J1mbo

Lost with DALI/KNX Lights (single room)

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I'm completely lost with DALI etc and hoping to find some help here! Current setup:

 

 

Works OK (though driver is always very hot).

 

I want to add this to HomeKit and have enough electronics, RaspberryPi and HomeBridge experience to glue the lot together once I figure out what's needed, and I want to retain a simple dimmer knob on the wall.

 

I probably have too many questions to list but am looking for a general approach and pointers - even if this means replacing the DALI stuff. I do want to retain high-frequency drive for the LEDs (sensitive to flicker).

 

Many thanks!

Edited by J1mbo

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The fundamental challenge you have here is two controllers trying to drive the same lighting fixture. DALI (and DMX) are really a 1:N relationship of controller (bus master) to actuators.

You'll need to decide whether the rotary knob or the RaspberryPi is the master, and have the other controller redirect commands to that master and hence to the lighting.

You didn't mention if this is the ONLY DALI device in the house, but I'm assuming it is, in which case it seems a bit overkill (and adding KNX even more so).

Personally I'd fine a simply constant voltage LED strip driver that takes some kind of digital input (Wifi HTTP, and bluetooth are common, but there's lots of alternatives), drive that from the PhPi (or ESP32) and have a big rotary dial as an input to the microcontroller.

 

If you do want to keep with DALI, getting one of these HTTP driven controllers may be a good place to start

https://www.amazon.co.uk/dp/B081TNRGMN/

 

from 

 

 

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On 12/01/2022 at 13:39, J1mbo said:

I'm completely lost with DALI etc and hoping to find some help here! Current setup:

 

 

Works OK (though driver is always very hot).

 

I want to add this to HomeKit and have enough electronics, RaspberryPi and HomeBridge experience to glue the lot together once I figure out what's needed, and I want to retain a simple dimmer knob on the wall.

 

I probably have too many questions to list but am looking for a general approach and pointers - even if this means replacing the DALI stuff. I do want to retain high-frequency drive for the LEDs (sensitive to flicker).

 

Many thanks!

So do you have a KNX system for control via HomeKit you want to interface to a 24V DC LED tape? Looks like you have an added stage of the DALI interface, so were you planning on going KNX-DALI Driver-LED Strip?

 

You could do this so many ways. You could drop the DALI and go KNX or mains dimmable via KNX mains module to a 24VDC PSU and lose the added complexity.

 

What is the power supply rating and how many meters of tape and what is the W/m? I tend to spec power supplies and drivers etc. with about 20% spare capacity to reduce load and hopefully heat, leading to a longer lifespan. 

 

 

Edited by Carrerahill

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Thanks for the replies!

 

There are six lengths of single colour 24V  LED tape totalling 70W. The current driver is 100W rated.

 

Im sure there are better products to use and that’s exactly the ideas I’m looking for. Has to work with a simple knob on the wall but also be HomeKit controllable however so - and of course not flicker at all.

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12 hours ago, J1mbo said:

Has to work with a simple knob on the wall but also be HomeKit controllable however so

I think one challenge with this is most rotary knobs have end stops for 0 and 100%. This is difficult to work with a remote control, as you either need to motorize the knob to move the the set location (as was very popular for the big volume knob mid range hifis in the 90s) or find one without end stops, which does remove one of the nice tactile feedback elements of using a knob.

That is a roundabout way of saying, I've not been able to find anything more convenient that meets this need.

My current thought is use a 0-10V rotary dial like https://www.aliexpress.com/item/32923159930.html

feed that into the microcontroller, and then have that drive an LED dimmer like https://www.aliexpress.com/item/1005002863778354.html

 

12 hours ago, J1mbo said:

and of course not flicker at all.

do you know minimum PWM frequency to meet this need? The one above is 500Hz which feels like it should be fine. It depends a bit on the exact LED used, if you have diffuser, and, in my experience, whether the emitter is directly visible to the eye or if it's only visible via reflection off a surface (which generally gives a much nicer light anyway)

 

 

 

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Thanks for the ideas and links. The current controller is 4kHz which looks great to me even at minimum brightness, but that is my only point of reference I have. The tape is in plaster-in aluminum profile in the ceiling (i.e. directly shining downwards into the room) and has opaque diffusers fitted. It is 7W per meter, fixed 4000K.

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3 hours ago, joth said:

I think one challenge with this is most rotary knobs have end stops for 0 and 100%. This is difficult to work with a remote control, as you either need to motorize the knob to move the the set location (as was very popular for the big volume knob mid range hifis in the 90s) or find one without end stops, which does remove one of the nice tactile feedback elements of using a knob.

That is a roundabout way of saying, I've not been able to find anything more convenient that meets this need.

My current thought is use a 0-10V rotary dial like https://www.aliexpress.com/item/32923159930.html

feed that into the microcontroller, and then have that drive an LED dimmer like https://www.aliexpress.com/item/1005002863778354.html

 

do you know minimum PWM frequency to meet this need? The one above is 500Hz which feels like it should be fine. It depends a bit on the exact LED used, if you have diffuser, and, in my experience, whether the emitter is directly visible to the eye or if it's only visible via reflection off a surface (which generally gives a much nicer light anyway)

 

 

 

Should be no flicker on a good constant voltage LED source as it dims by reducing voltage. Plenty of good 0Hz LED CV supplies.

 

 

Edited by Carrerahill

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