LEDgardener

guys. as you might know there are these (cheaper lm/$ than most COBs) Bridgelux Vesta LED-modules that have 2 different color temperature LED rows.
i have a few of these i want to run in parallel off my dimmable CC driver.

now here's the thing: i want to be able to control the color temperature with a slider (or similar), so that when it is in the middle both rows light up equally, and when i move the slider to either right or left only the cold- or warmwhite led rows are on. the current should just be gradually guided/divided to cold, warm or both LED rows.
what piece if electronic circuit or device would i need for that?
Thanks in advance for your help

i guess the only easy way is to add a 4-position-switch. however this would only allow for toggling between cold, warm, both or OFF. not gradually adjust CCT.

do you see a way to get gradual CCT-transitioning using only 1 potentiometer or similar?

I've been thinking about trying the same thing.

I believe the simplest way to accomplish this is with two drivers and a linear 100k voltage divider (or 3 contact potentiometer) as the dimmer.

One driver gets the 2700k strip and the other gets the 5000k. The pot 'fades' between them.

ATPinMotion wrote: ↑

Mon Dec 31, 2018 2:44 am

the simplest way to accomplish this is with two drivers and a linear 100k 3 contact potentiometer

theoretically it should have worked because when the pot is turned all the way "up" it has max resistance (ohm) over contact 1 and 2 but minimal resistance over 2 and 3. and when it's all the way turned down it's the opposite.

i guess it also depends on the driver used. anyway: with my TRP drivers it's not really possible to dim them inversely to each other with a single 3 contact potentiometer. as soon as i connect the second driver's dimming leads to the 2nd & 3rd contact of the potentiometer it dims differently (maybe because of voltage flow?).

guess it needs fully seperate driver and dimming circuits, which is lame. i bet there's a way somehow but since i have almost zero knowledge of electronics i can't think of one.

Interesting, pos to pin 2, negative 1 and 3?

ATPinMotion wrote: ↑

Wed Jan 02, 2019 10:31 pm

Interesting, pos to pin 2, negative 1 and 3?

i was not sure what u meant, but i changed polarity of the dimming wire on the potentiometer and now it works.

Good work! How does it look? (The light quality I mean)

Happy to be of assistance. I think setting the vesta's up the way you did is really slick. Frankly I'm surprised more people aren't doing this - maybe they are and just not talking about it..?

Personally I'm still waffling between the Vesta's and QB22 strips for a veg tent. Im just getting into LED's. Just got a 200watt COB fixture (20x 20watt cobs, run at half power), and it puts out a fair amount of heat, even at 160lm/w. Thinking anything I can do to up the efficiency will make for happier plants.

As much as I would like to run some veg trials on colour temperature, I'm thinking qb for the veg tent and Vesta's for my workshop!

ATPinMotion wrote: ↑

Fri Jan 04, 2019 4:15 pm

How does it look? (The light quality I mean)

it's really good. nice neutral CCT when both rows are used. actually i will be using the Vestas for photography/video/general lights as well as for starting plants indoor. i also have 2 F-series 4000K but they are CRI80 and therefore not as versatile.

when i first found the VESTAs i couldn't find a single forum entry anywhere on google.
but as you can see here among all LEDs with CRI90 and above vestas pretty much beats any COB (sorted by lm/$) on digikey (as of Oct. 2018) if you are still not sure about which one to chose (F-series or Vesta) this graph by livinglight sure put it all together: LM561c 3000k 80CRI vs VESTA (combined CCT)

Thanks for the info - interesting comparisons.

I think I will have to try both and see for myself!

Osram and NASA seem to like 2700k with uv, blue, and reds programable. They will have this system on the market next month. https://hortamericas.com/catalog/hortic ... tofy-rl-2/