Led Colourfade

In my Velbus Home installation I have a VMB4DC and a VMBRGBDC (with seperate Power supply) to program a RGB led strip in my kitchen. Everything works fine and on a VMBGPOB i programmed some static colours on several different knobs en pages. But what i really want is to make a long colourfade (eg Rainbow). I tried several things but nothing really works. Is it possible to make such a fade or is it to heavy load for the Databusline anyway? Since more and more lightfixtures are led or colourleds it has to be possible to integrate some fadeprograms/effects in the software. Does anyone know a good and easy way to program for example a fade between 3 colours (3 dim channels) for lets say 30 minutes,so that in these 30 minutes the colours slowly change in a cycle.


I’ve just done this for a client.

It’s not strictly a rainbow colour fade, but it does cross fade between different colours.

It’ll require using a spare virtual relay as a trigger.


Edit the multi-step dimmer profiles within each VMB4DC channel that are used for your RGB LED.
I set one as a ramp up.
The second as a ramp down.
And the third as a ramp up but with very different steps.

(Tip, use different amounts of steps in each dimmer channel to increase the range of colours your effect will step through.
Also, don’t fade to 100%, as you’ll not be able to decern a colour change)

The next step is to assign 3 actions to the output of the virtual relay channel.

The aim is for the ‘closure’ of the relay to trigger the next step in the multi-step dimmer, with whatever fade time you choose.

The next step is to program an action on any of your input devices to cause an interval timer to run on the Virtual relay channel.

It only needs to be the minimum close time, but the pause time is the interesting bit.

Once started, your virtual relay pulses should create a nice random cross fade.

One tip, you will need to program a button to stop the cross fade.

This will require 4 actions.

3 to switch off / dim off the 4DC dimmer channels, and the 4th to stop the interval timer.

Please let us all know how you get on.

Or if you come up with a better solution.

Of course, if you’re looking for something more predictable, you’ll have to map the function to an external logic device.

Maybe a small Linux box with some clever middleware software?

Thanks for your well described answer. I’ll let you know if i get it to work also,
It’s not a very easy sollution i must say but at least its a sollution ;-)next week i will try to program it.

There is a solution that is, let’s say, mathematically and technically very correct (perfect cycling of colors), but it involves 6 virtual (or real) relays.
We’ll name them:

  1. R on
  2. G on
  3. B on
  4. R off
  5. G off
  6. B off

These relays are coupled with the corresponding color (R, G or B) on the VMB4DC in the following manner:

  • the on-relays with action no. 11 “slow on”, let’s say 5 seconds
  • the off relays with action no. 6 “slow off”, also 5 seconds

Now you can make one color, when it switches off, turn on another one in cycles.
This is done as follows:

  1. VMB4DC channel R will do two actions on release:
  • start relay “G on” with action no.17 “trigger-on-release timer”, for just one second (a pulse)
  • start relay “B off” with same action a sabove
  1. VMB4DC channel G similarly, on release, sends a pulse to
  • relay “B on”
    *relay “R off”
  1. VMB4DC channel B similarly, on release, sends a pulse to
  • relay “R on”
  • relay “G off”

This gives a nice cycling through color blends which always goes well since one color triggers the others.

Now you just have to get it started and stopped.

To start: choose a button and connect it

  1. to relay “R on” with action no.16 “non retriggerable timer”, 1s
  2. to relay “G on” with action no. 22 “non restartable timer with slow on/off”, with parameter times 1s, 2s and 2s resp. (the important thing is that VMB4DC channel G is turned from on to off when R is at its peak, maybe there are better solutions for this detail)

To stop, do a “forced off” during 1s of all the relay channels and all the VMB4DC channels (otherwise you risk getting into a loop).

Seems to work here. Looks good, but only disadvantage is of course the 6 virtual relays that are needed…

And there are also some interesting possibilities using only 3 relay channels and the VMB4DC action no.20 “restartable timer with slow on/off” or no.23 “slow on at press/slow off at release”. This gives you a time for dimming on, an uptime, and a time for dimming out in one action. So you can produce a saw-tooth signal on your three colors. If you then succeed in triggering them with a correct time shift, using 3 virtual relays, you have color cycling also…

If anyone is looking for what I’m suggesting, have a look at the attached VLP file.

Good luck


ColourFade.vlp (14.5 KB)

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