VMBDMI-R % for dim value is not same range as % for minimum dim

Minimum dim set to 0%
I have a lamp that does not begin to show brightness until 60% DIM. Above that is very smooth fading all the way up to 100%
Anything less than 60% that is just OFF.
So I set the minimum DIM value to 60%.

Switch lamp on… it comes on at nearly full brightness.
Available DIM range from 1% to 100% looks more like 96% to 100%… All are almost full brightness, nothing gets as dim as 60% was before.

In order to get the operation I need I have to set minimum dim value to 30%
Then I get smooth dimming all the way from 1% up to 100%.

So it seems % for minimum dim is not the same as % for dim when min dim is 0.
How can I find sensible minimum dim values if I cannot just adjust brightness and note DIM % value and then use that value for minimum dim?

This depends on the lightbulb you are using … some of the more expensive LED bulbs have a minimum of voltage they need before they actually switch on …

Why Cheap LED Lights Keep Glowing - YouTube

Thanks but that is not the problem here.
The problem is that the % values used for Minimum Dim are not the same units as the % values used for dimming.

eg. if a lamp comes on at 50% (completely reliably) then setting 50% as minimum dim value does not give you a dim lamp at all… it gives you a fairly bright one. The corresponding value to use in minimum dim is a lot lower and seems only findable by trial and error which is a very fiddly process (you cannot find it by adjusting the value in “operate” of the device. Instead you have to configure the device, then sync changes back to the device, then operate the device and find that the value you set is wrong… AND REPEAT until you get it right.

I like minimum dim value.
Without it I find that my wife somehow manages to get lamps (set to on/off memory or dim) stuck in OFF (or appearing to be OFF)… where they switch on and off between eg. 0% and 10% (which still looks like OFF) every time you press a button. This gives the impression that a lamp is not working.
Without min dim there is also a delay at switch-on whilst the dimmer fades from 0 to 50% where nothing happens. This makes the control feel unresponsive.

Ah, yes… that would be a Velbus thing… if the minimum for on is 70% (lets take a big number for reference for Velbus staff) - and the dimmer itself still thinks it has to start at 0% when switching on the light - thats bad… - Lets say the dimmer takes 1 second per 10% - you’d still have to wait 7 seconds for the light to even start responding…

ideally the 70% should be 70% of it’s output power - which should be equal to 1% of the actual dim value used in the controller…

For the brightness part - so as explained in the video - some bulbs need to have a minimum of power (voltage/amps) to go through them to even start shining… a gated control switch (automatic) is placed inside the lamp circuit that triggers the lamp to on with a minimal setting within the lamp of let’s say 80% of power, the lamp by default turns on at 80% brightness only and can go to 100% with more power - but capacitors in the circuit might even prevent that also and provide 100% brightness only (despite the 80-100% load factor) by playing with voltage versus amps (at lower voltage, the lamp can draw more amps to achieve 100% power anyway) - this is done on purpose to prevent lights flickering as the voltage in your house is not a steady 230V, but usually fluctuates…

you cannot go any lower as it will drop the voltage (or current) to below its minimum value and the gated control in the lamp will open and shutoff the lamp completely…

its not something that Velbus or any controller can control. They (not sure which Velbus uses) can control the amount of Amps or Voltage - or even send quick pulses - but the gated trigger will only switch on the lamp when a minimum has been met…

Mostly its LED’s that have this circuitry - that is why there are special LED controllers - with diming capabilities using 0-10V, KNX, BACNET, DALI, etc protocols that work with the specific diode to ensure a smooth dimming and continuous output brightness.

Have you tested tested this? Or is this a guess?


My experience with setting up minimum dim is as follows.

Ensure no minimum dim is set.

Using the operate function within Velbuslink, find the point at which the lamp goes off when coming down.

Also find the point at which the lamp comes on from Zero.

These will be different values due to the electronics within the lamp.

Make a judgment as to the best compromise value.

Set this value as minimum dim.

Sync the setting

What you should see now is that the Dim % should be within the range of the minimum dim value and full.

As in

During operation, setting the dimmer to 10% should go to 10% of the difference between the minimum dim level and full.


Thats just the thing… THAT is what I would expect and would be nice and simple to set up however it’s not what I see.
Doesn’t matter what LED her I try it with (very well behaved constant current or voltage LED driver, or dimmable filament LED bulb(s), or Aurora in-ceiling downlights… they all have the same small issue.
If I determine the minimum dim value the way you suggest and use that same value as the minimum dim value then lamps come on far too bright.
eg. (min dim=50% with brightness then set to 1%) is WAY brighter than (min dim=0% with brightness set to 50% or 51%).
With a lamp that comes on/off at 50% (like the Aurora MPRO - fairly consistent on or off) I need to set minimum dim to about 20% (not 50%) to get the full range available (and then it dims smoothly from very dim all the way up to full brightness). If I set min dim to 50% then most of the lower dim range is not available.
The % values used by min dim are not the same as the % values used by dimming.
I have a lot of Aurora MPRO downlights - they’re OK, I just use 20% as min for all of them. But I have lots of different filament LEDs and LED strip drivers and they are all different so I would prefer not to have to fiddle about quite so much (and also any time I change a bulb).

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In that case, a separate 0-10V driver for the LED’s is probably the way to go … its way more consistent , and its how the system is supposed to work… - my house is entirely wired up with

180mA PHASE-CUT/1–10V SR


I’ve linked the 0-10V cable to each circuit (usually consisting of 6-8 LED drivers each with their individual LED’s)

@MDAR - seems this was one of the hits from my search engine…

230V LED’s simply are not built to reliably dimm - even if your LED’s are TRIAC dimmable, they are not as effective as indivual controllers in a 0-10V/Dali/other protocol…

"Because of how poorly it dims, a TRIAC dimmer has a limited dimming range. This limits the dimmer’s overall range of motion. Using this kind of dimmer has this drawback.
There is still a very slight amount of current going through the TRIAC switch even when it is turned down to its minimum setting. This is because the TRIAC switch’s function is to start electrical flow"

Hi RCZ, I think you are missing the point.
Yes, I know about VMB4DC and the finder 10V dimmers… I have some.
It’s not the LEDs. They dim fine, and consistently.
It’s the VMBDMI-R firmware.

I cannot switch to euro-style 10V dimming or DALI everywhere… it would really limit choices of lamp and luminaire (and chandeliers). Too many lamps here with SES or ES fittings. Plus all the 5A circuits (5A sockets at wall) and all the fire rated downlights.

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My Aurora MPRO downlights come on at about 44% normally.
I have found the best min dim value for these is about 12%.

If I set min dim to 12% and then sync… after that I get a good dim range from 1% to 100% (all illuminated, even 1%).

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