How hard can it be to control color LEDs using ZigBee? It may sound simple, but it’s fraught with hidden difficulties.
ZigBee is a low-power, low-data rate wireless standard for control and monitoring that allows us to control large numbers of lamps with battery-powered remote controls and also to link into internet connected control devices such as smartphones.
There are two ZigBee profiles that give us control of color lamps – ZigBee Light Link and ZigBee Home Automation, both designed to control large numbers of lamps in the home. To allow us to control many bulbs and to give good battery life on a remote control, the amount of wireless data that can be sent has to be limited. So, for example, to move from one color to another, it is impractical to send messages defining every color step on the way, the control protocol has to allow some intelligence in the lamp itself. ZigBee enables this by providing several ways that color can be represented.
The smartphone provides a great user interface where you can pick colors from a photograph or picture, or use a color chart to choose colors. It’s a lot harder for a simple remote control with limited functionality. In this case, a color display is not available and the simplest approach of mixing Red, Green and Blue is highly unintuitive for setting the right color. Defining color and brightness with Hue, Saturation (“Colorfulness”) and Brightness gives us an easier way to represent most colors on a simple remote control. A color wheel provides a way to access a wide range of colors with a simple circular user interface. You can also provide a color loop command where the bulb will continually traverse around the color wheel. Brightness and saturation can be set by simple up/down commands.
I’ll be discussing this and other issues related to controlling color lights with ZigBee at the European ZigBee Developers’ Conference next week in Munich. If you’re there, and you’d like to join, it’s on Thursday 7th November – Session 6 on “ZigBee Light” – and I’ll be presenting at 12.00 CET.
If you’re interested in Wireless IoT technologies for the home more generally, I’m also at the Wireless Congress in Munich on Wednesday 6th November, during Session 1 – “Wireless Internet of Things” – where I’ll be presenting at 10:30 CET.
Or, feel free to drop me a line in the comments below!