Hi,
I'm designing a downlight which is going to be rather extreme in terms of light features.
It will have:
That brings the total to 140 LED lights.
The combination of LED's might change but this is roughly the gist of it.
Thus far it's not a super complicated project.
It becomes slightly more complicated if i were to make all single color as "1 channel" dimmable. So effectively that would be just 6 different PWM levels to dim (1 for warm white, 1 for daylight white, 1 for amber, 1 for red, 1 for green and 1 for blue).
But i want to go a step further.
I want to individually control each and every single light point in this light.
Picture this light to be a circle. All the leds would be spaced around the edge.
If they are individually addressable then you could have actual animations happening there. So for instance a green dot circling around, but obviously much more then this would be possible.
Another thing that adds complexity is that i'm using LED's that don't exist with build in led driver (like the WS2813B).
Note that i must go this route because i want high quality white/warm white LED's (like this one). The White/warm white ones that you can buy with LED driver build in are of poor lighting quality. They are good for other purposes, not for a main lighting goal.
In the best case scenario i can use RGB leds with build in LED drivers to make them individually addressable, but i'm not counting on it.
So this brings me here as i'm not sure at all how to tackle this.
I do know of a few possible solutions but they all seem to have downsides as well.
But before i describe that further, please be aware of these PWM conditions.
I want the LED's to dim smoothly, also at the levels of - say - fading in from 0 to 10% brightness. When gamma correction is applied, a 10 bit PWM duty cycle is really not much, specifically in the low levels. With 10 bit you can actually see the individual brightness steps at the low levels. So, at the very least, the duty cycle must have a resolution of 12 bits. Preferably even 14 bits. The PWM frequency should also be "high enough" to consider it flicker free. Also at the low duty cycles.
Also look at this awesome video about LED frequencies.
I like to aim at having a 10Khz frequency with 12 bit duty cycle resolution as the lowest requirements.
More would be better but this seems to be good. It can be better but lets not start too difficult just yet for this project
What are my options to get at these specs?
There are LED drivers out there that seem to be capable of this. For example just 3 of these might even work if i understand the specs correctly. The downside here would be a wire to each LED. Whereas a "data line" would be more appealing to me. On the other side, if there would be a data wire then i'd probably need to place a chip next to each led to translate that data for that LED to a PWM. Thus in effect having 120 PWM driver IC's, that's overkill i'd think.
So yeah, i'm really looking for the best way with the minimal IC's and wiring to get this working.
I'm assuming that if i wire each "led group" (so all warm whites in one matrix, all amber lights in another matrix, etc...) that i can use those matrix ways of controlling them individually too.
In that case, i'd have 6 matrix sets.
I'm looking forward to your replies
Cheers,
Mark
I'm designing a downlight which is going to be rather extreme in terms of light features.
It will have:
- ~30 warm white LED's with a 95+ CRI
- ~30 daylight white LED's with a 95+ CRI
- ~20 candle/amber light LED's (for the really warm light output)
- ~20 RGB LED's (so 3-in-1 LED's thus in terms of actual "light points" this is 60)
That brings the total to 140 LED lights.
The combination of LED's might change but this is roughly the gist of it.
Thus far it's not a super complicated project.
It becomes slightly more complicated if i were to make all single color as "1 channel" dimmable. So effectively that would be just 6 different PWM levels to dim (1 for warm white, 1 for daylight white, 1 for amber, 1 for red, 1 for green and 1 for blue).
But i want to go a step further.
I want to individually control each and every single light point in this light.
Picture this light to be a circle. All the leds would be spaced around the edge.
If they are individually addressable then you could have actual animations happening there. So for instance a green dot circling around, but obviously much more then this would be possible.
Another thing that adds complexity is that i'm using LED's that don't exist with build in led driver (like the WS2813B).
Note that i must go this route because i want high quality white/warm white LED's (like this one). The White/warm white ones that you can buy with LED driver build in are of poor lighting quality. They are good for other purposes, not for a main lighting goal.
In the best case scenario i can use RGB leds with build in LED drivers to make them individually addressable, but i'm not counting on it.
So this brings me here as i'm not sure at all how to tackle this.
I do know of a few possible solutions but they all seem to have downsides as well.
But before i describe that further, please be aware of these PWM conditions.
I want the LED's to dim smoothly, also at the levels of - say - fading in from 0 to 10% brightness. When gamma correction is applied, a 10 bit PWM duty cycle is really not much, specifically in the low levels. With 10 bit you can actually see the individual brightness steps at the low levels. So, at the very least, the duty cycle must have a resolution of 12 bits. Preferably even 14 bits. The PWM frequency should also be "high enough" to consider it flicker free. Also at the low duty cycles.
Also look at this awesome video about LED frequencies.
I like to aim at having a 10Khz frequency with 12 bit duty cycle resolution as the lowest requirements.
More would be better but this seems to be good. It can be better but lets not start too difficult just yet for this project
What are my options to get at these specs?
There are LED drivers out there that seem to be capable of this. For example just 3 of these might even work if i understand the specs correctly. The downside here would be a wire to each LED. Whereas a "data line" would be more appealing to me. On the other side, if there would be a data wire then i'd probably need to place a chip next to each led to translate that data for that LED to a PWM. Thus in effect having 120 PWM driver IC's, that's overkill i'd think.
So yeah, i'm really looking for the best way with the minimal IC's and wiring to get this working.
I'm assuming that if i wire each "led group" (so all warm whites in one matrix, all amber lights in another matrix, etc...) that i can use those matrix ways of controlling them individually too.
In that case, i'd have 6 matrix sets.
I'm looking forward to your replies
Cheers,
Mark