LED Dimmer for 220-240V Lamps HowTo

This article is primary for those in a country with a 220-240V~50Hz electrical system.
Do you know how it is when you sit in a room, somebody comes in, turns the light on and it becomes way too bright? If you turn off the light again, then the other person won't be satisfied. So why not agree on a level between no light and full brightness?
This article explains how to dim 200-240 Volt Dimmable LED light bulbs. Two LED Dimmer technologies are presented with which you can control the brightness from a wall switch. Then, a specific LED Dimmer is chosen and discussed in detail. If you want to control not only the brightness but also the color, then see WHAT YOU NEED TO KNOW WHEN BUYING AND USING RGBW LEDS.

Why is it Difficult to Dim LED Lights?

The main reason, why dimming an LED is difficult, is because the dimmer and the LED must fit together. If they are not compatible, then the light bulb will flicker or make a humming noise.
Generally, a dimmer that is designed for LED lights will work together with more dimmable LED lights than a dimmer for light bulbs with filament. However you might find dimmable LED lights that work perfectly good with an existing dimmer. Further, even if you have a dimmer that is specifically for LED lights, then there are still many LED lights that will not work properly.
These difficulties have been addressed in two ways. First, you will usually get a list of compatible light bulbs when buying an LED dimmer (see eg Compatibility lists for dimmer on this Osram web page). Second, there are solutions to dim the light by sending digital commands from the dimmer to the light bulb.

What are the Two Technologies to Dim LED bulbs?

The first approach is to dim the light bulb by limiting the current within the dimmer. The disadvantage with this approach is, that the LED must be compatible with the dimmer. You cannot reliably say if a dimmer model is compatible with a light bulb model unless somebody has tested it.
The second approach is that the light bulb dims itself based on digital commands received by wire or wirelessly. Here the LED must also be compatible with the dimmer. However, if both implement the same transmission standard, then they must be compatible. Sending commands directly to the light bulb is not new. Colorful LEDs as RGBW LEDs, have been controlled by wireless signals for quite some time. Rather new, however, is to control colorful LEDs and white LEDs by sending digital commands through the electric circuit. An implementation of this is the industry-open standard called LEDOTRON. LEDOTRON was created by the light manufacturers Osram and Radium, together with manufacturers of electrical installation technology. Philips is not part of the group. With LEDOTRON, the dimmer is called a control unit. As the name suggests, it can do more than control the brightness. It can also adjust the color temperature and the color, if the light bulb supports it. You cannot control lights in the whole house, but only within the electric circuit of the control unit and the light bulbs. See LEDOTRON Website.

Which Technology should you Choose?

You can dim LED lights with both technologies. With LEDOTRON you have the advantage that you must not depend on compatibility tests. However LEDOTRON has the disadvantage that it is three times more expensive. Kits with control unit and light bulb currently cost about 100 EUR. See Amazon.de or Amazon.co.uk. Further you cannot control the light centrally from a home-automation software or from an app because the signal is only transferred in the electric circuit of the light bulb.
With the intertechno ITDM-250 dimmer for LED lights, you only pay about 35 EUR. Further, you can control the light with an 433 MHz transmitter. A disadvantage may be that you cannot use a round knob to control the dimmer (explained below). Another disadvantage might be that you cannot set the light to a specific brightness value. Rather you can only say, "I want it darker" and then, "stop that is dark enough" (explained below).
For the remaining of the article, I will focus on the intertechno ITDM-250 dimmer.

What Parts do you Need?

You will need a dimmer, a dimmable LED light and optionally a switch.
If you need a new dimmer, then I would recommend the intertechno ITDM-250 dimmer in the following picture.
Intertechno also has another dimmer for LED lights, the ITL-250. I do not recommend the ITL-250, because, with that one, the Osram dimmable LED was flickering.
As it says on the front, the dimmer is made for 220-240 Volts dimmable LED/ESL with 3-24 Watts. Its size is 45 mm x 41 mm x 13 mm. The dimmer can be controlled with an existing switch or with intertechno teaching switches and remote control transmitters. It does not need batteries.
The dimmer costs about 35 EUR on Amazon.de (see here). Many other LED dimmers are in the 50-100 EUR range.
I tried the dimmer with two different dimmable 10 W LEDs. One made a slight humming noise when dimmed and the other made almost no noise. From 1 m distance I cannot hear any noise. The silent one was an OSRAM LED SUPERSTAR 10-W with EAN 4052899911222. It has 806 Lumen, 2700 Kelvin (warm white) and 80 Ra (CRI) Color rendering index. It is about 14 EUR on Amazon.de (see here). If you need more lumen, then you might take a look at a similar Osram LED with 1055 lumen. It has the EAN 4052899153738.

To switch the dimmer, you can use your existing wall socket, or you can use an 433 MHz intertechno sender. The ITW-852 wireless wall transmitter, shown in the right side of the picture, can control one or two receivers. It looks like a rocker style wall-mount switch but it works more like the buttons on a computer mouse. You click and release in the upper half for on and you click and release in the lower half for off. It costs about 27 EUR on Amazon.de (see here). The ITLS-16, shown in the left side of the picture, can control four receivers. Both are battery powered.

Connecting and Programming the Intertechno ITDM-250 Dimmer

The dimmer can be installed at surface or concealed. It can be connected to an existing wall switch or the existing wall switch can be replaced with a wireless one. If you choose a wireless wall switch, then the dimmer could also be installed at the bulb socket. The two white wires would not be used in that case.
I will not give details about how to connect the dimmer. Be advised that mains electricity is dangerous and kills people. Only licensed electrical contractors should perform electrical installations.
Up to 6 transmitters can be paired to the dimmer. To pair a transmitter to the dimmer the electricity must be reactivated. Press the learn button on the dimmer until the dimmer-LED flashes. Then press the ON button on the transmitter. The connected lamp will flash two times.
You should adjust the minimum brightness of the dimmer. There are 4 stages. Initially it is set to the brightest stage. If you use the Osram dimmable LED, then you should use the 3 rd stage. Why is that? It is because an LED light can only light in its minimum brightness after it had a higher brightness. So, if you had set the minimum brightness to stage 1, then you could turn the LED on at a stage 4 brightness and then reduce it to a stage 1 brightness. But if you would turn it off at a stage 1 brightness and then on again, then it would not light up at all.
Intertechno could have designed the dimmer to always go to the maximum brightness when turned on and then fade-out to the last set brightness. Actually, this is how the other Interteno dimmer, the ITL-250, operates. Personally, I prefer how the ITDM-250 works, by going to the last set brightness directly when turned on, even if the minimum brightness must be set higher.
The minimum brightness can be adjusted as described in the Operating Instructions. In short, switch on the lamp, quickly press the learning button twice, use the ON and OFF buttons of the transmitter to set the minimum brightness, press the learning button twice to confirm.

How To Control the Dimmer with ON and OFF Commands

You can control the dimmer with a standard light switch or with an intertechno 433 MHz transmitter. How is that possible to dim the light with a wall switch? To understand how it works, remember that a switch, as it is usually used, either lets current through or cuts current off. The switch, when connected to the intertechno dimmer, cannot cut the current. Rather, it just communicates its current state to the dimmer. It is not any more an electric switch but an electronic one. This is also why you can turn off the light at the wall switch, and turn it on with the transmitter.
So, to turn the light on or off, you use the light switch as usual. If you use the transmitter, then the ON-Button will turn the light on and the OFF-Button will turn it off. Actually, when turned on, the lamp will go to 100 % brightness and then fade-out to the last set brightness. When turned off, the lamp will fade-out quickly, which is quite nice.
To change the brightness you start a dimmer run, in which the dimmer will increase the brightness until the maximum and then decrease it to the minimum and so forth. When the desired brightness is reached, then you stop the dimmer run. You can start a dimmer run any time when the light is on. With the light switch, you start the dimmer run, by quickly switching off and on. You stop it by switching off and on again. With the transmitter, you start the dimmer run, by pressing the ON-Button. You stop it by pressing the ON-Button again.
The dimmer will remember its brightness when you turn it off.

Further Thoughts

The intertechno dimmer controls the brightness of 220-240V LED lamps very well. However I would prefer to use a round knob instead of a rocker style switch. Having a number of existing RGBW LEDs it would be preferable to have a consistent way to control all lights. What I would like most is a wall-mount round knob with which a Limitless or MiLight RGBW lamp can be turned on/off and dimmed.

You may be interested in this article: WHAT YOU NEED TO KNOW WHEN BUYING AND USING RGBW LEDS