[DIY Perks] has long been a fan of lights that accurately mimic real daylight. Often choosing high-quality LEDs for his projects, lately he’s taken a different tack – using broken televisions to produce attractive home lighting solutions.
The hack involves removing the backlight from the damaged television or monitor. These have a powerful white light inside, but the real key is that they also features a Fresnel lens. This helps the backlight appear very similar to a real skylight, due to the way it scatters light around the room.
Due to the difficulty of driving most LED and CCFL backlights, the project strips the original lighting out and replaces it with a set of high-CRI LED strips readily available off eBay. These are easily driven from 12 volts and give a white light more similar to actual daylight compared to most backlights. With the LEDs in place, the monitor’s original diffusers and Fresnel lens are put back in place, and the light is finished off with an aluminium frame.
Fitted to an angled ceiling, the light really does look as if actual sunlight is streaming through a window on a rainy day. It’s a pleasant effect that does a great job of lighting a room, and we suspect it would be excellent for general video work, too. [DIY Perks] is no stranger to a good studio light build, after all. Video after the break.
Poor mans grow light. And look out for that UV output.
I thought the whole point of a grow light was to put out as wide of a spectrum as possible, and single frequency LEDs don’t work well for that.
If they did, these white LED strips sold for indoor lighting would be causing all sorts of problems everywhere.
Single-color LEDs are quite efficient (direct emitters rather than intermediate phosphor). Many grow lights only have blue and red LEDs. They skip green because, well, plants are green because that’s the color of light they reflect. It would be wasted energy. Full-spectrum grow lights have some advantages, but the main one is that humans don’t like living in purple light.
There’s two types of growlights – ones that are optimized for photosynthesis of particular plants, which means they have that funky hot pink hue.
The other type is a growlight meant for indoor decorative plants, which means it’s just a wide spectrum light that has been extended towards the UV region to give the appearance of a white light that also has the spectral components required by a variety of different houseplants.
Then there’s the ghetto growlight, which is a high pressure sodium lamp adapted for growing weed.
all he reuses is the diffusers. none of the electronics
Yes. That’s exactly what the HaD what the article said. Did you not read it and instead think you’d get in with some sort of Hot Take or something?
Buying those new isn’t cheap, they are good diffusers.
It’s surprising how difficult it is to find a quality fresnel lens in small quantities. I’ve never found any for sale at any price at the size used in a TV.
A 10cm square sheet at 10 qty tends to run about $200. The irony is 20 of them fit together would still be quite smaller, and about the same price as a brand new TV.
Keep your eye on the curb/recycling center etc. I have several that came from the old giant back-projection TVs that are easily several square meters large and made of somewhat flexible plastic. Also the mirrors from those are first-rate. Often people give them away when they’re no longer wanted because they’re such a mess to deal with.
Clearly he didn’t need the electronics to do what he wanted to do. The CFL lamps for LCD screens ar egoing the way of the Dodo bird, makes sense to use modern lighting componets
Amazing how I accumulated like over 20 free LED TV’s from the free listings on Facebook, Craigslist, Offerup and Letgo. Was quite the addiction for a winter season. Helped along with the other TV’s and electronics; practicing desoldering, testing components, learning about components/circuits and acquiring free components and modules as well as learning how to repair and repairing a few TV’s.
Other than doing some simple hacks to the driver boards so they get the correct signal to power on/off… seems easier to just use the backlight with same or a different power supply with the LCD screen removed and re-use or make a new frame.
I do like his flexible panel light. That’s a neat novel design I’ve not seen before.
Backlights for TVs make for poor room lighting because they’re optimized for the narrow-band RGB filters of the LCD panel itself. That’s because they don’t want to make any colors that won’t pass through the screen.
With three narrow spikes for a spectrum, the backlight produces a highly unnatural light that actually makes you see worse. Your ability to distinguish between similar hues goes away, and paint pigments stop working properly because they work by subtracting colors out of white light. If there isn’t the particular wavelength of light that the paint pigment is supposed to remove, then the color of the paint may change entirely. Prints, paintings, furniture, even makeup that people put on can appear completely different than what was intended. The impairment on your vision is much like having cataracts.
This is actually the topic where LED lighting in general struggles. Bright efficient LED lights have narrow spectra and they make “white” light that does not reproduce color properly. If you up the price and drop the efficiency, then the color gets better but your energy consumption is no better than fluorescent tubes.
Sorry Luke, I have to call BS on this one.
I have personally measured spectra from LED back-lit displays, with and without the RGB LCD panel. The spectra are NOT narrow spikes. The backlight spectrum is just like the spectrum published on white LED datasheets: big blue LED spike, deep notch in the blue-green, and the large, smooth phosphor hump in the green-yellow-red.
Similarly, the RGB spectra after passing through the LCD panel is also broad peaks, centered in the (not surprisingly) red, green and blue.
I have not got my hands on a wide-gamut RYGB panel yet. I’d like to see how they differ. And I’d like to find a LED source (for a reasonable price) that fills in that awful missing notch in the blue-green. It can be done with supplementary LEDs of the right color, but that’s a real kludge, mostly because they can’t match the angular spread without a lot of lossy diffusion.
You get better color saturation by employing narrower filters, at the expense of less light passing through (dimmer display, worse contrast). The width of the spectrum depends on what compromises the manufacturer has made.
The newer “eIPS” panels especially deal away with the inherent dimness of IPS by using less selective filters with LED backlights with narrower spectra. Less light lost at the filter, better contrast and brightness.
Beg pardon Luke ?
Your claim “That’s because they don’t want to make any colors that won’t pass through the screen.” doesn’t gel with contemporary issues of various commercial realities which would be obvious to those in the electronics design and optical engineering industries, think conjunction of economies of scale with capital cost to finesse a fab process for the semiconductor material and Then to produce it reliably in bulk With the exclusions controlled in production timing SPC to suit your idea, from whence dost that idea arise ;-)
ie why go to the trouble to, I quote “..don’t want to make..” when the cost of excluding specific spectra not by any means a trivial matter at the silicon doping level When very cost effective LEDs efficient for their light output already for the colours you want with any ‘extra’ spectra not relevant and at negligible energy cost too…
Please indicate/link to the most credible source of your claim hopefully with some pointers to comparative economics going down that path especially when bulk LEDs from many sources have been very cheap for a long time versus the comparatively advanced and ever improving diffuser/filter plastics cost also declining ie think on the chemical engineering path of most economical plastics selecting out spectra you might not want which don’t necessarily impact the final product anyway etc IOW. Something substantive please not arbitrary tech speak sales claims to impress the unwary which seem to sprout from marketing which miss conjunction of silicon fab vs filter/diffusers comparative costings ?
All that verbal diarrhea is adding up to exactly nothing.
LED manufacturing is difficult and the outcome is that LED dies come in a variety of wavelengths for the same color.
The manufacturer measures the dies and bins them according to how much you want to pay for having exactly the right wavelengths. The diodes at the tails of the distribution are sold to fly-by-night cheap manufacturers, and the diodes in the middle of the distribution are sold to reputable manufacturers of high end products.
For the higher end products, you get what you pay for. Cheaper products may as well use a random grab-bag of LEDs that coincidentally and collectively end up producing a more spread spectrum, since a TN or even a VA panel LCD isn’t going to give you much color fidelity anyhow: the gamma between color channels changes according to viewing angle.
For the cheaper products, absolute brightness is preferred because that improves the relative contrast ratio (and also burns your eyes out of their sockets). That means wider filters, and a washed out display that looks good under bright shop lights, and like a** in your living room.
There’s actually many different types of LEDs used in monitors and TVs, with pros and cons. The cheaper panels tend to use “white” diodes which are the typical blue diode and yellow-green-red phosphor affairs, which have a poor CRI for general lighting anyhow. The higher end models used to have RGB LEDs made out of individual diodes, but the wear-out mechanism meant that the colors would shift over time and getting them all balanced was costly.
What came to be used later was the GB-R LED, which is a green and a blue diode with a red phosphor between them. It produces three well-defined peaks that gives a wide color gamut. The alternative is RB-LED which is red and blue diodes with a green phosphor. The end result is approximately the same.
https://pcmonitors.info/wp-content/uploads/2013/01/GB-LED-spectrum.png
These are more common in televisions than in computer monitors, because the NTSC and PAL color gamut specifications are much wider than the sRGB specification for regular monitors. Wide gamut means the primary colors have to have narrow spectra, which means high color saturation. Watching TV broadcasts and DVDs on an sRGB monitor results in muted colors.
Then there’s the quantum dot displays, such as Samsung’s QDEF, which have blue diodes for backlights, and the phosphors that convert it to red and green light are located in a film underneath the panel. These displays also have three well defined peaks in the spectrum:
https://pcmonitors.info/wp-content/uploads/2013/01/QDEF-Spectrum.jpg
As compared to the “white” LEDs:
https://pcmonitors.info/wp-content/uploads/2013/01/WLED-spectrum.png
Ahh. Delighted to see that stuff get out of the labs. I’m sorry I missed it when the news arrived. I’d love to see these newer displays in the wild so I can measure one.
Well, since all this information is 5+ years old, you can find these newer LED TVs in the recycling centers and dumpsters.
Most of the small brand TVs and small/cheap panels are still WLED, but if you pick a larger panel and something from Samsung, LG, Sony, etc. it’s probably got the newer diodes in it.
I grabbed another today and coming home to-nite I passed up another. They seem so close to daylight that I am happy in the winter. The 5volt signal and keeping them on after the energy star says “no activity turn off” is a problem.
Wouldn’t it be fairly simple to hotwire the power supply to turn the backlight on?
I thought the same thing, but I have to admit with how cheap those LED strips are anymore, I don’t know if it’s worth the hassle trying to hack the original lights to stay on. Especially if it’s CFL. Plus even if you got it working, then you need to figure out how to house the original electronics.
Plus, the strip will give you a remote an probably RGB support, which is a considerable advantage.
You need the electrics to work to adjust the color balance, and you don’t actually want to use the LEDs they put in for light because they suck at it.
Smaller ones also make terrific slide sorters.
If you’re a hipster living in this century, it’s also a dandy backlit sketching board.
Or, leave one polarizer in and you get a high quality large-area source of polarized light, ideal for looking at strain or other polarization rotation in materials (when used with a second “analyzer” polarizer filter on your camera or eyeball).
I actually made one of these from a small monitor I had lying around after watching his video! My LED strip wasn’t as bright, but I was still happy with the results. I’d love to try it with RGB LEDs and see if I could mimic the outside light a bit instead of it being pure white.
RGB has a very bad light quality (look for CRI), only suitable for mood lighting. Try combining both the classic white LED and RGB strip for daylight simulation.
Oh wow, I didn’t think about that. I’ll definitely look into that instead! Cheers.
Youtube has been suggesting that video for me for sometime now. I never viewed, because I wasn’t going to chase broken TVs. Now that I have viewed it, I discovered, even if a I had a stock of TVs, this wouldn’t be project that I’d duplicate. Not a fit for my home.
I would put a light sensor (or camera behind diffuser) on the roof to read ambient light hue and intensity to adjust light output of the fake window.
I dissambled an old Dell P2312H and an 2311, too. I learned that modern monitors have lights on only one short side of the cage and the cage is thinner than my led stripe. The light from one of those cannot brighten a room, but it might be sufficient for a small work area shined from above.
Then I was lucky to pick a broken LED TV from the garbage, just the same size like the monitors mentioned above. Good sign was that the inner cage seemed to be bigger and it was. This device has a big cage, big enough to hold my led stripe in without complications. And, more important, it had lights at both long sides, which means a lot more leds, a lot more light. I am going to build it in the next days.
I’ve build a good spotlight from the first TV. I was able to use 24 LEDs distributed over 2 rows and it can indeed lighten a room. Well, if the room is more a rectangle rather than a cube. The light might last a long distance thanks to the fesnel lense but it does not spread a lot. There is a second TV I disassembled. Unfortunately it had no fresnel lense but a cage for diffusing. I was able to use 22 LEDs at two rows. So they both have almost the same light source and indeed they seem to lighten a dark room the same way. It looks so much the same, that I doubt the capabilites of the fresnel lense already.
My conclusion is that those light panel builds offer a good use for special cases. The fresnel lense and the monitor diffuser help not being blinded by the light when looking at the panel. But it is a strong light souce you don’t like to be placed head hight forcing you to look at every day. Finding a good place to put and having a good illumination is quite a task if you want it for your room.
Another point I haven’t solved yet: You loose the LCD-Panel and by that the front glas keeping the foils at place. The foils aren’t as much fixed as nescessary, especially when put over head – where to find a suitable front glas, inexpensive, is an open case, yet.
Thank you for this! I’d like to try. Can you recommend the appropriate specs for the led strip please?
I followed the recommendations and links from the youtube video.