Hello, I would appreciate advice about evenly illuminating a 40x40” (102x102 cm) area of a wall with LED light of about 5000K, CRI 95+ and also R9 and R12 each 90+. I am not sure how bright I’d like the wall to be, but let’s say about 500-1000 lux. I would like to attach the light sources to moveable tripods with height adjustable up to the ceiling, 96” (244 cm). There are several 120V wall outlets nearby.
Linear strips of Bridgelux Thrive 98 CRI are available from digikey (e.g., https://www.digikey.com/en/products/detail/bridgelux/BXEB-L1120Z-50S4000-C-C3/13181786). According at least to the manufacturer’s information, these should meet my CRI, R9, and R12 requirements. But I have never used LED light strips and wonder what will be involved in making suitable fixtures (panels?) with them, and what is needed to drive them safely. I am okay with soldering if need be, but I am not an electrician.
What approach do you think I should take? Should I consider anything else (e.g., are there suitable read-made bulbs for sale somewhere)? Has anyone done something similar? I guess that for even illumination I might also need to use a diffuser (especially with the strips?).
I initially considered using halogen instead of LED (SoLux MR16 bulbs, 4700K 50W), but I am concerned about the heat.
Thanks for your extremely informative reply, Hoop. A few follow-up questions:
1) Any thoughts about ILONA Zoom? Apart from the extra cost, are there any negatives to using it?
2) If I go with a COB + Ilona optics + Hekla socket + heat sink (e.g., I see many by Wakefield-Vette on digikey), how would you recommend I mount this? Hang it from a horizontal bar that I attach to the ball head on my tripod? Put it in some standard housing (borrowed from track lights or …) and then hang it from a bar on the tripod?
3) Regarding dimming the Meanwell LPF driver, do I understand correctly that I should use PWM dimming to not impact the CCT and, if so, that I need to add my own potentiometer — it is not included in the driver?
The Hekla socket for the V6 HD Thrive + Ilona optic is in stock at mouser by the part number F15255_HEKLA-SOCKET-C.
1) I recently acquired an ILONA Zoom but have not tested it yet. I was rather excited when I saw the press release. There a few downsides: one is that it is ~10% less efficient than the other Ilona optics, but 84% efficent with a V6 HD COB is still not bad, the regular Ilona optics are extraordinarily efficient. Another is that there might be some amount of artifacts or less perfect beam uniformity, but I am merely speculating, and Ledil has a video about the Zoom and it looks pretty smooth. It also requires a more complex or customized housing solution because it has moving parts, you need to be able to rotate the top lens.
2) Mounting could be done in a lot of different ways, even using D cell mag-lites for the housings, which take 50mm optics. The LPD driver wont fit in a D Mag tube however. I think you’ll probably need some amount of custom fabrication (machining) to make it all come together, but I am a machinist and so I think like one, maybe you could devise a way to do it without any machine work. Gutting some kind of large “work light” and mounting a heatsink to the back side could be an option.
3) You are correct that PWM dimming would be the way to go to keep the CCT and tint more consistent over the full range, although the CCT and tint shift may be acceptable with non PWM dimming at the output levels you will be using, and you may wish to avoid PWM depending on your application. There are three ways to dim the LPF, 0-10v signal, a 100k ohm potentiometer, or 10v PWM signal. I believe, but am not certain, that the 0-10v and pwm methods can be used simultaneously, meaning you could use pwm applied to for example an 8v source, which would reduce the current output to 80% of max, and then the PWM would adjust the duty cycle for further dimming. Dimming with 0-10V or an external pot is not PWM dimming, these methods adjust the current. For pot dimming, a 100k log taper pot should be more visually linear during adjustment than a linear taper pot, with more resolution at the lower end but less at the higher end. A multi turn pot would provide for finer adjustment if you require it. 100Hz-3KHz is the supported PWM frequency range. Higher PWM is generally less noticeable to the eye, so 3KHz would be the way to go, but this is not super fast PWM, so it may be noticeable upon moving objects, and also if you are filming or taking photographs, but maybe not, I don’t have experience with that. There are relatively inexpensive PWM signal generators such as the “xy-pwm1” which would do the job of providing a PWM signal. I like the version with the knob. An adjustable or fixed voltage power source would be needed to power it, such as a 9v wall wart.
An alternative driver solution would be the Taskled Ultraboost. The PWM dimming function supports up to a 10kHz PWM input frequency, with a 10v max PWM signal voltage. It also supports pot dimming with a 50k (preferably log taper) pot, which would be current limiting, non-PWM dimming.
A single 9V AC-DC power supply could power both the driver and the PWM generator, although you’d want to use one capable of 6 Amps or so such as Meanwell GST60A09-P1J.
Once again, thank you very much, Hoop. This is quite helpful. Using mag-lites for the housings is an interesting idea (and I happen to have some on hand). I’m going to investigate mounting options further. I suspect there are ready-made options for photography studio lighting setups.