Artificial Sunlight (official topic)

@fhr by measurement equipment, certainly, but human vision is far from a scientifically calibrated photometer.

The optical illusion I showed is one example. It's like human hearing in a way. Volume increases on a logarithmic scale (measured in phons). 

Vanta black wouldn't be much good if we truly perceived 95% gray as black, for example. As I recall the manufacturer has shown some demos but the problem with those is that we're relying on the sensitivity of the video equipment which is good (but not that good). Researchers now claim to have made it darker still although it's potentially dangerous.

Given we can't buy it though, I guess the point is moot however.

@marcdraco my point is not we can't ever perceive the difference, my point is that behind a fresnel lense, behind a Tyndall scattering filter and next to a super bright cob led, then it would be indistinguishable. 

And you can easily buy 99+ black paint

No progress on the physical light yet, but I have made some interesting discoveries. That company Yuer Skylight that seemed to make exactly what I was after? I found their patent on the WIPO website. Link's here for anyone interested. The original document is in Chinese, and the site translator might lose a few crucial points (one day's translation said a back plate needed to be a transparent window, today it was a reflective mirror). So if anyone's comfortable with Chinese and wants to take a look, be my guest. But here's a basic schematic of their window and my understanding of how it works.

LEDs on the side (7) shine into what they're calling a Rayleigh Plate (4). From their tiktoks, this seems like a piece of plexiglass colored very light blue-- the same color as those inkjet films. The light can either travel out through the front, or into an air cavity in the back (11) before hitting a reflective panel (9) and bouncing back. The buffer panel (12), back panel (8), and heat sink (6) hold everything in place. The heat sink hides the LEDs quite well and has space for a second set of LEDs (5). They shine against a diffuser (2) and give the illusion of direct sunlight hitting the sides of the window. Gotta admit, that little touch is pretty clever...

This design seems pretty similar in theory to the design I've been playing with, so perhaps some tweaks in my design are all I need. If I get somewhere new with my design I'll keep yall posted 🙂

It's a very small and unimportant thing, but I was able to find success for Tyndall scattering with a generic inkjet printer film off of Temu as well. 

Admittedly the color in the first picture is slightly exaggerated due to auto-brightness correction from the camera, the 10000 lumen lightbox in a dark room produced a pretty impressive effect. 

17 years ago, I laid down on my back and stared up at the sky in the middle of a courtyard of a 100 year old building, and realized that, from where I was laying, even if the sky were somehow fake, from nowhere in the courtyard, would I have been able to see any edges to prove it as such.

As a matter of intellectual honesty, I had to, in that moment, admit that I couldn't reasonably demonstrate that I was actually outdoors, and not in say, some elaborate spaceship or bunker or something akin to that. 

From there, it sparked in me one of my biggest dreams has been the creation of an artificial sky inside of a building, a dream which has grown with age, not diminished, given my rapidly declining health and intolerance for the heat and weather of the outdoors.

All the other particulars-- a sky that is seemingly infinite, light with parallel rays, no points of reference to dispel the illusion, all are pretty easy, but the blue? The blue was beyond me for a very long time. First time I've been able to achieve this, and it's pretty exciting. 

Just figured I'd share this, as a little "hey, there's cool stuff!"

Would photographer umbrella be a decent alternative to a parabolic dish? Judging from the image, it's not a proper shape so even determining "focal point" would not be obvious. 3 observations:

* It seems to provide some utility as it's widely used in relatively light quality-sensitive scenarios

* It can be perhaps significantly larger, maybe even allowing multiple LEDs positioned with lower wattage and perhaps better W/$ than 500W.

* I'm in a small rented apartment and need optionality/portability and this is foldable. Plus I can't easily find cheap large dish in my country for some reason.

Could this fall into category "good enough"? Or would it be completely unsuitable for reason I'm not seeing? 

How did I not find this thread years ago? I've been obsessed with a DIY sunlight simulator for years, I watched DIY perks videos but didn't realise there were this many clever people doing all this good work building their own.

My "electric window" v1 is about the simplest thing it's possible to build: an Amazon SAD lamp with a page magnifier Fresnel propped in front of it to project a rectangle of light on a parallel wall (writeup on Instructables here: https://www.instructables.com/Dont-Be-SAD-Have-Electric-Windows/)

For v2, Remichou's build https://forum.diyperks.com/postid/4588/ is *exactly* what I've been planning: grid of inexpensive Fresnels, array of small COB LEDs making a shallow modular panel I can hang on the wall. Ideally I'd like the lenses not parallel with the wall so the light can be projected at an oblique angle, but that might be version 3.

Finding likely lenses hasn't been easy and the AliExpress links in their previous post are now dead; does anyone know what the product was called or what kind of search terms I'd need to look for similar Fresnels I can get cheaply in bulk? Ideally I'm shooting for minimal cost so I don't want to be paying $10 a piece for crystal clear optical lenses when a simple plastic magnifier would do.

Been busy this month, but have made some large steps in the right direction. I'm finally at a point in the build where the front pane starts to resemble sky. The biggest issue that was holding me back was not having the inkjet film properly connected to the plexiglass. Turns out even if I pressed the film firmly against the glass, there was some thin layer of air keeping the light from reaching the film. How did I fix this in the short term? Liquid in between the two layers. I tested both oil and water, and they give pretty similar results since the liquid layer is so thin.

Here's the before pic, where no light reached the film

And here's after. This is just a proof of concept so excuse how ugly it looks, but hey it works!

There are a few things to fix with this setup. I need to keep the liquid in place so it doesn't run everywhere and short the LEDs. Would probably use a really thin epoxy in the final product instead since it's optically clear. I need to be REALLY careful with any liquid on the other side of the film since it dissolves the coating (see the small black holes in the after pic). I need to keep the light from diffracting too much and creating interference bands (dark bands of light followed by light bands on the top of the film near the LEDs. Finally, I need to fix the coloring. Even though the light shines through the front now, it's more of a greenish blue than the blue of the sky. This can potentially be fixed with a different inkjet manufacturer? I'll have to keep doing some research on that. I also did the same setup with the glass panel from the Empowline skylight glass, and the color looked much better (see the small spot where I put some vegetable oil between the glasses). 

A potential solution if I just wanted to make one of these panels is to just use the empowline panel instead of film. But I do wanna see if I can find an inkjet film that looks more blue. For reference, I'm using this film. If yall have thoughts or ideas, I'd love to hear them 🙂

Until next time!

To expand on my previous post:

This is the Electric Window v1 - an 8" diagonal SAD lamp and a page magnifier Fresnel. I don't think I've seen anyone use this particular approach before. 

and a before and after in my kitchen:

Pros:
- dirt cheap - under $40 total
- easiest possible setup, no holes in ceilings and easy to move
- nice uniform sharp-edged rectangle of projected light on a perpendicular wall

Cons:
- at a six foot throw (narrow British house!) the light is decently bright but it's only about a 60*75cm area. If it projects further the patch will be bigger but dimmer - more like accent lighting than sunlight
- the light isn't truly collimated, so the projection on the wall has sharp edges but objects in the path don't cast hard shadows
- no Tyndall effect skylight simulation, just a postcard sized bright patch

I'm a sucker for making things out of cheap easily accessible materials so for v2 I'd like to try a super simple lens array with no CNC parts or obscure materials - 1W star LEDs and plastic lenses. If that works, for v3 ideally I'd love to try angled Fresnels for oblique light from a shallow panel; "shiny satellite dish" has been done in depth but I think there's some more juice to be squeezed from lens array designs.

Our Brazil customer bought our CRI Ra 97+ daylight white led strip light to DIY LED Panel Light for his studio, below is his 5 stars positive feedback and DIY project pictures, 

It was worth every cent invested in this led, I couldn't measure the CRI, but by the quality of the light, I'm sure it exceeds 97%. My power supply does not support the total current, but as I did an arrangement of 4 groups, with three groups reached more than 6000 lm. 25% is already enough for lighting my studio. This store has my respect, for the price, I was afraid to buy, but with experience, I will buy a two-color COB on the next purchase, as the store only sells quality products.

Here is our CRI Ra 97+ led strip light, 

DIY LED U-Home offical brand store, https://c.c1nd.cn/n3UN6

DIY LED U-Home aliexpress store, https://www.aliexpress.com/item/33005666342.html

Posted by: @pkm_uk

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To expand on my previous post:

This is the Electric Window v1 - an 8" diagonal SAD lamp and a page magnifier Fresnel. I don't think I've seen anyone use this particular approach before. 

-- attachment is not available --

and a before and after in my kitchen:

-- attachment is not available --

Pros:
- dirt cheap - under $40 total
- easiest possible setup, no holes in ceilings and easy to move
- nice uniform sharp-edged rectangle of projected light on a perpendicular wall

Cons:
- at a six foot throw (narrow British house!) the light is decently bright but it's only about a 60*75cm area. If it projects further the patch will be bigger but dimmer - more like accent lighting than sunlight
- the light isn't truly collimated, so the projection on the wall has sharp edges but objects in the path don't cast hard shadows
- no Tyndall effect skylight simulation, just a postcard sized bright patch

I'm a sucker for making things out of cheap easily accessible materials so for v2 I'd like to try a super simple lens array with no CNC parts or obscure materials - 1W star LEDs and plastic lenses. If that works, for v3 ideally I'd love to try angled Fresnels for oblique light from a shallow panel; "shiny satellite dish" has been done in depth but I think there's some more juice to be squeezed from lens array designs.

 

I'm confused by how this light is still getting focused and collimated as AFAIK that lamp is using multiple leds, so lots of random directions/rays/diffused

I just purchased an 100w LED (almost got the full spectrum from DIY-LEDs but couldn't afford/justify 100$) and a frensel lens (300mm focal length, 300x400mm) this is going to end up insanely big, I'm really hoping to find a way to at the very least make it thinner as smaller is not possible without a slight angle to the beam.... I guess I don't really need full collimation? 10-5 degrees is probably fine and over a long distance (one wall to another) it'll help.

I also might use two lenses in a row to capture more of the light, but my gut tells me that i'd lose more light from the lens than gain from the focus.

I had to use a3 (too small) milky sheets, but my hope is that I can glue them side to side with packing tape and still get a good enough effect, I might use two sheets on the two ends to not make the tape visible in the middle? The cheapest a3+/a3 sheets I found were 50CAD for 50ocs.... I only need 1 sheet...

btw, did Mathew give up on the v2? I'd LOVE To see it, although I already spent 150CAD on the parts, not to mentin I still haven't designed a custom PCB for it, I want it to use an esp32 and a current limited driver so I can PWM it to slowly increase it.

I'm not trying to create an artificial window, but rather a sunrise alarm. if I had more money i'd simulate the sun slowly rising with a stepper motor mounted LED, but it's already too expensive 😛

If you could get your hands on an old 3D printer you could salvage parts from that. Just sayin' 😉

Is there a V2 of this project, I didn't know one had been proposed but it's not a topic I'm even adept at.

Posted by: @bunnyqueen

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I'm confused by how this light is still getting focused and collimated as AFAIK that lamp is using multiple leds, so lots of random directions/rays/diffused

...

I'm not trying to create an artificial window, but rather a sunrise alarm. if I had more money i'd simulate the sun slowly rising with a stepper motor mounted LED, but it's already too expensive 😛

My design is a compromise: the light isn't truly collimated, the rays aren't parallel - the lens is acting as a projector, focusing an image of the rectangular lamp on the wall. The light only has hard edges at the focal distance, things in between don't cast hard shadows, and some light does bleed around the edges. The only way to get really collimated light is with a small point source at the focus of a lens; something I'm hoping to do in a future project.

If you just want a sunrise alarm, I've done that with 12V LED strip and a PWM controller driven from a microcontroller. I like the idea of moving the LED to simulate sunrise though