CBUS & DALI Dimming

Hi All.

In my previous house, built 20 years ago, we used CBUS for all lighting which worked fine with incandescent lighting.

Not long after that, I created a separate test rig to try multiple "dimmable" LED options (multiple lights, drivers, load correctors, pairing, etc) that claim to enable satisfactory dimming behaviour with newer LEDs and the phase cut dimming used in the previous CBUS dimmers. This proved to me what I had already anticipated (and what you would predict from how these loads work) - that they are largely inadequate or inconsistent workarounds.

So I added a DALI gateway and demonstrated to myself that DALI dimming was the most reliable and predictable way to provide consistent LED dimming if I was going to use CBUS again. In the interim, Clipsal released the new improved DALI gateways (with built in DALI power supplies, etc) which seemed to indicate to me that Clipsal had come to a similar conclusion.

So I recently completed our new house, using multiple DALI gateways for all the dimmable lights (which is almost all of them), and CBUS relays for the rmaining simple switched loads (similar to what was described in this recent post (https://www.cbusforums.com/threads/cbus-with-all-lights-over-dali.11499/ from razor77). As people have mentioned, the evolving software situation requiring the use of two separate applications that don't always play nice was challenging, but we got there.

Everything works reliably and consistently, but I found that some driver-fixture combinations/groups have a limited dimming range, whilst others have a full range. All the drivers (multiple types) claim 1-100% dimming in their documentation, but when queried in the C-Bus Commission software, the fully dimmable combinations show levels from 1 - 254, but the others show limited ranges (eg as in screen shots below 78 - 254 or 99 - 254) which can't be adjusted to anything lower.







In practice, these lights dim to what looks like about 30% to the eye. This is a bit disappointing after the effort (and cost) to deploy a more modern dimming solution, but is probably my own fault for not paying attention to the detail of the actual fixtures finally chosen. Can someone explain how these levels are identified or generated in the software? I was intending to replace drivers or fixtures to achieve a full range of effective DALI dimming everywhere, but don't want to have to physically test each combination before I can order what to use. Some combinations seem to use PWM dimming which should be ideal, but others use "amplitude dimming" or other terms that seem somewhat unclear.

I've found many lighting suppliers are still largely out of their depth when trying to discuss things like this, and engagement often ends at "Yep, it's DALI dimmable".

Any guidance on what to look for (and what terminology to use) would be greatly appreciated.

Sorry about the long post. Thanks for any info.