What you Need to Know when Buying and Using RGBW LEDs

More and more stores and restaurants begin to use colorful light inside and outside. There are so many possibilities with color LED lighting that companies contract more and more illuminating consultants. Multi-color LED light bulbs have become so cheap that they can replace all existing lights at home. With RGBW LEDs you get the same white as with traditional LED lights, you can dim your light and you have many colors to create a mood.

Can you control an RGBW LED with an Existing Switch?

It depends. With an RGBW LED you need to be able to change the color and to dim the LED. An on-off switch cannot do this. So you typically use a separate remote control or an app on your phone or tablet.
I would recommend to avoid using the wall-mount switch for two reasons. First, if the switch is off and you want to use the remote control, then you cannot control the bulb because it has no current. Second, if you use the wall switch to turn on the light, then the bulb will have the color and brightness as it was when you turned off the wall switch. So you might get a very weak light. Imagine, you are in a hurry and are looking for something. Then you turn the wall switch on but you do not get much light. You will have to find the remote control first to make bright light.
One solution would be to replace the existing wall switch with one that wirelessly sends commands to the bulb. The switch could have two on buttons, one for the last state and one for bright white. Or it could even allow to change color and brightness. I will not go further into alternative switches in this article.

How Expensive are Good Quality RGBW Lights?

You can get RGBW lights for about twice the price of a standard white LED light. However you can also pay much more. A standard non-dimmable 800 lumen LED costs about 9 EUR / $10 online. Concerning RGBW lights, you could choose a Limitless or MiLight (not spelled MyLight) RGBW bulb with 800 lumen for only about 22 EUR / $23. But you could also choose the much more expensive Philips Hue with 600 lumen, which is about 60 EUR / $65.
This article will cover RGBW lights from one of the following brands: Limitless LED, MiLight, Easybulb, IWY, AppLamp, ROCKET LEDS. Note that there are differences within RGBW lights. The number of watts, which correlates with the maximum number of lumen differs. Then the white mode may display warm white (WW) with 2700K-3200K or cold white (CW) with 6000K-6500K. Further, there are different sockets available and adapters for sockets can be bought. Also the allowed input voltage range of the bulb should match the voltage with which the bulb is supplied.

What do you need?

At a minimum, you will need one or more RGBW light bulbs. You can already use them as white led without any other parts.
To control the RGBW color and to dim it, you need a controller and an app for your phone or tablet. The controller is shown in the next picture. Or you can use the remote control which does not need the controller because it sends 2.4 GHz signals directly to the bulb. See the second picture below. Usually, you will start with a kit that has a controller and remote control, so that you can use both in parallel.

How to Set Up the RGBW Lights?

You link the RGBW light to your remote control as follows.
First you screw the light in the socket. Then you turn on the wall switch and after about one second, you press one of the four on (I) buttons at the bottom of the remote. If successful, the light will flash a few times as confirmation. Now you can control your light with the remote.
The four on-off buttons at the bottom are called groups. You can assign one or more lights to each group. After you press the on button of a group, you can set the brightness and color of all lights in that group. So to change the brightness of a light that is in the second group, you would press the second on (I) button at the bottom and then use the slider to change the brightness. If you hold the on button for a few seconds, then the light will become white.
A bulb can only be assigned to one group. To release the bulb from a group, you turn on the wall switch and after about a second you press the on (I) button to which the light is currently assigned about 10 times in a row as fast as you can. Pressing it 20 times will not harm. When the release was successful, the light will flash a few times to confirm.
Assigning a bulb within a app works the same. How to set up the controller, which is used by the app, is described in the manual of the controller. My experience was that the setup with the app did not work at the first time. Resetting the controller and trying over again solved it. If you unplug the controller from power supply then the settings should be saved. However my experience was that the app did not want to talk to the controller after plugging the controller back in. So I would recommend to have the controler permanently power supplied.
One more note, if you set up a group for a light with the remote, then you still have to set up a group for the light with the app. The assignment of the light to a group with the app is saved in the controller, so all other apps on any device in your home network can use this setting.

Which App can you Use?

There are a number of apps to control the RGBW lights. Many of the apps can control the light but cannot set up the controller. The free Easybulb app for Android and iPhone/iPad can set up the controler and it works very well to control the lights. It also supports timer, night sleep mode (gradually dims), music sync, voice control, and calls and message notification.
If you have problems with that app, you can also use the milight 2 app. It does not have advanced functions as timer, but it works very well to setup the bulbs and to control the lights.

For Windows Phone 8, I use the Limitless LightSwitch app.
When you use an app, always make sure that the controller is plugged in.

Can you Set Up a Timed Fade with Raspberry Pi?

Yes you can.
Once the light bulb is assigned to a group with an app, then you can control the light bulb by sending a few well known hex values via UDP. The following picture shows the Android UDP Sender app. The hex value c20055 (also written as (0xc2, 0x00, 0x55) is sent to turn on white light for the first group. To turn off the light for the first group, you would send 410055.

You can find several scripts with google with which you can send those commands to the controller.
On this site, you can find a tool for python to control your light on the command line. In the source code of the tool, you will find the hex values of all commands. If you want the light to turn on at 7 o'clock in the morning and get slowly brighter, you would have to write a script. In the script you can set the brightness and color, then you pause the script one minute and then you increase the brightness slightly. The script could be scheduled with a cron job.
You might also be interested in controlling the RGBW light with a home automation software. The OpenHub Home Automation software, for example, has a binding for MiLight (see here).