I do not have the technical grasp of things to understand how I might accomplish this.
I am also not ready to supplement the green house in the larger picture.
I would love to see how this is done though.
I wonder if you could point me at a couple of the products you are referring to so I can start my homework.
99
I would just ask Fluence what to use. The idea is pretty simple, you would decide you want a minimum of 600 umol/sqm of light intensity 12 hours per day. You connect the photosensor/controller at the canopy to the Fluence dimmer. The light will instantaneously dim or brighten as needed to supplement the sun to get up to 600 umol/sqm. So on sunny days it doesn’t run at all, if clouds come out it cranks up just enough to reach 600.
This is how the pro’s use supplemental LED lighting, this couldn’t be done with HID lighting.
An example photocell, IND356-GE-Aware-Stand-Alone-Daylight-Harvesting-Photocell-LED-Driver-PCD-IN-SA.pdf (224.3 KB)
Though, this one requires a 0-10V supply and is horrendously overpriced. I’ll find some more appropriate ones. As Muleskinner notes, Fluence might have a suggested photocell dimmer that they recommend as well.
Leaving the pigtails unconnected results in 100% output.
I’m pretty sure Fluence uses Meanwell drivers. They have a 3-in-1 dimming option. Resistance mode, 0-10V mode, and PWM mode. That opens up the possibilities a bit. The only problem with the 3-in-1 is it is impossible to get them less than 10% with the dimmers (probably that 1V offset you see).
A photocell and a timer would do it, could get both at the hardware store. No need to mess with the dimming to extend greenhouse hour IMO.
We are topping out at just over 15 hours of sun. There may be a time when I am trying to max out the yield and it might help, but right now, I am keeping up with myself just fine.
Here’s another photosensor for dimming.
Installation information: WS-Install-LS301_03635r3.pdf (530.9 KB)
Probably could be wired as such:
A recent order of a couple of RAY44’s had this driver from “FSP Group” included:
I asked Fluence and they said any control system that works with 0-10v dimming will work fine. 0-10V is the industry standard. So basically any greenhouse photosensor/controller combo will work. They mentioned Argus controls as being good, I don’t know if they have anything that scales to the level of small home greenhouse.
Very cool, 99. Some jealousy over here. Please let us know how it works out!
Is that a Mean Well B series driver I see there? 
Yes it is.
Looks like the tinfoil forest will be dialed in in no time. 
So, again Fluence more than passes the test.
I opened up the timer, and of course, I am looking at pig tails on one side and plug-n-play on the other side, which means they messed up the order.
I sent an email out, and I kid you not, Ginger called within 2 minutes and the missing piece is in the mail!
oh yeah Ginger is great, she answered all my questions about spectral choices and photoacclimation! 
what a woman!
a US-made dimmer for under $100 is a nice benefit of using Fluence, usually controllers & stuff are way more expensive.
So jealous here with my T5’s and 4 more hermed plant 
New veg set up is sweet
4 more weeks of HPS pics and this light gets retired!
It is a 600W HPS Gavita ? ? ?
4 plants?? My condolences. That sounds rough
