Citizen LED simulator basic view.

The steps

Follow these steps to use the simulator.

You can choose desired CCT and Ra and selection simulator shows packages and product codes of existing products.

You can choose desired CCT and Ra and selection simulator shows packages and product codes of existing products.

  1. Select the CCT and Ra

First you need to select desired CCT and Ra from condition input field.

You can choose desired CCT and Ra and the selection simulator shows packages and product codes of existing products.

  1. Choose whether you want to search based on the desired lumen amount or driving current

After you have selected color temperature and CRI value, you can choose between driving current (forward current in simulator) or desired luminous flux.

  1. Input the Tc-temperature

Then you can input Tc-temperature. If you have no idea how much Tc is or would be in your solution, values around 60 degrees are realistic to use as many light sources reach temperatures close to that while being used.


In this example, I have chosen that I want my LED to be 4000K, Ra80 Min. And I want to see what options we have to get around 3000 lumens out from luminaire. Luminaire optics etc. will drain around 300-400 lumens in my solution. So I have determined that I need 3400 warm lumens from LED and estimated that Tc-temperature is 60 degrees.


I can see that I have ten different LED packages I can get the 3400 lumens from. In first column after product code you can see what current you should use to get these values. If you don’t have LED driver, in which you can choose output current, it is recommended to then select current value you have LED drivers available in. In this case, 700mA seems to be a good choice as many of the LED’s have driving current close to that.

So I change “forward current” instead of “luminous flux” from the condition input and insert 700mA.

LED packages which give you desired lumens with 700mA. We still have six options to choose from.

LED packages which give you desired lumens with 700mA. We still have six options to choose from.

This will give me a list of LEDs I can use with 700mA driver. And more importantly give me a good overview of LED packages that can give me my desired lumen amount. If you have problem that you can’t find driver with suitable current, you can contact me for help.

In this case, CLU028-1204 would suit my lumen need quite nicely and CLU048-1212, would probably be an overkill for this application. All the other options, might suit my solution although they give roughly 10% more lumens. Whether this is ok, depends really on my application and desired efficacy.

Other applications

Citizen LED simulator is also powerful tool to use when you want to see easily how much lumens you get when driving LED with different currents. Good example is that if you have LED driver which has different current options and flexible LED package, you can use only two components to realize many different lumen packages.

As an example I did this exercise with ELT 42W multicurrent LED-driver and Citizen CLU038-1205 LED package. This driver has option to select different driving currents with dipswitch. If we take Esko’s advice and look from driver datasheet, we can see that output voltage area is suitable from 500mA to 1000 mA.

Below you can see LED characteristics with different current. I have also added forward current column to make this table easier to read. Tc temperature is 60 degrees in all cases.

Table with CLU038-1205 4000K Ra80 LED from 500mA to 1000mA.

Table with CLU038-1205 4000K Ra80 LED from 500mA to 1000mA.

You can also use the LED simulator to estimate the amount of lumens lost due to your luminaire (optics etc.). If you measure LED Tc-point and input the driving current you use to simulator, you should have pretty good estimation that how much lumens you should get out from your luminaire.

If you find out that the loss is too big, the you can either change the LED to a different package or improve the optics of your luminaire.As you can see, you can use this driver & LED combo for a luminaire from ~2500lm to ~5000lm.

Please feel free to contact me if you have any questions.

You can download the latest simulator below.

Download COB Selection Simulator


Different Dimming Types for LED Lighting

You can use several different dimming options to dim LED Lighting. What are the possibilities and what dimming should you look from a LED driver? I’m going to answer these questions in this blog post by going through the different systems.

The goal is to give you the basic understanding of the dimming methods available at moment.

I am grouping the dimming methods in two main groups: analogue and digital.

When you want to control lighting, you have to know some basic issues of your lighting fixtures:

  • Are your fixtures dimmable? If yes, what is the dimming method which works together with your fixtures
  • If your fixtures are non-dimmable, then you can only have on/off – function.


Analogue dimming covers all dimming systems that don’t transform the dimming signal into bits and controls the lighting in analogue manner.

Phase dimming

Phase dimming systems dim the lights by altering the supply voltage.

Leading & trailing edge dimming

Before LEDs, we used to dim halogen lamps with wall dimmers.  We can still use these kinds of dimmers.  But dimmer, driver and LED-module must be compatible with each other.

This type of control is accomplished without any need for an additional control wire. It involves connecting a dimmer in series between one of the mains wire and the equipment.

The dimmer cuts part of the mains voltage sinusoidal waveform to a greater or lesser extent in order to dim luminous flux even from 1% to 100%  (this value depends on dimmer and driver).

Depending on how the driver makes the mains voltage cut, it is possible to distinguish between two types of dimming:

Leading-edge dimming

Leading-edge dimming

Trailing edge dimming

Trailing edge dimming

Leading-edge dimming:

Dimming cut-off in the wave on its ascending side, from the beginning (phase cut-off at ignition). This is traditionally used in halogen lamps supplied through electromagnetic transformers.

Trailing-edge dimming:

Dimming by cut-off in the wave on its descending side, from the end cutting backwards (phase cut-off at switch off).  And this way of dimming causes less interferences than leading-edge dimming.

There are dimmers and equipment that support both types of dimming, and others that support only one type.

Leading & Trailing-edge dimming LC

Leading & Trailing-edge dimming LC

Leading-edge dimming L

Leading-edge dimming L

Trailing-edge dimming  C

Trailing-edge dimming  C

1-10V regulation

The 1-10V system enables dimming of the luminous flux from around 1…10% to 100%. This is done by sending an analogue signal to the equipment over an additional, two-wire control line. These control wires have positive and negative polarities respectively and that must be kept in mind when wiring up the system.

The analogue signal has a direct voltage value of 1V to 10V. 1V or short-circuiting the fixture’s input control gives the minimum light level. While 10V or leaving the input control circuit open gives out the maximum light level.

International standard, IEC 60929, defines the regulation curve. The regulation curve represents the relationship between the control line voltage and the luminous flux. It reflects a practically linear relationship in the range of 3V to 10V.

To get a response adapted to that of the human eye it is possible to use logarithmically controlled potentiometers.

Regulation curve by IEC 60929

Regulation curve by IEC 60929

These in light fixtures generate power control with 1-10V dimming.  Driver supplies a current to the controller through equipment control terminals. The controller current must be from 10µA to 2mA. The maximum control line current is obtained with a voltage of 1V and the minimum with a voltage of 10V.

This dimming system is unidirectional, i.e. the information flows in one direction, from the controller to the light fixture. The latter generates no feedback to control. This means that this system can’t be controlled by a software. Groups have to be created by wiring. This system can be integrated into building control systems.

The voltage drop in the control line wiring limits its length. Therefore, the maximum distance is limited by the number of control gears connected. The latter establishes the current per line and the cable diameter used.

Touch Control Push Button  (analogue but can be connected to digital systems)

Touch Control is a system that enables the simple and economic dimming of luminous flux. It uses the mains voltage as a control signal, applying it with a standard push button on a control line, without any need for specific controllers.
The Touch Control system enables you to carry out the basic functions of a regulation system with a power-free pushbutton. Depending on how long the button is pressed it is possible to switch the light on or off or dim it. Switching the light on or off is done by short, sharp pressing or “click”. If the button is pressed for a long time it is possible to dim the luminous flux between the maximum and minimum levels alternately.

Touch Dimming

Touch Dimming

This is a unidirectional interface, i.e. information flows in one direction. The equipment does not generate any type of feedback, so it can’t be controlled with a software. Groups have to be created by wiring. This system cannot be integrated into building control systems.

The length of the wiring and the number of equipment that can be connected, are theoretically unlimited. But in, asynchronism may occur during switching on and dimming, at distances longer than 25 meters, and with a larger number of fixtures connected.
Owing to its characteristics, the use of this dimming method is recommended for individual offices, small meeting rooms or bedrooms, landings and small spaces in general.


Digital dimming covers all dimming systems that transform the dimming signal into bits and controls the lighting in digital format.

DALI Regulation (digital)

As revealed by the meaning of its acronym, Digital Addressable Lighting Interface, DALI is a digital and addressable communication interface for lighting systems.

This is an international standard system in accordance with IEC 62386, which ensures compatibility and interchangeabil­ity between different manufacturers’ equipment marked with the following logo: DALI controller



It is a bi-directional dimming interface with a master-slave structure. The information flows from a controller, which operates as the master, to the control gears that only operate as slaves. The latter carries out the orders or responds to the information requests received.

Digital signals are transmitted over a bus or two-wire control wire. These control wires can be negatively and positively polarized, though the majority control gears are designed polarity free to make connection indifferent.

DALI Dimming

DALI Dimming

You don’t need especially shielded cables. It is possible to wire the power line and DALI bus together with a standard five-wire cable.

Unlike other systems, you don’t need to create wiring groups. Therefore all the pieces of fixtures are connected in parallel to the bus. Without bearing in mind the grouping of these, simply avoiding a closed ring or loop topology.

You don’t require mechanical relays to switch the lighting on or off, given that this is done orders sent along the control line. You don’t need are bus termination resistors either.

Consequently, the DALI interfaces offer wiring simplicity in addition to great flexibility when it comes to designing the lighting installation.

The maximum voltage drop along the control line must not exceed 2V with the maximum bus current of 250mA. Therefore, the maximum wiring distance allowed depends on the cable cross-section, but it must never exceed 300m in any case.


After wiring, the DALI lighting system is configured with the software. You can create up to 16 different scenarios, addressing the equipment individually up to a maximum of 64 addresses.  This can be made with groups up to a maximum of 16, or simultaneously by means of a “broadcast” order. You can change the configuration at any time without any need for re-wiring.

The DALI system has a logarithmic regulation curve adjusted to human eye sensitivity, defined in the international standard, IEC 62386. The possible regulation range is set at from 0.1% to 100%. The driver manufacturer determines the minimum.

DALI Regulation Curve by IEC 62386

DALI Regulation Curve by IEC 62386

With the software, you can change the “fade rate”. “Fade rate”is the time needed to go from one light level to another(fade time) and the speed of the change.

The DALI system lies in the fringe between the complex and costly but powerful ones; control systems for buildings that offer total functionality and the most simple and econom­ic regulation systems, for example, the 1-10V one.

You can use this interface in simple applications indepen­dently, to control a luminaire or a small room. You can also use it in high-level applications such as being integrated by gateways into building smart control systems.

These are the most common systems you can use to dim LED. There are a lot of different dimming systems for different driver manufacturers. I can’t cover all of those in a single blog post. I will be writing a different post about wireless dimming options.

If you have anything you would like to know, you can always contact me .

Sources: ELT

CIE 1960 Chromaticity Diagram

Why the Same Color Temperatures Look Different?

We see more and more light sources that supposed to be exactly the same color temperature, but actually appear different to human eye. So why the same color temperatures look different?

When people talk about color temperature, they are usually talking about correlated color temperature instead (CCT). There is a difference between these two.

Color temperature (CT)

Color temperature (CT) defines what is the exact spot of the light source is on the planckian locus line.

This line in pictured in the below image as the black line in the middle.

So if there are two light sources, that have a color temperature of 4000K, they both look exactly the same as they both are on the same spot.

Correlated color temperature (CCT)

Correlated color temperature is used when the light source is off from the planckian locus. If CT defines the exact point on locus, then CCT defines the perpendicular line which runs directly through that exact point. So if a light source is off from the locus, then CCT is the CT point which is closest on the locust.

So for example if a light source has a CCT of 4000K, that means that it can be on any point on the line that runs through the 4000K point on the locus.

You can see these lines on the image.

Typically a light sources color temperature is announced as CCT. So if it is said that two light sources have a CCT of 4000K, this means that they are on the same line that runs through the 4000K spot, but may, in fact, look totally different.

CIE 1960 Chromaticity Diagram

CIE 1960 Chromaticity Diagram (image source)

Chromaticity coordinates

Usually, light source’s chromaticity is defined in diagram as chromaticity coordinates. In this diagram, you can’t determine that CCT is the shortest distance to the locus. You can see the chromaticity diagram in the image below.

(x, y) Chromaticity Diagram

(x, y) Chromaticity Diagram (image source)

So when you have three luminaires which have the same 4000K CCT, you can have three totally different colored lights.

If the light has a greenish white light, that will mean that the chromaticity coordinate is above the planckian locus.

If the light has a purple tone, then chromaticity coordinates are below the locus.

If the light is normal white light, then the chromaticity coordinates are on the locus or at least very close to it.

So please remember that staring at the CCT doesn’t always tell you everything. If you use two different light sources with the same CCT, you should always check the coordinates and see if these two are actually the same color.