Tackling this project made me wonder: how do manufacturers in the electronics industry illuminate those ultra-flat laptop displays and TV screens to get a perfectly uniform glow? Following a bit of internet research, I discovered a treasure trove of useful insights.īefore we dive too deep into how the consumer electronics industry solves this problem, I want to first walk you through an analogous hacker side-project: the laser-cut acrylic edge-lit display. I’ll dig into the some of the working principles, introduce you to my homebrew approach, and leave you with some inspirational source code to go forth and build your own. Today, I’d like to share my findings and introduce you to light guide plates, one of the key building blocks inside of much of today’s backlit screen technology. What I thought would be quick project ended up being a dive down the rabbit hole that yielded some satisfying results. As fate would have it, the crux of this project was finding a way to do just that: to diffuse light coming in from the edges so that it would emit evenly from the front. True to the original, my replica would need to be both slimmed down and backlit with a uniform, natural white glow. Stay tuned for cake at the end of this article. In hyperstylized video game fashion, they were also extremely thin. If you’ve played the game, you’ll remember these signs as the illuminated monoliths that postmarked the start of every test chamber. Yes, bulbs are fat and LED strips can make a thin panel, which may over-ride cost and performance.Last year, I found myself compelled to make a scaled-down replica of the iconic test chamber signs from the video game Portal. Bulbs eat right off (my) 120V lines, so the wiring costs some more, but there's no power-pack. The strips are very cheap in bulk but expect 12VDC power. While I did not account for dimmability, when I costed-out lighting my garage with LED-strips or LED bulbs, it was not a real difference. If so, 3 or 4 "60W" dimmable LED bulbs behind frosted plastic and a wall-dimmer would give large-area light source. I simply do not know if the LED ballast holds over an AC cycle. If you hadn't already built these panels, _I_ would put one dimmable household LED on a household lamp dimmer. Pressing on: 15V-12V is 3V drop, 2A assumed current, 3V*2A is 6 Watts heat in the regulator. Using cave-man technique, start with 15VDC into a 3-pin regulator. Or a linear current regulator, assuming the many-many parallel paths share well. You could contrive a linear voltage regulator over this range. Pick them staggered so you still have uniform light.Īs we have 3.5V LEDs stacked to nominal 10.5V, anything below 10.6V will be "out" and anything over 12V-13V will probably pop the LEDs. The most obvious and Dead-Easy answer is to switch-out 1/2 or 1/4 of the strings. What is your Real Problem? Is anything smoking? Is it bright enough? I would certainly expect +/-20% variation through a run of the same product, more if they are not the "same" modules. As marginally acceptable parts, the actual performance will vary a LOT, depending on factory slop and module-parts buying specs. However I am seeing that high-R LEDs seem to be readily available as near-rejects, and are built-up into light strips at shocking low prices. It is also possible, and not so uncommon, to use low-resistance LEDs with a resistor, user-supplied or built into a module. 12V across 3.5V+25r series-three is still 20mA. This is a reasonable current for the smaller LEDs. If we assume 25 Ohms in each LED's poor processing, 4V supplied across 3.5V+25r is 20mA. If you connect to 12V, the excess 1.5V would cause "infinite" current flow and instant death.īUT- real LEDs have some internal resistance and cheap LEDs have more. White LEDs ideally have a forward voltage near 3.5V and low internal resistance. Without specific product info, or more detailed measurements than you have done, calculations can only be wild guesses. I suggest these have no electrical significance.
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